摘要:

Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) The first phosphagermacyclopropane prepared via cycloaddition of dimethylgermylene to the C=P double bond of phosphaalkene Boris G. Kimel, Vasilii V. Tumanov, Mikhail P. Egorov* and Oleg M. Nefedov N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: mpe@cacr.ioc.ac.ru 10.1070/MC2001v011n03ABEH001445 The cycloaddition reaction of phosphaalkene 2 with dimethylgermylene generated thermally in situ leads to the first representative of phosphagermacyclopropanes 3. The [1+2] cycloaddition of heavy carbene analogues, silylenes and germylenes, to the C=C double bond has been successfully used for the synthesis of sila- and germacyclopropanes.1–3 The interactions of carbene analogues with isolated carbon–heteroatom multiple bonds are studied much lesser.In particular, only two examples of the cycloaddition of silylene4 and germylene5 to the carbon–phosphorus triple bond resulted in the formation of phosphasila- and phosphagermacyclopropenes, respectively, are known. Reactions of carbene analogues with C=P bonds of phosphaalkenes have not been described up to now.Here we report on the generation of the first phosphagermacyclopropane (phosphagermirane) by cycloaddition of shortlived dimethylgermylene to phosphaalkene (Me3Si)2C=PPh 2. The choice of 2 among the variety of known phosphaalkenes was prompted by the stability of 2 in an inert atmosphere at room temperature and, on the other hand, by the steric availability of the P=C double bond in 2, since our preliminary studies have shown that phosphaalkenes with bulkier substituents were inert towards dimethylgermylene.According to the 31P NMR spectroscopy data, the reaction of Me2Ge (thermally generated at 60 °C from 7,7-dimethyl-7- germanorbornadiene derivative 16) with phosphaalkene 27 (molar ratio 1:2 = 1.5:1) led to the formation of a single phosphoruscontaining reaction product.The reaction occurs with 100% conversion of the phosphaalkene; the overall integral intensity of the 31P NMR signals remained unchanged. An excess of the Me2Ge precursor should be used because of the polymerization of dimethylgermylene in the course of the reaction. The 31P NMR spectrum of the reaction product exhibits one singlet at –137.1 ppm.The position of this signal is characteristic of phosphiranes (–120 to –150 ppm).8 The 1H NMR spectrum of the product exhibits two signals of protons of two nonequivalent Me3Si groups of the (Me3Si)2C fragment (a singlet at –0.05 ppm and a doublet at 0.28 ppm, 4JPH 2.2 Hz) and two signals of protons of methyl groups of the Me2Ge fragment (a singlet at 0.70 ppm and a doublet at 0.62 ppm, 3JPH 3.3 Hz) with the integral intensity ratio 3:3:1:1. The characteristic constant 3JPH observed for one of the signals due to the Me2Ge group indicates the presence of a Ge–P bond in the product.The signals of phenyl protons are overlapped with those of 1,2,3,4-tetraphenylnaphthalene, which is formed upon the thermolysis of 7-germanorbornadiene 1.In the 13C NMR spectrum of the reaction product, the signal of the quaternary carbon atom of the (Me3Si)2C fragment is observed at 23.0 ppm (which is typical of phosphirane carbon atom signals9) as a doublet with the coupling constant 1JPC 69 Hz. We were unable to assign the signals of the carbon atoms of the Me3Si and Me2Ge groups since they overlap with numerous signals of the (Me2Ge)n polymers in the region from –5 to +5 ppm.In the 29Si NMR spectrum of the reaction product, two doublets (at 0.29 and 0.93 ppm) of the non-equivalent Me3Si groups are present. The coupling constants 2JPSi equal to 21.4 and 4.8 Hz, respectively, correspond to the suggested structure of 3. Thus, the spectroscopic data indicate that the product of the reaction of dimethylgermylene with phosphaalkene 2 has the structure of phosphagermirane 3.† Phosphagermirane 3 is a highly labile compound, which rapidly decomposes on air or upon heating.Our attempts to isolate 3 from solution were unsuccessful. We attempted to prepare other phosphagermiranes by reactions of phosphaalkene 2 with stable germylenes and their complexes.We found that GeI2 and [(Me3Si)2N]2Ge do not react with 2 at room temperature, while the interaction of 2 with GeCl2·dioxane resulted in a mixture of oxidation products of phosphaalkene 2. To obtain the silicon analogue of 3, we studied the reaction of phosphaalkene 2 with dimethylsilylene generated photochemically from the silicon analogue of 1, 7,7-dimethyl-7-silanorbornadiene 410 (C6D6, 20 °C, 2:4 = 1:1).The 31P NMR spectrum of reaction products exhibits a singlet at –132.4 ppm, which can be assigned to corresponding 1,1-dimethyl-2-phenyl-3,3-bis(trimethylsilyl)- 2-phosphasilirane 5 by analogy with phosphagermirane 3. Unfortunately, phosphaalkene 2 is a photolabile compound and partially photodecomposes during the reaction to give a number of products. These products exhibit signals in the 1H, 13C and 31P NMR spectra; thus, we failed to assign unequivocally the signals belonging to phosphasilirane 5 in the 1H and 13C NMR spectra.This work was supported by the Russian Foundation for Basic Research (grant nos. 98-03-32935 and 00-15-97387), the State Subprogramme ‘Fundamental Problems of Modern Chemistry’ (grant no. 9.3.03) and INTAS (grant no. 97-30344). References 1 W. P. Neumann, Chem. Rev., 1991, 91, 311. 2 O. M. Nefedov, M. P. Egorov and S. P. Kolesnikov, Sov. Sci. Rev. B. Chem., 1988, 12, 53. 3 W. Ando, H. Ohgaki and Y. Kabe, Angew. Chem., Int. Ed. Engl., 1994, 33, 659. 4 A. Shaefer, M. Weidenbruch, W. Saak and S. Pohl, Angew. Chem., 1987, 99, 806. Ge Ph Ph Ph Ph Me Me P Ge Me3Si Me3Si Me Me 1 3 C6H6 60 °C Me2Ge P Me3Si Me3Si 2 † 2,2-Dimethyl-1-phenyl-3,3-bis(trimethylsilyl)-1,2-phosphagermirane 3.An NMR sample tube was charged with 85 mg (0.32 mmol) of phosphaalkene 2 and 258 mg (0.48 mmol) of 7,7-dimethyl-1,4,5,6-tetraphenyl- 2,3-benzo-7-germanorbornadiene 1 in 1.0 ml of C6D6. The reaction mixture was heated at 60 °C in the spectrometer probehead. During the reaction the intensity of the 31P NMR signal of starting phosphaalkene 2 at +376 ppm decreased down to zero and another signal at –137.1 ppm appeared simultaneously.The reaction was complete in 3 h. 1H NMR (C6D6) d: –0.05 (s, 9H, Me3Si), 0.28 (d, 9H, Me3Si, 4JPH 2.2 Hz), 0.62 (d, 3H, Me, 3JPH 3.3 Hz), 0.70 (s, 3H, Me). 13C NMR (C6D6) d: 23.0 [d, C(SiMe3)2, 1JPC 68.9 Hz]. 29Si NMR (C6D6) d: 0.29 (d, Me3Si, 2JPSi 21.4 Hz), 0.93 (d, Me3Si, 2JPSi 4.8 Hz). 31P NMR (C6D6) d: –137.1 (s).Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) 5 A. H. Cowley, S. W. Hall, C. M. Nunn and J. M. Power, J. Chem. Soc., Chem. Commun., 1988, 753. 6 W. P. Neumann and M. Schriewer, Tetrahedron Lett., 1980, 21, 3273. 7 R. Appel, J. Peters and A. Westerhaus, Tetrahedron Lett., 1981, 22, 4957. 8 A. Marinetti and F. Mathey, Organometallics, 1984, 3, 456. 9 M. J. M. Vlaar, A.W. Ehlers, F. de Kanter and K. Lammertsma, Angew. Chem., Int. Ed. Engl., 2000, 39, 2943. 10 J. A. Hawari and D. Griller, Organometallics, 1984, 3, 11. Received: 23rd February 2001; Com. 01/1771

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) Luminescence properties of solid Eu, Sm, Tb and Dy compounds with the molybdoaluminate ion Al(OH)6Mo6O18 3– Alexander B. Yusov,* Alexander M. Fedosseev, Grigorii B. Andreev and Irina B. Shirokova Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow, Russian Federation. Fax: +7 095 335 2005; e-mail ioussov@ipc.rssi.ru 10.1070/MC2001v011n03ABEH001427 The structure and luminescence characteristics of new lanthanide complexes with the heteropoly anion Al(OH)6Mo6O18 3– were examined.The crystalline lanthanide complexes with planar IMo6O24 5– and TeMo6O24 6– heteropoly anions (HPA) of the Anderson structure were synthesised and investigated by luminescence spectroscopy and X-ray diffraction analysis.1,2 These HPA can form complexes with trivalent lanthanides in which the central ion has three or four oxygen atoms belonging to molybdate groups, which determine the luminescence properties of complexes.However, it is impossible to predict reliably the efficiencies of energy transfer to the central ion and luminescence quenching even if the structure of complexes is known.The results of a luminescence study of lanthanides in new complexes with the polyanion Al(OH)6Mo6O18 3– are given below, which seem unexpected. This HPA3 is structurally similar to IMo6O24 5– and TeMo6O24 6–; however, Al(OH)6 Mo6O18 3– was found a weaker ligand with respect to lanthanide ions than IMo6O24 5– and TeMo6O24 6–. The energy transfer from HPA to the central ion in crystalline complexes remains rather effective.However, luminescence quenching via electron transfer, which was expected for terbium complexes, is practically absent. The complexation of lanthanides with (NH4)3[Al(OH)6Mo6O18]· ·nH2O 1 in solution is rather weak. This is confirmed by spectrophotometric and luminescence† data. The absorption spectrum of a Nd(NO3)3 solution remained almost unchanged on the addition of compound 1 (0.03–0.04 mol dm–3) to the solution.Additional information can be obtained with the use of a 5felement, AmIII. The absorption spectra of AmIII in the presence of 1 are indicative of weak complexation with a stability constant of ~20 (m = 0.1, pH 3.9). The solutions of 1 containing europium(III) did not luminesce on exposure to light from a nitrogen laser because the absorption of the EuIII ion at this wavelength is insignificantly low, and intermolecular energy transfer to Eu3+ from 1 does not take place. The complexation with the polymolybdate ion also does almost not take place. Crystalline Eu, Tb, Sm and Dy compounds were separated from solutions.Single crystal X-ray data for a Sm compound suggested the composition Sm[Al(OH)6Mo6O18]·11H2O. According to powder X-ray diffraction data, all of the compounds are isostructural and have the composition Ln[Al(OH)6Mo6O18]· 11H2O.The crystalline europium complex intensely luminesces on excitation by a nitrogen laser because of energy transfer from the ligand to the f-element ion. The compounds were prepared in solutions in both H2O and D2O.‡ During the preparation of solids from D2O, crystal water from (NH4)3Al(OH)6Mo6O18·nH2O (n £ 10) was introduced into the solution and the resulting solids contained about 3% H2O (on a total water basis).The samples were sealed with supernatants in glass ampoules to prevent an additional introduction of H2O. Figure 1 shows the luminescence spectra of the europium(III) solid corresponding to emission transitions 5D0 ® 7Fi, i = 0, 1, 2, and the excitation spectra at 293 and 77 K.The low-intensity broad band at 270–370 nm and some narrow bands at 362, 375– 385 and 394 nm are present in the excitation spectrum. The broad band arises due to light absorption by HPA followed by energy transfer from the ligand to Eu3+, as it takes place in organic lanthanide complexes;4 the narrow bands correspond to the absorption of the Eu3+ ion.The symmetry of the oxygen environment of europium(III) is responsible for the relative bands intensities and the Stark splitting3 in emission spectra. At 77 K, a very weak band at 578.8 nm (transition 5D0 ® 7F0) and an additional peak at 583.0 nm are observed in the luminescence emission spectrum of the new europium complex.Usually, splitting of the transition 5D0 ® 7F0 indicates the existence of two (or more depending on the number of components) luminescence centres; however, according to X-ray data, all lanthanide atoms in the test complex are equivalent. We found that the peak at † The luminescence of lanthanide complexes with molybdoaluminate ions was excited by nitrogen laser (l = 337.1 nm, pulse duration of 7–9 ns, power of 120 mW at a frequency of 1000 Hz).Uncorrected luminescence spectra were recorded using an MSD-1 monochromator. Luminescence lifetimes were measured using an S1-70 oscillograph. Excitation luminescence spectra were obtained on an SFL-2 spectrofluorimeter with a DKsSh-500 xenon lamp as light source. (NH4)3[Al(OH)6Mo6O18]·nH2O 1 was synthesised as described previously3 and recrystallised from water. ‡ D2O (Izotop, Russia) of 99.8% purity was used. 250 300 350 400 575 585 595 605 615 625 l/nm excitation emission 293 K 77 K l/nm excitation emission 250 300 350 400 575 585 595 605 615 625 l/nm l/nm Figure 1 Excitation and emission luminescence spectra of crystalline Eu[Al(OH)6Mo6O18]·11H2O at 293 and 77 K. The spectral resolution is 2.0 or 0.5 nm for the excitation and emission spectra, respectively. 530 580 630 680 730 460 510 560 610 660 l/nm Sm Tb 293 K 77 K l/nm 530 580 630 680 730 460 510 560 610 660 l/nm l/nm Figure 2 Luminescence spectra of crystalline Ln[Al(OH)6Mo6O18]·11H2O (Ln = Sm or Tb) at 293 and 77 K. The spectral resolution is 0.5 or 0.8 nm for the spectra of Tb and Sm, respectively. 4G5/2 ® 6H5/2 4G5/2 ® 6H7/2 4G5/2 ® 6H9/2 4G5/2 ® 6H11/2 5D4 ® 7F6 5D4 ® 7F5 5D4 ® 7F4 5D4 ® 7F3Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) 583.0 nm corresponds to the transition 5D1 ® 7F3. At ambient temperature, this transition is masked by the much more intense transition 5D0 ® 7F1. Other transitions from the 5D1 level can be easily observed at 555, 535 and 525 nm even at ambient temperature.This interesting phenomenon has been observed earlier for europium molybdoiodate1,2 and molybdotellurate.1 The lowtemperature luminescence spectrum of K(NH4)[Eu(IMo6O24) (H2O)5]·4H2O also exhibits a peak near 585 nm.2 The lifetimes of the 5D1-luminescence of europium molybdoiodate and europium molybdotellurate were measured.1 The spectrum of Eu[Al(OH)6 Mo6O18]·11H2O is very similar to the spectrum of K(NH4)[Eu (IMo6O24)(H2O)5]·4H2O, in which the coordination polyhedron of EuIII is a tricapped trigonal prism.2 The X-ray data showed that lanthanide ion in Ln[Al(OH)6Mo6O18]·11H2O have the same polyhedron.The luminescence spectrum of europium molybdoaluminate corresponds to the lowest symmetry groups and agrees with structural data.According to X-ray diffraction data, the difference in the europium(III) surroundings in molybdoiodate2 and molybdoaluminate consists in the number of water molecules bonded to the lanthanide ion. In the former case, five oxygen atoms of H2O and four oxygen atoms of molybdate groups enter the coordination sphere of europium, whereas in the latter complex there are seven and two atoms, respectively.The luminescence method allowed us to evaluate rapidly the nature of compounds formed under changes in the synthesis conditions. An increase in the crystallisation temperature up to 90 °C remained the luminescence lifetime and spectra almost unchanged. The compound obtained from acid solutions luminesced very weakly under the supernatant.However, the luminescence intensity of the complex increased after drying, and the luminescence characteristics of dry compounds separated from neutral and acidic solutions were almost identical. The properties of complexes prepared from heavy water solutions differed only in the luminescence lifetime and intensity. Figure 2 shows the luminescence spectra of samarium and terbium molybdoaluminate complexes.These spectra exhibit bands corresponding to transitions from the levels 4G5/2 and 5D4, respectively. The luminescence spectrum of dysprosium molybdoaluminate exhibits two most intense poorly defined bands at about 479 and 572 nm; these bands correspond to the transitions 4F9/2 ® 6H15/2,13/2. At 77 K, the first band is split into two components with maximums at 479.3 and 484.1 nm.It should be noted that the bright luminescence of terbium(III) in the new solid is unexpected. Although TbIII is usually a brightly luminescent ion, it does not luminesce in isopolymolybdate solutions.6 The reason of this phenomenon is that terbium luminescence can be quenched by electron transfer from the terbium ion to its coordination sphere, if it contains MoVI, WVI or other ions possessing electron-acceptor properties.The quenching is a thermally activated process and hence strongly depends on temperature. In spite of the presence of MoVI in the coordination sphere of TbIII in the molybdoaluminate complex, the temperature quenching of its luminescence is rather weak and terbium luminesces in the temperature range from 77 to 350 K.Electron transfer proceeds through a system of chemical bonds. Therefore, the reason for the weak quenching of terbium luminescence by charge transfer (CT) through the state TbIV– MoV can consist in that oxygen atoms from molybdate groups in the coordination environment of the Tb3+ ion occupy only two places of nine. Previously, we found that an increase in the number of bonds (from 4 to 8) between the curium ion and ligands in polytungstate complexes leads to an increase in Cm3+ luminescence quenching by CT via the state CmIV–WV.7 The luminescence lifetimes of all compounds prepared from solutions in water (tH2O) and heavy water (tD2O) are given in Table 1. Water and D2O molecules, as well as other molecular groups in the environments of f-element ions, quench luminescence by an inductive-resonance mechanism.8 Using the equation9 the hydration numbers of lanthanide ions can be calculated (kH and kD are the rate constants of quenching of f-element ion luminescence by a molecule of H2O or D2O that enters the first coordination sphere of the f-element ion, respectively).To determine kH and kD, we used the hydration numbers n of 8.3, 8.0 and 8.0 for SmIII, EuIII and TbIII aqua-ions,10 respectively, and published data5 on the luminescence lifetimes of Ln3+ aq ions in H2O and D2O solutions.From the Eu, Tb and Sm luminescence data, the mean value is n = 7.65±1.44. From X-ray data for any lanthanide ion, n = 7. Possible errors were discussed in ref. 9. The inaccuracy of the luminescent method is noticeably larger than ±0.5 given by Horrocks et al.5 However, we suppose that this is due to a great value of n.Relative standard deviation in the determination of n is about 20%. Thus, the lanthanide complexes with the molybdoaluminate ion are formed in solution only at high ligand concentrations. The complexes can be easily separated as solids. Only two molybdenum atoms are bonded to Eu, Sm, Dy or Tb ions through oxygen atoms, and seven coordination places are occupied by water molecules.Effective energy transfer from the ligand to the central ion takes place in the solid molybdoaluminate complexes, and the characteristic luminescence of lanthanide ions arises on the UV excitation of the complexes. The bright 5D1-luminescence of EuIII is of interest.The luminescence of TbIII in a complex with Al(OH)6Mo6O18 3– is surprisingly intense, although the strong quenching by charge transfer to MoVI could be expected. This work was supported by the US Department of Energy (grant no. DE-FG-07-98ER-14940). References 1 M. S. Grigoriev, Yu. T. Struchkov, A.M. Fedosseev, A. B. Yusov and A. I. Yanovskii, Zh. Neorg. Khim., 1992, 37, 2507 (Russ.J. Inorg. Chem., 1992, 37, 1293). 2 A. M. Fedosseev, M. S. Grigoriev, N. A. Budantseva, I. B. Shirokova, E. Antic-Fidancev and J.-C. Krupa, J. Lumin., 2000, 87–89, 1065. 3 M. T. Pope, Heteropoly and Isopolyoxometalates, Springer, Berlin, 1983, p. 22. 4 V. L. Ermolaev, E. N. Bodunov, E. B. Sveshnikova and T. A. Shakhverdov, Bezyzluchatel’nyi perenos energii elektronnogo vozbuzhdeniya (Nonradiative Transfer of the Energy of Electron Excitation), Nauka, Leningrad, 1977, p. 182 (in Russian). 5 W. DeW. Horrocks and M. Albin, Prog. Inorg. Chem., 1984, 31, 1. 6 A. B. Yusov and A. M. Fedosseev, Zh. Prikl. Spektrosk., 1987, 47, 40 (in Russian). 7 A. B. Yusov and A. M. Fedosseev, Radiokhimiya, 1989, 31 (5), 19 [Sov. Radiochem. (Engl. Transl.), 1989, 31, 541]. 8 V. L. Ermolaev and E. B. Sveshnikova, Usp. Khim., 1994, 63, 962 (Russ. Chem. Rev., 1994, 63, 905). 9 W. DeW. Horrocks and D. R. Sudnick, J. Am. Chem. Soc., 1979, 101, 334. 10 F. David, J. Less-Common Met., 1986, 121 (1), 27. (kH – kD)n = 1/tH2O – 1/tD2O, (1) Table 1 Luminescence lifetimes t (µs) of solid Ln[Al(OH)6Mo6O18]· 11H2O (Ln = Eu, Tb and Sm) and hydration numbers n of lanthanide ions in the complexes. Lanthanide tH2O, 295 K tD2O, 295 K tH2O, 77 K n Eu 110±10 1150±50 110±10 7.7 Tb 310±10 1300±100 390±15 8.7 Sm 3.5±0.8 55±5 3.5±0.8 5.6a, 8.6b a t calculated by equation (1). b t calculated by the simplified equation kDn = 1/tD2O on the assumption that, in the case of Sm, only the rate of luminescence quenching by D2O molecules determines the value of tD2O and other quenching pathways are neglected. cLuminescence decay is not exponential. Dy 4–6c � 30c 4–6c — Received: 22nd January 2001; Com. 01/17

