摘要:

Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Transformation of diaminocarane on a triosmium cluster. Absolute configuration of a cluster with a bridging imidyl ligand Vladimir A. Maksakov,*a Vladimir P. Kirin,a Alexander V. Virovets,a Pavel A. Petukhovb and Alexey V. Tkachevb a Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation.Fax: +7 3832 35 5960; e-mail: maksakov@che.nsk.su b N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation The C–H activation of an NMe2 group in diaminocarane coordinated to an Os3 cluster results in the formation of (R,S)-{Os3(CO)10(m-H){m,h2(N,C)-(4R,6R,8S,10S)-1,7,7,10-tetramethyl-1,3-diazatricyclo[3.5.0.0]dec-1-en-2-yl}} diastereomers.The coordination of bulky optically active ligands in cluster complexes can be stereoselective.1 In the case of L-oxyproline esters, the reaction is stereospecific. Here, we report on a reaction of triosmium cluster Os3(CO)11(NCMe) 1 with the carane derivative (1S,3S,4R,6R)-3-(N,N-dimethylamino)-4-amino- 3,7,7-trimethylbicyclo[4.1.0]heptane (diaminocarane 2).Reactions of Os3(CO)12 and its derivatives with amines are among the best studied reactions of triosmium cluster complexes. 2 The interaction of Os3(CO)11L (L = CO, NCMe) with an excess of a primary or secondary amine results in formation of (m-H)Os3(m-O=CNRR')(CO)10 clusters.2 Decarbonylation of the bridging ligand and the formation of (m-H)Os3(m-NRR')(CO)10 clusters occur at refluxing the above species in octane.3 If these clusters have at least one N–H bond, they lose another CO group at 150 °C to form (m-H)2Os3(m-NR)(CO)9.4 Tertiary amines, having no active N–H hydrogen atoms, react with triosmium clusters under severe conditions. In these reactions, cleavages of C–H, C–N and C–C bonds take place, and clusters with imine, aminocarbene or aminocarbyne ligands are formed in low yields.5 The first step of the reaction of Os3(CO)11(NCMe) with diaminocarane 2 is similar to that of simple amines.According to TLC data, complex 3 was the main product in solution after 3 h. Its IR spectrum in the region of CO stretching† is characteristic of Os3(CO)11L clusters with terminally coordinated † IR (hexane, nCO/cm–1): 2106 (w), 2052 (s), 2034 (s), 2020 (m), 1995 (br.s), 1981 (sh.), 1966 (sh.). n-donor ligands.6 Like other triosmium clusters with terminally coordinated amines, this complex is unstable in solution in the absence of an excess of the ligand. When 3 is heated at 60 °C in the presence of an excess of diaminocarane, a complex transformation of the ligand results in the formation of cluster 4 with a bridging tricyclic imidyl ligand (Scheme 1).‡ ‡ A typical experimental procedure was as follows: 137 mg (1.5×10–4 mol) of Os3(CO)11(NCMe) and 250 mg (1.3×10–3 mol) of diaminocarane 2 in 25 ml of THF were stirred at room temperature until all Os3(CO)11(NCMe) was consumed.Then, the reaction mixture was heated at 60 °C for 18 h and evaporated to dryness; the residue was chromatographed on Silufol using a 4:1 hexane–benzene mixture as the eluent.The first intense yellow band afforded 4 as a mixture of two diastereomers [total yield 28 mg, 18% on an Os3(CO)11(NCMe) basis]. Scheme 1 NMe2 Os Os Os NCMe Os Os Os NH2 NMe2 NH2 THF, 20 °C, 3 h Os Os Os N N H THF, 60 °C, 18 h 1 3 4 1 2 21 3 4 5 6 7 8 81 82 11 Figure 1 Molecular structure of 4a (thermal ellipsoids at a 50% probability level).Numbering of atoms does not correspond to the IUPAC nomenclature. Selected bond lengths (Å): Os(1)–Os(2) 2.9397(8), Os(1)–Os(3) 2.8754(9), Os(1)–H(12m) 1.81(5), Os(1)–C(1) 2.10(1), Os(2)–Os(3) 2.8748(9), Os(2)– H(12m) 1.78(5), Os(2)–N(2) 2.08(1), C(1)–N(1) 1.39(2), C(1)–N(2) 1.26(2), N(1)–C(11) 1.45(2), N(1)–C(2) 1.51(2), N(2)–C(3) 1.49(2), C(2)–C(21) 1.53(2), C(2)–C(3) 1.53(2), C(2)–C(7) 1.57(2), C(3)–C(4) 1.53(2), C(4)– C(5) 1.49(2), C(5)–C(6) 1.50(2), C(5)–C(8) 1.49(2), C(6)–C(7) 1.50(2), C(6)–C(8) 1.52(2), C(8)–C(81) 1.50(2), C(8)–C(82) 1.45(2); selected bond angles (°): C(1)–Os(1)–Os(2) 65.7(4), C(1)–Os(1)–Os(3) 86.9(4), N(2)– Os(2)–Os(1) 66.8(3), N(2)–Os(2)–Os(3) 88.7(3), N(1)–C(1)–Os(1) 131(1), N(2)–C(1)–Os(1) 114(1), N(2)–C(1)–N(1) 115(1), C(1)–N(1)–C(11) 128(1), C(1)–N(1)–C(2) 109(1), C(11)–N(1)–C(2) 124(1), C(1)–N(2)–Os(2) 113(1), C(1)–N(2)–C(3) 110(1), C(3)–N(2)–Os(2) 136.7(9), N(1)–C(2)–C(21) 108(1), N(1)–C(2)–C(3) 101(1), N(1)–C(2)–C(7) 110(1), C(21)–C(2)–C(7) 112(1), C(3)–C(2)–C(21) 114(1), C(3)–C(2)–C(7) 112(1), N(2)–C(3)–C(2) 106(1), N(2)–C(3)–C(4) 113(1), C(4)–C(3)–C(2) 112(1), C(5)–C(4)–C(3) 111(1), C(4)–C(5)–C(6) 114(1), C(4)–C(5)–C(8) 124(1), C(8)–C(5)–C(6) 61(1), C(5)–C(6)–C(8) 59(1), C(7)–C(6)–C(5) 113(1), C(7)–C(6)–C(8) 121(1), C(6)–C(7)–C(2) 113(1), C(5)–C(8)–C(6) 60(1), C(81)–C(8)–C(5) 120(1), C(81)–C(8)–C(6) 122(2), C(82)–C(8)–C(5) 116(2), C(82)–C(8)–C(6) 112(2), C(82)–C(8)–C(81) 116(1). O(31c) C(31c) O(33c) C(33c) O(32c) C(32c) C(34c) O(34c) O(13c) C(13c) Os(3) O(23c) C(12c) O(12c) Os(2) C(21c) O(21c) C(22c) O(22c) C(23c) Os(1) C(1) N(2) C(11c) O(11c) C(3) C(4) C(5) C(8) C(81) C(82) C(6) C(7) C(2) N(1) C(11) C(21)Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) This transformation is surprising because severe conditions are required for activating tertiary amines on triosmium clusters.5 Taking into account that the key step of the amine interaction with transition metal carbonyls is the nucleophilic attack of the nitrogen lone pair on a carbonyl carbon atom,7 it is reasonably to suggest that the formation of cluster 4 proceeds through the nucleophilic attack of a dimethylamino group of terminally coordinated diaminocarane on the carbon atom of a carbonyl group coordinated to neighbouring osmium.As this takes place, the source of the imidyl ring carbon atom is the carbonyl group. However, experiments with Os3(CO)11(NCMe) enriched with 13CO have shown that the 13C label does not appear in the bridging ligand. Therefore, the source of the imidyl ring carbon atom is one of the methyl groups in NMe2 rather than CO, and the formation of 4 proceeds through the C–H activation of one of methyls in the dimethylamino group followed by formation of the N=C double bond. Mild conditions of the C–H activation may be caused by steric hindrances arising at coordination of a bulky diaminocarane ligand to a cluster like the reaction of Os3(CO)10(NCMe)2 with substituted pyridinealdimines, where the C–H activation occurs at ambient temperature.8 Because cluster 4 does not contain a symmetry plane, it is formed as a mixture of two diastereomers in the ratio ~4:3 (according to NMR data), which cannot be separated by TLC.Crystallization of the diastereomeric mixture from pentane afforded main diastereomer 4a as diastereomerically pure crystals. The mother liquor contained mainly the other diastereomer. Its spectra with subtracted signals of 4a were given as the spectral characteristics of 4b.§ The X-ray analysis of 4a has been performed, and the absolute configuration of this diastereomer has been determined.¶ Using the stereochemical nomenclature proposed by us for cluster complexes,1(a) its absolute configuration can be described as (R)-{Os3(CO)10(m-H){m,h2(N,C)-(4R,6R,8S,10S)-1,7,7,10-tetramethyl- 1,3-diazatricyclo[3.5.0.0]dec-1-en-2-yl}}.The adequacy of the absolute configuration determination has been verified by the coincidence of configurations of the C(5), C(6) and C(3) atoms in the cluster and in the free ligand. § 4a: 1H NMR (CDCl3) d: 3.43 (s, H3), 2.79 (s, H11), 1.91 (m, H7 + H4 a), 1.02 (s, H21), 0.97 (s, H82), 0.96 (s, H81), 0.54 (m, H4 b + H7 b), 0.18 (m, H5 + H6), –15.71 (s, m-H). 13C NMR (CDCl3) d: 183.82, 183.32, 179.41, 175.88, 175.65, 175.45, 174.55, 173.89 [Os3(CO)10], 160.44 (N=C–), 72.29 (C3), 63.95 (C2), 29.2 (C11), 28.29 (C82), 26.27 (C7), 25.14 (C21), 21.34 (C4), 17.86 (C5/C6), 17.35 (C8), 16.21 (C6/C5), 14.54 (C81). IR (hexane, nCO/cm–1): 2104 (m), 2062 (s), 2052 (s), 2022 (s), 2010 (s), 2002 (m), 1988 (s), 1975 (w), 1948 (w).MS, m/z: 1048 (M+, 192Os) (the atom numbering corresponds to that in Figure 1). [M]16 580 = –1186° (c 0.65, CHCl3). 4b: 1H NMR (CDCl3) d: 3.14 (dd, H3, 3J 4 and 2 Hz), 2.83 (s, H11), 1.97 (dd, H7 a, 2J 16 Hz, 3J 8 Hz), 1.87 (ddd, H4 a, 2J 16 Hz, 3J 8 and 2 Hz), 0.99 (s, H21), 0.93 (s, H82), 0.89 (s, H81), 0.62 (ddd, H4 b, 2J 16 Hz, 3J 9 and 4 Hz), 0.53 (dd, H7 b, J 16 and 9 Hz), 0.30 (ddd, H5, 3J 9, 9 and 8 Hz), 0.23 (ddd, H6, 3J 9, 9 and 8 Hz), –15.83 (s, m-H). 13C NMR (CDCl3) d: 183.89, 183.28, 178.58, 176.57, 175.72, 175.59, 175.11, 174.90, 174.64, 173.56 [Os3(CO)10], 160.38 (N=C–), 72.29 (C3), 64.07 (C2), 28.92 (C11), 28.45 (C21), 28.15 (C82), 25.69 (C7), 21.31 (C4), 18.69 (C5/C6), 18.57 (C8), 17.79 (C6/C5), 14.22 (C81).IR (hexane, nCO/cm–1): 2105 (m), 2060 (s), 2051 (s), 2020 (s), 2012 (s), 1999 (m), 1987 (s), 1973 (w), 1948 (w). MS, m/z: 1048 (M+, 192Os). The molecular structure of 4a is shown in Figure 1. The bridging organic ligand is coordinated at the same edge of the Os3-triangle as the m-H ligand. The Os2CN metal-containing ring is nearly planar (the atom deviations from a common plane are no higher than 0.021 Å), the dihedral angle Os2CN/Os3 is 77.7(2)°.The angle between the Os3 and Os2(m-H) planes is 40(5)°. The bond lengths and valence angles are indicative of some delocalization in the C(1)–N(1)–C(2)–C(3)–N(2) fivemembered ring. This work was supported by the Russian Foundation for Basic Research (grant nos. 96-07-89187 and 97-03-33292). References 1 (a) V.A. Maksakov, V. P. Kirin and A. V. Golovin, Izv. Akad. Nauk, Ser. Khim., 1995, 2021 (Russ. Chem. Bull., 1995, 44, 1941); (b) G. Süss- Fink, T. Jenke and H. Heitz, J. Organomet. Chem., 1989, 379, 311. 2 (a) A. Mayr, Y. C. Lin, N. M. Boag and H. D. Kaesz, Inorg. Chem., 1982, 21, 1704; (b) K. Burgess, Polyhedron, 1984, 3, 1175. 3 E. G. Bryan, B. F. G. Johnson and J. Lewis, J. Chem.Soc., Dalton Trans., 1977, 1201. 4 C. C. Yin and A. J. Deeming, J. Chem. Soc., Dalton Trans., 1974, 1013. 5 (a) C. C. Yin and A. J. Deeming, J. Organomet. Chem., 1977, 133, 123; (b) R. D. Adams and J. E. Babin, Organometallics, 1986, 5, 1924; (c) R. D. Adams and J. E. Babin, Organometallics, 1987, 6, 2236. 6 (a) B. F. G. Johnson, J. Lewis and D. A. Pippard, J. Organomet. Chem., 1978, 145, C4; (b) B.F. G. Johnson, J. Lewis and D. A. Pippard, J. Chem. Soc., Dalton Trans., 1981, 407. 7 (a) W. F. Edgell, M. T. Jang, B. J. Bulkin, R. Bayer and N. Koinzumi, J. Am. Chem. Soc., 1965, 87, 3080; (b) W. F. Edgell and B. J. Bulkin, J. Am. Chem. Soc., 1966, 88, 4839. 8 R. Zoet, G. van Koten, K. Vrieze, J. Jansen, K. Goubitz and C. H. Stam, Organometallics, 1988, 7, 1565.¶ Crystal data for 4a: C22H20N2O10Os3, M = 1043.00, F(000) = 1896, orthorhombic, a = 12.647(1), b = 13.370(1), c = 15.848(2) Å, V = = 2679.7(4) Å3, space group P212121, Z = 4, dc = 2.585 g cm–3, m = = 14.245 mm–1. Data were measured using an Enraf-Nonius CAD4 diffractometer (room temperature, graphite-monochromated MoKa radiation, l = 0.7107 Å, q/2q scan up to 2qmax = 50°). To determine the absolute configuration, all reflections were measured together with their Friedel equivalents in the negative-theta (–2q/–w) position. Total 5362 (2681 pairs) of reflections were measured.The structure was solved by direct methods and refined against F2 in an anisotropic approximation for non-hydrogen atoms using the SHELX-97 program package. The m-H ligand was located on difference electron density map and refined with fixed Uiso = 0.05 Å2. The rest hydrogen atoms were refined in a ride approximation. The final values are R1 = 0.0335, wR2 = 0.0666 for 3639 F > 4s(F). The absolute configuration was confirmed by a refinement of the Flack parameter, the final value is –0.03(2). Atomic coordinates, bond lengths, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 1999. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/55. Received: 3rd March 1999; Com. 99/1455

