摘要:

Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Quantum-chemical analysis of the chemical stability and cohesive properties of hexagonal TiB2, VB2, ZrB2 and NbB2 Alexander L. Ivanovsky,* Nadezhda I. Medvedeva and Julia E. Medvedeva Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation. Fax: +3 432 74 4495; e-mail: ivanovskii@ihim.uran.ru The cohesive properties and chemical stability of diborides MB2 have been analysed using the results of full-potential LMTO calculations.A comparison of interatomic M–M, M–B and B–B interactions in MB2 phases (M = Ti, V, Zr, Nb) shows that the changes in the cohesive properties are mainly controlled by the strength of the covalent M–B bonds. Among the known transition metal (TM) borides the hexagonal diborides of IVa and Va group metals (MB2) possess the highest melting temperatures, hardness and chemical stability.1,2 The stability and thermomechanical properties of MB2 depend on the kind of metal and get noticeably worse with the growth in TM atomic number (z) in the period and with reduction of z in the group of the Periodic Table.1,2 In the phenomenological models of the electronic structure of MB2 phases their properties are attributed to one of several possible types of interatomic interactions (see reviews 3 and 4).For example, it is supposed5 that B–B interactions are responsible for the structural peculiarities of diborides. The calculations of energy band structure were carried out by the authors of refs. 6 and 7 for some MB2 phases. Based on the total and local densities of states (TDOS, LDOS), the cohesive properties of MB2 (with the growth of z in the period) were explained by the changes in occupation of antibonding states with valence electron concentration (vec) in the cell. This approach6,7 is widely employed to interpret the thermodynamic properties of diborides such as melting temperature, entropy characteristic energies, etc.8 The model fails, however, to explain the differences in the properties of isostructural and isoelectronic MB2 (for example, TiB2 and ZrB2 or VB2 and NbB2).1,2 In the present paper the first-principle analysis of the chemical stability of MB2 (M = Ti, V, Zr, Nb) is performed and the contributions of different types of interatomic interactions to the cohesive energy of these phases are considered.The electronic energy band structure of MB2 was calculated using the self-consistent full-potential linear muffin-tin orbitals method (FP-LMTO).9 The structural data for diborides were taken from ref. 2. TDOS and LDOS of ZrB2, NbB2 are given in Figure 1. It was found that, in conformity with previous computations (reviews 3 and 4), the characteristic feature of the electronic structure of MB2 is the local TDOS minimum (pseudogap) between the bands of bonding (Md–Bp)- and antibonding Md*, Bp-states.For ZrB2 (vec = 3.33 e atom–1), the Fermi level (EF) is located at this TDOS minimum. This corresponds to the condition of maximum chemical stability of the crystal: bonding states are completely occupied and antibonding states are vacant.Going to NbB2 (vec = 3.67 e atom–1) the bands of the antibonding states become partially occupied and DOS on the Fermi level [N(EF)] increases: N(EF) = 4.35 and 15.56 Ry–1 for ZrB2 and NbB2, respectively. According to the traditional band concept of stability of chemical compounds,10,11 this determines a decrease in cohesive energy and chemical stability of NbB2 as compared with ZrB2.Analogous conclusions can be drawn from the TDOS for TiB2 and VB2. From numerous experimental data1,2 it follows that in accordance with cohesive properties these diborides make