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) Effect of supporting electrolytes on the positions of outer-sphere charge-transfer bands in electronic absorption spectra Sof¡�ya A. Kostina,a Vitalii Yu. Kotov*a and Galina A. Tsirlinab a Higher Chemical College, Russian Academy of Sciences, 125047 Moscow, Russian Federation. Fax: +7 095 200 4204 b Department of Chemistry, M.V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 939 0171; e-mail: tsir@elch.chem.msu.ru 10.1070/MC2001v011n03ABEH001441 The positions of the outer-sphere charge-transfer bands in the electronic absorption spectra of the EV2+.[Fe(CN)6]4. system depend on the nature and concentration of supporting-electrolyte cations. Aromatic N-heterocyclic cations are convenient objects for studying electron-transfer processes.1.5 The simultaneous presence of these cations and electron-donor anions in aqueous solutions results in the appearance of charge-transfer bands in electronic absorption spectra (EAS).The N,N'-dialkyl-4,4'-bipyridinium (alkyl viologen).hexacyanoferrate(II) systems are most informative for studying electron-transfer processes.A band due to the outer-sphere charge transfer (OSCT) from the [Fe(CN)6]4. ion to an aromatic cation is observed1,3 at 18000.20000 cm.1, where the self-absorption of ions is practically absent. A change in the supporting-electrolyte composition affects the positions of bands. The observed shift of band maxima was assumed1,3 to result from the fact that, in addition to the ion pairs MV2+, [Fe(CN)6]4.(MV2+ is methylviologen), associates in which two [Fe(CN)6]4. ions are accounted for one MV2+ cation or vice versa can be formed in this system. In this work, we studied the effect of supporting electrolytes on the position of OSCT bands in associates that include the [Fe(CN)6]4. ion and a homologue of MV2+, the N,N'-diethyl-4,4'-bipyridinium cation (ethylviologen, EV2+).The compound EV1.5K[Fe(CN)6]¡�12.5H2O was isolated by the isothermal evaporation (T = 277 K) of a solution of potassium hexacyanoferrate (analytical grade) and N,N'-diethyl-4,4'- bipyridinium iodide (Aldrich) in the 1:1 molar ratio. The EAS of freshly prepared solutions in twice-distilled water were measured on a Specord M400 spectrophotometer (Germany) in 1 cm quartz cuvettes at 298 K.Cyclic voltammograms were recorded on a PARC 273 potentiostat using a glassy carbon electrode at the potential scan rate v = 5.100 mV s.1. A saturated calomel electrode was used as the reference electrode. From .0.92 to +0.60 V, the heights of current peaks were proportional to v1/2. This fact allowed us to attribute these currents to redox processes uncomplicated by adsorption and chemical stages.Therefore, the half-wave potential (E1/2) was determined by averaging the potentials of anodic and cathodic peaks. The potentials were given with reference to a normal hydrogen electrode. The absorption band in the test system appears in the same spectral range as the bands observed previously.1.3 In the visible range, the EAS of EV1.5K[Fe(CN)6] (0.02mol dm.3) has a band at 18520 cm.1: The position of the band maximum remained unchanged when the solution was diluted to a concentration of 0.0028 mol dm.3.When supporting electrolytes were added to the system, the position of the band maximum changed. Thus, the EAS of an aqueous solution containing 0.01 mol dm.3 EVI2 and 0.109 mol dm.3 K4[Fe(CN)6] (Figure 1) has an OSCT band at 19060 cm.1.The addition of KCl or NaCl to this solution resulted in a greater shift of the band to the high-frequency region of the spectrum (Figure 2). The addition of Me4NCl to the system shifted the band in the opposite direction (Figure 2). As a result, in solutions of equal ionic strength, the positions of OSCT bands differed by 1400 cm.1 (~0.2 eV).The tendency illustrated by Figure 2 is similar to the dependence of the formal redox potential of a hexacyanoferrate system on the nature and concentration of supporting cations.6,7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 14000 16000 18000 20000 22000 A n/cm.1 Figure 1 Electronic adsorption spectrum of the ion associate EV2+, nK+, [Fe(CN)6]4. in an aqueous solution at 298 K, C[Fe(CN)6] = 0.109 mol dm.3, CEV = 0.01 mol dm.3.Table 1 Half-wave potentials of [Fe(CN)6]3./4. and EV2+/+ pairs, reorganization energies and OSCT band energies for EV1.5K[Fe(CN)6] (0.02 mol dm.3) in the presence of supporting electrolytes (1 mol dm.3). Supporting electrolyte E1/2 (EV2+/+)/V E1/2 {[Fe(CN)6]3./4.}/V .E1/2/V Ehv /eV c/eV no electrolyte 0.80a aThe value corresponds to the standard-potential difference. 2.30 1.56 Et4NBr .0.41 0.30 0.71 2.22 1.55 Me4NCl .0.42 0.38 0.80 2.28 1.52 EtNH3Cl .0.41 0.45 0.86 2.34 1.52 Me2NH2Cl .0.41 0.45 0.86 2.36 1.54 NaCl .0.42 0.46 0.88 2.37 1.53 MeNH3Cl .0.42 0.46 0.88 2.39 1.55 KBr .0.42 0.47 0.89 2.39 1.54 KCl .0.43 0.47 0.90 2.39 1.53 NH4Cl .0.43 0.47 0.90 2.40 1.54 EV2+, [Fe(CN)6]4. EV+, [Fe(CN)6]3.. hn Figure 2 Dependence of the position of the OSCT band of an ion associate in an aqueous solution on the supporting-electrolyte concentration.The conditions are specified in Figure 1. (1) KCl, (2) NaCl and (3) Me4NCl. 20000 19500 19000 18500 18000 0.0 0.5 1.0 1.5 2.0 2.5 n/cm.1 C/mol dm.3 1 2 3Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) We determined the E1/2 of the pairs [Fe(CN)6]3./4.and EV2+/+ in solutions containing simultaneously both reactants and different supporting electrolytes by voltammetry (Figure 3; Table 1, columns 2.4). The difference of E1/2 for two redox systems demonstrated the same dependence on the cation nature as reported earlier for hexacyanoferrate.6,7 It results from the fact that for EV2+/+, the E1/2 are practically independent of the nature of supporting-electrolyte cations and amount to .0.42¡¾0.01 V. Table 1 also compares the difference in E1/2 with the energies of OSCT bands in the same solutions.An increase in the E1/2 difference in the system leads to a corresponding increase in Ehv. The relationship between the redox-pair potential7 and the Ehv was also observed when we varied the supporting-electrolyte concentration (Table 2).Within the framework of the classical Marcus.Hush theory, we can write the following expression for the optical transition energy:8,9 Here, .E0 is the free energy of the reaction; Up and Ur are the electrostatic work terms for products and reactants, respectively; ci, cO and Fc are the components of reorganization energy corresponding to the intramolecular degrees of freedom, the solvent, and the ionic atmosphere, respectively.A constant half-width of bands (5700 cm.1) gives evidence for the same reorganization energy (c = ci + cO + Fc) for all test systems. The value of (Up . Ur) calculated for the studied range of supporting-electrolyte concentrations is low (0.02.0.04 eV) and independent of the nature of cations.Thus, .E0 makes the main contribution to the change in Ehv. This result can be explained, if we assume that this ionic associate includes the supporting- electrolyte cations, for example: It also agrees with the data of X-ray diffraction analysis of EV1.5K[Fe(CN)6]¡�12.5H2O.10 The standard redox potential of the hexacyanoferrate pair is equal to 0.355 V.6 For the pair K+,[Fe(CN)6]4./K+,[Fe(CN)6]3., the potential is 0.41 V, if we take into account data from refs. 6, 11. To explain the dependence of the energy of OSCT band maximum on the supportingelectrolyte concentration (Figure 2), it should be taken into account that a solution with a high alkali-metal concentration can contain associates with several cations in the periphery of [Fe(CN)6]4. ion,6,7,11 for example: In conclusion, a number of factors (solvent,4 pressure12 and temperature1) affects the position of the OSCT band maximum of the EV2+.[Fe(CN)6]4.system, and a shift of the redox potential was responsible for all these effects. The nature and concentration of supporting-electrolyte cations were also found to affect the band maximum positions. This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-32367). References 1 J. C. , B. P. Sullivan and T. J. Meyer, Inorg. Chem., 1980, 19, 3833. 2 H. E. Toma, Can. J. Chem., 1979, 57, 2079. 3 A. Nakahara and J. H. Wang, J. Phys. Chem., 1963, 67, 496. 4 A. M. Kj©¡r, I. Kristjansson and J. Ulstrup, J. Electroanal. Chem., 1986, 204, 45. 5 S. A. Kostina, I. F. Golovaneva and V. Yu. Kotov, Zh.Neorg. Khim., 2001, 46, 470 (in Russian). 6 G. I. H. Hanania, D. H. Irvine, W. A. Eaton and P. George, J. Phys. Chem., 1967, 71, 2022. 7 D. Krulic, N. Fatouros and D. E. Khostariya, J. Chim. Phys., 1998, 95, 497. 8 E. D. German and A. M. Kuznetsov, Elektrokhimiya, 1992, 28, 294 [Sov. Electrochem. (Engl. Transl.), 1992, 28, 240]. 9 E. D. German and A. M. Kuznetsov, Elektrokhimiya, 1987, 23, 1671 [Sov.Electrochem. (Engl. Transl.), 1987, 23, 1560]. 10 S. A. Kostina, A. B. Ilyukhin, B. V. Lokshin and V. Yu. Kotov, Mendeleev Commun., 2001, 12. 11 W. A. Eaton, P. George and G. I. H. Hanania, J. Phys. Chem., 1967, 71, 2016. 12 W. S. Hammack and H. G. Drickamer, Chem. Phys. Lett., 1988, 151, 469. Ehv = .E0 + Up . Ur + ci + cO + Fc. 0.08 0.06 0.04 0.02 0.00 .0.02 .0.04 .0.06 .0.08 .0.10 .1.0 .0.8 .0.6 .0.4 .0.2 0.0 0.2 0.4 0.6 0.8 I/mA E1/2/V (SCE) Figure 3 Cyclic voltammogram of a solution of EV1.5K[Fe(CN)6] (0.02 mol dm.3) in Me4NCl (1 mol dm.3); the potential scan rate is 5 mV s.1. Table 2 The difference between half-wave potentials of redox processes, reorganization energies and the optical transition energy for the ion pair EV2+,[Fe(CN)6]4. in an aqueous solution as functions of the concentration of potassium chloride (Figure 2). KCl concentration/ mol dm.3 .E1/2/V Ehv/eV c/eV 0.0 0.87 2.36 1.53 0.5 0.89 2.38 1.53 1.0 0.90 2.40 1.53 1.5 0.91 2.41 1.53 2.0 0.92 2.42 1.53 2.5 0.92 2.43 1.54 EV2+, K+, [Fe(CN)6]4. EV+, K+, [Fe(CN)6]3.. hv EV2+, nK+, [Fe(CN)6]4. EV+, nK+, [Fe(CN)6]3.. hv Received: 9th February 2001; Com. 01/1767