ISSN:0959-9436     

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) An ab initio study of the anionic clusters Cl–(HF)n (n = 1–5) Aleksandr V. Nemukhin,* Aleksandr A. Granovsky and Denis A. Firsov Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 939 0283; e-mail: anem@lcc.chem.msu.su By performing ab initio calculations several stationary points on the potential energy surfaces of the anionic clusters Cl–(HF)n (n = 1–5) were characterised with a special emphasis on the competition between interior and surface structures.The microsolvation theory which considers properties of both solvent and solute species at a discrete molecular level requires, at the initial stages of modelling, a detailed knowledge of the structure of solvation shells.The arrangements of the environmental particles of the solvent around trapped solute molecules may have peculiar shapes, which primarily depend on the intermolecular interaction potentials. When modeling solvation sites at a supramolecular level, one can design solvation shells by consequently adding solvent particles one by one to the solute species and determining the molecular arrangements that correspond to minima on the multidimensional potential energy surfaces.This approach to the microsolvation theory is also typical of the cluster science with relevance to experimental studies in the gas phase and to the corresponding modeling of cluster properties.1 For obvious reasons, the size-selected clusters containing anionic halogens surrounded by solvent molecules attract an increasing attention.Of special interest are, of course, the water clusters X–(H2O)n (X = Cl, Br, I)2–13 although other solvents like acetonitrile14 were also considered. To characterise solvation sites, different approaches ranging from the use of empirical functions describing intermolecular interaction potentials to a complete ab initio analysis by modern methods of quantum chemistry can be applied.Apparent difficulties of such an analysis are related to the shapes of flat multidimensional potential energy surfaces of heteroclusters with multiple stationary points which possess similar energies. In particular, the vast majority of approaches to the structure of Cl–(H2O)n clusters predict that surface states, namely the configurations with Cl– ions outside neutral water shells, are dominating; however, the energies of interior structures with Cl– ions surrounded by water molecules are slightly higher than that of the surface states, and the effects of temperature and zero-point energy may easily reverse the conclusions.In this work, we compare the properties of the anionic clusters Cl–(HF)n (n = 1–5) as predicted by ab initio methods of quantum chemistry.The above systems have not been described before, only ab initio calculations of the binary complexes ClF···HF have been reported.15–17 In addition to a better understanding of the properties of pure and doped molecular clusters, this work is aimed to provide reference data for the semiempirical diatomicsin- ionic-systems (DIIS) scheme in order to apply it to the modeling of solvation phenomena in this system. Previous data on the DIIS approach to pure hydrogen fluoride clusters (HF)n 18,19 offer promise to the construction of inexpensive and reliable intermolecular potential energy surfaces suitable for a detailed analysis of such species. A conventional strategy was used for the ab initio calculations carried out with the PC GAMESS version20 of the GAMESS package.21 Namely, the stationary points on the potential energy surfaces of Cl–(HF)n (n = 1–5) have been located, and the standard harmonic vibrational analysis has been performed by the MP2/6-311+G** procedure.Next, the MP4(SDTQ)/6-311+G** method was employed to recompute the energies at the MP2/ 6-311+G** minimum energy points.We started the geometry optimization from two sets of initial arrangements with no symmetry restrictions imposed. Namely, in the first series every HF molecule was bound to Cl–, and in the second series one hydrogen-bonded dimer (HF)2 was coupled to Cl–, while other (n – 2) monomeric HF species were bound directly to Cl– (n � 2).In both cases, the equilibrium configurations were located using the MP2/6-311+G** procedure, and we designate the structures of the second series by ‘a’. For instance, configuration 5 refers to the isomer of Cl–(HF)5 that corresponds to the interior structure with five HF species surrounding Cl–, and configuration 5a denotes the isomer corresponding to the surface structure in which three HF monomers and one (HF)2 dimer are bridged to Cl–.Different isomers for the structures of the same type are additionally designated by symbols I and II. Figure 1 shows the structures found for all species. Configurations 4 and 5 I, 5 II can be called interior states and 4a I, 4a II and 5a, surface states. For n � 2, all configurations na refer to the structures with some evidence for hydrogen-bonded networks.With respect to geometry, the following trends in the structures are noteworthy. Within the series of structures 1–5, the equilibrium Cl–H distances gradually increase from 1.91 (n = 1) Table 1 Harmonic vibrational frequencies computed with the MP2/ 6-311+G** wave functions. Numerical degeneracies (to within 1 cm–1) given in parentheses do not necessarily reflect the true symmetry of species.The shifts of the highest frequencies referred to the H–F vibrations in the cluster are given with respect to the harmonic frequency of pure HF (4162 cm–1). Species Harmonic frequencies/cm–1 Shifts of the highest frequencies with respect to HF/cm–1 1 262 879(2) 3109 –1053 2 28 854 227 3303 251 3371 798 810 812 –859 –791 3 23 769 26(2) 792(2) 194 3485(2) 230(2) 3566 728 744(2) –677 –596 4 21(2) 730 28(3) 732 169 3620(3) 209(3) 3707 666(3) 723(3) –542 –455 5 I (C4v) 4 156 635(2) 3759 25(2) 189 675 3840 33(2) 195(2) 683(2) 34 539 724 37 595(2) 3725 136 600 3753(2) –437 –409 –403 –322 5 II (D3h) 5(2) 192(2) 704(2) 27(2) 556(2) 3733(2) 32(2) 577(2) 3755 33 613 3765 137 650 3841 156 671(2) –429 –407 –398 –321 2a 51 1046 228 2396 379 3578 833 835 947 –1766 –584 3a 8 770 2799 26 773 3432 48 777 3685 215 803 231 879 343 1003 –1363 –730 –478 4a I 9 208 723 3555 24 220 739 3608 26 316 760 3764 28 707 847 45 719 932 193 721 3081 –1081 –607 –554 –399 4a II 6 205 723 3563 17 223 725 3616 24 319 757 3778 26 710 844 46 714 919 179 720 3092 –1070 –599 –546 –384 5a 6 44 637 699 3681 18 163 654 703 3742 21 191 655 776 3830 24 201 678 878 27 202 680 3294 27 295 698 3674 –868 –488 –481 –421 –333Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) to 2.10–2.12 Å (n = 5) while the H–F distances decrease from 0.97 (n = 1) to 0.94 Å (n = 5). The valence angles HClH do not show large variations: 110° (n = 2), 111° (n = 3), 109° (n = 4), 90°–120° (n = 5). A tetrahedral configuration for Cl–(HF)4 and two structures for Cl–(HF)5, a bipyramid (D3h) and a tetragonal pyramid (C4v), were obtained in these calculations.For structures 2a–5a, a familiar motive of the hydrogen fluoride dimer (H1–F1···H2–F2) is easily recognised22 with the F–F distances 2.52 (n = 2), 2.56 (n = 3), 2.59 (n = 4) and 2.61 Å (n = 5); the F1···H2 hydrogen bond lengths 1.58 (n = 2), 1.62 (n = 3), 1.65 (n = 4) and 1.68 Å (n = 5), and a value of 4° for the hydrogen bond angles H2F2H1 practically independent on the cluster size.The distances from Cl– to the closest hydrogen of the (–H1–F1··· ···H2–F2) chain H1 are noticeably shorter than the Cl–H distancesthe series of 2–5 (1.76, 1.82, 1.88 and 1.93 Å for 2, 3, 4 and 5, respectively), while the tendencies for changes in the remaining geometry parameters are approximately the same as for the series of 2–5.Table 1 contains unscaled harmonic frequencies computed with the MP2/6-311+G** wave functions at the corresponding equilibrium configurations. The main reason to show these values is to confirm that the found structures correspond to the true minimum energy points. However, it is interesting to trace the shifts in high frequencies obviously originated from vibrations of the H–F fragments with respect to the frequency of a pure HF molecule accompanying its association into Cl–(HF)n clusters.The predicted red shifts, which may be important for practical identification of these complexes, are presented in Table 1. Table 2 summarises the computed energies at the equilibrium points for all species predicted by the MP2/6-311+G** and MP4//MP2/6-311+G** procedures.Corrections due to zero points vibrations are taken into account. The binding energies are referred to one HF molecule: Eb = {E[Cl–(HF)n] – E(Cl– + nHF)}/n. The clear tendency of gradual reduction of Eb with cluster size is demonstrated. Another tendency is a gradual reduction of the gap between the energies of n and na configurations. For n = 5, the energy of surface state 5a is lower than those of interior states 5 I and 5 II.A conclusion drawn from these calculations is that in the case of hydrogen fluoride complexes Cl–(HF)n the structures with hydrogen-bonded networks (denoted as 2a–5a), which may be called surface structures, are unfavourable as compared to interior structures (2–5), in which Cl– is surrounded by HF molecules, by energy criteria.The energy differences between configurations n and na decrease with n. Note that, in spite of differences between the absolute values of energies computed with the MP2 and MP4 approaches, the energy gaps between structures n and na are reproduced well already at the MP2 level. Additionally, the energies of structures na with respect to the decomposition Cl–(HF)n ® Cl–(HF)n – 2 + (HF)2 were estimated at the MP2 level (with corrections for zero point vibrations).We found that all these clusters are stable towards dissociation not only to hydrogen fluoride, but also to a hydrogen fluoride dimer and a smaller size cluster with the binding energies gradually decreasing with n from 147 (2a) to 81 kJ mol–1 (5a).We cannot exclude the possibility that a refinement of the treatment like a basis set extension, more accurate calculations of correlation contributions, or the inclusion of basis set superposition corrections will force us to change qualitative conclusions on the relative stability of the isomers. The corresponding energy differences are so small, especially for n = 4 and 5, that the final choice is hard to formulate unambiguously.We cannot also exclude the chances for another geometry arrangements beyond those reported in this work. Some initial guesses based on the previous experience with (HF)n 19 may be easily suggested, e.g., for the (HF)n chains ended up with Cl– or for the (HF)m rings (m � 3) bound to Cl–(HF)n – m.However we believe that a more efficient strategy in this respect is to construct a cheap interaction potential for Cl–(HF)n in the spirit of the DIIS theory, to scan large areas of the configuration space with its help and to verify predictions for the stationary points by ab initio methods. Less expensive potentials will allow us to use more powerful algorithms to locate minimum energy points in the surfaces. 23,24 Studies along this line are in progress, and the configurations found and reported here provide valuable information for checking the semiempirical potential functions. Table 2 Total and relative energies of Cl–(HF)n clusters with zero-point energy corrections. Binding energies are referred to a single HF ligand: Eb = {E[Cl–(HF)n] – E(Cl– + nHF)}/n, where the total energies of Cl– are –459.735676 (MP2) and –459.751701 au (MP4) and the total energies of HF are –100.297417 (MP2) and –100.305374 au (MP4). Species Total energies/au Relative energies/kJ mol–1 Binding energies/Eb Energies of na with respect to n MP2 MP4 MP2 MP4 MP2 MP4 1 –560.069069 –560.093178 94.45 94.79 — — 2 –660.395734 –660.427906 85.62 85.93 — — 3 –760.716961 –760.757191 77.92 78.21 — — 4 –861.033913 –861.082195 71.26 71.54 — — 5 I (C4v) –961.344339 –961.400790 63.84 64.18 — — 5 II (D3h) –961.344580 –961.400975 63.97 64.27 — — 2a –660.391134 –660.423293 79.58 79.87 +6.04 +6.06 3a –760.714303 –760.754522 75.59 75.88 +2.33 +2.34 4a I –861.032787 –861.081061 70.52 70.80 +0.74 +0.74 4a II –861.032412 –861.080687 70.28 70.55 +0.99 +0.99 5a –961.347373 –961.403708 65.43 65.71 –1.47 –1.44 1 2 2a 3a Cs Td Cs Cs 4 4a I 4a II 5 I 5 II 5a H1 H2 F1 F2 C•v C2v C4v D3h Cs 1.91 0.97 110° 1.96 0.96 1.76 121° 1.01 1.58 174° 0.95 0.95 1.98 107° 1.82 0.99 120° 1.62 174° 0.94 3 C3v 0.95 2.01 111° 0.94 2.05 0.95 2.0 108° 1.8 0.97 121° 1.65 174° 0.94 0.95 2.03 113° 1.88 0.97 124° 1.65 174° 0.94 0.94 2.10 2.11 0.94 0.94 2.12 2.10 0.94 0.94 2.07 107° 1.93 0.96 123° 1.68 174° 0.93 Figure 1 Geometry configurations optimised at the MP2/6-311+G** level.Bond lengths are given in Å.Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) This work was supported in part by the Russian Foundation for Basic Research (grant no. 98-03-33168). We are grateful to the Intel Technologies Inc.for the donation of computational facilities. References 1 G. Markovich, S. Pollack, R. Giniger and O. Cheshnovsky, in Reaction Dynamics in Clusters and Condensed Phases, ed. J. Jortner, Kluwer, Amsterdam, 1994, p. 13. 2 G. Markovich, R. Giniger, M. Levin and O. Cheshnovsky, J. Chem. Phys., 1991, 95, 9416. 3 X. G. Zhao, A. Gonzalez-Lafont, D. G. Truhlar and R. Steckler, J.Chem. Phys., 1991, 94, 5544. 4 J. E. Combariza, N. R. Kostner and J. Jortner, Chem. Phys. Lett., 1993, 203, 423. 5 J. E. Combariza, N. R. Kostner and J. Jortner, J. Chem. Phys., 1994, 100, 2851. 6 S. S. Xantheas and T. H. Dunning, J. Phys. Chem., 1994, 98, 13489. 7 C.-G. Zhan and S. Iwata, Chem. Phys. Lett., 1995, 232, 72. 8 R. C. Dunbar, T. B. McMahon, T. B. Thölmann, D. S. Tonner, D.R. Salahub and D. Wei, J. Am. Chem. Soc., 1995, 117, 12819. 9 S. S. Xantheas, J. Phys. Chem., 1996, 100, 9703. 10 Y. Okuno, J. Chem. Phys., 1996, 105, 5817. 11 M. Roeselova, G. Jacoby, U. Kaldor and P. Jungwirth, Chem. Phys. Lett., 1998, 293, 309. 12 J.-H. Choi, K. T. Kuwata, Y.-B. Cao and M. Okumura, J. Phys. Chem., A, 1998, 102, 503. 13 P. Ayotte, G. H. Weddle, J. Kim, J.Kelley and M. A. Johnson, J. Phys. Chem., A, 1998, 103, 443. 14 G. Markovich, L. Perera, M. L. Berkowitz and O. Cheshnovsky, J. Chem. Phys., 1996, 105, 5817. 15 W. B. De Almeida, D. A. Barker, A. Hinchliffe and J. S. Craw, J. Mol. Struct., 1993, 285, 277. 16 W. B. De Almeida, D. A. Barker and A. Hinchliffe, J. Chem. Phys., 1993, 99, 5917. 17 I. Röggen and G. R. Ahmadi, J. Mol. Struct., 1994, 307, 9. 18 B. L. Grigorenko, A. V. Nemukhin and V. A. Apkarian, J. Chem. Phys., 1998, 108, 4413. 19 B. L. Grigorenko, A. A. Moskovsky and A. V. Nemukhin, J. Chem. Phys., 1999, 111, 4442. 20 A. A. Granovsky, URL http://classic.chem.msu.su/gran/gamess/index.html 21 M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S. Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. J. Su, T. L. Windus, M. Dupuis and J. A. Montgomery, J. Comput. Chem., 1993, 14, 1347. 22 W. Klopper, M. Quack and M. A. Suhm, J. Chem. Phys., 1998, 108, 10096. 23 D. J. Wales and J. P. K. Doye, J. Phys. Chem., A, 1997, 101, 5111. 24 A. A. Moskovsky and A. V. Nemukhin, J. Chem. Inf. Comput. Sci., 1999, , 370. Received: 22nd April 1999; Com. 99/1481

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) The molecular structure and the puckering potential function of octamethylcyclotetrasilane, Si4Me8, determined by gas electron diffraction and ab initio calculations Vladimir P. Novikov,*a Svetlana A. Tarasenko,a Svein Samdalb and Lev V. Vilkova a Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation.Fax: +7 095 932 8846; e-mail: VPNovikov@phys.chem.msu.ru b Department of Chemistry, University of Oslo, N-0315 Oslo, Norway The structural parameters, the barrier of inversion and the equilibrium puckering angle of Si4Me8 were determined using a dynamic model (V0 = 1.0±0.5 kcal mol–1, je = 28.3±1.9°). The reactivity of silacyclobutane derivatives is closely related to the ring strain energy.Since the balance of angular and torsional strains in the ring determines the degree of its planarity,1 it can be expected that the structure of this class of compounds is responsible for their reactivity. However, the data on the molecular structure of cyclotetrasilane derivatives are inconsistent in many respects. Thus, for crystals of Si4Cl8 and Si4Br8, a planar ring structure was found,2 whereas a vibrational spectroscopy study revealed a nonplanar ring structure.3 The molecule of octamethylcyclotetrasilane shows no exception.The results of X-ray analysis give evidence of a planar ring, while it is nonplanar according to vibrational spectroscopy data.5 Earlier, the Si4Me8 molecule was studied by gas electron diffraction within the static model approximation,6 and the average dihedral angle j (Figure 1) was found to be 29.4±4.0°.Note that this angle can differ from zero even if the ring has a planar equilibrium configuration. This follows from the fact that the static model produces the mean value of j averaged over vibrational levels of the puckering motion. As a rule, the puckering of four-membered rings is a large-amplitude motion of high anharmonicity.Therefore, to solve the problem whether the ring is planar or not, we should introduce a potential function to describe this motion and use a dynamic model which takes into account contributions to the scattering from all local conformations arising along the puckering pathway in accordance to their population.To describe the ring puckering, it is convenient to use the puckering coordinate z (Figure 1), which is defined as a half-height between the diagonals Si···Si in the ring and characterises the displacement of atoms from a planar configuration. This description corresponds to the normal mode of ring puckering. The Si4Me8 molecule has D2d symmetry for the nonplanar ring and D4h for the planar one.With these types of symmetry, the relation between the dihedral angle and the coordinate z can be expressed as follows: where a is the Si–Si–Si angle: a = 2arctan[cos(j/2)], which is valid if the Si–Si bond length does not change during the ring puckering. However, an electron diffraction study7 of 1,1-dichlorosilacyclobutane showed that changes in the bond lengths and valence angles of the ring are sufficiently large, and that these changes should be included in the structure analysis. Therefore, in this work, for more accurate determination of the structure of Si4Me8, we applied a dynamic model which takes into account the relaxation of geometric parameters estimated from ab initio calculations.These calculations were also used to obtain the mean-square amplitudes and vibration corrections. We used the total scattering intensity It(s) and the background line Ib(s) data obtained in the Budapest laboratory of electron diffraction6 and deposited at the British Library.8 The range of experimental sM(s) values was 2–36 Å–1. The numbering of atoms of the Si4Me8 molecule is shown in Figure 1.The deviations of the bisectors of the C–Si–C angles from the Si–Si–Si planes are denoted as dC.The relaxation effects were estimated by an optimization of the geometric parameters for a number of fixed j values in the range 0–50° with a step of 10°. The ab initio MO calculations were carried out at the Hartree–Fock level of the theory using the 6-311G** basis set with polarization functions and the GAUSSIAN-94 program.9 It was found that the puckering potential of Si4Me8 is adequately described by the following quadratic-quartic function: V(j) = V0[(j/je)2 – 1]2, where V0 = = 0.65 kcal mol–1 and je = 25.6°.z = 0.5r(Si–Si)cos(a/2)sin(j/2), H(13) H(22) H(21) C(5) H(29) H(30) H(17) C(9) H(23) H(24) H(14) C(6) H(19) H(33) H(34) C(11) H(15) H(26) H(25) C(7) H(36) H(20) H(35) C(12) H(32) C(10) H(18) H(28) H(16) H(27) C(8) H(31) Si(1) Si(2) Si(3) Si(4) dC 2z j dC Figure 1 Molecular structure of Si4Me8; definition of the puckering coordinate z.aDistances, Å; angles, degrees; the GED parameters ra and �a; errors are given in parentheses as 3s. bJoint analysis of GED and ab initio data. cFound from ab initio calculations. Table 1 Main geometric parameters of Si4Me8 a (gas electron diffraction, GED, ab initio HF/6-311G** calculations, AI, and X-ray data).Parameter This work GED6 X-ray4 GED + AIb AI Si–C 1.896(3) 1.903 1.893(3) 1.889 Si–Si 2.370(2) 2.398 2.362(4) 2.363 C–H 1.104(3) 1.087 1.096(11) — �CSiC 109.5(6) 108.6 110.8(16) 110.0 �SiSiSi 88.2(2) 88.6 88.1(5) 90.0 �SiCH 111.7(6) 112.0 111.7(15) — dC 4.1c 4.1 0.8(17) — V0/kcal mol–1 1.0(5) 0.65 — — je 28.3(19) 25.6 29.4(40) 0.0 R-factor (%) 4.8 — 10.3 —Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) The ab initio calculations showed that the bond lengths can change by 0.01 Å during the puckering motion, and the valence and d angles, by 2.5 and 4.2°, respectively. Thus, the relaxation effects in Si4Me8 are too large to be neglected in the description of the geometry of local conformers.To take into account these relaxation effects, the calculated geometric parameters P(j) were approximated by the third degree polynomials P(j) = a0 +Sanjn. The polynomial factors an were used in the structural analysis to compute the geometric parameters at a given value of j, while the factors a0 were variable parameters. For the angle dC, the factor a0 is equal to zero by symmetry reasons because d = 0° at j = 0°.Therefore, these angles were parametrised by the function d(j) = k0Sanjn, where k0 is a variable parameter having the meaning of a scale factor. For a complete description of the molecular geometry, the following six parameters were used: r(Si–C), r(Si–Si), �CSiC, dC, �SiCH, r(C–H). All of the parameters, with the exception of r(C–H), were parametrised as functions of the angle j.The frequencies and normal modes of Si4Me8 were calculated using the force field on Cartesian coordinates obtained in the full geometry optimization by the GAUSSIAN-94 program using the HF/6-311G** basis set. The transformation of the force field to symmetry coordinates and the optimization of scaling factors were carried out by the SHRINK4 program10 using experimental frequencies.5 The results of normal coordinate calculations agree well with the frequency assignment of Si4Me8 made earlier in the 900–100 cm–1 region.5 Normal coordinate analysis showed that the puckering mode has the lowest frequency, 33 cm–1 (A1 symmetry).The nearest frequency of the same symmetry is the SiC2 deformation, but it lies considerably higher than the ring puckering frequency at 161 cm–1.Other low-frequency vibrations have different types of symmetry: SiC2 twist, 87 cm–1 (A2); SiC2 rock, 74 cm–1 (B1) and 73 cm–1 (E). Therefore, the puckering mode can be reliably separated from the framework vibrations, which were treated in a harmonic approximation. The amplitudes and vibration corrections were calculated for the framework at fixed j values (0, 10, 20, 30, 40, and 50°) using the optimised geometry for the corresponding j values.The root-mean-square amplitudibration corrections (d = ra – ra) were calculated using the technique10 which applies a nonlinear transformation of internal coordinates into Cartesian displacements of atoms.This technique gives more reliable values of d corrections than the standard method11 if the molecule possesses low-frequency vibrations. For each internuclear distance, the functions u(j) and d(j) were interpolated during calculations of the reduced molecular intensity sM(s) in the range j = 0–50° with a step of 2.5° according to the formula where W(j) is the classical probability density of the angle j, W(j) = Q–1exp[–V(j)/RT], where R is the gas constant, T is the absolute temperature, V(j) is the potential function and Q is the normalising factor.The structural analysis was carried out using the modified ELED program12 with the starting values of the parameters taken from the ab initio calculations. The refinement of the geometry was carried out using a conventional procedure.7 At the first stage of the structural analysis, we varied the set of well-defined parameters (the Si–Si and Si–C bond lengths and the �CSiC angles) as well as the parameters V0 and je for the potential function.The model with the planar ring configuration and the puckering potential function V(j) = Aj4 + Bj2 was also tested. All starting approximations were shown to converge to the nonplanar ring conformation with the dihedral angle je = 28°.After the background correction, the rest of geometric parameters and the amplitudes were sequentially added to the set of parameters under determination according to their contributions to the scattering. A variation in the scale factor k0 for the angle dC leads to an extremely unstable solution.Therefore, we put k0 = 1 for dC, i.e., it was fixed at its ab initio value. The final results of the structural analysis are presented in Table 1 and compared with the data obtained from ab initio calculations and previous investigations. As can be seen in Table 1, the dynamic model gives better agreement with the experimental data as compared to the static model:6 the R-factor was halved, and this led to a decrease of the error limits.The parameters for both of the models are quite similar. However, this fact cannot be predicted beforehand. This situation can occur when the barrier height V0 is high so that the most populated puckering vibrational levels lie under the barrier. In this case, the potential function can be approximated by a parabola near its minimum, and a simple harmonic approximation can be used for the puckering vibration. Thus, static and dynamic models will give essentially the same results. The dihedral angle and the barrier height clearly indicate that the ring is puckered in the gas phase.This agrees with the vibrational spectra analysis. The planar ring in the solid phase found in an X-ray study4 of Si4Me8 can apparently be explained by the crystal packing effect.Note that cyclotetrasilane has also a puckered conformation according to ab initio calculations: je = 31.2° and V0 = = 0.3–0.4 kcal mol–1.13 The replacement of hydrogen atoms with methyl groups increases the puckering barrier in Si4Me8 up to 1.0±0.5 kcal mol–1, which is seemingly caused by an increase of the torsional strain energy.This is confirmed by the fact that the distances between the nearest nonbonded atoms C(8)···C(9) increase from 3.89 to 3.98 Å when the conformation of the ring changes from planar to puckered with the angle je. This means that in the equilibrium configuration the distance between adjacent methyl groups is equal to the sum of the van der Waals radii of the methyl groups, 4.0 Å.14 The predominance of the torsional strain over the angular strain determines the puckered conformation of the ring in Si4Me8, as it is the case in cyclobutane, though the absolute values of angular and torsional strain energies decrease when carbon atoms of cyclobutane are replaced with silicon atoms.15 This work was supported by the Russian Foundation for Basic Research (grant nos. 99-03-32511a and 96-15-97469) and by the Research Council of Norway (Programme for Supercomputing). References 1 A. C. Legon, Chem. Rev., 1980, 80, 231. 2 J. R. Koe, D. R. Powell, J. J. Buffy and R. West, Polyhedron, 1998, 17, 1791. 3 (a) E . Hengge and D. Kovar, Z. Anorg. Allg. Chem., 1979, 458, 163; (b) K. Hassler, E. Hengge and D. Kovar, J. Mol. Struct., 1980, 66, 25. 4 C. Kratky, H. G. Schuster and E. Hengge, J. Organomet. Chem., 1983, 247, 253. 5 K. Hassler, Spectrochim. Acta, 1981, A37, 541. 6 V. S. Mastryukov, S. A. Strelkov, L. V. Vilkov, M. Kolonits, B. Rozsondai, H. G. Schuster and E. Hengge, J. Mol. Struct., 1990, 238, 433. 7 V. P. Novikov, S. A. Tarasenko, S. Samdal and L. V. Vilkov, J. Mol. Struct., 1998, 445, 207. 8 British Library Lending Division, Boston Spa, Wetherby, Yorkshire LS23 7BQ, Gr.Britain, Supplementary Publication No. SUP 26396. 9 M. J. Frisch, G.W. Trucks, H. B. Schlegel, P. M.W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian 94 Program, Revision B.3, Gaussian, Inc., Pittsburgh PA, 1995. 10 (a) V. A. Sipachev, J. Mol. Struct., 1985, 121, 143; (b) V. P. Novikov, V. A. Sipachev, E. I. Kulikova and L. V. Vilkov, J. Mol. Struct., 1993, 301, 29. 11 R. Stolevik, H. M. Seip and S. J. Cyvin, J. Chem. Phys. Lett., 1972, 15, 263. 12 V. P. Novikov, S. Samdal and L. V. Vilkov, J. Mol. Struct., 1997, 413/414, 279. 13 R. S. Grev and H. F. Schaefer, J. Am. Chem. Soc., 1987, 109, 6569. 14 Yu. V. Zefirov and P. M. Zorky, Zh. Strukt. Khim., 1976, 17, 745 [J. Struct. Chem. (Engl. Transl.), 1976, 644]. 15 R. L. Rosas, C. Cooper and J. Laane, J. Phys. Chem., 1990, 94, 1830. sM(s) = W(j)sM(s,j)dj, ò0 jmax Received: 7th June 1999; Com. 99/14