up the series ZrB2 > NbB2 > TiB2 > VB2. In the framework of the FP-LMTO9 method the cohesive energy of the system is N(E)/Ry–1 E/Ry EF 40 0 20 0 10 0 –0.5 0.0 0.5 1.0 1.5 2.0 0.0 1.0 N(E)/Ry–1 EF E/Ry 40 0 20 0 10 0 ZrB2 Zr(s,p,d) B(s,p) NbB2 Nb(s,p,d) B(s,p) Figure 1 Total and local densities of states of ZrB2 and NbB2.aE(M–M) and E(B–B) correspond to the Edif values from a calculation of hypothetical M 2 and B2 compounds. bDE is the energy difference for 3dand 4d-metal borides. Table 1 Cohesive energies (Edif/Ry cell–1) of Ti, V, Zr, Nb diborides and energies of different types of bonds according to FP-LMTO calculations.Phase –Edif(MB2) –E(M–M)a –E(B–B)a –[E(M–M) + E(B–B)] –E(M–B) TiB2 1.58 0.36 0.86 1.22 0.36 VB2 1.53 0.40 0.88 1.28 0.25 DEb 0.05 –0.04 –0.02 –0.06 0.11 ZrB2 1.78 0.44 0.82 1.26 0.52 NbB2 1.78 0.56 0.85 1.41 0.37 DE 0.00 –0.12 –0.03 –0.15 0.15Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) calculated as Edif = Etot – SEat, where Etot is the total energy of the crystal and Eat is the energy of free atoms constituting its lattice. Edif was found to decrease in the order ZrB2 ~ ~ NbB2 > TiB2 > VB2 (see Table 1), i.e. in conformity with the experimentally established regularity. The value of Edif is an integral characteristic of chemical bonding and describes the overall energy effect of atomic interaction rearrangement in the lattice.Therefore, our next aim was to determine the role of separate interatomic interactions in the formation of the cohesive properties of MB2. The main types of chemical bonding in diborides are M–M, B–B interactions in metal and boron plane nets (Figure 2) and the covalent ‘interlayer’ M–B bond.These types of interatomic bonds in different planes of the ZrB2 unit cell are visually illustrated in Figure 3. To evaluate the energy contributions of separate bonds [E(M–M), E(B–B) and E(M–B)] to Edif, the electronic structure of isolated diboride sublattices — hypothetical defect structures M 2 and B2 — (M = Ti, V, Zr, Nb; = = vacancies in the corresponding sublattice) was calculated with retention of their geometry in real phases.The energies of M–M and B–B bonds were then determined as The energy of the covalent M–B interaction was defined as the difference between the cohesion energy of the real phase and the sum of the cohesive energies of its non-interacting sublattices It follows from Table 1 that the main contribution to the chemical bonding for diborides is due to strong B–B bonds. The bonding between B atoms dominates both M–M and M–B interactions.E(B–B) in hypothetical B2 compounds depends only on the interatomic distances B–B in the structure of MB2 and closely follows any changes occurring in them.2 The values of E(M–M) for M 2 correlate with the known cohesive energies for pure 3d, 4d-metals (Nb > Zr > V > Ti).11,12 The sum of Edif for two non-interacting sublattices (M 2+ B2) gives a change in chemical stability: NbB2 > VB2 > ZrB2 > TiB2.Thus, the interlayer M–B interaction has a determining effect on the integral Edif value for these phases (see Table 1). The first-principle analysis of chemical stability and cohesive properties of diborides performed here makes it possible to draw the following conclusions.The thermomechanical properties of MB2 result from the strength of the M–M, M–B and B–B bonds. In spite of the leading role of B–B interatomic interactions they are not responsible for the variety of diboride properties, as proposed in some phenomenological models. Depending on the nature of the metallic sublattice the changes in separate types of bonding take place in different ways.The cohesive energy of these diborides changes mainly owing to interlayer covalent M–B interactions and E(M–B) increases with the growth of metal atomic number z in the group and decreases as z grows in the period. Hence, it is possible to assert that the relative change in chemical stability and cohesive properties of the diborides considered is controlled by the covalent boron-metal interaction.References 1 H. J. Goldschmidt, Interstitial Alloys, Butterworths, London, 1967, vol. 1. 