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) Photoisomerization of 2,4,4,6-tetraaryl-4H-selenopyrans: a new heterocyclic ring contraction Ji í Kroulík,*a Jan ejka,b Pavel Šebek,a Petr Sedmera,c Petr Halada,c Vladimír Havlí ek,c Stanislav Nešp rek,d Bohumil Kratochvílb and Josef Kuthana a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic.Fax: +42 022 431 1082; e-mail: Jiri.Kroulik@vscht.cz b Department of Solid State Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic c Institute of Microbiology, Academy of Sciences of the Czech Republic, 141 20 Prague 4, Czech Republic. Fax: +42 022 475 2749 d Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic.Fax: +42 022 251 6969 10.1070/MC2001v011n03ABEH001430 The UV illumination of title compounds 3a,b in acetonitrile solutions leads to corresponding five-membered ring isomers 4a,b, probably, via open-ring intermediates, whereas the photocolouration was observed in the solid state. The photochromism has recently highlighted a considerable application potential for data storage technologies.1 The increasing activity focused on the development and features of new compounds with photochromic properties1 prompted us to investigate possible consequences of the integration of selenium with a favourable photochromic system. 2,4,4,6-Tetraaryl-4H-thiopyrans 1 are known to exhibit UV photocolouration2 followed by multi-step transformations to final 2,3,4,6-tetraaryl-2H-thiopyrans 2.2(c),(d) Contrary, the properties and photochemistry of analogous 2,4,4,6-tetraaryl-4H-selenopyrans 3 remain almost unknown.3 Hitherto reports are mostly intent on similar 2,4,6- triphenyl-4H-selenopyrans.3 Of the considered 2,4,4,6-tetraphenyl derivatives, only parent 2,4,4,6-tetraphenyl-4H-selenopyran 3a, prepared by the reaction of a 2,4,6-triphenylselenopyrylium salt with phenylmagnesium bromide, and its reaction with bromine have been reported.4 Hence, here we report that the replacement of the sulfur 1-heteroatom by selenium dramatically changes the photoisomerization. Thus, acetonitrile solutions of 2,4,4,6-tetraphenyl- 4H-selenopyran 3a or 2,6-bis(4-fluorophenyl)-4,4-diphenyl- 4H-selenopyran 3b, prepared by the cyclocondensations of corresponding 1,5-diones (ArCOCH2)2CPh2 with the H2Se–HCl reagent, have been directly irradiated with a high-pressure 125W mercury UV lamp in a quartz photoreactor at 12 °C for 1 h under argon† to afford approximately 2:3 equilibrium mixtures of (E)-3,3,5-triphenyl-2-(phenylmethylidene)-2,3-dihydroselenophene 4a or (E)-5-(4-fluorophenyl)-2-[(4-fluorophenyl)methylidene]- 3,3-diphenyl-2,3-dihydroselenophene 4b and starting 4Hselenopyran 3a or 3b.Prolonged UV exposures lead to irreversible degradation of photoisomers 3a,b and 4a,b to complex mixtures of unidentified compounds. In the solid state, a photocolouration was observed. A sample of the polycrystalline powder of 3a in MgO showed a green photocolouration after irradiation (300 s) with a high-pressure 200 W mercury discharge lamp.The correct structures of 3a,b of the starting 4H-selenopyrans follow from their 1H and 13C NMR and EI mass spectra.† On the other hand, the molecular structures of their photoisomers could not be positively derived in the same way. Therefore, the photoproduct from difluoro derivative 3b was analysed by X-ray diffraction,‡ which confirmed the structure of 4b (Figure 1).Then, the analogous structure of 4a can be assigned to the photoisomer of 3a by comparison of the corresponding spectral data.§ The results indicate that the photochemically induced isomerization 3 ® 4 in the 4H-selenopyran series surprisingly differs from the isomerization 1 ® 2 in the 4H-thiopyran series and probably proceeds via a labile acetylenic intermediate like PhCºC–CPh2–CH=C(SeH)Ph, which may undergo two parallel intramolecular ring-closures to either 2,3-dihydroselenophenes 4 or to 4H-selenopyrans 3.For the sake of completeness, the UV–VIS absorption spectrum of an acetonitrile solution consists of a main maximum at 238 (log e = 3.73 dm3 mol–1 cm–1) or 273 nm (log e = r C c u S Ar Ar Ar Ar Se Ar Ar Ph Ph 1 S Ar Ar 2 3 Ar Ar H Se Ar Ph Ph Ar 4 a Ar = Ph b Ar = 4-FC6H4 1 2 3 4 5 6 1 2 2 2 1 1 2 1 2 3 4 5 1 † The photochemical reactions were monitored by HPLC with an UV detector (254 nm) on Separon SGX C18 (Tessek, Czech Republic), particle size of 5 µm, eluent MeOH. The photoisomer mixtures were separated by preparative TLC.NMR spectra were measured on a Varian VXR-400 or INOVA-400 (399.90 and 100.57 MHz for 1H and 13C, respectively) instrument in CDCl3 solutions at 25 to 30 °C.The assignments were based on COSY, HOM2DJ, HMQC, HMBC, 1D-TOCSY, and 1D-NOE experiments; the methine (exocyclic) carbon of compounds 4 is indicated with the number 6; i- ipso, o- ortho, m- meta, p- para. In fluorine-containing compounds, capital letters denote multiplicity due to protons, lowercase letters are used for fluorine-related multiplicity.Positive-ion mass spectra were recorded on a Finnigan MAT 95 doublefocusing instrument of BE geometry equipped with an EI ion source [ionization energy of 70 eV, source temperature of 250 °C, emission current of 0.5 mA, accelerating voltage of 5 kV, direct inlet (150–160 °C)]. For high resolution experiments, the instrument was tuned to a resolution of about 8000 (10% valley definition), and the measurements were carried out by the peak-matching method against the Ultramark 1600F (PCR Inc.Gainesville, USA) as an internal standard. For 3a: mp 138–140 °C (lit.,4 mp 138–139 °C). 1H NMR (CDCl3) d: 6.453 (s, 2H, 3,5-H), 7.240 (m, 4H, m-2,6-Ph), 7.293–7.380 (m, 12H, aromatic), 7.560 (m, 4H, o-2,6-Ph). 13C NMR (CDCl3) d: 56.11 (s, 1C, 4-C), 126.37 (d, 2CH, p-4,4-Ph), 126.87 (d, 4CH, o-2,6-Ph), 127.49 (d, 2CH, 3,5-CH), 128.24 (d, 4CH, m-4,4-Ph), 128.36 (d, 4CH, o-4,4-Ph), 128.41 (d, 2CH, p-2,6-Ph), 128.61 (d, 4CH, m-2,6-Ph), 130.71 (s, 2C, i-2,6-Ph), 139.74 (s, 2C, i-4,4-Ph), 147.56 (s, 2C, 2,6-C). MS, m/z (%): 450.0884 (100, M+, C29H22Se), 373.0495 (85), 291.1174 (56), 267.1174 (19), 215.0861 (25), 191.0861 (16), 165.0704 (22).For 3b: mp 113–115 °C. 1H NMR (CDCl3) d: 6.368 (s, 2H, 3,5-H), 7.041 (m, 4H, o-2,6-C6H4F, 2×0.5 of AA'BB'X spectrum, JHF 8.5 Hz, S J 8.9 Hz), 7.242 (m, 2H, p-4,4-Ph), 7.285 (m, 4H, o-4,4-Ph), 7.338 (m, 4H, m-4,4-Ph), 7.506 (m, 4H, m-2,6-C6H4F, 2×0.5 of AA'BB'X spectrum, JHF 5.3 Hz, S J 8.9 Hz). 13C NMR (CDCl3) d: 56.17 (S, 1C, 4-C), 115.56 (Dd, 4CH, m-2,6-C6H4F, JCF 21.7 Hz), 126.51 (D, 2CH, p-4,4-Ph), 127.68 (D, 2CH, 3,5-CH), 128.18 (D, 4CH, m-4,4-Ph), 128.44 (D, 4CH, o-4,4-Ph), 128.63 (Dd, 4CH, o-2,6-C6H4F, JCF 8.2 Hz), 129.69 (S, 2C, i-4,4-Ph), 135.78 (Sd, 2C, i-2,6-C6H4F, JCF 3.2 Hz), 147.48 (S, 2C, 2,6-C), 162.85 (Sd, 2CF, p-2,6-C6H4F, JCF 248.2 Hz).MS, m/z (%): 486.0692 (100, M+, C29H20F2Se), 409 (78), 391 (5), 327 (27), 309 (25), 285 (22), 251 (7), 233 (15), 209 (13), 165 (17).Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) = 3.79 dm3 mol.1 cm.1) and a shoulder at about 287 or 283 nm for compound 3a or 3b, respectively.A similarity between the UV.VIS spectra of selenopyrans and appropriate derivatives of thiopyrans2(c) is evident, and it can be attributed to identical quantal transitions.To our knowledge, the described conversion 3 ¢ç 4 is a unique example of photochemical ring conversion among six-membered selenium heterocycles5 and, contrary to other 2,4,4,6-tetraaryl- 4H-(hetero)pyrans,2 no photochemical di-¥�-methane rearrangement of one of the 4,4-phenyl groups has been observed.The photochemistry of such di-¥�-selenide systems belongs to an unexplored area.6 Laser-induced photolysis of selenophene seems to be a formally similar process.7 Note that a topologically analogous isomerization has been only observed8 after lithiation of 2,6-di-tert-butyeno-4-pyron, where the acetylenic intermediate ButC��C.CO.CH=C(SeMe)But was evidently trapped with methyl triflate.The selenopyran derivatives and their reactivity, including the solid-state UV photocolouration of 3-like 4H-selenopyrans, will be considered in detail elsewhere. References 1 Chem. Rev., Photochromism: Memories and Switches, ed. M. Irie, 2000, 100 (5). 2 (a) Y. Mori and K. Maeda, J. Chem. Soc., Perkin Trans. 2, 1991, 2061; (b) H. Pirelahi, I. Parchamazad, M. S. Abaii and S.Sheikhebrahimi, Phosphorus Sulfur Silicon, 1991, 59, 251; (c) P. .ebek, S. Ne.p rek, R. Hrabal, M. Adamec and J. Kuthan, J. Chem. Soc., Perkin Trans. 2, 1992, 1301; (d) S. Bohm, P. .ebek, S. Ne.p rek and J. Kuthan, Collect. Czech. Chem. Commun., 1994, 59, 1115; (e) J. Kroulik, M. Chadim, M. Pola.ek, S. Ne.p rek and J. Kuthan, Collect. Czech. Chem. Commun., 1998, 63, 662. 3 J.Kuthan, P. .ebek and S. Bohm, Adv. Heterocycl. Chem., 1994, 59, 179. 4 B. I. Drevko, M. I. Smushkin and V. G. Kharchenko, Khim. Geterotsikl. Soedin., 1997, 604 [Chem. Heterocycl. Compd. (Engl. Transl.), 1997, 33, 520]. 5 L. E. E. Christiaens, in Comprehensive Heterocyclic Chemistry, ed. A. McKillop, Pergamon, Oxford, 1996, vol. 5, ch. 5.11, p. 619. 6 A. A. Leone and P. S. Mariano, Rev.Chem. Intermed., 1981, 4, 81. 7 J. Pola and A. Ouchi, J. Org. Chem., 2000, 65, 2759. 8 M. R. Detty and L.W.McGarry, J. Org. Chem., 1988, 53, 1203. 9 (a) G. M. Sheldrick, SHELXS-86, Program for Crystal Structure Solution, University of Gottingen, Gottingen, Germany, 1986; (b) D. J. Watkin, R. J. Carruthers and P. Betteridge, CRYSTALS, Chemical Crystallography Laboratory, Oxford, UK, 1998, issue 10; (c) J.R. Carruthers and D. J. Watkin, Acta Crystallogr., Sect. A, 1979, 35, 698; (d) L. Zsolnai and G. Huttner, XPMA, ZORTEP, University of Heidelberg, 1994. ¢Ô Crystal data for 4b: C29H20F2Se, M = 485.43, monoclinic, space group P21/c, a = 11.495(2) A, b = 11.909(4) A, c = 16.353(1) A, b = 90.50(1)¡Æ, V = 2238.7 A3, Z = 4, dcalc = 1.44 g cm.3, F(000) = 982.88, m = 2.52mm.1. 8525 reflections measured with an Enraf Nonius CAD4 diffractometer (293 K, graphite-monochromated CuK¥á radiation, l = = 1.54184 A, w/2q scan mode, 2q range of 5.134¡Æ). The structure was solved by direct methods and anisotropically refined by full-matrix least squares.9 Hydrogen atoms were located from a ..r map, positions and isotropical thermal motion were refined. The final agreement factors are R = 4.11% and Rw = 4.11%.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, 2001. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/85.¡× For 4a: mp 150.152 ¡ÆC, preparative yield 11%. 1H NMR (CDCl3) d: 6.588 (s, 1H, 6-H), 6.701 (s, 1H, 4-H), 7.218.7.368 (m, 14H, aromatic), 7.382 (m, 4H, o-3,3-Ph), 7.480 (m, 2H, o-5-Ph). 13C NMR (CDCl3) d: 74.73 (s, 1C, 3-C), 126.83 (d, 2CH, o-5-Ph), 126.92 (d, 2CH, o-6-Ph), 127.08 (d, CH, p-6-Ph), 127.89 (d, 2CH, p-3,3-Ph), 128.32 (d, 4CH, m-3,3-Ph), 128.45 (d, 2CH, m-5-Ph), 128.49 (d, 1CH, p-5-Ph), 128.53 (d, 4CH, o-3,3-Ph), 128.60 (d, 2CH, m-6-Ph), 129.85 (d, 1CH, 6-CH), 129.91 (d, 1CH, 4-CH), 135.11 (s, 1C, i-5-Ph), 136.22 (s, 1C, 5-C), 137.59 (s, 1C, i-6-Ph), 144.42 (s, 1C, 2-C), 145.26 (s, 2C, i-3,3-Ph).MS, m/z (%): 450.0885 (100, M+, C29H22Se), 373 (47), 291 (52), 278 (9), 215 (35), 191 (23), 165 (11). For 4b: mp 159.161 ¡ÆC, preparative yield 34%. 1H NMR (CDCl3) d: 6.535 (s, 1H, 6-H), 6.619 (s, 1H, 4-H), 7.034 (m, 2H, m-5-C6H4F, 0.5 of AA'BB'X spectrum, JHF 8.4 Hz, ¥Ò J 8.9 Hz), 7.060 (m, 2H, m-6-C6H4F, 0.5 of AA'BB'X spectrum, JHF 8.6 Hz, ¥Ò J 8.7 Hz), 7.265 (m, 2H, o-6- C6H4F, half of AA'BB'X spectrum, JHF 5.3 Hz, ¥Ò J 8.7 Hz), 7.290 (m, 2H, p-3,3-Ph), 7.337.7.367 (m, 8H, o-3,3-Ph and m-3,3-Ph), 7.442 (m, 2H, o-5-C6H4F, 0.5 of AA'BB'X spectrum, JHF 5.2 Hz, ¥Ò J 8.9 Hz). 13C NMR (CDCl3) d: 74.66 (S, 1C, 3-C), 115.41 (Dd, 2CH, m-5-C6H4F, JCF 21.5 Hz), 115.59 (Dd, 2CH, m-6-C6H4F, JCF 22.0 Hz), 126.94 (D, 2CH, p-3,3-Ph), 128.38 (D, 4CH, m-3,3-Ph), 128.48 (D, 4CH, o-3,3- Ph), 128.59 (Dd, 2CH, o-5-C6H4F, JCF 8.3 Hz), 128.87 (Dd, 1CH, 6-CH, JCF 1.5 Hz), 129.50 (Dd, 2CH, o-6-C6H4F, JCF 8.3 Hz), 129.93 (Dd, 1CH, 4-CH, JCF 1.5 Hz), 131.29 (Sd, 1C, i-5-C6H4F, JCF 2.9 Hz), 133.77 (Sd, 1C, i-6-C6H4F, JCF 2.9 Hz), 134.89 (S, 1C, 5-C), 143.31 (S, 1C, 2-C), 145.05 (S, 2C, i-3,3-Ph), 161.73 (Sd, 1CF, p-6-C6H4F, JCF 247.6 Hz), 162.77 (Sd, 1CF, p-5-C6H4F, JCF 249.0 Hz).MS, m/z (%): 486.0698 (100, M+, C29H20F2Se), 409 (37), 405 (58), 391 (11), 327 (29), 309 (29), 285 (9), 233 (32), 209 (24), 183 (13), 165 (6). F(2) C(28) C(27) C(29) C(30) C(25) C(26) C(5) Se(1) C(2) C(6) C(7) C(8) C(9) C(10) F(1) C(11) C(12) C(3) C(19) C(20) C(21) C(22) C(23) C(24) C(4) C(14) C(13) C(15) C(16) C(17) C(18) Figure 1 Molecular structure of compound 4b. Selected bond lengths (A): Se(1).C(2) 1.920(3), Se(1).C(5) 1.907(3), C(2).C(6) 1.331(4), C(2).C(3) 1.531(3), C(3).C(4) 1.519(3), C(4).C(5) 1.329(4); selected bond angles (¡Æ): C(2).Se(1).C(5) 87.43(9), Se(1).C(2).C(3) 110.8(2), C(2).C(3).C(4) 105.7(2), C(3).C(4).C(5) 120.2(2), Se(1).C(5).C(4) 112.1(2), Se(1). C(2).C(6) 119.2(2); selected torsion angles (¡Æ): C(2).Se(1).C(5).C(4) 7.8(2), C(5).Se(1).C(2).C(3) .16.4(2), Se(1).C(2).C(3).C(4) 20.1(2), Se(1).C(2).C(6).C(7) .179.9(2). u u u Received: 25th January 2001; Com. 0