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) An unexpected allyl-transfer reaction under conditions of Lewis acid-promoted cyclization of homoallylic alcohols with aldehydes Vyacheslav V. Samoshin,*a Irina P. Smoliakova,*b Mingming Hanb and Paul H. Grossa a Department of Chemistry, University of the Pacific, Stockton, California 95211, USA Fax: +1 209 946 2607; e-mail: vsamoshi@vms1.cc.uop.edu b Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202, USA.Fax: +1 701 777 2331; e-mail: ismoliakova@mail.chem.und.nodak.edu The title reaction was observed along with cyclization in the SnCl4-promoted reaction of 2-[3,4,6-tri-O-benzyl-2-deoxy-2- (p-tolylsulfanyl)-b-D-glucopyranosyl]ethanal with pent-4-en-2-ol and this result was interpreted in terms of anchimeric assistance by sulfur to the unusual fragmentation of an intermediate alkoxycarbenium ion.The Lewis acid-promoted cyclization of homoallylic alcohols with aldehydes or their acetals was suggested for the preparation of 2,6-disubstituted tetrahydropyran derivatives,1,2 potential precursors of C-glycosides2 and other cyclic polyethers.An application of this cyclization to recently synthesised 2-[2-deoxy- 2-arylsulfanyl-b-D-gluco(or manno)pyranosyl]ethanals3 (e.g. 1, Scheme 1) promised to provide a convenient route to C-(1®1)- disaccharides. However, we have found that the SnCl4-promoted reaction of 2-[3,4,6-tri-O-benzyl-2-deoxy-2-(p-tolylsulfanyl)-b-D-glucopyranosyl] ethanal3(c) 1 with pent-4-en-2-ol 2 under standard conditions2,† did not lead to the anticipated smooth formation of compound 3 (Scheme 1), but a complicated mixture of many products was formed.A flash-chromatographic separation of this mixture afforded two new homoallylic alcohols (2S)-4 and (2R)-4 as the major isolated products (33% and 13%, respectively). A single set of signals was observed in 1H and 13C NMR spectra for each of compounds (2S)-4 and (2R)-4, thus proving that these are individual diastereomers.‡ The signals in wellresolved 1H NMR spectra (300 MHz) were assigned using the † A solution of SnCl4 (86 mg, 0.33 mmol) in CH2Cl2 (10 ml) was added dropwise to a stirred cold (–50 °C) solution of pent-4-en-2-ol (25 mg, 0.29 mmol) and aldehyde 13 (140 mg, 0.24 mmol) in CH2Cl2 (15 ml) under N2.The mixture was stirred for 28 h at room temperature and quenched at 0 °C by the dropwise addition of cold 1 M HCl (5 ml). The standard extraction procedure and evaporation gave a colourless oil, which was separated by flash chromatography (silica gel, hexane:ether = = 4:1) affording 60 mg of a complex mixture of cyclization products (1H and 13C NMR data) in addition to 50 mg (33%) of (2S)-4 and 20 mg (13%) of (2R)-4. The purity of (2S)-4 and (2R)-4 (not less than 95%) was confirmed by 1H and 13C NMR spectroscopy.The composition was proved by HRMS. COSY and homonuclear decoupling techniques. The large spin– spin coupling constants H1'–H2', H2'–H3', H3'–H4' and H4'–H5' proved the trans-diaxial orientation of these pairs of protons and, consequently, the equatorial position of all substituents (Figure 1).More interestingly, large coupling constants were also observed for the H1'–H1a and H1a–H2 interactions in (2S)-4 (Table 1, Figure 1) in both C6D6 and CDCl3 indicating a predominantly antiperiplanar orientation of these pairs of protons [compare to the corresponding couplings in (2R)-4 and to the medium size of 3JH2H3a and 3JH2H3b, Table 1].This fact points to the strong predominance of a certain conformation for the side chain of the molecule. Only the (S)-configuration of the new chiral ‡ (2S)-1-[3,4,6-tri-O-benzyl-2-deoxy-2-(p-tolylsulfanyl)-b-D-glucopyranosyl] pent-4-en-2-ol (2S)-4: white crystals, mp 113–114 °C. [a]D 25 = –22.2° (c, 0.02, CHCl3). 1H NMR (300 MHz, C6D6) d: 1.53 (dt, 1H, H1a, J 14.4 and 9.6 Hz), 1.98 (s, 3H, MeAr), 2.25 (br.ddd, 1H, H3b, J 6.1, 7.6 and 13.8 Hz), 2.42 (br. dt, 1H, H3a, J 13.8 and 6.3 Hz), 2.59 (dt, 1H, H1b, J 14.4 and 2.1 Hz), 2.97 (t, 1H, H2', J 10.4 Hz), 3.30 (ddd, 1H, H5', J 2.1, 5.5 and 9.3 Hz), 3.42 (ddd, 1H, H1', J 2.1, 9.6 and 10.4 Hz), 3.45 (br. t, 2H, H3' + H4', J ~ 10 Hz), 3.52 (m, 2H, H6'), 3.70 (br. s, 1H, OH), 4.02 (ddt, 1H, H2, J 2.1, 9.6 and 6.2 Hz), 4.26 (d, 1H, OCH2Ph, J 12.1 Hz), 4.31 (d, 1H, OCH2Ph, J 12.1 Hz), 4.50 (d, 1H, OCH2Ph, J 11.3 Hz), 4.81 (d, 1H, OCH2Ph, J 11.3 Hz), 4.91 (d, 1H, OCH2Ph, J 10.4 Hz), 5.08 (br.d, 2H, H5a + H5b, J ~ 14 Hz), 5.11 (d, 1H, OCH2Ph, J 10.4 Hz), 6.02 (dddd, 1H, H4, J 6.5, 7.6, 9.5 and 18.0 Hz), 6.81 (d, 2H, SC6H4Me, J 8.0 Hz), 7.03–7.24 (m, 11H, Ar), 7.28 (d, 2H, Ar, J 7.1 Hz), 7.41 (d, 2H, Ar, J 6.9 Hz), 7.47 (d, 2H, SC6H4Me, J 8.0 Hz). 13C NMR (75.5 MHz, C6D6) d: 21.13 (Me), 39.54 (CH2), 42.81 (CH2), 58.46 (CH), 69.69 (CH2), 71.83 (CH), 73.66 (CH2), 75.05 (CH2), 76.37 (CH2), 78.91 (CH), 80.24 (CH), 82.17 (CH), 84.94 (CH), 116.99 (=CH2), 127.85 (CHAr), 127.92 (CHAr), 128.25 (CHAr), 128.52 (CHAr), 128.60 (CHAr), 128.68 (CHAr), 130.13 (CHAr), 132.42 (CAr), 132.77 (CHAr), 135.84 (=CH–), 137.34 (CAr), 138.64 (CAr), 138.97 (CAr), 139.27 (CAr); some CHAr signals overlapped with C6D6 signals.HRMS, m/z: found 625.3010; calc. for C39H44O5S (MH+) 625.2990. (2R)-1-[3,4,6-tri-O-benzyl-2-deoxy-2-(p-tolylsulfanyl)-b-D-glucopyranosyl] pent-4-en-2-ol (2R)-4: colourless oil, [a]D 25 = ~0° (c, 0.01, CHCl3). 1H NMR (300 MHz, C6D6) d: 1.81 (ddd, 1H, H1a, J 2.2, 7.7 and 14.6 Hz), 1.98 (s, 3H, MeAr), 2.05 (br.dt, 1H, H3b, J 14 and 7 Hz), 2.17 (br. dt, 1H, H3a, J 14 and 7 Hz), 2.33 (ddd, 1H, H1b, J 2.8, 9.3 and 14.6 Hz), 2.60 (br. s, 1H, OH), 3.12 (t, 1H, H2', J 10.7 Hz), 3.25 (dt, 1H, H5', J 9.8 and 3.0 Hz), 3.49 (dd, 1H, H3', J 8.7 and 10.7 Hz), 3.56 (d, 2H, H6', J 3.0 Hz), 3.70 (br. t, 2H, H1' + H4', J ~ 9.2 Hz), 3.93 (ddt, 1H, H2, J 2.2, 9.3 and 7 Hz), 4.27 (d, 1H, OCH2Ph, J 12.1 Hz), 4.35 (d, 1H, OCH2Ph, J 12.1 Hz), 4.58 (d, 1H, OCH2Ph, J 11.3 Hz), 4.86 (d, 1H, OCH2Ph, J 11.3 Hz), 4.93 (d, 1H, OCH2Ph, J 10.7 Hz), 5.00 (br.d, 2H, H5a + H5b, J ~ 13 Hz), 5.12 (d, 1H, OCH2Ph, J 10.7 Hz), 5.80 (ddt, 1H, H4, J 9.6, 17.7 and 7 Hz), 6.80 (d, 2H, SC6H4Me, J 8.0 Hz), 7.02–7.30 (m, 13H, Ar), 7.43 (br.d, 2H, Ar, J 7.7 Hz), 7.50 (d, 2H, SC6H4Me, J 8.0 Hz). 13C NMR (75.5 MHz, C6D6) d: 21.11 (Me), 39.18 (CH2), 42.82 (CH2), 57.33 (CH), 68.05 (CH2), 69.44 (CH), 73.61 (CH2), 75.01 (CH2), 76.29 (CH2), 78.88 (CH), 79.05 (CH), 80.16 (CH), 85.06 (CH), 117.07 (=CH2), 127.84 (CHAr), 128.23 (CHAr), 128.49 (CHAr), 128.57 (CHAr), 128.63 (CHAr), 130.09 (CHAr), 132.51 (CAr), 132.83 (CHAr), 135.74 (=CH–), 137.21 (CAr), 138.80 (CAr), 139.23 (CAr), 139.42 (CAr); some CHAr signals overlapped with C6D6 signals.HRMS, m/z: found 625.2982; calc. for C39H44O5S (MH+) 625.2990. O O BnO BnO OBn STol HO Me SnCl4 CH2Cl2 – 50 ºC O BnO BnO OBn S O Tol Cl Me O BnO BnO OBn S OH Tol * 1 2 3 (2R,2S)-4 C-(1®1)-disaccharides Scheme 1Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) centre can enable the molecule to adopt the lowest energy conformation with a relaxed zigzag shape of the C1'C1C2C3 side chain and a stabilising intramolecular hydrogen bond (Figure 1). The downfield shift of the OH signal in C6D6 for (2S)-4 (3.7 ppm) as compared to that for (2R)-4 (2.6 ppm) is an indication of such a hydrogen bond.4 This interpretation is also supported by a measurement in [2H6]acetone.Being a strong hydrogen-bond acceptor, acetone is capable of breaking the intramolecular hydrogen bond. This decreases the relative stability of the conformation depicted in Figure 1 and increases the population of other possible conformations (cf. ref. 5). As a result, the observed averaged coupling constants 3JH1aH2 and 3JH1bH2 have changed towards the medium values in an acetone solution of (2S)-4 (Table 1).These changes are stronger for 3JH1aH2 and 3JH1bH2 than for 3JH1'H1a and 3JH1'H1b. This indicates a larger degree of freedom for the internal rotation around the C1–C2 bond as compared with the rotation around the C1'–C1 bond. Similarly, the large values of 3JH1'H1a and 3JH1bH2 measured for (2R)-4 in an [2H6]acetone solution (Table 1) attest to a predominance of the low energy zigzag conformation of the C1'C1C2C3 side chain (Figure 1).The possibility of intramolecular hydrogen bonding in C6D6 and CDCl3 solutions makes alternative unstable conformations less unfavourable and changes 3JH1'H1a and 3JH1'H1b towards medium values. The transfer of an allyl moiety from a homoallylic alcohol to an aldehyde has never been observed in Lewis acid-promoted cyclizations.1,2 However, this interesting type of transfer was described recently6 for essentially different conditions: a catalytic amount of Sn(OTf)2 as a Lewis acid, molecular sieves and various derivatives of 2-methylpent-4-en-2-ol at –25 °C or at room temperature were used for allylation of aldehydes.Due to an additional 2-methyl group in the homoallylic alcohol, the reaction could proceed via a stable tertiary alkoxycarbenium ion, and emission of acetone appeared to be the driving force of the process.6 Tin(II) triflate was unable to stabilise the intermediate cation(s) by providing a nucleophile for addition or a base for proton removal.Contrary to that, in this work we used a 40% excess of tin(IV) chloride providing the abundance of nucleophilic chloride anions.Therefore, we anticipated the transformation of intermediate cyclic cation 5 into the cyclization product 3 (Scheme 2, cf. refs. 1,2). The unexpected formation of allyl-transfer products 4 can be explained by the alternative reaction pathway depicted in Scheme 2. The act of allyl transfer can occur via alkoxycarbenium ion 7 formed either by the ‘oxa-Cope’ rearrangement1(k),6 of alkoxycarbenium ion 6 or by its cyclization into cation 5 followed by ring opening.The anchimeric assistance by sulfur must play a crucial role in the ejection of acetaldehyde, transforming 7 into stable bicyclic sulfonium ion 8. It is reasonable to assume that the randomly oriented allyl group in 8 is able to adopt eventually the more stable pseudo-equatorial position due to the reversible breaking of the C–S bond with the formation of cation 9 or a corresponding chloride.§ The last step of transformations occurred during a standard treatment of the reaction mixture.The predominant formation of (2S)-4 diastereomer should be expected as a result of a rear-side nucleophilic displacement by water of the C–S bond (Scheme 2).In order to prove this mechanism unambiguously, we are currently exploring the possibility of using nucleophiles other than H2O. § Homoallylic cation 9 can be stabilised by the participation of neighbouring double bond leading to formation of a nonclassic carbenium ion.7 This latter can result in various cyclization products. O H5b H5a H4 H3a H3b H2 O H1a H1b H1' S Tol H3' BnO BnO H4' OBn H H5' H2' H6' H6' O H5b H5a H4 H3a H3b OH H2 H1a H1b H1' S Tol H3' BnO BnO H4' OBn H5' H2' H6' H6' (S) (R) (2S)-4 (2R)-4 Figure 1 Table 1 Selected coupling constants, 3JHH/Hz, in 1H NMR (300 MHz) spectra of (2S)-4 and (2R)-4. 3JHH (2S)-4 (2R)-4 CDCl3 C6D6 [2H6]acetone CDCl3 C6D6 [2H6]acetone H1'–H1a 9.9 9.6 9.5 7.4 7.7 9.5 H1'–H1b 1.9 2.1 2.2 3.0 2.8 2.0 H1a–H2 9.9 9.6 7.8 2.2 2.2 2.3 H1b–H2 1.9 2.1 4.4 9.1 9.3 9.6 H2–H3a 6.1 6.2 6.0 7 7 6.5 H2–H3b 6.3 6.1 6.3 7 7 6.5 O S OBn BnO OBn Tol O OSnCl3 Me O S OBn BnO OBn Tol O Me O S OBn BnO OBn Tol O Me 1 + 2 SnCl4 – Cl– 5 6 O S OBn BnO OBn Tol O Me O S OBn BnO OBn Tol O Me 3 7 Cl Cl– 'oxa-Cope' O S OBn BnO OBn Tol 9 O BnO BnO BnO S H H H Tol H H2 O 8 – MeCHO O BnO BnO BnO S H H OH Tol H H H2 O – H+ (2S)-4 Scheme 2Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) I. S. and M. H. are grateful to ND EPSCoR (grant no. OSR-9452892) and the National Institute of General Medical Sciences (grant no. 1 R15 GM/OD55965-01) for financial support. References 1 (a) M. L. Melany, G. A. Lock and D. W. Thompson, J. Org. Chem., 1985, 50, 3925; (b) R. C.Winstead, T. H. Simpson, G. A. Lock, M. D. Schiavelli and D. W. Thompson, J. Org. Chem., 1986, 51, 275; (c) N. A. Nikolic, E. Gonda, C. P. Desmond Longford, N. T. Lane and D. W. Thompson, J. Org. Chem., 1989, 54, 2748; (d) Z. Y. Wei, J. S. Li, D. Wang and T. H. Chan, Tetrahedron Lett., 1987, 28, 3441; (e) Z. Y. Wei, J. S. Li and T. H. Chan, J. Org. Chem., 1989, 54, 5768; (f) F.Perron and K. F. Albizati, J. Org. Chem., 1987, 52, 4128; (g) F. Perron-Sierra, M. A. Promo, V. A. Martin and K. F. Albizati, J. Org. Chem., 1991, 56, 6188; (h) L. Coppi, A. Ricci and M. Taddei, J. Org. Chem., 1988, 53, 911; (i) L. Marko and D. J. Bayston, Tetrahedron, 1994, 50, 7141; (j) L. D. M. Lolkema, H. Hiemstra, C. Semeyn and W. N. Speckamp, Tetrahedron, 1994, 50, 7115; (k) L.D. M. Lolkema, C. Semeyn, L. Ashek, H. Hiemstra and W. N. Speckamp, Tetrahedron, 1994, 50, 7129; (l) C. Semeyn, R. Blaauw, H. Hiemstra and W. N. Speckamp, J. Org. Chem., 1997, 62, 3426; (m) J. Yang, G. S. Viswanathan and C.-J. Li, Tetrahedron Lett., 1999, 40, 1627; (n) M. J. Cloninger and L. E. Overman, J. Am. Chem. Soc., 1999, 121, 1092. 2 (a) P. H. Gross, Carbohydr.Polym., 1998, 37, 215; (b) M. Valdayo, D. Ngyen and P. H. Gross, Abstracts of 207th ACS National Meeting, San Diego, 1994, CARB 4; (c) P. H. Gross, M. Suarez-Contreras, M. Valdayo, D. E. Gremyachinskiy and V. V. Samoshin, Abstracts of 215th ACS National Meeting, Dallas, 1998, CARB 36; (d) V. V. Samoshin, D. E. Gremyachinskiy and P. H. Gross, Mendeleev Commun., 1999, 53. 3 (a) I. P. Smoliakova, R. Caple, D. Gregory, W. A. Smit, A. S. Shashkov and O. S. Chizhov, J. Org. Chem., 1995, 60, 1221; (b) I. P. Smoliakova and M. Han, Abstracts of 215th ACS National Meeting, Dallas, 1998, ORGN 335; (c) I. P. Smoliakova, M. Han, J. Gong, R. Caple and W. A. Smit, Tetrahedron, 1999, 55, 4559. 4 R. M. Silverstein and F. X. Webster, Spectrometric Identification of Organic Compounds, Wiley, New York, 1998, p. 163. 5 (a) N. S. Zefirov, V. V. Samoshin, O. A. Subbotin, I. V. Baranenkov and S. Wolfe, Tetrahedron, 1978, 34, 2953; (b) V. V. Samoshin, O. V. Bychkova, V. A. Chertkov, A. K. Shestakova, L. P. Vatlina, N. A. Smirnov and L. P. Kastorsky, Zh. Org. Khim., 1996, 32, 1104 (Russ. J. Org. Chem., 1996, 32, 1066). 6 J. Nokami, K. Yoshizane, H. Matsuura and S. Sumida, J. Am. Chem. Soc., 1998, 120, 6609. 7 J. March, Advanced Organic Chemistry, Wiley, New York, 1992, p. 312. Received: 30th June 1999; Com. 99/1508