2 T. I. Serebryakova, V. A. Neronov and P. D. Peshev, Vysokotemperaturnye Boridy (High-Temperature Borides), Metallurgia, Moscow, 1991 (in Russian). 3 G. P. Shveikin and A. L. Ivanovskii, Usp.Khim., 1994, 63, 751 (Russ. Chem. Rev., 1994, 63, 711). 4 A. L. Ivanovskii and G. P. Shveikin, Kvantovaya khimiya v materialovedenii. Bor, ego splavy i soedineniya (Quantum Chemistry in Materials Science. Boron, its Alloys and Compounds), Izd. ‘Ekaterinburg’, Ekaterinburg, 1997 (in Russian). 5 E. Dempsy, Phil. Mag., 1963, 8, 285. 6 J. K. Burdett, E. Canadell and G. J.Miller, J. Am. Chem. Soc., 1986, 108, 6561. 7 X.-B. Wang, D.-C. Tian and L.-L. Wang, J. Phys.: Condens. Matter, 1994, 6, 10185. 1 2 3 x y z M B Figure 2 Fragment of the crystal structure of diborides MB2. Designated are the planes of metallic atoms (1), boron atoms (3) and ‘interlayer’ plane (2). E(M–M) = Edif(M 2) = Etot(M 2) – Eat(M), E(B–B) = Edif( B2) = Etot( B2) – 2Eat(B). E(M–B) = Edif(MB2) – [Edif(M 2) + Edif( B2)].B 1.00 0.80 0.60 0.40 0.20 0.00 1.20 1.40 1.60 B B Zr Zr Zr 0.00 0.20 0.40 1.00 0.80 0.60 0.40 0.20 0.00 0.20 0.40 0.60 0.80 1.00 Figure 3 Contour maps of total charge density of ZrB2 in different planes of the unit cell [(1)–(3), Figure 2] showing the main types of interatomic interactions in the crystal: Zr–Zr (1), Zr–B (2) and B–B (3). FP-LMTO calculations. 3 2 1 BMendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) 8 A. F. Guillermet and G. Grimvall, J. Less Common Metals, 1991, 169, 257. 9 M. Methfessel and M. Scheffler, Physica, 1991, B172, 175. 10 A. R. Williams, C. D. Gelatt, J. W. D. Connolly and V. Moruzzi, in Alloy Phase Diagrams, eds. L. H. Bennett, T. B. Massalski and B. Giessen, North-Holland, New York, 1983, p. 17. 11 J. Xu and A. J. Freeman, Phys. Rev., 1989, B40, 11927. 12 R. E.Watson, G.W. Fernando, M.Weinert, Y.Wang and J.W. Davenport, Phys. Rev., 1991, B43, 1455. 13 P. H. T. Philipsen and E. J. Baerends, Phys. Rev., 1996, B54, 5326. Received: Moscow, 5th May 1998 Cambridge, 25th June 1998; Com. 8/03646B

ISSN:0959-9436     

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) 1,3,4-Oxa(thia)diazino [i,j]-annelated quinolines: a new type of key intermediate in the synthesis of tricyclic fluoroquinolones Galina N. Lipunova, Emiliya V. Nosova, Valerii N. Charushin,* Larisa P. Sidorova and Olga M. Chasovskikh Department of Organic Chemistry, Urals State Technical University, 620002 Ekaterinburg, Russian Federation.Fax: +7 3422 44 0458; e-mail: mike@htf.ustu.ru The synthesis of new derivatives of 1,3,4-oxa(thia)diazino[6,5,4-i,j]quinolines, which have a structure that is very similar to the ofloxacin skeleton, by intramolecular cyclizations of ethyl 3-(R-carbonylhydrazino)- and 3-(R-thiocarbonylhydrazino)-substituted 2-polyfluorobenzoyl acrylates, is described. 