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) A new nitrene to carbene rearrangement upon photolysis of 4-amino-2,6-diazido-3,6-dichloropyridine Sergei V. Chapyshev*a and Paul R. Serwinskib a Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation. Fax: +7 096 515 3588; e-mail: chap@icp.ac.ru b Department of Chemistry, University of Massachusetts, Amherst, MA 01003–4510, USA.Fax: +1 413 545 4490; e-mail: serwinsk@chem.umass.edu 10.1070/MC2001v011n03ABEH001439 A novel rearrangement of quintet 2,6-dinitrenopyridine to 3-nitreno-1,2-diazacycloheptatrienylidene was discovered by EPR spectroscopy during the photolysis of 4-amino-2,6-diazido-3,5-dichloropyridine in a cryogenic matrix at 77 K.Despite years of scrutiny,1 the complete picture of the photochemistry of aromatic azides has only recently begun to unfold. Beyond offering mechanistic novelty, these compounds are widely used as photoresists in microelectronics1,2 and as photoaffinity labelling reagents in biochemistry.3 Early IR4 and EPR5 investigations revealed that triplet phenylnitrene 1 (formed on irradiation of phenyl azide in cryogenic matrices) readily isomerises into azacycloheptatetraene 2 and pyridylcarbene 3.This reaction can be suppressed by introduction of two ortho substituents to the nitrene unit of 1.6 Much less is known on the stability of polysubstituted á-heteroarylnitrenes. Thus, it was found7 that pyridyl-2,6-dinitrenes 4a–c or their nitrenoazide precursors are thermally and photochemically stable in cryogenic matrices and do not undergo isomerization involving intramolecular insertions of nitrenes into heterocyclic rings.On the other hand, a recently8 discovered rearrangement of 5 into 6 has demonstrated that such intramolecular reactions are in principle possible. Assuming that photochemical rearrangements of polysubstituted 2,6-dinitrenopyridines might yield new spin-carrying species with distinctive EPR spectral characteristics, encouraged us to obtain the EPR spectra of open-shell products formed on irradiation of diazide 7 in cryogenic matrices at 77 K.The irradiation of diazide 7† in a degassed frozen 2-methyltetrahydrofuran (MTHF) solution for 5 min with a xenon arc lamp (Pyrex filtered, > 300 nm) at 77 K led to the appearance of an EPR spectrum displaying strong signals at 463, 3356, 5310, 6788 and 7039 G (Figure 1).Based on the results of an eigenfield simulation10 [Figure 1(a)], the signals at 463 and 3356 G can be assigned to quintet dinitrene 9 with the zero field splitting (zfs) parameters |D/hc| = 0.247 cm–1 and |E/hc| = 0.052 cm–1. The zfs parameters deduced for 9 are very close to those reported for quintet dinitrene 4c.7(c) The presence of three strong signals at 5310, 6788 and 7039 G in the spectrum indicates the formation of new open-shell products in the photolysis of 7, species which were not observed previously upon irradiation of related polysubstituted 2,6-diazidopyridines.‡ By analogy with triplet nitrene11 and carbene spectra,12 the signals at 6788 and 7039 G can be assigned to two different triplet nitrene species, while † The synthesis of diazide 7 is described elsewhere.9 ‡ Weak signals of triplet carbenes were also observed previously in the EPR spectra of 4a,c.7(b),(c) That time we were unable to assign these signals.FTIR studies of the photolysis of dicyano derivatives of 4a,c in argon at 7 K revealed that these dinitrenes mostly undergo the opening of the pyridine ring to form presumably intermediates of the 12-type (appearance of new strong absorption at 2090 cm–1 and disappearance of bands of the pyridine ring).7(a) The PM3 geometry optimization of closedshell singlet configurations of 10-S'' yielded the structure of 12.The energies of open-shell 10-singlet and 11 lie 23.2 and 24.4 kcal mol–1 (PM3) above the energy of quintet 9, while the energy of 12 (formed from 10-S'') lies 4.1 kcal mol–1 below the energy of quintet 9.The EPR observations of weak carbene signals7(b),(c) along with the absence of the IR absorptions of N=C=C bonds of structures 117(a) during the photolysis of 4a–c are consistent with the results of these computations.Both experimental and computational data indicate that further transformations of quintet pyridyl-2,6-dinitrenes involve the intermediate formation of carbenes and opening of the pyridine rings rather than rearrangements of quintet 2,6-dinitrenes into structures 11. N N N H l = 485 nm l = 334 nm N R Cl Cl N N 1 2 3 4a–c N N N N Cl Cl 5 N N N N Cl Cl 6 l > 420 nm l > 320 nm a R = N3 b R = N c R = 3-azatricyclo[3.2.1.0]octane N NH2 Cl Cl N3 N3 7 N NH2 Cl Cl N N 9 N NH2 Cl Cl N N3 8 hv hv N N N Cl NH2 Cl 10 N N N Cl NH2 Cl 11 hv ? N N N Cl NH2 Cl 10-S'' NH2 Cl N2 NC Cl 12 ? N R N l > 254 nm 13a,b N N R 14a,b l > 254 nm N N R 15a,b 13–15: a R = H b R = CF3 N 16Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) the signal at 5310 G can be attributed to a single triplet carbene unit.The formation of all of the triplet species produced during the photolysis of 7 can readily be explained by a reaction scheme, which includes the rearrangement of quintet dinitrene 9 to carbenonitrene 10.¢Ô Similar rearrangements leading to 1,3-diazacycloheptatrienylidenes 14a (|D/hc| = 0.425 cm.1 and |E/hc| = 0.0222 cm.1)13(a) and 14b (|D/hc| = 0.450 cm.1 and |E/hc| = = 0.0059 cm.1)13(b) were detected previously in the photolysis of azides 13a,b.Unlike precursors 13a,b, diazide 7 has chlorine atoms at 3- and 5-positions of the pyridine ring; therefore, the ring expansion of 9 to 10 (such as that of 5 to 6) has precedent. According to the theory,14 the spin-carrying units of carbenonitrene 10 should be isolated from mutual ferromagnetic exchange interactions and give rise to EPR signals of isolated triplet nitrene and carbene units.The close similarity between the D-parameters of 14a,b and 10 (|D/hc| = 0.462 cm.1) supports the proposed formation of carbenonitrene 10. The signal at 6788 G can be assigned to triplet nitrene 8 (|D/hc| = 0.98 cm.1, |E/hc| = 0.002 cm.1), while the high-field signal at 7039 G can be attributed to an isolated nitrene unit of 10 (|D/hc| = 1.08 cm.1, |E/hc| = 0.002 cm.1).This is in good agreement with the previously studied azatricyclo[3.2.1.0]octane-substituted derivative of 8 (|D/hc| = 0.976 cm.1).11 This assignment is consistent with data from ref. 15 which demonstrate that vinyl nitrenes have substantially larger D-values than aromatic nitrenes. Previous attempts16,17 to explain the formation of seven-membered cyclic carbenes (CCs) and azacycloheptatetraenes (AHTs) upon the photolysis of aryl azides as a sequence of thermal transformations of singlet nitrenes into AHTs and the latter into CCs are in conflict with direct observations of photochemical interconversions of triplet nitrenes 1 and 5, on the one hand, and 2 and 6, on the other hand.4(b),8 Strong arguments in favour of the photochemical rearrangements of triplet nitrenes in AHTs come also from an analysis of the trapping of AHTs with dimethylamine during the photolysis of para-substituted phenyl azides (Table 1).16 Despite almost equal stability of all 5-substituted AHTs relative to the parent triplet nitrenes,¡× the yields of 3H-azepines (products of AHTs with dimethylamine) vary drastically.On the other hand, a nice correlation between the D-values of triplet nitrenes¢Ò and the yields of 3H-azepines indicates that the triplet units of nitrenes are the reactive centres in rearrangements of nitrenes into AHTs. Table 1 shows that the strengthening of electronic interactions between substituents and triplet units (this can be seen as a decrease in D-values for donorsubstituted nitrenes and as an increase in D-values for acceptorsubstituted nitrenes)15,18 increases the stability of nitrenes to the level at which they only undergo thermal self-dimerization to form corresponding azobenzenes in high yields.An analysis of the D-values of triplet nitrenes is also instructive for prediction of photochemical reactivity of pyridylnitrenes.¢Ò Thus, it has been shown7(b),11 that many substituted 2-nitrenopyridines with zfs parameters of |D/hc| = 0.976.1.040 cm.1 are very stable upon irradiation at l > 300 nm.By contrast, nitrenes 13a (|D/hc| = = 1.051 cm.1)13(a) and 13b (|D/hc| = 1.087 cm.1)13(b) readily rearrange into 15a,b on photolysis in cryogenic matrices.13 These results are consistent with our observations7(a).(c) that 2-nitrenopyridines with |D/hc| = 1.051.1.22 cm.1 are very photolabile and almost completely decompose to some diamagnetic products even at 7 K.¢Ô On the ground of these observations, we assume that 10 can only arise from 9 rather than due to initial rearrangement of 8 (|D/hc| = 0.98 cm.1) into a cyclic azidocarbene followed by deazetation of the latter to 10. The intense EPR signals of 10 evidence for relatively high photochemical stability of this intermediate.According to the theory,12(a) the larger the energy gap between the ground and highest-spin states of radicals, the higher the stability. Using CASSCF(8,8)/6-31G* computations, it has been shown17 that the triplet.singlet energy gaps in carbenes 14a and 16 are 2.6 and 1.4 kcal mol.1, respectively.Almost the same .E(T.S) values (2.2 kcal mol.1 for 14a and 1.3 kcal mol.1 for 16) were obtained by PM3 computations.¡× Despite this quite small difference in the triplet.singlet gaps of 14a and 16, the former carbene has a sufficiently long lifetime to be observable by EPR spectroscopy.13(a) The PM3 computations indicate that carbenonitrene 10 has the singlet ground state, which lies 1.2 and 10.4 kcal mol.1 below its triplet and quintet states, respectively. Obviously, the observable EPR signals of triplet carbene and extra-nitrene upon photolysis of 7 belong to thermally populated triplet spins of 10. Thus, many 4,4'-dinitrenostilbenes also display intense EPR signals of triplets in cryogenic matrices at 77 K despite the singlet ground ¡× According to our PM3 calculations, the energies of all 5-substituted derivatives of 2 (Table 1) lie 22.24 kcal mol.1 above the energies of the respective triplet nitrenes. The energy gap between 1 and 2 evaluated by CASSCF(8,8)/6-31G* computations is equal to 21.2 kcal mol.1.17 The structures of all open- and closed-shell singlet, triplet and quintet molecules under consideration were calculated with the full geometry optimization parameters using the PM3 method (RHF or UHF, SCF level).20 Table 1 D-values of para-substituted phenylnitrenes and the yields of azobenzenes and 3H-azepines from the photolysis of relevant phenyl azides. Nitrene |D/hc|a/cm.1 aD-values from ref. 18. bPhotolysis in neat cyclohexane.16 cPhotolysis in a mixture of cyclohexane and dimethylamine.16 Azobenzeneb (%) 3H-Azepinec (%) PhN 0.999 15 80 p-MeOC6H4N 0.936 80 27 p-Me2NC6H4N 0.896 92 0 p-ClC6H4N 0.951 80 100 p-BrC6H4N 0.911 80 71 p-IC6H4N 0.871 96 34 p-NCC6H4N 0.951 74 68 p-O2NC6H4N 0.964 73 < 3 ¢Ò Depending on the electronic properties of substituents, all substituted phenylnitrenes are divided into several groups.18 Within each of these groups, the chemical properties of nitrenes correlate well with D-values (Table 1).The electronic properties of nitrene centres in pyridyl-2- nitrenes are less sensitive to individual effects of substituents and mostly depend on the total electron-deficiency of the pyridine ring.11 Owing to this, a good correlation between the chemical properties and D-values of 2-nitrenopyridines is observed within all series of these compounds.The correlation between D-values and the chemical behaviour of cyano- and nitro-substituted phenylnitrenes (Table 1) resembles that observed for pyridyl-2-nitrenes. The drastically differing reactivities of cyano- and nitrosubstituted phenylnitrenes, despite a small difference in their D-values (0.013 cm.1), demonstrate that even small changes in spin densities on nitrene centres dramatically affected the reactivities of such species.Figure 1 (a) Simulated10 EPR spectrum for a randomly oriented system 9 with S = 2, |D/hc| = 0.247 cm.1 and |E/hc| = 0.052 cm.1; (b) EPR spectrum from the photolysis of diazide 7 (n0 = 9.607 GHz) at 77 K in an 2-methyltetrahydrofuran glass.The peaks TN, QN, TCN and R correspond to triplet nitrene 8, quintet dinitrene 9, triplet carbenonitrene 10 and a radical impurity from MTHF, respectively. (a) (b) QN QN R TCN TN TCN 0 2000 4000 6000 8000 10000 Magnetic field/GMendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) states of these species.19 The rather large singlet–quintet energy gap of carbenonitrene 10 suggests that this species is even more photochemically stable than triplet carbenes 14a,b.To our knowledge, the rearrangement of 9 into 10 is the first chemical reaction discovered for quintet dinitrenes. The high reactivity of 9 can be rationalised by an analysis of the D-values of this (|D/hc| = 0.247 cm–1) and two other parent 4a (|D/hc| = = 0.283 cm–1)7(b) and 4c (|D/hc| = 0.257 cm–1)7(c) quintet dinitrenes. The smallest D-value for 9 indicates that exchange interactions between unpaired electrons of two nitrene units in 9 are the weakest.15 This is also supported by the results of PM3 computations, which show that the molecule of 9 has the longest N–C=N–C–N distance between two nitrene units and the shortest C(4)–N, C(2)–C(3) and C(6)–C(5) bonds.Obviously, the weakening of conjugation between the nitrene units and the pyridine ring in quintet pyridyl-2,6-dinitrenes, as in the case of triplet pyridyl-2-nitrenes, favours the localization of spin density on the nitrene centres, thus increasing their reactivity. As has been noted earlier, the border between ‘stable’ and ‘reactive’ triplet pyridyl-2-nitrenes lies in the region of nitrenes with |D/hc| = = 1.04–1.05 cm–1. Judging on results of the photolysis of 4a, 4c and 9, a similar border between ‘stable’ and ‘reactive’ quintet pyridyl-2,6-dinitrenes lies in the region of nitrenes with |D/hc| = = 0.25–0.26 cm–1.Taking into account small magnitudes of the D-parameters of quintet dinitrenes, it is reasonable to assume that even very small changes in the D-values of quintet pyridyl- 2,6-dinitrenes (much smaller than in the case of triplet nitrenes)¶ evidence for essential changes in the reactivities of such species.We are grateful to Professor P. M. Lahti (University of Massachusetts, Amherst) for EPR simulations of quintet dinitrene 9 and to Professor M. S. Platz (Ohio State University, Columbus) for helpful discussions.References 1 (a) P. A. S. Smith, in Azides and Nitrenes, Reactivity and Utility, ed. E. F. V. Scriven, Academic Press, New York, 1984, ch. 3; (b) E. F. V. Scriven and K. Turnbull, Chem. Rev., 1988, 88, 297; (c) G. B. Schuster and M. S. Platz, Adv. Photochem., 1992, 17, 69. 2 (a) D. S. Breslow, in Azides and Nitrenes, Reactivity and Utility, ed. E. F. V. Scriven, Academic Press, New York, 1984, ch. 10; (b) E. W. Meijer, S. Nijhuis and F. C. B. M. van Vroonboven, J. Am. Chem. Soc., 1988, 110, 7209. 3 (a) H. Bayley and J. V. Staros, in Azides and Nitrenes, Reactivity and Utility, ed. E. F. V. Scriven, Academic Press, New York, 1984, ch. 9; (b) S. A. Fleming, Tetrahedron, 1995, 51, 12479. 4 (a) O. L. Chapman and J. P. LeRoux, J. Am. Chem. Soc., 1978, 100, 282; (b) J.C. Hayes and R. S. Sheridan, J. Am. Chem. Soc., 1990, 112, 5879. 5 O. L. Chapman, R. S. Sheridan and J. P. LeRoux, J. Am. Chem. Soc., 1978, 100, 6245. 6 (a) I. R. Dunkin and P. C. P. Thomson, J. Chem. Soc., Chem. Commun., 1982, 1192; (b) I. R. Dunkin, T. Donnelly and T. S. Lockhart, Tetrahedron Lett., 1985, 26, 359. 7 (a) S. V. Chapyshev, A. Kuhn, M. Wong and C. Wentrup, J.Am. Chem. Soc., 2000, 122, 1572; (b) S. V. Chapyshev, R. Walton, J. A. Sanborn and P. M. Lahti, J. Am. Chem. Soc., 2000, 122, 1580; (c) S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 114; (d) S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 187. 8 G. Bucher, F. Siegler and J. J. Wolff, J. Chem. Soc., Chem. Commun., 1999, 2113. 9 S. V. Chapyshev and M. S.Platz, Mendeleev Commun., 2001, 56. 10 (a) Y. Teki, I. Fujita, T. Takui, T. Kinoshita and K. Itoh, J. Am. Chem. Soc., 1994, 116, 11499; (b) K. Sato, PhD Thesis, Osaka City University, 1994. 11 S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 7. 12 (a) W. Sander, G. Bucher and S. Wierlacher, Chem. Rev., 1993, 93, 1583; (b) S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 138. 13 (a) C. Wentrup, M. Kuzaj and H. Luerssen, Angew. Chem., Int. Ed. Engl., 1986, 25, 480; (b) R. A. Evans, M. Wong and C. Wentrup, J. Am. Chem. Soc., 1996, 118, 4009. 14 S. Nimura and A. Yabe, in Magnetic Properties of Organic Materials, ed. P. M. Lahti, Marcel Dekker, New York, 1999, ch. 7. 15 E. Wasserman, Prog. Phys. Org. Chem., 1971, 8, 319. 16 Y.-Z. Li, J. P. Kirby, M. W. George, M. Poliakoff and G. B. Schuster, J. Am. Chem. Soc., 1988, 110, 8092. 17 W. L. Karney and W. T. Borden, J. Am. Chem. Soc., 1997, 119, 1378. 18 J. H. Hall, J. M. Fargher and M. R. Gisler, J. Am. Chem. Soc., 1978, 100, 2029. 19 M. Minato and P. M. Lahti, J. Am. Chem. Soc., 1997, 119, 2187. 20 (a) J. J. P. Stewart, J. Comput. Chem., 1989, 10, 221; (b) Spartan, version 4.0, Wavefunction, Inc., USA, 1995. Received: 1st February 2001; Com. 01/1765