ISSN:0959-9436     

出版商:RSC    

年代:1999

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摘要:

Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Structure and rearrangements of 7-(1,2,3,4,5,6,7-heptaphenylcycloheptatrienyl) isocyanate, isothiocyanate and isoselenocyanate Galina A. Dushenko,*a Igor E. Mikhailov,a Adolf Zschunke,b Gunter Reck,b Burkhard Schulzb and Vladimir I. Minkina a Institute of Physical and Organic Chemistry, Rostov State University, 344090 Rostov-on-Don, Russian Federation.Fax: +7 8632 28 5667; e-mail: mikhail@ipoc.rnd.runnet.ru b Federal Institute for Materials Research and Testing, D-12200 Berlin, Germany. Fax: +4 9306 392 5972 In 7-(1,2,3,4,5,6,7-heptaphenylcycloheptatrienyl) isothiocyanate and isoselenocyanate, migration of isothiocyanate and isoselenocyanate groups along the perimeter of the seven-membered ring occurs via an intramolecular dissociation–recombination mechanism with high free energy barriers (DG� 298) of 24.3 and 22.4 kcal mol–1, respectively.Recently, we have shown that migration of the isothiocyanate group in the three-membered ring of 3-(1,2,3-triphenylcyclopropenyl) isothiocyanate occurs via a dissociation–recombination mechanism (DG� 298 K = 14.5–15.6 kcal mol–1), while circumambulation of selenocyanate (DG� 298 K = 16.7 kcal mol–1) and isoselenocyanate (DG� 408 K = 22 kcalmol–1) groups along the periphery of the pentaphenylcyclopentadiene ring proceeds as a series of 1,5-, and 3,3-sigmatropic shifts, respectively.1–3 To examine the effect of the size of a conjugated carbocycle on the migratory ability of –NCX (X = O, S or Se) groups, we have synthesised isocyanate, isothiocyanate and isoselenocyanate derivatives of heptaphenylcycloheptatriene and studied their structure and fluxional behaviour by dynamic 13C and 1H NMR techniques and X-ray diffraction analysis.Parent 1,2,3,4,5,6,7- heptaphenylcycloheptatriene (C7Ph7H)4 has been found to possess a structure with an axial position of the phenyl substituent at the sp3 carbon in the boat conformation of the cycloheptatriene ring.5 Few examples are known of substituent rearrangements in this system.Among these are an irreversible high-energybarrier 1,5-sigmatropic shift of a phenyl group (300 °C, 45 min) in C7Ph7H and a hydrogen migration in the same compound (DG� 298 K ~ 25 kcal mol–1), which exhibits a high energy barrier because of the necessity of the flipping seven-membered ring to arrange the hydrogen axially.5,6 7-(1,2,3,4,5,6,7-Heptaphenylcycloheptatrienyl) isocyanate, isothiocyanate and isoselenocyanate 1–3 have been obtained by treatment of 7-bromo-1,2,3,4,5,6,7-heptaphenylcycloheptatriene4 with equimolar amounts of potassium cyanate, thiocyanate or selenocyanate, respectively, in an acetonitrile solution (Scheme 1).† No cyanate, thiocyanate or selenocyanate isomers of 1–3 have been isolated.The structure of isothiocyanate 2 has been determined by X-ray diffraction analysis (Figure 1).‡ The molecule of 2 possesses a boat-like conformation of the cycloheptatriene ring. The dihedral angles between the planes of the cycloheptatriene ring [C(6)–C(7)–C(1)/C(1)–C(2)–C(5)–C(6) 55.4(2)° and C(1)– C(2)–C(5)–C(6)/C(2)–C(3)–C(4)–C(5) 35.2(1)°] show that the bending of the sp3 carbon is larger than that in cycloheptatriene C7H8 (36°); this minimises sterical interactions between the phenyl groups.5 The isothiocyanate substituent occupies the pseudo-equatorial position, while the phenyl ring is arranged at the more sterically favoured pseudo-axial site.All phenyl rings are twisted relative to the central cycloheptatriene ring (the corresponding dihedral angles vary from 41.26 to 87.08°, Figure 1). † Compounds 1–3.Potassium cyanate (thiocyanate or selenocyanate) (5 mmol) was added to a suspension of 7-bromo-1,2,3,4,5,6,7-heptaphenylcycloheptatriene (5 mmol) in acetonitrile (100 ml). The mixture was stirred for 0.5 h at 25 °C. The precipitated KBr was separated using a hot-air filter funnel, and the solvent was evaporated in vacuo.The residue was recrystallised from acetonitrile. Yields 92–94%. 1: yellow crystals, mp 242–243 °C. IR (vaseline oil, n/cm–1): 2255, 1610, 1570, 1490, 1465. MS, m/z: 666 (51.3%) [Ph7C7NCOH=MH]+, 665 (100) [Ph7C7NCO = M]+, 649 (0.4) [M – O]+, 648 (0.9) [M – OH]+, 637 (9.6) [M – CO]+, 636 (7.1) [M – HCO]+, 623 (13.9) [M – NCO = Ph7C7]+, 622 (8.2) [Ph7C7 – H]+, 588 (10.3) [M – Ph]+, 560 (42.4) [M – Ph – CO]+, 546 (33.4) [Ph7C7 – Ph = Ph6C7]+, 545 (69.7) [Ph6C7 – H]+, 534 (30.6) [Ph6C7 – C = Ph6C6]+, 467 (9.0) [Ph7C7 – 2C6H6]+, 367 (6.0) [Ph5C5 – C6H6]+, 267 (2.8) [Ph3C3]+, 91 (3.4) [C7H7]+, 77 (11.9) [C6H5]+. 2: yellow crystals, mp 263–265 °C (decomp.). IR (vaseline oil, n/cm–1): 2125, 1600, 1575, 1490, 1475.MS, m/z: 682 (27.3%) [Ph7C7NCSH =MH]+, 681 (51.1) [Ph7C7NCS = M]+, 649 (2.3) [M – S]+, 648 (3.9) [M - SH]+, 624 (29.4) [MH – NCS = Ph7C7H]+, 623 (51.2) [Ph7C7]+, 622 (25.1) [Ph7C7 – H]+, 604 (2.5) [M – Ph]+, 546 (46.1) [Ph7C7 – Ph = Ph6C7]+, 545 (100) [Ph6C7 – H]+, 534 (2.4) [Ph6C7 – C = Ph6C6]+, 467 (10.3) [Ph7C7 – 2C6H6]+, 367 (7.0) [Ph5C5 – C6H6]+, 267 (3.6) [Ph3C3]+, 103 (21.1) [PhCN]+, 91 (3.4) [C7H7]+, 77 (11.9) [C6H5]+. 3: yellow crystals, mp 269–270 °C (decomp.).IR (vaseline oil, n/cm–1): 2050, 1600, 1580, 1490, 1470. MS, m/z: 729 (1.6%) [Ph7C7NCSeH =MH]+, 728 (3.0) [Ph7C7NCSe = M]+, 702 (0.8) [Ph7C7SeCN – CN]+, 701 (0.8) [Ph7C7SeCN – HCN]+, 650 (16.4) [M – C6H6]+, 649 (31.6) [M – Se]+, 648 (9.8) [M – SeH]+, 623 (90.7) [M – NCSe = Ph7C7]+, 622 (63.0) [Ph7C7 – H]+, 572 (16.6) [M – 2C6H6]+, 571 (16.0) [M – Se – C6H6]+, 546 (58.9) [Ph7C7 – Ph = Ph6C7]+, 545 (100) [Ph6C7 – H]+, 534 (3.8) [Ph6C7 – C = Ph6C6]+, 467 (18.3) [Ph7C7 – 2C6H6]+, 367 (18.0) [Ph5C5 – C6H6]+, 267 (10.6) [Ph3C3]+, 194 (15.3) [PhCNCSe]+, 105 (7.4) [NCSe]+, 91 (37.1) [C7H7]+, 77 (55.6) [C6H5]+.‡ Crystal data for 2. C50H35NS·0.5C6H6, monoclinic, space group P21/n, a = 19.126(4) Å, b = 11.349(5) Å, c = 18.952(4) Å, b = 100.18(2)°, V = = 4049(2) Å3, Z = 4, dcalc = 1.183 g cm3.The X-ray diffraction experiments were carried out on an Enraf Nonius CAD-4 diffractometer [T = 293(2) K, graphite-monochromated MoKa radiation, l = 0.71069 Å, q/2q scan technique, 3° < 2q < 40°]. The structure was solved by direct methods using SHEXS-97 (G.Scheldrick, University of Göttingen, 1990). Independent reflections: 3754. Refinement method: full-matrix least-squares (SHELXL-97, G. Sheldrick, University of Göttingen, 1997), data/parameters 3754/497, goodness-of-fit 1.035, final R indices [I > 2s(I)] R1 = 0.0353, wR2 = 0.0993; R indices (all data) R1 = 0.0418, wR2 = 0.1040, Dfmax = = 0.087 eÅ–3.Hydrogen atoms were placed in geometrically calculated positions and included in the refinement using the riding model. Atomic coordinates, bond lengts, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 1999. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/54.Br N KXCN – KBr 1 X = O 2 X = S 3 X = Se 1–3 Scheme 1 C XMendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) The structure of compounds 1–3 has been confirmed by IR and NMR spectroscopy and mass spectrometry. In the IR spectra of compounds 1–3, broad absorption peaks characteristic of the –N=C=O, –N=C=S and –N=C=Se stretching vibration region7 were observed at 2255, 2125 and 2050 cm–1, respectively.In the 13C NMR spectra of compounds 1–3§ in C6D6, the –N=C=O, –N=C=S (Figure 2) and –N=C=Se carbon signals appear in their characteristic regions8,9 5, 138.30 and 133.00 ppm, respectively. No carbon signals of the C7Ph7–XCN (X = O, S or Se) isomers of 1–3 were detected in the characteristic regions of d 110–113 ppm.8,9 The o- and m-carbon atoms of the phenyl rings at C1,6 of the cycloheptatriene ring are magnetically nonequivalent at 20 °C.With increasing temperature of the solutions of 1–3, these two pairs of signals broaden, coalesce and become narrow at 75 °C (Figure 2). Such a spectral behaviour indicates the hindered rotation of these rings.From line shape analysis of the indicator signals of the o- and m-carbons of the rings at C1,6 in the dynamic 13C NMR spectra (25–90 °C), the kinetic and activation parameters of the hindered rotation of the phenyl rings at C1,6 in 1–3 have been calculated using the DNMR-5 program10 (Table 1). The shape of the cycloheptatriene ring signals as well as para- and ipso-aromatic carbon signals are almost unaffected by the temperature of solutions in the range from –70 to +100 °C (C6D6, [2H8]toluene).The hindered rotation of the phenyl rings at C2,5 and C3,4 for compounds 1–3 can also be detected at low temperatures in the 13C NMR spectra. It § 1: 1H NMR (300 MHz, 20 °C, C6D6) d: 6.36 (dd, 4H, ortho, Ph at C3,4, J 6.9 and 1.6 Hz), 6.54–6.64 (m, 6H, meta, para, Ph at C3,4), 6.76–6.80, 6.88–6.93, 7.02–7.08 (m, 18H, Ph at C1,6 and C2,5), 7.24 (tq, 1H, para, Ph at C7, J 7.5 and 1.2 Hz), 7.40 (dd, 2H, meta, Ph at C7, J 8.3 and 7.5 Hz), 7.61 (dd, 2H, ortho, Ph at C1,6, J 7.8 and 1.5 Hz), 8.23 (dd, 2H, ortho, Ph at C7, J 7.2 and 1.6 Hz). 13C NMR (75.47 MHz, 20 °C, C6D6) d: 72.73 (C7), 126.09 (para, Ph at C3,4), 126.56 (para, Ph at C2,5), 126.73 (meta, Ph at C3,4), 126.75 (para, Ph at C1,6), 127.34 (ortho, Ph at C7), 127.52 (meta, Ph at C2,5), 127.54, 127.87 (meta, Ph at C1,6), 128.72 (para, Ph at C7), 129.39 (meta, Ph at C7), 131.45 (ortho, Ph at C2,5), 131.59 (ortho, Ph at C3,4), 131.76, 131.87 (ortho, Ph at C1,6), 124.75 (NCO), 139.41, 140.03, 141.10 (ipso, Ph at C1–6), 137.77, 143.51, 144.03 (C1–6), 146.65 (ipso, Ph at C7). 2: 1H NMR (300 MHz, 20 °C, [2H8]toluene) d: 6.29 (dd, 4H, ortho, Ph at C3,4, J 7.0 and 1.5 Hz), 6.48–6.59 (m, 6H, meta, para, Ph at C3,4), 6.71–6.80, 6.83–6.88, 6.95–7.15 (m, 18H, Ph at C2,5 and C1,6), 7.24 (tq, 1H, para, Ph at C7, J 7.5 and 1.2 Hz) 7.41 (dd, 2H, meta, Ph at C7, J 8.2 and 7.5 Hz), 7.66 (dd, 2H, ortho, Ph at C1,6, J 7.8 and 1.5 Hz), 8.21 (dd, 2H, ortho, Ph at C7, J 7.2 and 1.5 Hz). 13C NMR (75.47 MHz, 20 °C, C6D6) d: 76.44 (C7), 126.06 (para, Ph at C3,4), 126.61 (para, Ph at C2,5), 126.66 (meta, Ph at C3,4), 126.85 (para, Ph at C1,6), 127.40 (ortho, Ph at C7), 127.49 (meta, Ph at C2,5), 127.60, 127.78 (meta, Ph at C1,6), 129.04 (para, Ph at C7), 129.36 (meta, Ph at C7), 131.32 (ortho, Ph at C2,5), 131.42 (ortho, Ph at C3,4), 131.57, 131.67 (ortho, Ph at C1,6), 138.30 (NCS), 137.69, 141.81, 143.95 (C1–6), 138.94, 139.77, 140.65 (ipso, Ph at C1–6), 144.35 (ipso, Ph at C7). 3: 1H NMR (300 MHz, 20 °C, [2H8]toluene) d: 5.91 (dd, 4H, ortho, Ph at C3,4, J 6.8 and 1.6 Hz), 6.14–6.19 (m, 6H, meta, para, Ph at C3,4), 6.37–6.53, 6.57–6.65, 6.73–6.82 (m, 18H, Ph at C1,6 and C2,5), 6.87 (tq, 1H, para, Ph at C7, J 7.5 and 1.2 Hz) 7.03 (dd, 2H, meta, Ph at C7, J 8.2 and 7.5 Hz), 7.31 (dd, 2H, ortho, Ph at C1,6, J 7.8 and 1.5 Hz), 7.84 (dd, 2H, ortho, Ph at C7, J 7.2 and 1.5 Hz). 13C NMR (75.47 MHz, 20 °C, C6D6) d: 77.19 (C7), 126.10 (para, Ph at C3,4), 126.64 (para, Ph at C2,5), 126.68 (meta, Ph at C3,4), 126.98 (para, Ph at C1,6), 127.50 (meta, Ph at C2,5), 127.55 (ortho, Ph at C7), 127.78, 127.83 (meta, Ph at C1,6), 129.23 (para, Ph at C7), 129.43 (meta, Ph at C7), 131.32 (ortho, Ph at C2,5), 131.42 (ortho, Ph at C3,4), 131.58, 131.64 (ortho, Ph at C1,6), 133.00 (NCSe), 138.59, 139.71, 140.55 (ipso, Ph at C1–6), 137.78, 141.20, 143.44 (C1–6), 143.97 (ipso, Ph at C7).manifests itself in considerable broadening of the ortho- and meta-carbons in these rings (T < –10 °C for Ph at C2,5, DG� 223 K ª ª 12 kcal mol–1; T < –50 °C for Ph at C3,4, DG� < 9 kcalmol–1).Note that in C7Ph7H the rotation barriers for the phenyl rings at C1,6 (C3,4) and C2,5 were evaluated as ª 9 and 11 kcal mol–1, respectively.5 An increase in the barrier for the hindered rotation of the phenyl rings at C1,6 in 1–3 can be explained by the additional overcrowding of the heptaphenylcycloheptatriene ring by –NCX substituents.The 1H and 13C NMR spectral signals of compounds 1–3 were assigned on the basis of the characteristic values of Table 1 Kinetic and activation parameters of rotation of the phenyl rings at C1,6 in 1–3. Compound Solvent DH�/ kcal mol–1 DS� (e.u.) k298/s–1 DG� 298 K/ kcal mol–1 1, X = O C6D6 12.6±0.3 –10.9±0.9 14.1 15.9 2, X = S [2H8]toluene 13.1±0.4 –8.8±1.1 17.8 15.7 3, X = Se [2H8]toluene 13.2±0.3 –8.9±0.9 15.1 15.8 C(11) C(12) C(13) C(14) C(15) C(16) C(21) C(22) C(23) C(24) C(25) C(26) C(31) C(32) C(33) C(34) C(35) C(36) C(41) C(42) C(43) C(44) C(45) C(46) C(51) C(52) C(53) C(54) C(55) C(56) C(61) C(62) C(63) C(64) C(65) C(66) C(72) C(73) C(74) C(75) C(76) C(1) C(2) C(3) C(4) C(5) C(6) C(7) N(1) C(111) S(1) Figure 1 The molecular structure of compound 2.Selected bond lengths/Å: N(1)–C(7) 1.457(3), N(1)–C(111) 1.148(3), S(1)–C(111) 1.575(3), C(1)–C(7) 1.537(3), C(6)–C(7) 1.536, C(7)–C(71) 1.539, C(1)–C(11) 1.487(3), C(2)– C(21) 1.499(3); selected bond angles/°: C(111)–N(1)–C(7) 165.1(2), N(1)–C(111)–S(1) 177.1(2), N(1)–C(7)–C(6) 108.84(16), N(1)–C(7)–C(1) 108.42(17), N(1)–C(7)–C(71) 104.06(15), C(1)–C(7)–C(6) 104.53(15).Dihedral angles between the cycloheptatriene ring and the phenyl rings/°: [C(1)–C(2)–C(3)–C(4)–C(5)–C(6)–C(7)]/[C(11)–C(12)–C(13)–C(14)–C(15)– C(16)] 74.65(8), [C(1)–C(7)]/[C(21)–C(26)] 68.97(8), [C(1)–C(7)]/[C(31)– C(36)] 87.08(8), [C(1)–C(7)]/[C(41)–C(46)] 41.26(9), [C(1)–C(7)]/[C(51)– C(56)] 58.28(8), [C(1)–C(7)]/[C(61)–C(66)] 86.80(9), [C(1)–C(7)]/[C(71)– C(76)] 78.92(8).Ph Ph Ph Ph Ph Ph Ph N C X Ph Ph Ph Ph Ph Ph Ph N C X Ph Ph Ph Ph Ph Ph Ph NCX – 2,3 4 2',3' ... ... ... ... ... ... ... 2 X = S 3 X = Se Scheme 2 1 2 3 4 5 6 7 7 6 5 4 3 2 1Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) chemical shifts and the integral intensities, the application of the APT techniques and by means of monoresonance 13C spectra, heteronuclear correlation of the 1H and 13C chemical shifts (XHCOORR), 1H–1H COSY and NOE measurements (see footnote; § Figures 2 and 3).The assignments are consistent with those reported previously for heptaphenylcycloheptatriene.5 The NOE experiments pointed to the notable interaction between the ortho-protons of the rings at C3,4 and C7 thus confirming a pseudo-axial position of the phenyl ring at C7 of 1–3. The proton signals of a single phenyl ring at C7 of 1–3 (Figure 3) are shifted relative to those of the rings at C3,4 and found in the most downfield part of the 1H NMR spectra, whereas the proton signals of the rings at C3,4 are detected in the most upfield part.The proton signals of the phenyl rings at C2,5 and C1,6 are partially overlapped; one of the o-protons (which are nonequivalent at £ 25 °C) of the rings at C1,6 appears separately as a doublet of doublet signal at d 7.66–7.31 ppm.As the temperature of [2H5]nitrobenzene solutions of 1–3 was increased from 25 to 100 °C (Figure 3), broadening and coalescence of signals of both nonequivalent o- and m-protons of the rings at C1,6 were observed. At 140–180 °C for 2 and at 120–160 °C for 3, synchronous reverdening and coalescence of the proton signals of all the phenyl rings take place, indicating a random dissociation–recombination mechanism11 of displacement of isothiocyanate and isoselenocyanate groups along the perimeter of the seven-membered ring (2,3 = 2',3' =…; Scheme 2).Upon varying the concentration of solutions (c 0.003–0.3 mol dm–3) of 2 and 3, no changes in the dynamic NMR spectral patterns were observed.This proves the intramolecular tight ion pair mechanism of the migrations. For isocyanate derivative 1, the NMR spectra did not show any temperature dependence up to 180 °C. Such a spectral behaviour indicates the stereochemical rigidity of 1 on the characteristic NMR time scale (DG� 298 K > 25 kcalmol–1).By comparison of the experimental line shape of the indicator proton signals of the phenyl rings at C1–7 in the dynamic 1H NMR spectra (120–180 °C) with the theoretical shape the kinetic parameters of the –NCX (X = S or Se) group migrations in 2 and 3 in [2H5]nitrobenzene solutions have been calculated using the DNMR-5 program.10 The activation parameters have been calculated from the ln k/T–1/T relationship for eight temperature measurements (Table 2).The –NCO and –NCS group migrations along the periphery of the unsubstituted cycloheptatriene ring in cycloheptatrienyl isocyanate and isothiocyanate is known9,12,13 to occur via tight ion pair reaction paths with low free activation barriers DG� of 16.5 and 14.8 kcal mol–1, respectively.An increase in the energy barriers of the –NCX group migrations over the heptaphenylcycloheptatriene ring as compared to those for the unsubstituted seven-membered ring is most probably caused by steric hindrances created by the phenyl substituents in the C7Ph7 + cation, which is formed in intermediate 4 of the rearrangement.¶ ¶ A similar increase of the energy barrier against a boat inversion of the seven-membered ring in C7Ph7H (DG� � 25 kcal mol–1) due to sterical hindrances, as compared to that for unsubstituted cyloheptatriene C7H6 (DG� 6.1 kcal mol–1) was observed earlier.5,14 The high barrier of the boat inversion in the heptaphenylcycloheptatriene system restricts the symmetry-allowed suprafacial sigmatropic shifts of substituents, which can occur when migrants are axially positioned.Table 2 Kinetic and activation parameters of –NCX group migrations in 2 and 3. Compound DH�/ kcal mol–1 DS� (e.u.) k298/s–1 DG� 298/ kcal mol–1 2, X = S 26.5±0.4 +7.3±1.0 8.9×10–6 24.3 3, X = Se 22.9±0.3 +1.8±0.9 2.2×10–4 22.4 Ph Ph Ph Ph Ph Ph N C S i o m p 1 2 3 4 5 6 7 145 140 132 131 129 128 127 126 75 d/ppm (c) 75 °C (b) 35 °C (a) 18 °C i, Ph i, Ph at C1,6 C1,6 o, Ph at C1,6 NCS o, Ph at C3,4 o, Ph at C2,5 m, Ph at C7 p, Ph at C7 m, Ph at C1,6 m, Ph at C2,5 o, Ph p, Ph m, Ph at C3,4 p, Ph at C2,5 p, Ph at C3,4 C7 at C1,6 at C7 at C7 Figure 2 13C NMR (75.47 MHz) spectra of 2 in C6D6 at (a) 18 °C, (b) 35 °C, (c) 75 °C.Spectra (b) and (c) are given in the region 126–132 ppm; the pattern of the rest spectral parts is not changed at these temperatures. Solvent signals are excluded from the spectra.N C S o m p 1 2 3 4 5 6 7 d/ppm 8.8 8.6 8.4 8.2 8.0 7.8 7.6 7.4 7.2 7.0 6.8 6.6 6.4 180 °C (80 MHz) 180 °C 160 °C 140 °C 100 °C 60 °C 40 °C 20 °C o, Ph at C2,5 o, Ph at C7 m, Ph at C7 p, Ph at C7 m, Ph at C2,5 p, Ph at C1,6 and C2,5 o, Ph at C3,4 m, p, Ph at C3,4 o, Ph at C1,6 o, Ph at C1,6 m, Ph at C1,6 o, Ph at C2,5 m, Ph at C2,5 Figure 3 1H NMR (300 MHz) spectra of 2 in [2H5]nitrobenzene at 20, 40, 60, 100, 140, 160, 180 °C and 180 °C (80 MHz).Solvent signals are excluded from the spectra.Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) In the case of compound 3, a minor component of the selenocyanate species (Ph7C7SeCN) was detected in the gas phase by the appearance of low-intensity peaks in the mass spectrum, originated from fragmentation of this species: m/z (%), 702 (0.8) [Ph7C7SeCN – CN]+ and 701 (0.8) [Ph7C7SeCN – HCN]+, unlike compounds 1 and 2.† This fact points to the principal possibility of an additional competitive mechanism for the isoselenocyanate group migration in the seven-membered ring of 3 in the gas phase.Thus, the migratory ability of –NCX groups decreases in proportion to the increase in the ring size of the perphenylcyclopolyene Ph3C3 > Ph5C5 > Ph7C7 due to changes in the mechanism of the circumambulations in the cyclopentadiene derivatives and a lower stability of the sterically overcrowded Ph7C7 + cation in 4 as compared to the Ph3C3 + cation in the ionpair transition state of the migrations over the cyclopropene ring. This work was supported by the Russian Foundation for Basic Research (grant no. 98-03-33062) and by the programme ‘Russian Universities: Fundamental Research’ (grant no. 4058). References 1 G. A. Dushenko, I. E. Mikhailov, I. V. Dorogan, R. M. Minyaev, A. Zschunke and V. I. Minkin, Mendeleev Commun., 1995, 213. 2 G. A. Dushenko, I. E. Mikhailov, A. Zschunke, N. Hakam, C. Mugge, R. V. Skachkov and V. I. Minkin, Mendeleev Commun., 1995, 182. 3 V. I. Minkin, I. E. Mikhailov, G. A. Dushenko, O. E. Kompan and A. Zschunke, Izv. Akad. Nauk, Ser. Khim., 1998, 913 (Russ. Chem. Bull., 1998, 47, 884). 4 M. A. Battiste, Chem. Ind. (London), 1961, 550. 5 L. S. F. Chao, H. K. Gupta, D. W. Hughes, J. F. Britten, S. S. Rigby, A. D. Bain and M. J. McGlinchey, Organometallics, 1995, 14, 1139. 6 J. A. Harvey and M. A. Ogliaruso, J. Org. Chem., 1976, 41, 3374. 7 B. H. Williams and I. Fleming, in Spectroskopische Metoden in der Organischen Chemie, G. Thieme Verlag, Stuttgart, 1971 (in German). 8 G. C. Levy and G. L. Nelson, in Carbon-13 Nuclear Magnetic Resonance for Organic Chemists, Wiley–Interscience, New York, 1972. 9 M. Feigel, H. Kessler and A. Walter, Chem. Ber., 1978, 111, 2947. 10 D. S. Stephenson and G. Binsch, J. Magn. Reson., 1978, 32, 145. 11 B. E. Mann, in Comprehensive Organometallic Chemistry, eds. G. Wilkinson, A. G. F. Stone and E. Abel, Pergamon Press, New York, 1982, vol. 3, ch. 20, p. 90. 12 H. Kessler and M. Feigel, Acc. Chem. Res., 1982, 15, 2. 13 H. Kessler, Chimia, 1973, 27, 444. 14 M. Oki, Applications of Dynamic NMR Spectroscopy to Organic Chemistry, VCH, Weinheim, 1985, pp. 310, 374. Received: 28th May 19