ISSN:0959-9436     

出版商:RSC    

年代:2001

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) Are aroylnitrenes species with a singlet ground state? Nina P. Gritsan*a and Elena A. Pritchinab a Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation. Fax: +7 3832 34 2350; e-mail: gritsan@ns.kinetics.nsc.ru b Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russian Federation 10.1070/MC2001v011n03ABEH001376 The B3LYP calculations of the properties of singlet and triplet benzoylnitrenes and naphthoylnitrenes testify to the stabilization of the 1A' state relative to the 3A'' state due to the intermediacy of an NCO structure between nitrene and oxazirene in the 1A' state.Nitrenes are the key intermediates of azide photolysis and thermolysis.It is well known1 that alkyl- and arylnitrenes have a triplet ground state. The case with aroylnitrenes1.4 is more complicated and inconsistent. Taking into account that aroylnitrenes have a singlet ground state, Melvin and Schuster5 proposed acetyl-substituted aroyl azides as potential photolabeling agents. Nitrenes, as well as better studied carbenes, have a nontrivial electronic structure with two valence electrons, which are distributed between two nonbonding molecular orbitals (NBMOs).In carbenes, one of the NBMOs is a pure p-AO; the second hybridised ¥ò orbital exhibits a considerable 2s character and thus a much lower energy. The ground state of the parent carbene CH2 is a triplet state.The singlet state, in which both of the nonbonding electrons occupy the ¥ò NBMO, is only 38 kJ mol.1 higher in energy. Phenyl6 and methyl7 substituents reduce .EST by 20.30 kJ mol.1, and halogens make a singlet state to be the ground state.8 Unlike carbenes, in the parent nitrene NH, both of the NBMOs are pure p-AOs. Lower Coulomb repulsion in a triplet state cannot be compensated by occupation of the lower MO by two electrons in a singlet state, as in the case of carbene.Therefore, .EST in NH (151 kJmol.1)9 is four times higher than that in CH2. The methyl substituent reduces .EST by 21 kJ mol.1 (ref. 10) (Figure 1) similarly to the case of carbene. However, .EST in phenylnitrene is almost halved (75 kJ mol.1)11. Calculations12( a) demonstrated that the relative energy of the closed-shell singlet (1A1) in phenylnitrene is reduced slightly (~16 kJ mol.1, Figure 1) as in phenylcarbene.The lowest singlet state of phenylnitrene has the open-shell electronic configuration (1A2).12 This state is substantially stabilised due to localization of the unpaired ¥�-electron in the phenyl ring.12(b) Nevertheless, of two states of nitrenes with the same open-shell electronic configurations, the triplet state should be lower in energy (Hund¡�s rule) due to lower Coulomb repulsion in this state.¢Ó Knowing the electronic structure of nitrenes and the influence of substituents on .EST, it is difficult to explain why the singlet state of aroylnitrenes could be a ground state.Therefore, this fact was not explained in the literature.3.5 The goal of this work was to understand whether it is really possible for aroylnitrene to have a singlet ground state and what is the reason for its dramatic stabilization.For this purpose, we calculated the properties of benzoylnitrene 1, 2-naphthoylnitrene 2 and formylnitrene 3 as a model compound in the lowest singlet and triplet states. The calculations were performed by the standard B3LYP/6-31G* method14 using the Gaussian-98 program.15 The DFT calculations with the B3LYP functional were very successful for determining .EST in carbenes.16.18 In model formylnitrene, the CASSCF(8,8) calculations19 were also performed.All structures were found to be the minima on the potential energy surfaces. The zero point energies were calculated using harmonic frequencies, and they were taken into account in the calculations of .EST.The stability of SCF solutions was tested. The instability of the triplet wavefunctions under perturbations was found, and the reoptimization of triplet wavefunctions to lower energy solutions was performed. The calculated energies of the lowest singlet and triplet states of aroylnitrenes 1 and 2 and formylnitrene 3 are displayed in Figure 1, which demonstrates a dramatic (100.130 kJ mol.1) reduction of .EST for these nitrenes as compared with NH, MeN and PhN.The reason for this wonderful stabilization of a singlet state can be understood from the calculated geometry of singlet species. The bond lengths and bond angles of the CNO fragment in the same spin states of nitrenes 1.3 are very similar (differences are less than 0.01 A and 1��).As an example, Figure 2 displays the calculated geometry for nitrene 1. In the triplet nitrene, the C=O bond length (1.242 A) has a typical value, and the C.N bond length (1.381 A) is intermediate between those of 3PhN (1.34 A)12(b) and 3MeN (1.42 A).20 In the singlet 1A' state (Figure 2), the CO bond (1.316 A) is much longer than that in the triplet state and close to the single bond length. The CN bond length (1.267 A) is substantially shorter than that in the triplet state and close to the CN double bond length.The NCO bond angle is very small (~86¡Æ). There is no alteration in C.C bond lengths in the phenyl rings of both triplet and singlet aroylnitrenes (Figure 2). The highest doubly occupied Kohn.Sham orbital in the singlet 1A' state is the ¥�-type orbital delocalised in the CON fragment.The CON fragment in the 1A' state exhibits the structure of cyclic oxazirene; however, the N.O distance (1.761 A) is longer than the normal ordinary N.O single bond (about 1.4 A or ~1.5 A in strained cycles).21 Note that the singlet formylmethylene (1FM) has a similar unusual geometry.22 The CCO bond angle is also small (~91¡Æ), and the CO distance (1.87 A) is somewhat longer than the NO distance in 11.Oxirene (Ox) is a very flat minimum on the potential energy surface, and the activation energy of its rearrangement to 1FM is as low as 0.3 kcal mol.1.22 Unlike HC(O)CH, the singlet potential energy surface of R-C(O)N has only one minimum, i.e., the species in the 1A' ¢Ó This statement does not concern the situation with para-phenylenedinitrenes, para-nitrenophenylcarbenes and related species.13 150 100 50 0 Relative energy/kJ mol.1 NH MeN PhN 1 2 3 B3LYP/6-31G* CISD+Q/DZ+d 3A'' 3A2 3¥Ò. 3A2 3A'' 3A'' 1A' 1A' 1A' 1A2 1A1 1A' 1. B3LYP/6-31G* Figure 1 Comparison of relative energies of lowest singlet and triplet states of nitrenes, experimental (NH, MeN, PhN) and calculated by CISD+Q [PhN, ref. 12(a)] and B3LYP/6-31G* (PhN, 1, 2 and 3, this work). C N O C N O 1.394 1.397 1.399 1.403 1.391 1.484 119.7 1.381 1.242 2.225 115.9 1.403 1.391 1.399 1.397 1.393 1.401 1.403 1.451 142.4 1.267 1.316 1.761 85.9 Figure 2 Bond lengths (A) and bond angles (¡Æ) in the singlet 1A' and triplet 3A'' states of benzoylnitrene calculated using the B3LYP/6-31G* method. 3A'' 1A'Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) with the structure superimposed of nitrene and oxazirene. The formation of this singlet species can be responsible for the unusual properties of aroylnitrenes.3.5 According to the B3LYP/6-31G* calculations, the energy differences between these species (1A') and triplet nitrenes (3A'' ) are small, but the triplet states (31.33) are lower in energy (Figure 1).The results of our CASSCF(8,8)/cc-pVTZ calculations for model formylnitrene are very similar to those obtained by the B3LYP method (Figure 1). The singlet species in the 1A' state has a structure superimposed of nitrene and oxazirene, and its energy is 10.2 kJ mol.1 higher than that of 33 (34.1 kJ mol.1 in DFT calculations). Shapley and Bacskay23 performed highlevel calculations of a potential-energy surface associated with the dissociation of the formaldiminoxy radical CH2NO. Along with other products and intermediates, they calculated the structures es of triplet formylnitrene (3A'') and ¡®cyclic¡�- C(H)NO (1A').The structures of these intermediates calculated using the MP2/6-31G* and CASSCF(11,11)/cc-pVDZ methods are very similar to those calculated in this work.The .EST values calculated from published data23 are 14.9 kJ mol.1 and 3.1 kJ mol.1 at the CASPT2(11,11) and QCISD(T) levels of the theory with the cc-pVTZ basis set, respectively. Using the G2 method,23 .EST was calculated to be .10.6 kJ mol.1. Therefore, the standard B3LYP/6-31G* calculations (Figure 1) overestimated .EST by 20.40 kJ mol.1.Taking into account this overestimation, we can predict that the .EST values for aroylnitrenes 1 and 2 will be close to or, most probably, lower than zero. The B3LYP calculations using the PCM model24 for solvation showed the further reduction of .EST for all nitrenes 1.3 by 5.6 kJ mol.1 in heptane and by 9.10 kJ mol.1 in acetonitrile.Therefore, the calculations revealed that, in the case of aroylnitrenes, the singlet 1A' state should be lower in energy than the triplet 3A'' state. However, the species in the 1A' state has a structure superimposed of the nitrene and oxazirene. If the 1A' state is the lowest energy minimum, it is easy to explain why the EPR spectra of triplet aroylnitrenes were not detected upon photolysis of aroyl azides.3,4 The direct measurement of spectra should be performed and the reaction kinetics of intermediates should be studied to prove that the singlet species with the structure superimposed of nitrene and oxazirene is really the reactive intermediate of aroyl azide photolysis.To predict the electronic absorption spectra of these intermediates, the time-dependent DFT calculations25 at the B3LYP/ 6-31+G* level were performed.The near-UV and visible spectrum of the species in the 1A' state has transitions at 532 ( f = 0) and 306 nm ( f = 6¡¿10.3) in the case of benzoylnitrene. The spectrum of naphthoylnitrene has two transitions with non-zero intensities at 319 ( f = 3.4¡¿10.3) and 313 nm ( f = 1.5¡¿10.2). This is in agreement with the fact that no intermediates with absorption in the region 350.600 nm were observed upon photolysis of benzoyl and naphthoyl azides.3,5 This work was supported by the Russian Foundation for Basic Research (grant no. 01-03-32864), the Ministry of Higher Education of the Russian Federation and the Swiss National Science Foundation (SCOPES 2000.2003, grant no. 7SUPJ062336). References 1 Azides and Nitrenes. Reactivity and Utility, ed. E. F. V. Scriven, Academic Press, New York, 1984. 2 (a) M. Inagaki, T. Shingaki and T. Nagai, Chem. Lett., 1981, 1419; (b) M. Inagaki, T. Shingaki and T. Nagai, Chem. Lett., 1982, 9. 3 T. Autrey and G. B. Schuster, J. Am. Chem. Soc., 1987, 109, 5814. 4 M. E. Sigman, T. Autrey and G. B. Schuster, J. Am. Chem. Soc., 1988, 110, 4297. 5 T. Melvin and G. B. Schuster, Photochem. Photobiol., 1990, 51, 155. 6 P. R. Schreiner, W. L. Karney, P. R. Schleyer, W. T. Borden, T. P. Hamilton and H. F. Schaefer, J. Org. Chem., 1996, 61, 7030. 7 S. Matzinger and M. P. Fulscher, J. Phys. Chem., 1995, 99, 10747. 8 R. L. Schwartz, G. E. Davico, T. M. Ramond and W. C. Lineberger, J. Phys. Chem. A., 1999, 103, 8213. 9 P.C. Engelking and W. C. Lineberger, J. Chem. Phys., 1976, 65, 4323. 10 M. J. Travers, D. C. Cowles, E. P. Clifford, G. B. Ellison and P. C. Engelking, J. Chem. Phys., 1999, 111, 5349. 11 M. J. Travers, D. C. Cowles, E. P. Clifford and G. B. Ellison, J. Am. Chem. Soc., 1992, 114, 8699. 12 (a) S.-J. Kim, T. P. Hamilton and H. F. Schaefer, J. Am. Chem. Soc., 1992, 114, 5349; (b) W. L.Karney and W. T. Borden, J. Am. Chem. Soc., 1997, 119, 1378. 13 (a) M. Minato and P. M. Lahti, J. Am. Chem. Soc., 1997, 119, 2187; (b) A. Nicolaides, T. Enoyo, D. Miura and H. Tomioka, J. Am. Chem. Soc., 2001, 123, 2628. 14 (a) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; (b) C. Lee, W. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785. 15 M. J. Frisch, G.W. Trucks, H. B. Schlegel, G. E.Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A. Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich, J. M. Mnillam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Cliford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K.Raghavachari, J. B. Foresman, J. Cioslowski, J. V. Ortiz, B. B. Stafanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Goperts, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, C. Gonzalez, M. Challacombe, P. M.W. Gill, B. Johnson, W. Chen, M.W. Wong, J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle and J. A. Pople, Gaussian-98, Revision A.6, Gaussian, Inc., Pittsburgh, PA 1998. 16 S. H. Worthington and C. J. Cramer, J. Phys. Org. Chem., 1997, 10, 755. 17 J. C. Poutsma, J. J. Nash, J. A. Paulino and R. R. Squires, J. Am. Chem. Soc., 1997, 119, 4686. 18 M. H. Lim, S. E. Worthington, F. J. Dulles and C. J. Cramer, in Chemical Applications of Density Functional Theory, ACS Symposium Series, eds. B. B. Laird, R. B. Ross and T.Ziegler, ACS, Washington, DC, 1996, vol. 629, p. 402. 19 B. O. Roos, Adv. Chem. Phys., 1987, 69, 339. 20 C. R. Kemnitz, G. B. Ellison, W. L. Karney and W. T. Borden, J. Am. Chem. Soc., 2000, 122, 1098. 21 (a) A. I. Kitaigorodskii, P. M. Zorkii and V. K. Belskii, Struktura organicheskikh soedinenii. Dannye strukturnykh issledovanii. 1929.1970 (Structure of the organic compounds. Data of structure study. 1929. 1970), Nauka, Moscow, 1980 (in Russian); (b) A. I. Kitaigorodskii, P. M. Zorkii and V. K. Belskii, Struktura organicheskikh soedinenii. Dannye strukturnykh issledovanii. 1971.1973 (Structure of the organic compounds. Data of structure study. 1971.1973), Nauka, Moscow, 1982 (in Russian). 22 A. P. Scott, R. H. Nobes, H. F. Schaefer and L. Radom, J. Am. Chem. Soc., 1994, 116, 10159. 23 W. A. Shapley and G. B. Bacskay, J. Phys. Chem., 1999, 103, 4514. 24 M. Cossi, V. Barone, R. Cammi and J. Tomasi, Chem. Phys. Lett., 1996, 255, 327. 25 (a) E. K. U. Gross and W. Kohn, Adv. Quantum Chem., 1990, 21, 255; (b) M. E. Casida, in Recent Advances in Density Functional Methods, ed. D. P. Chong, World Scientific, Singapore, 1995, vol. 1; (c) K. B. Wiberg, R. E. Stratmann and M. J. Frisch, Chem. Phys. Lett., 1998, 297, 60. C C H O H 1.355 A 1.873 A C C H O H 1 2 1.274 A 2 1 1 2 1.491 A 1.276 A 1FM Ox 90.8¡Æ Received: 14th September 2000; Com. 00/17

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) New type of pyrimidinophanes with á,ù-bis(uracil-1-yl)alkane and bis(uracil-5-yl)methane units Vyacheslav E. Semenov,* Valentin D. Akamsin, Vladimir S. Reznik, Yurii Ya. Efremov, Dilyara R. Sharafutdinova, Adilya A. Nafikova and Nail M. Azancheev 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: zobov@iopc.kcn.ru 10.1070/MC2001v011n03ABEH001440 New pyrimidinophanes containing four uracil units connected with methylene bridges through the N(1) and C(5) atoms of pyrimidine rings were obtained by treatment of 1,4-bis(3,6-dimethyluracil-1-yl)butane with paraform.Macrocyclic compounds consisting of purine and pyrimidine bases are interesting model objects for the study of stacking structures in nucleic acids and can serve as precursors for host– guest molecules.While purinophanes of different types have been synthesised and well studied, pyrimidinophanes have been reported only recently.2–6 In the course of an investigation aimed at the creation of effective macrocyclic complexating agents, T.Itahara2,5 elaborated a direct method of pyrimidinophane preparation. These pyrimidinophanes, which were synthesised for the first time previously,7–10 consisted of two uracil or 2,4-dithiouracil units linking each other with polymethylene bridges through the N(1) and N(3) atoms of pyrimidine rings. They were obtained by the treatment of uracils and 2,4-dithiouracils, respectively, with dihaloalkanes in DMF as a solvent in the presence of NaH.Almost all of the pyrimidinophanes reported before are structurally similar to the above compounds, and they were synthesised by either the interaction of salts with dihaloalkanes and 1,3-bis(bromoalkyl)uracils6 or the oxydation of substituents at the N(1) atom of the pyrimidine ring in á,ù'-bis(uracil-3-yl)- alkanes.3,11 A pyrimidinophane consisting of two uracil units was obtained by the reaction of 1-(hydroxyethyl)-3,6-dimethyluracil and paraform to afford 5,5'-bis[(2-hydroxyethyl)-3,6-dimethyluracilyl]- methane followed by sequential replacement of hydroxyls with thiol groups and oxidation to disulfide bridges.12 Note that uracils have a property to afford 5,5'-methylene bis-derivatives with paraform in water.13,14 We applied the reaction to the direct preparation of the polycyclic pyrimidinophanes.We examined the interaction of bis(3,6-dimethyluracil-1-yl)- butane15 1 with paraform in aqueous 0.1 M HCl at different 1:paraform ratios (1:1–1:10) and temperatures (50–100 °C). In no cases marocyclic compounds were detected among the final products of the reactions by electron-ionization mass spectrometry, and only compounds with linear structures were found.When the reaction between 1 and paraform at the 1:paraform ratio 1:1.1 and at 95–98 °C was performed in aqueous 0.1 M HCl containing an equimolar amount of copper(I) ions 8,14,23,29,31,32,33,34-octamethyloctaazapentacyclo[25,3,1,16,10, 112,16,121,25]tetratriaconta-10(34),12(33),25(32),27(31)-tetraene- 7,9,13,15,22,24,28,30-octaone 2 was obtained in 10% yield.† The participation of monovalent copper in this reaction is unclear.However, because copper(I) complexes with pyrimidine derivatives were reported elsewhere,16 we suppose that 1 can be associated with copper(I) ions to promote ring-closure reactions at the 5-positions of the pyrimidine rings.The structure of compound 2 was confirmed by mass spectrometry and NMR spectroscopy. The high-resolution mass spectrum exhibits the most intense peak of the molecular ion M+· with m/z 692.328. The found mass of the molecular ion is in a very good agreement with the calculated value 692.3282 for C34H44N8O8. Moreover, the formation of the doubly charged ion (z = 2) with m/z 346.166 (calculated 346.1641 for C34H44N8O8) additionally confirms the suggested structure.The only fragment in the region of heavy masses is [M – Me]+. The 1H NMR spectra exhibit five peaks with the integral intensity ratio 2:3:3:1:2, and the signal assigned to C(5)–H of the pyrimidine ring (5.65 ppm15) is absent, whereas a signal appears at 3.69 ppm, which is typical of a methylene group bridging the C(5) atoms of two uracils.14 In the 13C NMR spectra, the peak of C(5) of pyrimidine rings is observed with the multiplicity corresponding to only far C–H interactions (nJCH £ 5 Hz) unlike the doublet structure of the signal with 1JCH 178 Hz for initial compound 1.Thus, this approach can be promising for the preparation of pyrimidinophanes with the structure like 2; moreover, the initial units can carry functional substituents.References 1 F. Seyama, K. Akahori, Y. Sakata, S. Misumi, M. Aida and C. Nagata, J. Am. Chem. Soc., 1988, 110, 2192. 2 T. Itahara, Bull. Chem. Soc. Jpn., 1996, 69, 3239. † Pyrimidinophane 2. A mixture of 1 (3 g, 9 mmol), paraform (0.3 g, 10 mmol) and Cu2Cl2 (0.9 g, 4.5 mmol) was stirred for 30 h in 150 ml of an aqueous 0.1 M HCl solution at 95–98 °C.The precipitate was filtered off, dried and refluxed in 50 ml of chloroform. The undissolved residue was filtered off, and the rest solution was concentrated and chromatographed on Al2O3 with activity II. A dichloromethane–methanol (60:1) eluent was used, and the fraction with Rf 0.30 (Silufol; CH2Cl2–MeOH, 20:1) was separated.After evaporation of the solvent, 25 ml of diethyl ether were added to the residue and filtered to give 0.3 g (10%) of 2. Small white crystals soluble in CH2Cl2 and CHCl3, mp > 320 °C. 1HNMR (250 MHz, CDCl3) d: 1.65 (br. m, 8H, CCH2C), 2.19 (s, 12H, CpyrMe), 3.31 (s, 12H, NMe), 3.69 (s, 4H, CpyrCH2Cpyr), 3.89 (br. m, 8H, NCH2C). 13C NMR (250 MHz, CDCl3) d: 16.59 [MeC(6)pyr], 22.33 [CH2C(5)pyr], 25.52 (CCH2C), 28.43 (MeN), 44.81 (CH2N), 110.36 [C(5)pyr], 149.26 [C(6)pyr], 151.61 [C(2)pyr], 162.77 [C(4)pyr].MS, m/z (%): 693 (40), 692 (100) [M+], 677 (24), 347 (17), 346 (23) [M2+], 195 (36), 153 (31). Mass spectra were recorded on an MX-1310 instrument, the ionization energy was 60 eV, the emission current was 60 µA, the direct evaporation system was kept at 306 °C.N N Me O Me O (CH2 )4 N N Me O Me O 1 N N Me O Me O (CH2 )4 N N Me O Me O 2 N N Me O Me O (CH2 )4 N N Me O Me O H2C CH2 (CHOH)n 0.1 M HCl, Cu2Cl2Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) 3 V. Caplar, L. Tumur and M. Zinic, Croat. Chem. Acta, 1996, 69, 617. 4 S. Kumar, D. Paul and H. Singh, Tetrahedron Lett., 1997, 38, 3607. 5 T. Itahara, J. Heterocycl. Chem., 1997, 34, 687. 6 A. S. Mikhailov, N. G. Pashkurov, V. S. Reznik, R. Kh. Giniyatullin, V. I. Skuzlova, Yu. Ya. Efremov, D. R. Sharafutdinova, R. R. Shagidullin, A. V. Chernova, G. M. Dorozhkina, A. A. Nafikova and N. M. Azancheev, Dokl. Ross. Akad. Nauk, 1998, 362, 643 [Dokl. Chem. (Engl. Transl.), 1998, 203]. 7 M. M. Htay and O. Meth-Cohn, Tetrahedron Lett., 1976, 1, 79. 8 Yu.S. Shvetzov, A. N. Shirshov and V. S. Reznik, Izv. Akad. Nauk SSSR, Ser. Khim., 1976, 1103 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1976, 25, 1072). 9 A. S. Mikhailov, N. G. Pashkurov and V. S. Reznik, Izv. Akad. Nauk SSSR, Ser. Khim., 1982, 930 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1982, 31, 822). 10 K. Golankiewicz and B. Skalski, Polish J. Chem., 1978, 52, 1365. 11 T. Kinoshita, S. Odawara, K. Fukumura and S. Furukawa, J. Heterocycl. Chem., 1985, 22, 1573. 12 T. Kinoshita, H. Tanaka and S. Furukawa, Chem. Pharm. Bull., 1986, 34, 1809. 13 W. Pfleiderer, F. Sagi and L. Grozinger, Chem. Ber., 1966, 99, 3530. 14 T. Kinochita, M. Kondo, H. Tanaka and S. Furukawa, Synthesis, 1986, 859. 15 V. E. Semenov, V. D. Akamsin and V. S. Peznik, Zh. Obshch. Khim., 2001, in press. 16 P. Akrivos, P. Karagiannidis, J. Herrema and M. Luic, J. Coord. Chem., 1995, 36, 259. Received: 7th February 2001; Com. 01/1766