ISSN:0959-9436     

出版商:RSC    

年代:1999

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Molecular structure of 2-chloro-3,5-di-tert-butyl-1,3,2-oxazaphospholene as determined by electron diffraction and ab initio calculations Victor A. Naumov,*a Marwan Dakkouri,*b Rida N. Ziatdinovaa and Heinz Oberhammerc a A. E. Arbuzov Institute of Organic and Physical Chemistry, Russian Academy of Sciences, 420088 Kazan, Russian Federation.Fax +7 8432 76 7424; e-mail: vanaumov@iopc.kcn.ru b Department of Electrochemistry, University of Ulm, 89069 Ulm, Germany. Fax: +49 731 502 5409; e-mail: marwan.dakkouri@chemie.uni-ulm.de c Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany. Fax: +49 7071 29 6910; e-mail: heinz.oberhammer@uni-tuebingen.de The diheterophospholene ring of the title compound possesses a P-envelope conformation with the axial orientation of the P–Cl bond, which is very long [ra = 2.177(6) Å].The molecular structure of unsaturated 1,3,2-diheterophospholenes is scantily known. Only 2-chloro-5-methyl-1,3,2-oxathiaphospholene 1,1 2-chloro-1,3,2-dioxaphospholene 22 and 2-fluoro- 3,5-di-tert-butyl-1,3,2-oxazaphospholehe 33 have been studied by electron diffraction.These studies have demonstrated that the P–Hal bond length depends on the nature of substituents at phosphorus. In compounds 1–3 the P–Hal bond lengths are 2.08(2), 2.101(6) and 1.641(11) Å, respectively. In this work, we investigated the stucture of 2-chloro-3,5-di-tert-butyl-1,3,2- oxazaphospholene in the gas phase using electron diffraction and ab initio calculations.The diffraction patterns were recorded at 60 °C on Kazan EMR-100M ED-instruments using two camera distances. The long and short camera distances covered the s-ranges 4.00–14.75 and 12.00–27.25 Å–1, respectively. The refinements of the structure were performed by applying a least-squares procedure based on the molecular intensities. The molecular structure optimization by means of ab initio calculations was carried out at the HF/6-31G**, MP2/6-31G** and b3pw91/6-31G** levels.4,5 The vibrational amplitudes lij and perpendicular corrections Kij were derived from the theoretical force field provided by the basis set HF/6-31G** and used in the structural analysis.For describing the geometry of the five-membered ring, the P–O, P–N, C=C and N–C(4) bond lengths, the O–P–N, P–N–C(4) and N–C=C bond angles and the O–P–N–C(4) torsional angle were chosen as independent parameters (Figure 1).The N–C=C–O moiety was assumed to be planar. This assumption is justified by ab initio calculations, which predicted this dihedral angle to be 0.4° (MP2/6-31G**), 0.7° (b3w91/6-31G**) or 0.2° (HF/6-31G**). The structure of the exo-groups and their orientations were described by the P–Cl, N–C(7), C(5)–C(8), C–CMe and C–H bond lengths, the O–P–Cl, N–P–Cl, P–N–C(7), C(4)–N–C(7), C=C–C(8), N–C(7)–CMe and C(5)–C(8)–CMe bond angles and the P–N–C(7)–C(9) and C=C–C–C(21) torsional angles. Because of large correlations between some of the geometric parameters, the following assumptions were made during the structural refinement: (i) C3v symmetry was assumed for the methyl and tertbutyl groups, and all C–C bond lengths and CMe–C–CMe bond angles in the two tert-butyl groups were set equal.These assumptions are justified by ab initio calculations, which predicted deviations to be less than 0.005 Å and 0.9°; (ii) the differences between bond lengths d(NC) = r[N–C(4)] – r[N–C(7)], d(CC) = r[C(8)–CMe] – r[C(5)–C(8)] were adopted from the MP2/6-31G** and b3pw91/6-31G** results, averaged and introduced as separate parameters.The bond length differences were applied to the ra structure. The refined bond lengths were converted to ra distances. According to preliminary experimental results, the diheterophospholene ring possesses a P-envelope conformation with the axial orientation of the P–Cl bond.These results have also shown that the sum of the angles at the N atom is 360°, which is in a good agreement with the ab initio results 357.3 (MP2/6-31G**), aExperimental uncertainties 3s are given in parentheses. Average values are given in square brackets. bDependent parameters. Table 1 Geometric parameters for 2-chloro-3,5-di-tert-butyl-1,3,2-oxazaphospholene as found by the electron diffraction analysis and ab initio calculations.a Experiment Calculation Bond length/Å ra ra HF/6- 31G** MP2/ 6-31G** b3pw91/ 6-31G** P–Cl 2.177(6) 2.167 2.169 2.196 2.225 P–O 1.657(10) 1.653 1.623 1.664 1.657 P–N 1.698(15) 1.694 1.676 1.700 1.700 C–Ob 1.392(27) 1.389 1.386 1.401 1.391 C=C 1.348(16) 1.344 1.319 1.350 1.342 N–C(4) 1.398 (13) 1.396 1.413 1.409 1.404 N–C(7) 1.474 1.468 1.478 1.479 1.481 d(NC) 0.072(39) 0.054 0.070 0.077 C–CMe 1.557 (5) 1.542 [1.537] [1.530] [1.537] C(5)–C(8) 1.510 1.506 1.506 1.493 1.502 d(CC) [0.036] 0.031 0.037 0.035 C–H 1.091(5) 1.055 [1.084] [1.089] [1.095] Bond angle/° O–P–N 94.5(12) 91.4 90.8 90.7 P–N–C(4) 108.7(19) 109.1 110.0 110.1 C–N–Cb 121.7(21) 122.1 121.5 122.4 C=C–N 112.2(28) 112.7 112.3 112.7 C=C–Ob 115.0(23) 111.0 111.5 111.2 P–O–Cb 108.8(15) 112.9 112.0 113.0 O–P–Cl 99.1(10) 99.0 99.1 99.6 N–P–Cl 101.1(8) 103.4 103.5 103.8 P–N–C(7) 129.6(11) 127.7 125.8 126.0 C=C–C 134.6(24) 133.1 132.9 132.6 N–C–CMe 109.3(8) [109.4] [109.0] [109.2] C–C–CMe CMe–C–Cb Me 109.6(8) [109.9] [109.9] [108.7] Torsion angle/° O–P–N–C(4) 8.4(16) 15.0 16.6 16.7 C(9)–C(7)–N–P 139.9(30) 133.9 138.8 134.8 C(21)–C(8)–C=C 120.3(131) 120.4 120.1 121.0 R(sMs)long 4.20 R(sMs)short 7.45 R(sMs)average 5.67 R[f(r)] 3.31 Cl(6) P(2) O(1) N(3) C(4) C(5) C(7) C(9) C(13) C(17) C(8) C(29) C(21) C(25) Figure 1 Molecular structure of 2-chloro-3,5-di-tert-butyl-1,3,2-oxazaphospholene.Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) 358.5 (b3pw91/6-31G**) and 358.9° (HF/6-31G**).Therefore, we include the P–N–C(7) and P–N–C(4) angles in the final refinement. The results of the final least-squares analysis of ED data and ab initio calculations are shown in Table 1. The following correlation coefficients have values higher than |0.6|: PN/PO –0.82, PN/NC –0.73, PO/NC 0.67, PN/CC 0.72, CC/NC 0.77, CC/OPN 0.65, PNC(7)/OPN –0.74, NC=C/PNC(4) 0.91, ClPO/PNC(4) 0.69, CC=C/NC=C 0.68, CMeCN/PNC(4) 0.77, CMeCN/NC=C –0.75.The experimental curve f(r) is shown in Figure 2. The electron diffraction investigation of the structure of 2-chloro-3,5-di-tert-butyl-1,3,2-oxazaphospholene indicates that the P–Cl bond of 2.177(6) Å is very long, as compared with other compounds.6 For instance, this bond is about 0.13 Å longer than that in PCl3 [2.042(2) Å7].Note that the P–Cl bond in oxazaphospholene is remarkably longer than the sum of the covalent radii of P and Cl (2.09 Å). On the other hand, the structural analysis shows that both C–O and C–N bonds within the ring are shorter than ordinary bonds. This indicates conjugative interaction within the O–C=C–N fragment of the ring. Note that the P–O and P–N bond lengths in the ring are comparable with those in non-cyclic compounds such as P(OMe)3 [r(P–O) = 1.620(2) Å6], P(NMe2)3 [r(P–N) = = 1.70(1) Å6], ClP(NMe2)2 [r(P–N) = 1.730(5) Å6].In cyclic compounds such as 2-chloro-3-methyl-1,3,2-oxazaphospholane or in 1,3,4,2-oxadiazaphospholene, the P–O and P–N bonds are 1.62–1.63 and 1.70 Å, respectively.6 In 2-chloro-1,3,2-dioxaphospholene, 2 the P–O bond length is 1.633(3) Å, and the P–Cl bond length is 2.101(3) Å.These values are considerably shorter than the corresponding bond lengths in 2-chloro-3,5-di-tertbutyl- 1,3,2-oxazaphospholene. For direct comparison of the influence of fluorine and chlorine substituents on the geometry of an oxazaphospholene ring, the most important parameters which have been obtained from the structural investigations of 2-fluoro- and 2-chloro-3,5- di-tert-butyl-1,3,2-oxazaphospholenes are summarised in Table 2.It is of particular importance to note that the oxazaphospholene ring has a P-envelope form. The sum of endocyclic angles is 537.7 or 539.2° for F and Cl derivatives, respectively. The dihedral angle between the O–P–N and O–C=C–N planes in chlorooxazaphospholene is 8.4 (1.6)°.In fluorooxazaphospholene, this angle is larger. A comparison the C–O and C–N terminal bonds within the X–P–N–C and X–P–O–C chains in fluoro- and chlorooxazaphospholenes shows that these differ by about 0.03 and 0.04 Å, respectively. We suppose that these differences are due to the different electronegativities of F and Cl atoms. This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-04004G) and by Deutsche Forschungsgemainschaft. We are grateful to Dr. Yu. V. Balitzkii for the sample of oxazaphospholene. References 1 R. N. Siatdinova, V. Yu. Nesterov, N. M. Zaripov, V. A. Naumov and A. R. Burilov, Zh. Strukt. Khim., 1990, 31, 169 (in Russian). 2 L. S. Khaikin, V. A. Sipachev, A. V. Beklemishev, N. M. Pozdeev, E.A. Zhilinskay, M. V. Proskurnina and L. V. Vilkov, Vestn. Mosk. Univ., Ser. 2: Khim., 1997, 38, 222 (in Russian). 3 V. A. Naumov, M. Dakkouri, R. N. Ziatdinova and H. Oberhammer, Mendeleev Commun., 1998, 89. 4 M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M.A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M.W.Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian 94, Revision D.4, Gaussian, Inc., Pittsburgh PA, 1995. 5 Spartan 5.0, Wavefunction, Inc., 18401 Von Karman Avenue, Suite 370, Irvine, CA 92612 USA. 6 V. A. Naumov and L. V. Vilkov, Molekulyarnye struktury fosfororganicheskikh soedinenii (Molecular Structures of Organophosphorus Compounds), Nauka, Moscow, 1986, p. 319 (in Russian). 7 K. Hedberg and M. J. Iwasaki, Chem. Phys., 1962, 36, 589. f(r) 1 2 3 r/Å 0 1 2 3 4 5 6 7 8 Figure 2 Experimental radial distribution function with (1) b = 0.0031, (2) b = 0.000001 and (3) difference curve f(r)exp – f(r)theor, 3D. aAssumed value. bDependent parameters. Table 2 Comparison between the geometrical parameters of 2-fluoro-3,5- di-tert-butyl-1,3,2-oxazaphospholene (F-OAP) and 2-chloro-di-tert-butyl- 1,3,2-oxazaphospholene (Cl-OAP). Bond length/Å F-OAP Cl-OAP P–O 1.645(9) 1.657(10) P–N 1.706(9) 1.698(15) N–C(4) 1.435(9) 1.398(13) C=C 1.344a 1.348(16) N–C(7) 1.494(9) 1.474(13) C–Ob 1.365(9) 1.392(27) Bond angle/° O–P–N 92.7(11) 94.5(12) P–N–C(4) 107.5(12) 108.7(19) C=C–N 112.4(16) 112.2(28) C=C–Ob 113.0(18) 115.0(23) P–O–Cb 112.1(20) 108.8(15) C(4)–N–C(7) 119.9(9) 121.7(21) Torsion angle/° O–P–N–C(4) 13.2(54) 8.4(16) X–P–N–C(4)b –90.4 –91.8 X–P–O–C(5)b 92.2 93.7 Received: 19th March 1999; Com. 99/1464