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) Transformation of myrtenoic acid nitrile to aminophospholene oxide by the reaction with dibenzylphosphine oxide: the X-ray structure of (1S*,2R*,6R*,8R*)-5-benzyl-9,9-dimethyl-5-oxo-4-phenyl- 5-phosphatricyclo[6.1.1.02,6]dec-3-en-3-ylamine Vasilii D. Kolesnik,a Tatyana V. Rybalova,b Yury V. Gatilovb and Alexey V. Tkachev*b a Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russian Federation b N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation. Fax: +7 3832 34 4752; e-mail: atkachev@nioch.nsc.ru 10.1070/MC2001v011n03ABEH001449 The reaction of dibenzylphosphine oxide with myrtenoic acid nitrile in tert-butyl methyl ether in the presence of sodium hydride results in the formation of substituted aminophospholene oxide in good yield (83%).For a long time the addition of phosphorus(III) halides to dienes has been the basic way for the synthesis of five-membered phosphorus- containing heterocycles.1.3 It was found that the reaction of ¥á,¥â-unsaturated esters4 and ketones5 with secondary phosphine oxides containing a benzyl group results in the formation of corresponding phosphorus-containing heterocycles. We found that treatment of myrtenoic acid nitrile 1 (prepared from racemic myrtenal oxime according to the known method6) with dibenzylphosphinous acid7 in the presence of sodium hydride results in the formation of aminophospholene oxide 3 (Scheme 1).In contrast to the previously reported procedures for ¥á,¥â-unsaturated esters and ketones with the use of THF,4,5 we carried out the reaction in tert-butyl methyl ether as a solvent. The new solvent for this condensation possesses a good dissolving ability towards the sodium salt of dibenzylphosphinous acid. Additionally, tert-butyl methyl ether is immiscible with water and improves the isolation procedure as compared to the traditional procedures.¢Ó The mechanism of addition of disubstituted phosphinous acids to unsaturated esters8 includes the primary addition of phosphinites to the carbon.carbon double bond followed by the addition of a C-anion of the benzylic type to the carbonyl group.The mechanism of the reaction of ¥á,¥â-unsaturated nitriles seems to be similar, and the addition of the sodium salt of dibenzylphosphine oxide to the carbon.carbon double bond results in primary adduct 2 (Scheme 1), which then undergoes intramolecular cyclisation to form aminophospholene oxide 3.It was shown8 that in case of the reaction of bulky substrates the use of the second equivalent of a base (to generate a dianion) increased the yields of phospholene oxides.We also used two equivalents of the base because the substrate is sterically hindered. 1H, 13C and 31P NMR data show the reaction product to be a single stereoisomer.¢Ô The addition of dibenzylphosphine oxide to nitrile 1 is possible only at the least hindered ¥á-side of the molecule. According to PM3 calculations, the cis-fusion of a phospholene ring and a pinane moiety is preferable to the transfusion (..H0 f = 12.15 kcal mol.1).In case of the trans-fusion, the vicinal spin.spin coupling constants of P.C(6).C(2).C(1) and P.C(6).C(7).C(8) in the NMR spectra should be high. However, the experimental values 3JC.P 0.3 Hz lend support to the cis-fusion. The structure of compound 3 with a chiral phosphorus atom (phosphoryl oxygen trans- to the H6 atom) was confirmed by X-ray analysis¡× (Figure 1).Bond lengths in compound 3 were found to be usual.9 ¢Ó Powdered NaH (0.27 g, 6.80 mmol, Fluka, assay 55.65%) was added portionwise to a solution of dibenzylphosphine oxide (1.56 g, 6.80 mmol) in tert-butyl methyl ether (25 ml). The suspension was refluxed with stirring for 20 min.A solution of myrtenoic acid nitrile 1 (6.80 mmol) in tert-butyl methyl ether (10 ml) was then added dropwise, and the resulting mixture was stirred at reflux for 1 h. A new portion of NaH (0.27 g, 6.80 mmol) was added, and the mixture was additionally refluxed for 1 h. The reaction mixture was cooled to room temperature, diluted with tert-butyl methyl ether (10 ml), washed with brine (30 ml) and dried over Na2SO4.Removal of the solvent left crude aminophospholene oxide as a crystalline solid in 83% yield. Scheme 1 The numbering is given only for NMR interpretation. CN O P H Ph Ph NaH ButOMe N P O Ph Ph 1 2 P H2N O 1 2 3 4 6 7 8 9 10 11 12 a b c d a' b' c' d' 83% 3 C(12) C(11) C(9) C(1) C(8) C(10) C(7) C(6) C(2) C(3) N(27) C(4) P(5) O(14) C(21) C(22) C(23) C(24) C(25) C(26) C(13) C(15) C(16) C(17) C(18) C(19) C(20) Figure 1 Molecular structure of compound 3.The rings C(1).C(2).C(6). C(7).C(8).C(9) and C(1).C(2).C(6).C(7).C(8).C(10) adopt the sofa shape, for which the atoms C(9) and C(10) deviate from the plane C(1).C(2). C(6).C(7).C(8) [planar within 0.056(1) A] by 1.043(3) and .1.104(3) A, respectively. The four-membered ring is bent by 37.4(1)¡Æ along the C(1)¡�¡�¡� C(8) line.The phosphorus-containing ring takes the shape of an envelope, the C(6) atom being out of plane by 0.202(2) A. The amino group is planar and conjugated with the double bond whereas the C(21).C(26) phenyl ring is removed from conjugation: the dihedral angle between the double bond and ring planes is 71.04(7)¡Æ. Molecular chains along the a axis are formed by hydrogen bonds N(27).H¡�¡�¡�O(14) (0.5 .x, y . 0.5, z) [H¡�¡�¡�O 1.95(3) A, N.H¡�¡�¡�O 164(2)��].Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) Thus, the reaction of dibenzylphosphine oxide with an unsaturated nitrile led to aminophospholene oxide. Previously, aminophospholene oxides were prepared by multi-step syntheses.10,11 This work was supported by the Russian Foundation for Basic Research (grant no. 99-07-04729) and INTAS (grant no. 97-0217). References 1 L. D. Quin, J. P. Gratz and T. P. Barket, J. Org. Chem., 1968, 33, 1034. 2 G.Markl, Angew. Chem., Int. Ed. Engl., 1965, 4, 1023. 3 L. D. Quin, The Heterocyclic Chemistry of Phosphorus: Systems Based on the Phosphorus.Carbon Bond, Wiley-Interscience, New York, 1981, p. 235. 4 R. Bodalski and K. M. Pietrusiewicz, Tetrahedron Lett., 1972, 41, 4209. 5 R. Bodalski, K. M. Pietrusiewicz and J. Koszuk, Tetrahedron, 1975, 31, 1907. 6 G. Sosnovsky, J. A. Krogh and S. G. Umhoefer, Synthesis, 1979, 722. 7 R. C. Miller, J. S. Bradley and L. A. Hamilton, J. Am. Chem. Soc., 1956, 78, 5299. 8 W. R. Purdum and K. D. Berlin, J. Org. Chem., 1974, 39, 2904. 9 F. A. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S.1. 10 R. S. Jain, H. F. Lawson and L. D. Quin, J. Org. Chem., 1978, 43, 108. 11 L. D. Quin and R. C. Stocks, J. Org. Chem., 1974, 39, 687. ¢Ô (1S*,2R*,6R*,8R*)-5-Benzyl-9,9-dimethyl-5-oxo-4-phenyl-5-phosphatricyclo[ 6.1.1.02,6]dec-3-en-3-ylamine 3: white crystals, mp 218.220 ¡ÆC (CCl4.MeCN, 5:1 v/v), [a]25 0.0. 1H NMR (500 MHz, CDCl3) d: 0.84 (s, H11), 1.17 (s, H12), 1.43 (d, H10¥â, J 9.7 Hz), 1.76 (ddddd, H7¥â, J 13.7, 13.2, 11.7, 1.4 and 1.4 Hz), 1.88 (dddd, H8, J 5.7, 5.7, 3.9 and 2.1 Hz), 2.00 (m, H1), 2.02 (m, H10¥á), 2.19 (dddd, H6, J 10.5, 9.7, 9.4 and 2.8 Hz), 2.41 (dddd, H7¥á, J 20.6, 13.7, 3.8 and 2.8 Hz), 2.88 (dddd, H2, J 16.3, 9.0, 1.0 and 1.0 Hz), 3.12 (d, CH2Ph, J 16.4 Hz), 4.46 (s, NH2), 7.00 (m, Hb'), 7.09.7.22 (m, Hc', Hd' and Hd), 7.35 (t, Hc, J 7.5 Hz), 7.52 (d, Hb, J 7.5 Hz). 13C NMR (125 MHz, CDCl3) d: 20.13 (C11), 22.52 (C7, JC.P 3.5 Hz), 22.91 (C6, JC.P 65.4 Hz), 25.08 (C10), 26.24 (C12), 38.05 (C9), 38.73 (CH2Ph, JC.P 64.4 Hz), 40.12 (C8), 42.39 (C1, JC.P 3.2 Hz), 46.14 (C2, JC.P 3.7 Hz), 100.04 (C4, JC.P 116.3 Hz), 126.01 (Cb', JC.P 2.8 Hz), 126.09 (Cd'), 128.10 (Cd), 128.12 (Cc, JC.P 3.8 Hz), 128.91 (Cb), 129.39 (Cc', JC.P 5.1 Hz), 133.83 (Ca&(Ca, JC.P 8.8 Hz), 157.77 (C3, JC.P 44.3 Hz). 31P NMR (162 MHz, CDCl3) d: 64.49. IR (CHCl3, n/cm.1): 3500, 3400, 3100.2900, 1630, 1490, 1150. MS, m/z (%): 377.19167 (M+, 13%), 362 (10), 350 (22), 320 (17), 309 (10), 286 (49), 230 (13), 139 (21), 91 (100).¡× 3624 independent reflections were measured on a Bruker P4 diffractometer with graphite monochromated MoK¥á radiation using q/2q scans with q < 25¡Æ. Compound 3 is orthorhombic, space group Pbca, a = = 15.359(2), b = 11.693(1), c = 22.960(3) A, V = 4123.5(8) A3, C24H28NOP, M = 377.44, Z = 8, dcalc = 1.216 g cm.3, m = 0.147 mm.1, F(000) = 1616, crystal size 0.15¡¿0.43¡¿1.08 mm. The structure was solved by the direct methods (SHELXS-86) and refined in the anisotropic-isotropic approximation using SHELXL-97 to wR2 = 0.1190, S = 1.032 for all reflections (R = 0.0441 for 2890 F > 4s). The positions of hydrogen atoms were located from a D-map. 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, 2001. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/86. Received: 14th March 2001; Com. 01/17

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摘要:

Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) 1-Trifluoroacetyl-2-trimethylstannyl- and 1-trifluoroacetyl-2-bromoacetylenes as new dienophiles in the Diels–Alder reactions Andrei B. Koldobsky, Olga S. Shilova and Valery N. Kalinin* A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 117813 Moscow, Russian Federation. Fax: +7 095 135 5085; e-mail: vkalin@ineos.ac.ru 10.1070/MC2001v011n03ABEH001401 Trifluoroacetic anhydride exotermically reacts with bis(trimethylstannyl)acetylene to form previously unknown 1-trifluoroacetyl- 2-trimethylstannylacetylene, which interacts with bromine to produce 1-trifluoroacetyl-2-bromoacetylene.Diels–Alder reactions with the participation of acetylene dienophiles activated with electron-withdrawing groups are widely employed in organic synthesis.1,2 The strong electron-withdrawing trifluoroacetyl group can impart both activating and regiocontrolled effects on cycloaddition reactions and provide further useful transformations of cycloadducts.Trifluoromethylketones are of great interest to synthetic, physical and medicine chemists because of their unique properties.3,4 The synthesis of trifluoroacetyl ketones with the acetylene moiety was described.4,5 However, only 1-phenyl-2-trifluoroacetylacetylene6 and 1-chloromethyl- 2-trifluoroacetylacetylene7 were investigated in Diels– Alder reactions. Here, we report the preparation of 1,1,1-trifluoro-4-trimethylstannylbut- 3-yn-2-one 1 and 4-bromo-1,1,1-trifluourobut-3-yn- 2-one 2, new versatile dienophiles, and their application to [4 + 2]-cycloaddition reactions.It was found that trifluoroacetic anhydride exothermically reacts with easily available bis(trimethylstannyl)acetylenes8 in THF to form acetylene 1 and trimethylstannyltrifluoroacetate, which can be readily separated. Acetylene 1 can be distilled in vacuo, and it is stable at room temperature in the absence of air.It is an active dienophile affording cycloadducts 3† (Table 1). Thus, the reaction of 1 with cyclopentadiene proceeds even at 10°. The reaction with spiro-(2,4)-hepta-4,6-diene occurs when refluxing in CH2Cl2. However, with less active dienes such as cyclohexadiene, 2,3-dimethylbutadiene and 1,3-butadiene it is necessary to reflux the components in THF. Note that cycloaddition reactions of trimethylstannylacetylenes activated with cyano, acetyl or alkoxycarbonyl groups proceeded under more severe conditions to form cycloadducts in moderate yields, and in the case of cyclohexadiene aromatization takes place as a result of ethylene extrusion. 9 We found that acetylene 1 reacts with bromine in CH2Cl2 at –30 °C to afford previously unknown 1-trifluoroacetyl-2-bromoacetylene 2 in almost 100% yield: Me3SnCºCSnMe3 + (CF3CO)2O CF3COCºCSnMe3 + CF3COOSnMe3 THF, 20 °C 1 (98%) Table 1 Diels–Alder reactions of 1.Entry Diene Reaction conditions Product Yield (%) a Et2O, 24 h, 20 °C 78 b CH2Cl2, 6 h, 50 °C 69 c THF, 6 h, 60 °C 63 d THF, 8 h, 65 °C 60 e THF, 8 h, 80 °C 52 SnMe 3 COCF3 3a SnMe 3 COCF3 3b SnMe 3 COCF3 3c Me Me Me Me SnMe 3 COCF3 3d SnMe 3 COCF3 3e † Characteristics and spectroscopic data. 1H NMR spectra were recorded on a Bruker AMX-400 spectrometer (400.13 MHz) in CDCl3, TMS was used as an internal standard. IR spectra were measured on a ‘Nicolett’ FT spectrometer. 1: bp 50–52 °C (10 Torr). 1HNMR, d: 0.05 (s, 9H, SnMe3). IR, n/cm–1: 2140 (CºC), 1705 (C=O). Found (%): C, 29.81; H, 3.49; Sn, 40.53; F, 19.45.Calc. for C7H9F3OSn (%): C, 29.53; H, 3.19; Sn, 41.64; F, 20.01. 2: bp 39–42 °C (100 Torr). IR, n/cm–1: 2180 (CºC), 1700 (C=O). Found (%): C, 29.43. Calc. for C4BrF3O (%): C 23.91. 3a: bp 68–69 °C (1 Torr). 1H NMR, d: 0.25 (s, 9H, SnMe3), 2.09 (d, 1H, H-7, 2J 12 Hz), 2.20 (d, 1H, H-7, 2J 12 Hz), 4.11 (d, 2H, H-1, H-4, 2J 10 Hz), 6.63 (m, 1H, H-5), 6.87 (m, 1H, H-6). Found (%): C, 41.34; H, 4.56; F, 15.93; Sn, 33.01.Calc. for C12H15F3OSn (%): C, 41.08; H, 4.31; F, 16.25; Sn, 33.80. 3b: bp 88–89 °C (2 Torr). 1H NMR, d: 0.21 (s, 9H, SnMe3), 0.45–0.65 (m, 4H, CH2CH2), 3.50 (d, 2H, H-1, H-4, 2J 11 Hz), 6.90 (m, 1H, H-6). Found (%): C, 44.08; H, 4.21; F, 15.40; Sn, 31.74. Calc. for C14H17F3OSn (%): C, 44.62; H, 4.55; F, 15.12; Sn, 31.47. 3c: bp 70–71 °C (1 Torr). 1H NMR, d: 0.25 (s, 9H, SnMe3), 1.05–1.51 (m, 4H, CH2CH2), 4.23 (d, 2H, H-1, H-4, 2J 11 Hz), 6.23 (d, 1H, H-6), 6.40 (d, 1H, H-6). Found (%): C, 43.01; H, 4.92; F, 15.93; Sn, 31.87. Calc. for C13H17F3OSn (%): C, 42.79; H, 4.70; F, 15.62; Sn, 32.50. 3d: bp 80–81 °C (1.5 Torr). 1H NMR, d: 0.18 (s, 9H, SnMe3), 1.63 (s, 3H, Me), 1.68 (s, 3H, Me), 3.05 (d, 2H, H2C-3, 2J 8 Hz), 3.12 (d, 2H, H2C-6, 2J 8 Hz).Found (%): C, 42.85; H, 5.36; F, 15.27; Sn, 32.01. Calc. for C13H19F3OSn (%): C, 42.56; H, 5.22; F, 15.54; Sn, 32.33. 3e: bp 64–66 °C (1 Torr). 1H NMR, d: 0.21 (s, SnMe3), 3.04 (d, 2H, H2C-3, 2J 8 Hz), 3.08 (d, 2H, H2C-6, 2J 8 Hz), 5.70–5.85 (m, 2H, CH=CH). Found (%): C, 38.53; H, 4.27; F, 17.05; Sn, 35.32. Calc. for C11H15F3OSn (%): C, 38.99; H, 4.46; F, 16.82; Sn, 35.00. 4a: bp 65–67 °C (2 Torr). 1H NMR, d: 2.23 (d, 1H, H-7, 2J 10 Hz), 2.36 (d, 1H, H-7, 2J 10 Hz), 3.69 (s, 1H, H-4), 4.10 (s, 1H, H-1), 6.85 (m, 1H, CH=CH), 6.89 (m, 1H, CH=CH). Found (%): C, 40.61; H, 2.42. Calc. for C9H6BrF3O (%): C, 40.48; H, 2.26. 4b: bp 75–76 °C (1 Torr). 1H NMR, d: 0.50–0.72 (m, 4H, CH2CH2), 3.30 (d, 1H, H-4, 2J 11 Hz), 3.59 (d, 1H, H-1, 2J 11 Hz), 6.88 (m, 1H, H-6), 6.95 (m, 1H, H-5).Found (%): C, 45.24; H, 3.08. Calc. for C11H8BrF3O (%): C, 45.08; H, 2.75. 4c: bp 69–70 °C (1 Torr). 1H NMR, d: 1.40–1.70 (m, 4H, CH2CH2), 4.05 (m, 1H, H-1), 4.41 (m, 1H, H-4), 6.30–6.48 (m, 2H, CH=CH). Found (%): C, 42.48; H, 2.44. Calc. for C10H8BrF3O (%): C, 42,73; H, 2.87. 4d: bp 68–69 °C (1 Torr). 1H NMR, d: 1.63 (s, 6H, 2Me), 2.91 (dd, 2H, H2C-6), 3.24 (dd, 2H, H2C-3).Found (%): C, 42.63; H, 3.77. Calc. for C10H10BrF3O (%): C, 42.43; H, 3.56. Me3SnCºCCOCF3 BrCºCCOCF3 + Me3SnBr 1 2 Br2 CH2Cl2, –30 °CMendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) Acetylene 2 exibits high reactivity in Diels–Alder reactions (Table 2). With active dienes sush as cyclopentadiene and spiro- (2,4)-hepta-4,6-diene, an exothermic reaction takes place even at –30 °C, while less active dienes exothermically react at 0–20 °C.Note that the isolation of 2 is not necessary when cycloadducts 4† and trimethylstannyl bromide can be easily separated by distillation. In such cases, a diene can be added to the reaction mixture when the colour of bromine disappears. Unfortunately, the reactions of 2 with isoprene and 1,3-butadiene give a mixture of products.In conclusion we developed the preparation of two acetylenic dienophiles activated by trifluoroacetyl group. Their cycloaddition reactions afford á,â-unsaturated trifluoromethyl ketones containing trimethylstannyl substituents or bromine in the â-position, which open a wide range of further transformations. References 1 W.Carruthers, Cycloaddition Reactions in Organic Synthesis, Pergamon Press, Oxford, 1991. 2 H. Waldmann, Synthesis, 1994, 535. 3 J. T. Welch and S. Eshwarakrishman, Fluorine in Bioorganic Chemistry, Wiley, New York, 1991. 4 J.-P. Begue and D. Bonnet-Delpon, Tetrahedron, 1991, 47, 3207. 5 A. Yu. Zenova, V. V. Platonov, M. V. Proskurnina and N. S. Zefirov, Vestn. Mosk. Univ., Ser. 2: Khim., 1997, 38, 115 (in Russian). 6 A. Yu. Zenova, V. V. Platonov, M. V. Proskurnina and N. S. Zefirov, Zh. Org. Khim., 1996, 32, 992 (Russ. J. Org. Chem., 1996, 32, 951). 7 A. B. Koldobsky, E. V. Solodova and V. N. Kalinin, Dokl. Ross. Akad. Nauk, 1999, 366, 58 [Dokl. Chem. (Engl. Transl.), 1999, 110]. 8 Organometallic Synthesis, eds. R. Bruce King and J. J. Eisch, Elsevier, Amsterdam, 1986, vol. 3, p. 559. 9 B. Lousseanme and P. Villeneuve, Tetrahedron, 1989, 45, 1145. Table 2 Diels–Alder reactions of 2. Entry Diene Reaction conditions Product Yield (%) a CH2Cl2, 15 min, –30–20 °C 77 b CH2Cl2, 15 min, –30–20 °C 83 c CH2Cl2, 6 h, 0–20 °C 84 d CH2Cl2, 6 h, 20 °C 72 Br COCF3 4a Br COCF3 4b Br COCF3 4c Me Me Me Me Br COCF3 4d Received: 27th November 2000; Com. 00/1727