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Molecular complex of isosteviol with aniline Vladimir A. Alfonsov,* Galina A. Bakaleynik, Aidar T. Gubaidullin, Vladimir E. Kataev, Galina I. Kovyljaeva, Alexander I. Konovalov, Igor A. Litvinov, Irina Ju. Strobykina, Olga V. Andreeva and Maya G. Korochkina A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, 420088 Kazan, Russian Federation.Fax: +7 8432 75 2253; e-mail alfonsov@iopc.kcn.ru Isosteviol forms a crystalline molecular complex with aniline in the ratio 2:1, whose supramolecular structure looks like a double chiral helix cross-linked by aniline molecules. Earlier, we have isolated the glycoside stevioside1 and tetracyclic diterpenes of the kaurenic structure, steviol and isosteviol 1, from an extract of the plant Stevia rebaudiana Bertoni.2 We have examined the reactivity of these kaurenoids and the interaction of isosteviol 1 with aniline 2.Regardless of the reaction conditions, the interaction results in formation of crystal compound 3 with mp 225–228 °C, which consists of 1 and 2 in the ratio 2:1, according to elemental analysis.According to X-ray single-crystal diffraction data,†,3 isosteviol forms a molecular complex with aniline in the ratio 2:1. An asymmetric part of the unit cell of 3 contains two independent molecules of isosteviol 1a and 1b and a molecule of aniline 2. A proton of the amino group of aniline forms an intermolecular hydrogen bond with the carbonyl oxygen of the COOH group of 1a, and another, with the hydroxyl oxygen of the COOH group of a symmetrically transformed (1 – y, x, –1/4 + z) molecule of 1b'.In turn, each of the molecules of 1a † An Enraf-Nonius CAD4 diffractometer was used; crystals of 3 are tetragonal, at 20 °C a = 10.819(4), c = 35.169(3) Å, V = 4117(2) Å3, dcalc = = 1.27 g cm–3, Z = 8, space group P43, lCuKa radiation, w/2q scan, q £ 74.3°, 3577 reflections with I � 3s(I).The structure was solved by direct methods SIR,6 hydrogen atoms were solved from difference Fourier syntheses. Absolute structures were established by the Hamilton test ratio7 with a probability of 90%. R = 0.052 , wR = 0.065 for 3368 unique reflections. All calculations were carried out on a DEC Alpha Station 200 computer with the MolEN8 system. H-bonds, free volume calculations and PLUTO diagrams were performed using the PLATON program.9 and 1b' forms dimers with other isosteviol molecules by intermolecular H-bonding between protons of the COOH groups of 1a and 1b' and oxygen atoms of the keto groups of other molecules of 1b'' (1 + x, y, z) and 1a''' (1 – y, x – 1, –1/4 + z), respectively.Thus, two isosteviol molecules form a pseudocage structure of the ‘head-to-tail’ type (Figure 1). It is interesting that the amino group of aniline is a proton donor, and the COOH group of isosteviol is a proton acceptor in this compound. Note that a motif of hydrogen bonds results in the structure of a chiral double spiral of isosteviol molecules around the crystallographic axis 43 strands of which are cross-linked by amino groups of aniline molecules.Aniline molecules are located strictly at one side of the spiral (Figure 2). In turn, each chiral spiral interacts with others spirals by intermolecular H-bonding between isosteviol molecules (Figure 3). Because isosteviol is an enantiopure compound with the definite absolute configuration of all asymmetric centres (4R, 5S, 8R, 9S, 10S, 13S), all spirals in a crystal are only left-hand.Thus, the supramolecular structure of complex 3 shown in Figures 2 and 3, namely, the shape of a double helix and the alternation of acidic and basic functional groups, is somewhat similar to the structure of nucleic acids. Complex 3 is a host–guest compound like complexes of urea, cholic acid, etc.4,5 It is of interest that the calculated free volume, which is potentially accessible for a guest molecule in the unit cell of compound 3, is equal to 180 Å3, whereas it is only 39 Å3 in individual crystals of isosteviol.2 A molecule of aniline fits loosely into the cavity.Thus, large amplitudes of thermal vibrations of carbon atoms remote from the NH2 group are observed for aniline.Thus, isosteviol forms with aniline a crystal molecular complex in the ratio 2:1, which is characterised by (i) a supra- Me C H O HO Me Me O 1 1a 2 1b' 1b'' 1a''' H N O H H O O O O O O O O O H Figure 1 A motif of hydrogen bonds in the crystal structure of 3. 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Figure 2 Double helix of isosteviol molecules cross-linked by amino groups of aniline.Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) molecular structure of H-bonded chiral double spirals around the 43 axes, (ii) pseudocage structure of isosteviol dimers of the head-to-tail type and (iii) a system of hydrogen bonds, in which the NH2 group of aniline is a donor, and the COOH group of isosteviol is an acceptor of protons.References 1 K.C. Phillips, Dev. Sweeteners, 1987, 1. 2 V. A. Alfonsov, G. A. Bakaleynik, A. T. Gubaidullin, V. E. Kataev, G. I. Kovyljaeva, A. I. Konovalov, I. A. Litvinov and I. Ju. Strobykina, Zh. Obshch. Khim., 1998, 68, 1813 (Russ. J. Gen. Chem., 1998, 68, 1735). 3 V. A. Alfonsov, G. A. Bakaleynik, A. T. Gubaidullin, V. E. Kataev, G. I. Kovyljaeva, A. I. Konovalov, I. A. Litvinov, I. Ju. Strobykina, O. V. Andreeva and M. G. Korochkina, Zh. Obshch. Khim., submitted. 4 Cambridge Structural Database System, Version 5.14, November 1997, Cambridge. 5 M. Shibakami and A. Sekiya, J. Chem. Soc., Chem. Commun., 1994, 429. 6 A. Altomare, G. Cascarano, C. Giacovazzo and D. Viterbo, Acta Crystallogr., Sect. A, 1991, 47, 744. 7 W. C. Hamilton, Acta Crystallogr., 1965, 18, 502. 8 L. H. Straver and A. J. Schierbeek, MolEN. Structure Determination System, Nonius B.V., Delft, Netherlands, 1994, vols. 1 and 2. 9 A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46, 34. Figure 3 Intermolecular hydrogen bonds between isosteviol molecules in separate spirals (top view). Received: 22nd April 1999; Com. 99/14