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年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85.124) 1,4-Conjugate addition of higher-order cyanocuprates to 3-alkyl substituted 2(5H)-furanones Felix S. Pashkovsky,*a Fedor A. Lakhvich,a Alfredo Riccib and Mauro Comes-Franchinib a Institute of Bioorganic Chemistry, Academy of Sciences of Belarus, 220141 Minsk, Republic of Belarus. Fax: +7 0172 63 7274; e-mail: evk@ns.iboch.ac.by b Dipartimento di Chimica Organica ¡°A.Mangini¡±, Facolta di Chimica Industriale, Universita di Bologna, 40136 Bologna, Italy.Fax: +39 051 209 3654; e-mail: ricci@ms.fci.unibo.it 10.1070/MC2001v011n03ABEH001397 The results of model investigations concerning 1,4-addition of higher-order cyanocuprate (n-Bu)2Cu(CN)Li2 to 3-alkyl-substituted butenolides are presented. The 1,4-conjugate addition of different nucleophiles to 2(5H)- furanones (butenolides) is widely used for preparing compounds with a ¥ã-butyrolactone ring.1 Among Michael donors, organocopper reagents are of special importance because their nucleophilic addition to unsubstituted2 or 5-alkyl-substituted butenolides3 is a key step in the synthesis of naturally occurring products and their congeners. Surprisingly, almost nothing is known about the 1,4-addition of organocopper species to 3-alkyl-substituted butenolides in which an alkyl moiety is directly attached to the conjugated double bond of the heterocycle.Only one example of the Michael addition of the diarylmethane anion to 3-methyl-2(5H)-furanone in the presence of catalytic amounts of copper(I) iodide has been described.4 In connection with the synthesis of biologically active 10-oxaprostaglandin analogues, we required a method for 1,4-conjugate addition of alkyl and alkenyl moieties to the butenolides with a preformed ¥á-prostanoid chain.Therefore, firstly we attempted model investigations concerning the Michael addition of organocopper reagents to 3-alkyl-substituted 2(5H)-furanones.In our hands, the use of butyllithium in the presence of catalytic amounts of copper(I) iodide,4 as well as the corresponding Gilman reagent, in this reaction was unsatisfactory. This is in accordance with the published data concerning low reactivity of ¥á,¥â-unsaturated esters5 and 5-alkyl-2(5H)-furanones3 towards lower-order dialkyl cuprates. On the contrary, higher-order cyanocuprates are suitable reagents for this synthetic purpose.In this communication, we report the results of our investigations concerning the 1,4-addition of higher-order dibutylcyanocuprate (n-Bu)2Cu(CN)Li2 to the 3-alkyl-substituted butenolides. The presence of oxygen in the five-membered ring reduces the reactivity of butenolides as Michael acceptors as compared to their carbocyclic counterparts.3,5 We have found that the use of diethyl ether as a solvent in this reaction is essential. When THF or a mixture of diethyl ether and THF was employed, the reaction proceeded very slowly with almost quantitative recovery of the starting materials. Even in diethyl ether, higher temperatures (gradual increase from .75 to .15 ¡ÆC) and prolonged reaction times (4.5 h) are necessary for completion of the reaction.The 1,4-addition of an alkyl moiety to 5-unsubstituted butenolides results in the formation of cis- and trans-isomers of the corresponding 3,4-disubstituted ¥ã-butyrolactones, the trans-isomers being the major components. Elongation of a 3-alkyl substituent in the butenolide leads to an increased concentration of the transisomer.For example, the reaction of 3-methylfuran-2(5H)-one 1a with 1.2 equiv. of higher-order dibutylcyanocuprate gives rise to the corresponding mixture of diastereomeric lactones 2a and 3a in 80% combined yields; the cis:trans ratio of 2a/3a is 1.1:2.0. The cis-isomer showed a lower vicinal coupling constant JH-3/H-4 7.6 Hz in the 1H NMR spectrum as compared with that of the trans-isomer (11.5 Hz).The 3-alkylaryl-substituted butenolide 1b reacts with 1.2 equiv. of the same cuprate to give a mixture of diastereomeric 3-arylalkyl-4-butyl lactones 2b and 3b (71% yield) separable by column chromatography in an approximate cis:trans ratio of 2b/3b = 1:3. The stereochemical assignment of 2b, 3b is based on the observation that JH-4/H-5 for the trans-isomers is higher (8.5 Hz for Ja/a and 7.0 Hz for Ja/e) as compared with those for the cis-isomers (6.0 and 5.5 Hz, respectively).On the contrary, in the case of sterically hindered 3,5-dialkyl-substituted butenolide 1c, 1,4-addition of a butyl group proceeded stereoselectively to give only all-trans-trialkyl lactone 2c in 66% yield. The vicinal coupling constant JH-5/H-4 8.4 Hz in the 1H NMR spectrum of lactone 2c supports the trans-orientation of methyl and butyl substituents.6 It follows from these experiments that the reaction of an almost equal amount of higher-order cyanocuprate with butenolides bearing an ester group in the side chain is chemoselective and extremely useful for the selective transformations of functionalised 2(5H)-furanones.Only small amounts of exhaustively alkylated products 4b,c (4 and 7%, respectively) were isolated from the reaction mixtures.Trialkylated materials 4b,c are the main products when a large excess (3.4 equiv.) of the cuprate reagent is used.¢Ó O O R1 R2 O O R1 R2 O O R1 R2 Bu2Cu(CN)Li2 Et2O, .78 to .15 ¡ÆC 4.5 h 1a.c 2a. c 3a, b O O R2 4b,c OH a R1 = Me, R2 = H b R1 = , R2 = H (CH2)3 CO2Me c R1 = , R2 = Me (CH2)3 CO2Me ¢Ó General procedure.To a stirred slurry of 54 mg (0.6 mmol) of CuCN in 8 ml of diethyl ether cooled at .78 ¡ÆC, in an argon atmosphere, 0.75 ml (1.2 mmol) of a 1.6 M BuLi solution in hexane was added dropwise with a syringe. Then, the reaction mixture was allowed to gradually warm up to .30 ¡ÆC. During this time, the clear yellowish solution of higher-order cyanocuprate was formed.To the resulting solution of the complex cooled to .78 ¡ÆC 50 mg (0.5 mmol) of 3-methyl-2(5H)-furanone 1a in 2 ml of diethyl ether was added dropwise with a syringe. In the case of butenolides 1b,c sparingly soluble in Et2O, 0.5 mmol of a compound was added to the reaction vessel in one portion under a stream of argon. The reaction temperature was gradually raised from .78 ¡ÆC to .15 ¡ÆC for 4.5 h with stirring.The reaction mixture was cooled again to .78 ¡ÆC and quenched with saturated aqueous NH4Cl. The cooling bath was removed, and the mixture was stirred until room temperature was reached. The ether layer was separated, the aqueous phase was extracted with diethyl ether (2¡¿25 ml) and the combined ether extracts were dried with MgSO4.The residue obtained after evaporation of the solvent was separated by column chromatography (silica gel, Et2O.hexane).Mendeleev Communications Electronic Version, Issue 3, 2001 (pp. 85–124) The structures of 4b,c were unambiguously assigned on the basis of 1H NMR spectra and characteristic peaks of [M – H2O]+ ions in their mass spectra.‡ Interestingly, trialkylated product 4b had only the trans-orientation of substituents at C-3 and C-4.We also found that 3-alkyl-substituted butenolides are unreactive towards Grignard-derived higher-order cyanocuprate: even at room temperature the reaction with 1a was extremely slow as compared to decomposition of the complex. This work was supported by INTAS (grant no. 97-0084). References 1 (a) T. Jaworsky, W.Kolodzejek, J. Prejzner and M. Wlostowsky, Polish J. Chem., 1981, 55, 1321; (b) V. Alcazar, J. R. Moran and J. de Mendoza, Tetrahedron Lett., 1995, 36, 3941; (c) M. Fiorenza, A. Ricci, M. N. Romanelli, M. Taddei, P. Dembech and G. Seconi, Heterocycles, 1982, 19, 2327; (d) S. W. McCombie, W. Stuart, J. R. Tagat, W. A. Metz, D. Nazareno and M. S. Puar, Tetrahedron, 1993, 49, 8073; (e) P.Lakshmipathi and A. W. R. Rao, Tetrahedron Lett., 1997, 38, 2551. 2 S. Tsuboi, J.-I. Sakamoto, H. Jamashita, T. Sakai and M. Utaka, J. Org. Chem., 1998, 63, 1102. 3 A. M. Gilbert, R. Miller and W. D. Wulff, Tetrahedron, 1999, 55, 1607. 4 K. Cruz-Almanza and F. P. Higareda, Heterocycles, 1992, 34, 2323. 5 B. H. Lipshutz, Synthesis, 1987, 325. 6 C. Gunther and A. Mosandl, Liebigs Ann.Chem., 1986, 2112. ‡ For 2a: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.91 (t, 3H, Me, J 7.0 Hz), 1.25 (d, 3H, Me, J 7.6 Hz), 1.25–1.48 (m, 6H, 3CH2), 2.03– 2.15 (m, 1H, H-4), 2.15 (dq, 1H, H-3, J 11.5, 7.6 Hz), 3.77 (dd, 1H, H-5, J 8.5, 8.5 Hz), 4.38 (dd, 1H, H-5, J 8.5, 7.0 Hz). IR (CCl4, n/cm–1): 1777 (C=O lactone). MS, m/z: 156 [M]+. Found (%): C, 69.09; H, 10.29.Calc. for C9H16O2 (%): C, 69.19; H, 10.32. For 2b: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.88 (t, 3H, Me, J 7.0 Hz), 1.16–1.43 (m, 6H, 3CH2), 1.50–1.65 (m, 1H), 1.70 (m, 2H, CH2), 1.79–1.93 (m, 1H), 2.11–2.25 (m, 2H, H-4, H-3), 2.70 (t, 2H, CH2Ar, J 7.5 Hz), 3.78 (dd, 1H, H-5, J 8.5, 8.5 Hz), 3.88 (s, 3H, CO2Me), 4.35 (dd, 1H, H-5, J 8.5, 7.0 Hz), 7.24 (d, 2Harom, J 8.4 Hz), 7.95 (d, 2Harom, J 8.4 Hz).IR (CCl4, n/cm–1): 1780 (C=O lactone), 1720 (C=O ester), 1605. MS, m/z: 318 [M]+. Found (%): C, 71.64; H, 8.49. Calc. for C19H26O4 (%): C, 71.67; H, 8.23. For 2c: colourless oil. 1H NMR (300MHz, CDCl3) d: 0.89 (t, 3H, Me, J 6.5 Hz), 1.18–1.36 (m, 4H, 2CH2), 1.39 (d, 3H, Me, J 6.3 Hz), 1.48 (m, 2H, CH2), 1.68–1.80 (m, 4H, 2CH2), 1.84–1.96 (m, 1H, H-4), 2.28– 2.36 (m, 1H, H-3), 2.70 (m, 2H, CH2Ar), 3.90 (s, 3H, CO2Me), 4.12 (dq, 1H, H-5, J 8.4, 6.3 Hz), 7.26 (d, 2Harom, J 8.4 Hz), 7.96 (d, 2Harom, J 8.4 Hz).IR (CCl4, n/cm–1): 1774 (C=O lactone), 1724 (C=O ester), 1609. MS, m/z: 332 [M]+. Found (%): C, 72.40; H, 8.44. Calc. for C20H28O4 (%): C, 72.26; H, 8.49. For 3a: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.91 (t, 3H, Me, J 7.0 Hz), 1.16 (d, 3H, Me, J 7.6 Hz), 1.27–1.48 (m, 4H), 1.58–1.71 (m, 2H), 2.47 (m, 1H, H-4), 2.66 (quint, 1H, H-3, J 7.6, 7.6 Hz), 4.00 (dd, J 8.5, 5.5 Hz, 1H, H-5), 4.27 (dd, 1H, H-5, J 8.5, 6.0 Hz).IR (CCl4, n/cm–1): 1777 (C=O lactone). MS, m/z: 156 [M]+. Found (%): C, 68.82; H, 10.31. Calc. for C9H16O2 (%): C, 69.19; H, 10.32. For 3b: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.86 (t, 3H, Me, J 7.0 Hz), 1.10–1.35 (m, 6H, 3CH2), 1.40–1.53 (m, 1H), 1.61–1.75 (m, 2H, CH2), 1.80–1.93 (m, 1H), 2.38–2.55 (m, 2H, H-4, H-3), 2.71 (m, 2H, CH2Ar), 3.89 (s, 3H, CO2Me), 4.04 (dd, 1H, H-5, J 8.5, 5.5 Hz), 4.19 (dd, 1H, H-5, J 8.5, 6.0 Hz), 7.24 (d, 2Harom, J 8.4 Hz), 7.95 (d, 2Harom, J 8.4 Hz).IR (CCl4, n/cm–1): 1780 (C=O lactone), 1720 (C=O ester), 1605. MS, m/z: 318 [M]+.Found (%): C, 71.61; H, 8.17. Calc. for C19H26O4 (%): C, 71.67; H, 8.23. Received: 10th November 2000; Com. 00/1723 For 4b: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.77–0.92 (m, 9H, 3Me), 0.95–1.09 (m, 2H), 1.14–1.40 (m, 10H), 1.50–1.65 (m, 4H), 1.65–1.90 (m, 7H), 2.10–2.25 (m, 2H, H-4, H-3), 2.61 (t, 2H, CH2Ar, J 7.5 Hz), 3.77 (dd, 1H, H-5, J 8.5, 8.5 Hz), 4.34 (dd, 1H, H-5, J 8.5, 7.0 Hz), 7.12 (d, 2Harom, J 8.4 Hz), 7.25 (d, 2Harom, J 8.4 Hz). IR (CCl4, n/cm–1): 1781 (C=O lactone). MS, m/z: 384 [M – H2O]+. Found (%): C, 77.51; H, 10.49. Calc. for C26H42O3 (%): C, 77.56; H, 10.51. For 4c: colourless oil. 1H NMR (300 MHz, CDCl3) d: 0.80–0.98 (m, 9H, 3Me), 0.98–1.10 (m, 2H), 1.15–1.36 (m, 10H), 1.38 (d, 3H, Me, J 6.3 Hz), 1.43–1.53 (m, 2H), 1.56–1.65 (m, 2H), 1.65–1.91 (m, 7H), 2.27–2.35 (m, 1H, H-3), 2.56–2.76 (m, 3H), 4.13 (dq, 1H, H-5, J 8.4, 6.3 Hz), 7.13 (d, 2Harom, J 8.4 Hz), 7.28 (d, 2Harom, J 8.4 Hz). IR (CCl4, n/cm–1): 1774 (C=O lactone). MS, m/z: 398 [M – H2O]+. Found (%): C, 77.75; H, 10.65. Calc. for C27H44O3 (%): C, 77.84; H, 10.64.

ISSN:0959-9436     

出版商:RSC    

年代:2001

数据来源: RSC