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) 1,4-Dimethyl-2,5-dioxabicyclo[2.2.1]heptane-3,6-dione: optical resolution, absolute configuration and circular dichroism Igor V. Vystorop,*a Andrei N. Utienyshev,a Victor M. Anisimova and Remir G. Kostyanovsky*b a Institute for Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax: +7 096 515 3588; e-mail: vystorop@icp.ac.ru b N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow, Russian Federation. Fax: +7 095 938 2156; e-mail: kost@center.chph.ras.ru The title dilactone has been resolved into its enantiomers (+)-(S,S)-1 and (–)-(R,R)-1, whose absolute configurations were found by X-ray diffraction analysis of intermediate lactonic amide 2a; the magnitude of the n–p* Cotton effect increased with an increase in folding or a diminution in twist of the boat conformation of a dilactone ring.Optically active a,a'-dihydroxyglutaric acid dilactones are of interest as conformationally rigid model systems of C2 symmetry, 1 which provide an opportunity to perform a detailed analysis of the structure–chiroptical properties relationship in these compounds in order to reveal the structural characteristics that are responsible not only for the observed optical rotation sign, but also for the magnitude of the Cotton effect. Previously, we have developed a procedure2,3 for optical resolution of 1,4-di-tert-butyl dilactone (±)-3 and examined chiroptical properties of its enantiomers by the electronic (CD)2,3 and vibrational (VCD)4 circular dichroism methods. In this work, we have resolved dilactone of (±)-a,a'-dihydroxy- a,a'-dimethylglutaric acid (±)-1 (Zelinsky’s dilactone5,6) into its antipodes (Scheme 1)† by a modified procedure.The difference between this procedure and that described earlier2,3 for the resolution of dilactone (±)-3 consists in the ring opening in bicycle (±)-1 under the action of (S)-a-methylbenzylamine (MBA) to form acyclic diastereomers, which were converted into a mixture of monocyclic diastereomers 2a,b using an Amberlyst 15 cation exchanger.Diastereomerically pure lactonic amides 2a and 2b (d.e. > 98%, 1H NMR data) were separated by column chromatography (Scheme 1) followed by acid-catalysed cyclization into enantiomeric dilactones (+)-1 and (–)-1 (e.e.> 96%, Pirkle’s reagent7), respectively. The cyclization resulted in lower yields‡ as compared with the formation of di-tert-butyl antipodes (+)-3 (61%) and (–)-3 (64%) under similar conditions.3 The absolute configurations of all optically active compounds were determined from X-ray diffraction analysis data§ for highmelting isomer 2a (Figure 1), which possesses an asymmetric carbon atom C(8) with the known (S)-configuration. The characteristic feature of a molecule of 2a in a crystal (Figure 1) is that the g-lactone ring (phase angle10 y2 = 198.6°) has the shape of an almost ideal envelope (3E, y2 = 198°)11 stabilised by intermolecular H-bonds of the C(7)=O(4)···H(3)–O(3) type [the O(4)···H(3) and O(4)···O(3) distances are equal to 1.91 and 2.78 Å, respectively].The experimental long-wave Cotton effect for (–)-1 (Figure 2), associated with the dilactone n–p* transition,3 is negative; this fact is consisted with the optical activity calculations for (1R,4R)-1 (RHF/6-31G*//6-31+G*, Gaussian 92).2 Thus, we experimentally supported a correlation, which was suggested previously2,3 for bridging 1,4-dialkyl dilactones, between the sign of the n–p* Cotton effect and the inherent dilactone ring chirality of the boat enantiomeric form of the S-type11 [BS, (+)-j1 (O–CO–C–O), (–)-n–p* Cotton effect] or N-type11 [BN, (–)-j1, (+)-n–p* Cotton effect]. The CD spectra12 of conformationally flexible (S,S)-lactide 4 {De221 = –5.7 [(MeO)3P=O], De218 = –5.9 [(CF3)2CHOH)]} stabilised12 in the boat conformation (BS) by equatorial methyl groups are also consistent with this correlation. According to the octant projection of Klyne’s sector rule13 applied to either of the homotopic lactone groups of dilactones,3 the perturbation effects caused by the 1,4-dialkyl substituents, which are close to the symmetry plane of lactone chromophore [j(CAlk–C–C=O) = 10.4, 10.0 or –18.1° for 1, 3 or 4, respectively], § are generally small and mutually compensated.Moreover, the contribution of dilactone bridging bonds to the optical rotation is opposite to the observed sign of the n–p* Cotton effect. Therefore, not only the sign, but also the magnitude of the n–p* † Characteristics and spectroscopic data. IR spectra were measured on a Specord-80M spectrometer.NMR spectra were recorded on a Bruker WM-400 spectrometer (using TMS as an internal standard) at 400.13 (1H) and 100.62 MHz (13C) (data in square brackets were obtained under conditions of {2,4-Me}). Optical rotations were measured on a Polamat A polarimeter. CD spectra were taken on a Jasco J-500A spectropolarimeter with a DP-500N data processor. (1S,4S)-(+)-1: yield 28%, mp 97–98 °C.[cf. ref. 6 for (±)-1, mp 102– 104 °C], [a]D 18 = +130.0° (c 0.30, CHCl3), De = +9.895 (228 nm) (c 2.94×10–3 mol dm–3, MeOH). 1H NMR (CD3OD) d: 1.64 (s, 6H, 2Me), 2.63 (s, 2H, CH2). 1HNMR (C6D6) d: 0.94 (s, 2H, CH2), 1.07 (s, 6H, 2Me). (1R,4R)-(–)-1: yield 30%, mp 96–97 °C, [a]D 18 = –130.6° (c 0.31, CHCl3), De = –10.441 (228 nm) (c 2.67×10–3 mol dm–3, MeOH). 1H NMR spectral data for (+)-1 and (–)-1 in CDCl3 were identical to those for (±)-1 in ref. 6. (2S,4S,8S)-(–)-2a: yield 27.3%, mp 150–152 °C (benzene–hexane), Rf 0.30 (acetone–benzene, 1:3), [a]D 20 = –30.1° (c 0.73, CHCl3), De = +1.748 (228 nm), De = –2.817 (216 nm) (c 15.6×10–3 mol dm–3, MeOH). 1HNMR (CDCl3) d: 1.48 (d, 3H, MeCH, 3J 6.9 Hz), 1.55 (s, 3H, Me-2), 1.60 (s, 3H, Me-4), 2.09 and 3.00 (dd, 2H, CH2, 2JAB –14.1 Hz), 2.60 (br.s, 1H, OH), 5.09 (m, 1H, MeCH), 6.78 (br. d, 1H, NH, 3J 8.1 Hz), 7.29–7.35 (m, 5H, Ph). 13C NMR (CDCl3) d: 21.39 (dq, MeCH, 1J 127.9 Hz, 2J 3.6 Hz), 24.07 (dq, Me-2, 1J 129.3 Hz, 3JH(1) 4.4 Hz), 25.38 (dq, Me-4, 1J 129.3 Hz, 3JH(1) 4.4 Hz), 46.71 [ddm, CH2, 1JH(1) 130.8 Hz, 1JH(2) 138.1 Hz], 48.88 (dm, CHPh, 1J 141.0 Hz, J 2.9 Hz), 73.59 [br.d, C(2), J 5.8 Hz], 83.11 [m, C(4)], 125.99 (dm, o-CPh, 1J 159.0 Hz), 127.41 (dt, p-CPh, 1J 160.1 Hz), 128.63 (dd, m-CPh, 1J 160.2 Hz), 142.46 (m, i-CPh), 171.37 (m, CONH, 3JH(1) 6.0 Hz, J 5.0 and 3.5 Hz), 176.60 (m, ring C=O, [br. d, 3JH(2) 5.8 Hz, 3JH(1) 0.5 Hz]). IR (CH2Cl2, n/cm–1): 3680 (OH), 3424 (NH), 1788 (ring C=O), 1678 (C=O, amide I), 1520 (d, NH, amide II), 1184, 1126, 1054, 964, 860.(2R,4R,8S)-(–)-2b: yield 15.3%, mp 72–74 °C (hexane), (Rf 0.48), [a]D 20 = –31.8° (c 0.54, CHCl3), De = –9.848 (216 nm) (c 0.024 mol dm–3, MeOH). 1H NMR (CDCl3) d: 1.39 (s, 3H, Me-2), 1.47 (d, 3H, MeCH, 3J 6.9 Hz), 1.61 (s, 3H, Me-4), 1.98 and 2.88 (dd, 2H, CH2, 2JAB –14.1 Hz), 3.60 (br. s, 1H, OH), 5.07 (m, 1H, MeCH), 6.69 (br.d, 1H, NH, 3J 7.8 Hz), 7.20–7.29 (m, 5H, Ph). 13C NMR (CDCl3) d: 21.63 (dq, MeCH, 1J 128.2 Hz, 2J 3.6 Hz), 23.91 (dq, Me-2, 1J 128.1 Hz, 3JH(1) 2.9 Hz), 25.64 (dq, Me-4, 1J 129.4 Hz, 3JH(1) 5.2 Hz), 46.46 (ddm, CH2, 1JH(1) 132.7 Hz, 1JH(2) 137.2 Hz, 3JMe 3.5 Hz), 48.79 (dm, CHPh, 1J 140.8 Hz), 73.53 (m, C2, 2J 5.2 Hz, 2J 5.0 Hz), 83.15 (dm, C4, 2J 4.9 Hz), 126.02 (dm, o-CPh, 1J 158.0 Hz, J 3.8 Hz), 127.29 (dt, p-CPh, 1J 160.2 Hz, J 3.2 Hz), 128.53 (dd, m-CPh, 1J 160.6 Hz, J 4.7 Hz), 142.35 (m, i-CPh), 171.32 (m, CONH), 176.64 (m, ring C=O).IR (CH2Cl2, n/cm–1): 3680 (OH), 3428 (NH), 1786 (ring C=O), 1678 (C=O, amide I), 1522 (d, NH, amide II), 1186, 1128, 1054, 964, 860. O O O O But But O O O O But But H Me H Me O O 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 O 7O 8 (+)-(1R,4R)-3, (BN) (–)-(1S,4S)-3, (BS) (+)-(1S,4S)-4, (BS)Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Cotton effect are probably related to the stereochemistry of the dissymmetric dilactone chromophore. In contrast to the experimental VCD spectra4 of dilactones (–)-1 and (–)-3, the similarity of their CD spectra (Figure 2), as well as the spectra of (S,S)-4,12 allowed us to analyse the influence of structural features of their monocyclic dilactone rings upon the magnitude of the Cotton effect.The latter is proportional to the rotatory strength for the CD bands having almost Gaussian shapes (Figure 2). A comparison of the geometric models§ of homochiral bicyclic dilactones (R,R)-1 and (S,S)-3 and slightly distorted monocyclic dilactone (S,S)-4 demonstrates that the enantiomeric boat form (BS) of a dilactone ring for these molecules (y2 = 270.4, 271.1 or 277.7° for 1, 3 or 4, respectively) is similar to the canonical boat shape (y2 = 270°).11 As follow from a comparison of the molecular structures of dimethyl dilactones (R,R)-1 and (S,S)-4, the introduction of a ‡ Crystallographic data for 2a: C15H19NO4, M = 277.31, orthorhombic crystals, space group P212121, 293(2) K, a = 19.368(4), b = 9.889(2), c = 7.944(2) Å, V = 1521.5(6) Å3, dcalc = 1.211 g cm–3, Z = 4.Intensities of 1891 reflections were measured on an automatic KM-4 four-circle diffractometer (lMoKa radiation, 2.10° < q < 97.02°). The structure was solved by a direct method (SHELXS-868) and refined using the fullmatrix least-squares procedure (SHELXL-939) in the anisotropic approximation for all non-hydrogen atoms.Hydrogen atoms were located from the difference Fourier synthesis with the exception of the hydrogens of the methyl groups, the positions of which were calculated and included in the further refinement using a riding motion model. The refinement is converged to wR2 = 0.1053 and GOF = 1.024 for all independent reflections [R1 = 0.040 is calculated against F for 1001 observed reflections with I > 2s(I)].Atomic coordinates, bond lengths, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details, see ‘Notice to Authors’, Mendeleev Commun., 1999, Issue 1. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/56.§ The geometry of dilactones (R,R)-1, (S,S)-3 and (S,S)-4 was completely optimised at the ab initio theoretical level of the second-order Møller– Plesset (MP2) theory with the conventional 6-31G* basis set using procedures implemented in the Gaussian 94 program package.14 Convergence criteria for the density matrix were set to 1×10–8.All calculations were performed on an SGI Power Challenge computer. The calculated energies (in hartrees) and dipole moments (in debyes) are (1) –570.80912 and 5.622, (3) –805.82048 and 5.175, or (4) –532.80678 and 3.362, respectively. bridge is accompanied by a close approach of C(1) and C(4) atoms to each other [distances of (1) 2.20 and (4) 2.66 Å], and by a decrease in the angle between the planes of O(2)C(1)C(6) and O(5)C(4)C(3) groups [w1 = (1) 52.3 or (4) 81.3°] or ester groups (O–C=O) [w2 = (1) 109.8 or (4) 137.3°]. Therefore, in general, this leads to an increase in the dilactone ring folding {folding amplitude10 S2 = (1) 1.132 or (4) 0.795; j1 [O–C(=O)– C–O] = (1) 69.2 or (4) 42.8°}, and also to an approach of carbonyl groups to each other [the C(3)···C(6) distance is (1) 2.73 or (4) 2.82 Å; the O(8)···O(9) distance is 4.84 Å (1) and the O(7)···O(8) distance is 5.14 Å (4)].However, an increase in the volume of 1,4-alkyl substituents in the conformationally rigid bridged dilactone structure leads to a negligible decrease of the dilactone ring folding in (S,S)-3 [S2 = 1.128, j1 = 68.2°, the C(1)···C(4) distance is 2.22 Å, the C(3)···C(6) distance is 2.74 Å, the O(8)···O(9) distance is 4.86 Å, w1 = 53.2° and w2 = 110.4°], as compared with that in 1.Moreover, an increase in the twist angle of the dilactone ring for 3 {j0[C–O–C(=O)–C] = 1.8°} and 4 (j0 = 7.3°), as compared with that for 1 (j0 = 0.9°), is probably responsible for a noticeable change in the relative orientation of carbonyls [the projected dihedral angle j2 (O=C···C=O) = (1) –34.5, (3) –27.6 or (4) –20.0°].Scheme 1 Reagents and conditions: i, (S)-a-MBA, room temperature, 120 h, 74.5%; ii, Amberlyst 15 (H+ form, Fluka)/CHCl3, room temperature, 48 h, 79.5%; iii, column chromatography, silica gel (60 Å, 200–125 mesh, Aldrich), acetone–benzene (1:3); iv, TsOH–toluene, reflux, 5 h, then sublimation (50–60 °C/15 Torr).O O O O Me Me 1 2 3 4 7 9 5 6 8 H1 H2 OH Me C7(O)NH O O Me C Ph Me H O O O O Me Me H1 H2 HO Me C7(O)NH O O Me C Ph Me H O O Me Me O O (–)-(2S,4S,8S)-2a (–)-(2R,4R,8S)-2b (±)-1 i–iii iv iv (+)-(1S,4S)-1, (BN) (–)-(1R,4R)-1, (BS) 1 1 2 2 3 3 4 4 8 8 H(1) H(2) H(3) C(2) C(3) C(5) O(3) C(1) O(1) C(4) C(6) C(7) O(4) H(4) N H(8) C(8) C(9) C(10) H(15) C(15) C(11) H(11) O(2) C(14) H(14) C(13) H(13) C(12) H(12) Figure 1 Molecular structure of lactonic amide 2a.Selected bond lengths (Å): O(1)–C(1) 1.351(5), O(1)–C(4) 1.461(4), C(1)–C(2) 1.519(5), O(2)– C(1) 1.199(4), O(4)–C(7) 1.228(4), N–C(7) 1.332(5) C(4)–C(7) 1.524(6); selected bond and dihedral angles (°): O(1)–C(1)–O(2) 120.7(4), O(1)– C(1)–C(2) 111.0(3), O(2)–C(1)–C(2) 128.3(4), N–C(7)–O(4) 122.9(4), N– C(7)–C(4) 116.6(3), O(4)–C(7)–C(4) 120.4(3), C(2)–C(1)–O(1)–C(4) –0.1 (j0), O(1)–C(1)–C(2)–C(3) 17.1, C(1)–C(2)–C(3)–C(4) –26.4, C(2)–C(3)– C(4)–O(1) 27.3, C(3)–C(4)–O(1)–C(1) –17.2. 10 8 6 4 2 0 –2 –4 –6 –8 –10 l/nm De 200 220 240 260 280 1 2 3 Figure 2 CD spectra of enantiomers (1) (+)-(S,S)-1, (2) (–)-(R,R)-1 and (3) (–)-(S,S)-3 (De = –7.861, lmax = 231 nm) in MeOH.Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Therefore, both an increase in the folding and a decrease in the twist angle of the boat conformation of a dilactone ring, which decrease the distance and increase the skew angle between carbonyl groups, respectively, can be considered as the geometric factors responsible for increasing magnitude of the n–p* Cotton effect.The calculations (CNDO–SCFMO)15 of the optical activity of a glyoxal molecule resulted in a similar relationship between the relative disposition of equivalent carbonyl groups and the calculated rotatory strength of the ketone n–p* transition. In summary, we conclude that both the sign and the magnitude of the n–p* Cotton effect of the dilactones reflect inherent dissymmetry springing in chiral distortions of the dilactone ring, which, therefore, can be considered as an inherently dissymmetric chromophore.16 Note that the observed relations between the sign or magnitude of the n–p* Cotton effect and the spatial arrangement of the lactone group [i.e., the sign or magnitude of the twist angle (j0), respectively] are opposite to the corresponding relations for the lactam chromophore [(–)-j0, (–)-n–p* Cotton effect and vice versa],17 for which the enforced n–p* Cotton effect is observed with increasing the twist angle (j0).This work was supported by the Russian Foundation for Basic Research (grant nos. 97-03-33021 and 98-07-90290). References 1 W. Hug and G. Wagniere, Tetrahedron, 1972, 28, 1241. 2 I. V. Vystorop, G. V.Shustov, A. Rauk and R. G. Kostyanovsky, Mendeleev Commun., 1994, 97. 3 I. V. Vystorop and R. G. Kostyanovsky, Izv. Akad. Nauk, Ser. Khim., 1998, 108 (Russ. Chem. Bull., 1998, 47, 107). 4 A. Rauk, J. L. McCann, H. Wieser, P. Bour, I. V. Vystorop, Yu. I. El’natanov and R. G. Kostyanovsky, Can. J. Chem., 1998, 76, 717; Correction: Can. J. Chem., 1998, 76, 1931. 5 N. D. Zelinsky, Ber., 1891, 24, 4006. 6 R. G. Kostyanovsky, V. P. Leshchinskaya, Yu. I. El’natanov, A. E. Aliev and I. I. Chervin, Izv. Akad. Nauk SSSR, Ser. Khim., 1989, 408 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1989, 38, 355). 7 W. H. Pirkle, D. L. Sikkenga and M. S. Pavlin, J. Org. Chem., 1977, 42, 384. 8 G. M. Sheldrick, Acta Crystallogr., 1990, A46, 467. 9 G. M. Sheldrick, SHELXL-93, Program for Crystal Structure Refinement, University of Göttingen, D-37077, Germany, 1993. 10 N. S. Zefirov and V. A. Palyulin, Dokl. Akad. Nauk SSSR, 1980, 252, 111 [Dokl. Chem. (Engl. Transl.), 1980, 252, 207]. 11 I. V. Vystorop, A. Rauk, C. Jaime, I. Dinares and R. G. Kostyanovsky, Khim. Geterotsikl. Soedin., 1995, 1479 [Chem. Heterocycl. Compd. (Engl. Transl.), 1995, 31, 1280]. 12 C. Toniolo, V. Perciaccante, J. Falcetta, R. Rupp and M. Goodman, J. Org. Chem., 1970, 35, 6. 13 J. P. Jennings, W. Klyne and P. M. Scopes, J. Chem. Soc., 1965, 7211, 7229. 14 M. J. Frisch, G.W. Trucks, H. B. Schlegel, P. M.W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Manayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M.W.Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian 94, Revision D.1, Gaussian, Inc., Pittsburgh PA, 1995. 15 W. Hug and G. Wagniere, Theor. Chim. Acta, 1970, 18, 57. 16 C. W. Deutsche, D. A. Lightner, R. W. Woody and A. Moscowitz, Ann. Rev. Phys. Chem., 1969, 20, 407. 17 D. N. Kirk, Tetrahedron, 1986, 42, 777. Received: 21st July 1999; Com. 99/1520

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年代:1999

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) A route to fluorocontaining 1,3-thiazolines via internal polyfluorooxiranes Lyudmila V. Saloutina, Aleksandr Ya. Zapevalov, Mikhail I. Kodess, Viktor I. Saloutin* and Oleg N. Chupakhin Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation. Fax: +7 3432 74 5954; e-mail: saloutin@ios.uran.ru The reaction of internal fluoroolefin oxides with thiourea results in 2-amino-5-fluoro-4-hydroxy-4,5-di(polyfluoroalkyl)-1,3- thiazolines, providing a route to an unknown type of fluorine-containing thiazolines with two fluoroalkyl substituents.Recently, we have shown that oxides of internal fluoroolefins, in contrast with hexafluoropropylene oxide,1 give heterocyclic compounds, polyfluoroalkylated diazinols and oxazinols, when they are treated with ethylenediamine or 2-aminoethanol, respectively. 2 However, other reactions of the former compounds with nucleophiles containing more than one functional group, are unknown.We describe here the interaction of polyfluoro-2,3-epoxyalkanes 1 and 2a,b3 with thiourea. We found that the reaction does not occur under mild conditions reported for terminal fluorooxiranes, which easily interact with thiourea resulting in 5-fluoroalkyl-4-oxothiazolines.4 The interaction of 1 and 2a,b with thiourea was carried out at elevated temperature (70–90 °C, sealed tubes in the case of 1, 2a) at the molar ratio oxirane:thiourea = 1:3 using MeOH, DMSO or DMF as a solvent.As a result, 2-amino-5-fluoro-4-hydroxy-4,5-di(polyfluoroalkyl)- 1,3-thiazolines 3,†,‡ 4a, 5a, 4b and 5b§ were obtained.Symmetrical octafluoro-2,3-epoxybutane 1 (E:Z ~ 90:10) reacting with thiourea gave one regioisomer, 2-amino-5-fluoro- 4-hydroxy-4,5-bis(trifluoromethyl)-1,3-thiazoline 3. We found stereoisomer (E)-3 to be the principal product along with 2–8% of (Z)-3 when the reaction was carried out both in DMF and in MeOH (Scheme 1, Table 1).The reaction of unsymmetrical oxiranes 2a (E:Z ~ 90:10) and 2b (E:Z ~ 85:15) with thiourea afforded mixtures of regioisomers 4a, 5a and 4b, 5b in the E-form as major products and those in the Z-form as minor products (Scheme 2, Table 1). The structural assignment for (E)-3 and (Z)-3 was made on the basis of their 19F NMR spectra¶ by comparison of the coupling constants 4J(F5',F6') and 5J(F6',F7') of the formers.Thus, the coupling constant 4J(F5',F6') in (E)-3 is considerably † All new compounds (E)-3, (E)-4a,b and (E)-5a gave satisfactory elemental analyses and were characterised by IR (Vazeline oil), 19F NMR (75.3 MHz, [2H6]acetone, C6F6) and 1H NMR (100 MHz, [2H6]acetone, Me4Si) spectroscopy and mass spectrometry; compound (E)-3, additionally, by 13C NMR spectroscopy (20.1 MHz, [2H6]acetone, Me4Si). ‡ 2-Amino-5-fluoro-4-hydroxy-4,5-bis(trifluoromethyl)-1,3-thiazoline (E)-3 (typical procedure).A mixture of oxirane 1 (E:Z ~ 90:10) (4.1 g, 19 mmol), thiourea (4.3 g, 56.6 mmol) and DMF (10 ml) was heated in a sealed tube for 2 h at 70–75 °C (water bath) with intermittent shaking.After cooling, the tube was opened and the reaction mixture was poured into water (50 ml). The resulting precipitate was collected by filtration and washed with a small amount of water. The solid residue was dissolved in water (120 ml) and filtered to remove an insoluble material. The filtrate was extracted with diethyl ether; the organic layer was dried over MgSO4 and evaporated.The solid residue was recrystallised from benzene to give (E)-3. greater (21.5 Hz) than that in (Z)-3 (3.9 Hz). In contrast, compound (Z)-3 exhibited a greater coupling constant 5J(F6',F7') (11.7 Hz) than that in (E)-3 (5.4 Hz). This fact can be explained by the geometrical vicinity of the interacting nuclei [CF5' and CF3 6' in (E)-3; CF3 6' and CF3 7' in (Z)-3] resulting in a rise of through-space scalar coupling along with the through-bond transmitted coupling between the latters.Analogous regularities were reported for the coupling constants 4JF,F and 5JF,F of (E)- and (Z)-isomers of internal fluorooxiranes.5 The assignment of the 19F NMR spectra for (E)- and (Z)- isomers of 4a,b and 5a,b was made by comparison with those of (E)-3, (Z)-3.The (E)-configuration of 4a,b was determined from the greater coupling constant 4J(F5',F9') (21 Hz) as compared with that in 4a,b having the (Z)-configuration (3.9 Hz). The (E)-configuration of 5a,b was inferred from the large coupling constant 4J(F5',FA 6 ' ) (41–41.5 Hz). The coupling between these § (E)-3: yield 64% (MeOH), 37% (DMF); mp 158–159 °C (from benzene). 1H NMR, d: 7.38 (br.s, 2H, NH2), 6.83 (s, 1H, OH). 19F NMR, d: 93.1 (dq, 3F, CF3 7' ), 86.4 (dq, 3F, CF3 6' ), 20.1 (qq, 1F, CF5' ); 4J5',6' 21.5 Hz, 3J5',7' 10.3 Hz, 5J6',7' 5.4 Hz. 13C NMR, d: 161.4 (C2), 123.7 (C6, 1J 287.5 Hz), 122.7 (C7, 1J 283.2 Hz, 2J7,5' 34.8 Hz), 116.9 (C5, 1J 143.2 Hz, 2J5,7' 30.8 Hz), 104.7 (C4, 2J4,6' 30.5 Hz, 2J4,5' 23.8 Hz). IR, n/cm–1: 3470, 3370 (NH), 3050 (br., OH, NH), 1640 (C=N), 1625, 1575 (NH).MS, m/z: 272 (M+). 2-Amino-5-fluoro-5-heptafluoropropyl-4-hydroxy-4-trifluoromethyl-1,3- thiazoline (E)-4a: yield 35% (MeOH), 17% (DMSO); mp 157–158 °C (from benzene). 1H NMR, d: 7.35 (br. s, 2H, NH2), 6.72 (s, 1H, OH). 19F NMR, d: 87.2 (t, 3F, CF3 9' ), 83.1 (ddd, 3F, CF3 8' ), 57.2 (tq, 1F, CFA 6 ' ), 45.2 (m, 1F, CFB 6 ' ), 42.2 (dd, 1F, CFA 7 ' ), 40.1 (t, 1F, CFB 7 ' ), 20.7 (m, 1F, CF5' ); J6'A,6'B 289.1 Hz, J7'A,7'B 288.1 Hz; 4J5',7'A 24.4 Hz, 4J5',9' = 5J6'B,9' = 21.0 Hz, 4J6'A,8' 13.7 Hz, 4J6'B,8' 9.8 Hz.IR, n/cm–1: 3470, 3370 (NH), 3010 (br., OH, NH), 1645 (C=N), 1625, 1585 (NH). MS, m/z: 372 (M+). 2-Amino-5-fluoro-5-(1,1,2,2,3,3-hexafluoropropyl)-4-hydroxy-4-trifluoromethyl- 1,3-thiazoline (E)-4b: yield 23% (DMSO), mp 122–123 °C (from benzene). 1H NMR, d: 7.18 (br. s, 2H, NH2), 6.60 (tt, 1H, HCF2), 6.51 (s, 1H, OH). 19F NMR d: 87.2 (t, 3F, CF3 9' ), 56.2 (tt, 1F, CFA 6 ' ), 44.0 (m, 1F, CFB 6 ' ), 37.4 (ddq, 1F, CFA 7 ' ), 35.2 (ddq, 1F, CFB 7 ' ), 26.0 (dm, 2F, CF2 8' ), 21.4 (m, 1F, CF5'); J6'A,6'B 289.6 Hz, J7'A,7'B 284.4 Hz; 2J8',H 51.6 Hz, 5J6'B,9' = 4J5',9' = 4J5',7'A = 21.0 Hz, 3J7',8' = 3J7',H = 5.9 Hz.IR, n/cm–1: 3465, 3370 (NH), 3050 (br., OH, NH), 1645 (C=N), 1625, 1585 (NH). MS, m/z: 354 (M+). 2-Amino-5-fluoro-4-heptafluoropropyl-4-hydroxy-5-trifluoromethyl-1,3- thiazoline (E)-5a: yield 16% (MeOH), 105–107 °C (obtained by reprecipitation from MeOH by water). 1HNMR, d: 7.22 (br. s, 2H, NH2), 6.65 (s, 1H, OH). 19F NMR, d: 93.6 (ddd, 3F, CF3 9' ), 83.0 (t, 3F, CF3 8' ), 48.8 (dm, 1F, CFA 6 ' ), 44.9 (m, 1F, CFB 6 ' ), 43.0 (t, 1F, CFA 7 '), 40.6 (t, 1F, CFB 7 '); 20.0 (m, 1F, CF5' ), J7'A,7'B 285.6 Hz, J6'A,6'B 282.2 Hz, 4J5',6'A 41.0 Hz, 5J6'B,9' 13.7 Hz, 3J5',9' = 4J6',8' = 9.8 Hz, 5J6'A,9' 3.9 Hz.IR, n/cm–1: 3510– 3150 (OH, NH), 1670, 1650, 1600 (NH, C=N). ¶ (Z)-3: 19F NMR, d: 92.2 (dq, 3F, CF3 7' ), 85.0 (qd, 3F, CF3 6' ), 26.3 (qq, 1F, CF5' ); 3J5',7' = 5J6',7' = 11.7 Hz, 4J5',6' 3.9 Hz.(Z)-4a: 19F NMR, d: 86.3 (td, 3F, CF3 9' ), 83.2 (m, 3F, CF3 8' ), 51.5 (m, 1F, CFA 6 ' ), 42.9 (m, 1F, CFB 6 ' ), 40.9 (dt, 2F, CF2 7' ), 27.7 (m, 1F, CF5' ); J6'A,6'B 287.1 Hz, 4J5',7' 20.5 Hz, 5J6',9' 18.6 Hz, 5J5',8' = 4J5',9' = 3J6',7' = = 3.9 Hz. (Z)-5a: 19F NMR, d: 93.6 (ddd, 3F, CF3 9' ), 83.0 (t, 3F, CF3 8' ), 43.4 (m, d6'A6'B), 41.9 (t, 2F, CF2 7' ), 29.3 (q, 1F, CF5'); 5J6'B,9' 20.5 Hz, 5J6'A,9' 16.6 Hz, 3J5',9' 12.7 Hz, 3J6',7' 2.9 Hz.(E)-5b: 19F NMR, d: 93.2 (dd, 3F, CF3 9' ), 45.6 (dm, 1F, CFA 6 ' ), 39.3 (m, 1F, CFB 6' ), 38.1 (m, 1F, CFA 7 ' ), 35.0 (m, 1F, CFB 7 ' ), 26.0 (dm, 2F, CF2 8' ), 19.2 (m, 1F, CF5'); J7'A,7'B 277.5 Hz, J6'A,6'B 275.2 Hz, 2J8',H 51.6 Hz, 4J5',6'A 41.5 Hz, 3J7',H 5.9 Hz.Scheme 1 Reagents and conditions: i, MeOH, NH2CSNH2 (a three-fold excess), sealed tube, 70–75 °C, 2 h; ii, DMF, NH2CSNH2 (a three-fold excess), sealed tube, 70–75 °C, 2 h. FC CF O CF3 F3C Nu 1 CF3 F F F3C O NH S NH2 H+ S N F CF3 OH F3C NH2 1 2 3 4 5 6 6' 7 7' 5' – HF 3 i, iiMendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) atoms in (Z)-5a,b was not observed.As can be seen in Table 1, the fraction of the reaction products in the (Z)-form increases with increasing fraction of the (Z)-isomer in the starting oxirane. Note that the nature of the solvent influences the relative amounts of the resulting stereoisomers. When the reaction of 2a [(E):(Z) ~ 60:40] was performed in DMSO, the total molar ratio (E):(Z) of 4a and 5a had nearly the same value as in the starting oxirane: [(E)-4a+(E)-5a]: [(Z)-4a+(Z)-5a] ~ 63:37.At the same time, in MeOH, the relative quantity of (Z)-thiazolines decreased: [(E)-4a+(E)-5a]:[(Z)-4a+ +(Z)-5a] ~ 76:24. It is evident that the reaction is stereospecific for both (E)- and (Z)-oxiranes when it is carried out in DMSO, and the predominant formation of (E)-thiazolines is observed in the presence of MeOH.Individual thiazolines (E)-3, (E)-4a,b and (E)-5a were isolated as stable colourless crystals by recrystallization or reprecipitation from corresponding isomer mixtures. Thus, we have developed an approach to the synthesis of functionalised 1,3-thiazolines with two fluoroalkyl substituents, which are of interest as biologically active compounds6 and new convenient building blocks for complex heterocyclic systems.References 1 H. Kawa, H. A. Hamouda and N. Ishikawa, Bull. Chem. Soc. Jpn., 1980, 53, 1694. 2 L. V. Saloutina, A. Ya. Zapevalov, M. I. Kodess and V. I. Saloutin, J. Fluorine Chem., 1998, 87, 49. 3 (a) I. P. Kolenko, T. I. Filyakova, A. Ya. Zapevalov and E. P. Lurye, Izv. Akad. Nauk SSSR, Ser. Khim., 1979, 2509 (Bull.Acad. Sci. USSR, Div. Chem. Sci., 1979, 28, 2323); (b) L. V. Saloutina, M. I. Kodess and A. Ya. Zapevalov, Zh. Org. Khim., 1993, 29, 1325 (Russ. J. Org. Chem., 1993, 29, 1097). 4 I. L. Knunyants, V. V. Shokina and I. V. Galakhov, Khim. Geterotsikl. Soedin., 1966, 873 [Chem. Heterocycl. Compd. (Engl. Transl.), 1966, 666]. 5 (a) A. Ya. Zapevalov, T. I. Filyakova, I.P. Kolenko, N. V. Peschanskii and M. I. Kodess, Zh. Org. Khim., 1984, 20, 2267 [J. Org. Chem. USSR (Engl. Transl.), 1984, 20, 2066]; (b) T. I. Filyakova, N. V. Peschanskii, M. I. Kodess, A. Ya. Zapevalov and I. P. Kolenko, Zh. Org. Khim., 1988, 24, 371 [J. Org. Chem. USSR (Engl. Transl.), 1988, 24, 327]. 6 A. M. M. Abdelal, S. M. M. Kheira and F. A. Badria, Sci. Pharm., 1997, 65, 99. Table 1 Composition and molar ratios of the products of the reaction of oxiranes 1 and 2a,b with thiourea at the molar ratio oxirane:thiourea = 1:3 (from 19F NMR data).Starting oxirane (E:Z) Solvent Reaction products (molar ratio) 1 (90:10) DMF (E)-3, (Z)-3 (92:8) 1 (90:10) MeOH (E)-3, (Z)-3 (98:2) 2a (90:10) DMSO (E)-4a, (Z)-4a, (E)-5a, (Z)-5a (51: 7:39: 3) 2a (90:10) MeOH (E)-4a, (Z)-4a, (E)-5a, (Z)-5a (59: 2:39: 1) 2a (60:40) MeOH (E)-4a, (Z)-4a, (E)-5a, (Z)-5a (43:16:33: 8) 2a (60:40) DMSO (E)-4a, (Z)-4a, (E)-5a, (Z)-5a (36:26:27:11) 2a (85:15) DMSO (E)-4b, (Z)-4b, (E)-5b, (Z)-5b (76: 9:13: 2) S N RF OH F CF3 NH2 5' 9' O RF F CF3 F S N F RF CF3 HO NH2 5' 9' i–iii i–iii 4a,b 5a,b 2a,b Nu Path A Path B a RF = CF2CF2CF3 b RF = CF2CF2CF2H 6' 7' 8' 6' 7' 8' Scheme 2 Reagents and conditions: i, 2a, NH2CSNH2 (a three-fold excess), MeOH, sealed tube, 85–90 °C, 3 h; ii, 2a, NH2CSNH2 (a threefold excess), DMSO, sealed tube, 85–90 °C, 10 h; iii, 2b, NH2CSNH2 (a three-fold excess), DMSO, 60–65 °C, 1.5 h. Received: 15th February 1999; Com. 99/1443

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年代:1999

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Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) First example of cine-substitution for halogens in azolopyrimidines Gennady L. Rusinov,* Pavel V. Plekhanov, Anna U. Ponomareva and Oleg N. Chupakhin Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation. E-mail: rusinov@ios.uran.ru 6-Bromo-1,2,4-triazolo[1,5-a]pyrimidine reacts with indoles in the presence of BF3 to form sH-adducts, which undergo aromatization on treatment with triethylamine.Nucleophilic substitution of hydrogen has currently become a successfully developed methodology for the introduction of electron-rich aromatic and heteroaromatic fragments into the pyrimidine ring. Usually, the SN H processes proceed through the formation of sH-adducts, which can be aromatised either by oxidation or via auto-aromatization facilitated by auxiliary groups (cine-, tele- and vicarious substitution).1 These processes can successfully compete with the SN ipso substitution, because the primary kinetically controlled nucleophilic attack on heteroarenes is always directed at an unsubstituted carbon atom.While studying the interaction of nucleophilic agents with 6-bromo-1,2,4-triazolo[1,5-a]pyrimidine 2 derived from direct bromination of 1, it has been found that the bromine atom can be replaced by cycloalkylimine moieties, although Br in this position of the pyrimidine ring was previously considered as a bad nucleofugal group.2 Thus, we have first succeeded to perform the synthesis of 6-morpholino- and 6-piperidino-1,2,4- triazolo[1,5-a]pyrimidines 3a,b.† Compound 2 was expected to react with C-nucleophilic indoles 4a,b to form 6-indolylsubstituted azolopyrimidines. However, we found that indoles attack the C-7 position of 2, yielding corresponding 6-bromo- 7-indolyl-substituted 4,7-dihydrotriazolopyrimidines 5a,b.‡ The reaction proceeds smoothly at room temperature in the presence of catalytic amounts of BF3.Final products 5a,b are stable crystalline compounds. Compounds 5a,b were found to undergo aromatization under basic conditions (triethylamine in boiling acetonitrile) to give 7-(indol-3-yl)triazolopyrimidine 6a and 7-(1-methylindol-3-yl)triazolopyrimidine 6b.§ The overall transformation of compound 2 into 6a,b is an example of the cinesubstitution which proceeds as a step-by-step reaction.It seems to be the first example of isolation of a key intermediate in the course of cine-substitution. Note that, contrary to the majority of the well-known cases of cine-substitution, an alternative aryne mechanism is completely excluded in the above examples. In general, the mechanism suggested is similar to the classical cine-substitution in the 5-halopyrimidine series.3 The aromatization of adducts 5a,b is likely preceeded by their conversion into 6,7-dihydrotriazolopyrimidines 7a,b.Some examples of similar tautomeric transformations in the 4,7-dihydropyrimidine series have been reported previously.4 On the other hand, we have found this procedure to be useful for the introduction of † The 1H NMR spectra were recorded in [2H6]DMSO solutions using a Tesla BS 587A spectrometer at 80 MHz. 6-Morpholino-1,2,4-triazolo[1,5-a]pyrimidine 3a. Compound 2 (0.5 mmol, 99 mg) was refluxed in morpholine (2.5 ml) for 3 h, the mixture was evaporated in vacuo and residue was recrystallised from toluene. Yield 90 mg (88%), mp 203–204 °C. 1H NMR, d: 8.98 (d, 1H, H5, J5,7 2.8 Hz), 8.81 (d, 1H, H7), 8.49 (s, 1H, H2), 3.84–3.72 (m, 4H, H3',H5'), 3.25–3.13 (m, 4H, H2',H6').Found (%): C, 52.35; H, 5.69; N, 33.95. Calc. for C9H11N5O (%): C, 52.69; H, 5.41; N, 34.14. 6-Piperidino-1,2,4-triazolo[1,5-a]pyrimidine 3b. Prepared in a manner similar to that described for 3a from compound 2 and piperidine. Yield 25%, mp 110–112 °C. 1H NMR, d: 8.95 (d, 1H, H5, J5,7 2.8 Hz), 8.75 (d, 1H, H7), 8.46 (s, 1H, H2), 3.17 (m, 4H, H2', H6'), 1.59 (m, 6H, H3', H4',H5' ).Found (%): C, 59.21; H, 6.66; N, 34.40. Calc. for C10H13N5 (%): C, 59.10; H, 6.45; N, 34.46. ‡ 6-Bromo-7-(indol-3-yl)-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine 5a. Indole 4a (1.5 mmol, 175.5 mg) and 6-bromotriazolopyrimidine 2 (1.5 mmol, 299 mg) was dissolved in methanol (7 ml), several drops of BF3·OEt2 were added and the mixture was kept for 5 h at room temperature.The precipitate formed was filtered off, washed with 95% ethanol and dried to yield 290 mg (61%) of 5a. Mp 169–172 °C (from methanol). 1H NMR, d: 11.12 (br. s, 1H, NH), 10.12 (d, 1H, NH, J4,5 3.6 Hz), 7.50 (s, 1H, H2), 7.49 (d, 1H, H2'), 7.37 (d, 1H, H7'), 7.21 (d, 1H, H4' ), 7.1–6.9 (m, 3H, H5', H6', H5), 6.37 (s, 1H, H7).Found (%): C, 49.25; H, 3.05; N, 22.11. Calc. for C13H10N5Br (%): C, 49.37; H, 3.16; N, 22.15. 6-Bromo-7-(1-methylindol-3-yl)-4,7-dihydro-1,2,4-triazolo[1,5-a]- pyrimidine 5b. Prepared in a manner similar to that described for 5a from compounds 2 and 4b. Yield 71%, mp 154–156 °C. 1H NMR, d: 10.12 (d, 1H, NH, J4,5 4.2 Hz), 7.48 (s, 2H, H2, H2'), 7.41 (d, 1H, H7' ), 7.22 (d, 1H, H4'), 7.2–6.9 (m, 3H, H5', H6', H5), 6.34 (s, 1H, H7), 3.78 (s, 3H, N–Me).Found (%): C, 51.13; H, 3.62; N, 21.17. Calc. for C14H12N5Br (%): C, 50.93; H, 3.66; N, 21.21. § 7-(Indol-3-yl)-1,2,4-triazolo[1,5-a]pyrimidine 6a. Compound 5a (0.3 mmol, 95 mg) was refluxed in a mixture of acetonitrile (3 ml) and triethylamine (0.7 mmol) for 0.5 h. The mixture was cooled and diluted with water (10 ml), the precipitate was collected by filtration, washed with water and dried.Yield 55 mg (78%), mp 263–265 °C. 1H NMR, d: 12.23 (br. s., 1H, NH), 9.12 (s, 1H, H2), 8.83 (d, 1H, H5, J5,6 5.0 Hz), 8.75 (s, 1H, H2'), 7.87 (d, 1H, H6), 8.23–7.27 (m, 4H, H4'–7'). Found (%): C, 66.36; H, 3.70; N, 29.90. Calc. for C13H9N5 (%): C, 66.38; H, 3.83; N, 29.79. 7-(1-Methylindol-3-yl)-1,2,4-triazolo[1,5-a]pyrimidine 6b.Prepared in a manner similar to that described for 6a from compound 5b. Yield 77%, mp 191 °C. 1H NMR, d: 9.11 (s, 1H, H2), 8.81 (d, 1H, H5, J5,6 5.0 Hz), 8.76 (s, 1H, H2'), 7.85 (d, 1H, H6), 8.28–7.32 (m, 4H, H4'–7' ), 4.01 (s, 3H, N–Me). Found (%): C, 67.56; H, 4.42; N, 28.30. Calc. for C14H11N5 (%): C, 67.46; H, 4.45; N, 28.09.N N N N N N N N Br N R N R 4a,b MeOH/BF3 1 2 N N N N Br H H Br2 AcOH 5a,b N N N N N Q 3a,b N R N N N N 6a,b 3: a Q = O b Q = CH2 4,5,6: a R = H b R = Me HN QMendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) indole substituents into the 7-position of the s-triazolo[1,5-a]- pyrimidine system. The conversion of compound 1 into 6a,b can formally be considered as nucleophilic substitution for hydrogen via the following steps: (i) introduction of an auxiliary leaving group (Br) in the position adjacent to the reaction centre; (ii) addition of a nucleophile to form a sH-adduct and (iii) elimination of HBr under basic conditions.The procedure suggested does not include an oxidation step, which is undesirable in SN H reactions because it restricts the range of nucleophiles in use and requires a suitable oxidising agent. References 1 O. N. Chupakhin, V. N. Charushin and H. C. van der Plas, Nucleophilic Aromatic Substitution of Hydrogen, Academic Press, San Diego, California, 1994. 2 Y. Makisumi, Chem. Soc. Bull., 1961, 9, 808. 3 C. A. H. Rasmussen, H. C. van der Plas, P. Grotenhuis and A. Koudijs, J. Heterocycl. Chem., 1978, 15, 1121. 4 S. M. Desenko, V. D. Orlov and V. V. Lipson, Khim. Geterotsikl. Soedin., 1990, 1638 [Chem Heterocycl. Compd. (Engl. Transl.), 1990, 1362]. 5a,b B: N R N N Br H BH+ N R N N Br H 7a,b 6a,b – BH+Br– B: Received: 23rd June 1999; Com. 99/1507

ISSN:0959-9436     

出版商:RSC    

年代:1999

数据来源: RSC