6-Fluoroquinolones are a well-known class of fully synthetic antibacterials.During the last decade an enormous amount of data on their structural modifications have been accumulated in the literature.1–4 Condensed derivatives of 6-fluoro-4-oxo- 1,4-dihydroquinoline-3-carboxylic acid are of special interest since some of them possess not only antibacterial, but also antiviral and anticancer activity.1,5–7 The most important representatives of condensed fluoroquinolones are ofloxacin and its active enantiomer levofloxacin which are characterized chemically by a tricyclic structure of 7-oxo-2,3-dihydro- 7H-pyrido[1,2,3-d,e][1,4]benzoxazine-6-carboxylic acid.2–4 We have recently described a new approach to the synthesis of pentacyclic fluoroquinolones which is based on intramolecular cyclizations of 3-(azol-2-yl)hydrazino substituted 2-(polyfluorobenzoyl) acrylates.8,9 In continuation of our studies on the reactions of 3-hydrazino substituted 2-(polyfluorobenzoyl)- acrylates we wish to report on the synthesis of novel derivatives of 9,10-difluoro-7-oxo-7H-pyrido[1,2,3-d,e][1,3,4]-benzoxa(thia)- diazine-6-carboxylic acids.These tricyclic 1,3,4-oxadiazinoand 1,3,4-thiadiazino[6,5,4-i,j] annelated quinolines have a very similar skeleton to ofloxacin and can be regarded as aza- and thia-analogues.Moreover, derivatives of 1,3,4-thiadiazino[i,j] fused quinolines represent a new heterocyclic system, and seem to be a new type of key intermediate in the synthesis of tricyclic fluoroquinolones. We have found that heating ethyl 3-hydrazino-2-polyfluorobenzoyl acrylates 1a–h, bearing pyridin-3-carbonyl, pyridin- 4-carbonyl or cycloalkylaminocarbonyl substituents at N(2), in toluene or acetonitrile in the presence of KF for 1–3 h, is sufficient to cause nucleophilic displacement of two fluorine atoms, thus affording derivatives of 7-oxo-7H-pyrido[1,2,3- d,e][1,3,4]-benzoxa(thia)diazine-6-carboxylic acids 3a–h in 48–87% yields (Scheme 1).† Starting materials 1a–h were obtained in high yields (70–90%) from the reaction of ethyl 3- ethoxy-2-[tetra(penta)fluorobenzoyl]acrylates with hydrazides of nicotinic or isonicotinic acids and cycloalkylaminosubstituted thiosemicarbazides in dry toluene or ethanol at room temperature.All compounds 1a–h gave satisfactory elemental analysis, NMR and mass spectroscopic data.Tricyclic compounds 3a–h are formed through the intermediate bicyclic fluoroquinolones 2a–h. This path is substantiated by 1H and 19F NMR studies which revealed the formation of mixtures of 2a–d and 3a–d during the course of the reaction. Individual quinolone 2a (X = H, Y = O, R = pyridin-4-yl) could be isolated in 40% yield only in one case, i.e. on heating acrylate 1a in toluene for 1 h.‡ Refluxing 2a in toluene for 2 h gave tricyclic derivative 3a in 85% yield.However, we failed to obtain compounds 2e–h since their cyclizations into tricyclic quinolones 3e–h proceed much faster than those of 1a–d. X F F F F O COOEt NHNH C R Y – HF 1a–h X F F F N O COOEt C R Y 2a–h NH – HF X F F Y N O COOEt 3a–h N R a X = H, Y = O, R = pyridin-4-yl b X = H, Y = O, R = pyridin-3-yl c X = F, Y = O, R = pyridin-4-yl d X = F, Y = O, R = pyridin-3-yl e X = H, Y = S, R = hexamethylenimin-1-yl f X = H, Y = S, R = pyrrolidin-1-yl g X = F, Y = S, R = hexamethylenimin-1-yl h X = F, Y = S, R = pyrrolidin-1-yl Scheme 1 C(13) C(12) C(11) C(10) C(9) C(8) C(7) C(6) C(5) C(4) C(3) C(2) C(1) S(1) N(1) N(2) N(3) F(1) F(2) F(3) O(1) O(2) O(3) C(14) C(15) C(16) C(17) C(18) C(19) Figure 1 Molecular structure of compound 3g.Numeration of atoms does not correspond to the IUPAC nomenclature. Selected bond lengths/Å and angles/° for compound 3g: S(1)–C(1) 1.77(1), S(1)–C(3) 1.74(1), F(1)– C(4) 1.35(1), F(2)–C(5) 1.33(1), F(3)–C(6) 1.34(1), O(1)–C(8) 1.24(1), N(1)–C(1) 1.27(1), N(2)–C(2) 1.40(1), N(2)–C(10) 1.34(1), N(3)–C(1) 1.38(1), C(2)–C(3) 1.42(1), C(2)–C(7) 1.40(1), C(3)–C(4) 1.40(1), C(4)– C(5) 1.38(1), C(5)–C(6) 1.35(1), C(6)–C(7) 1.42(1), C(7)–C(8) 1.49(1), C(8)–C(9) 1.46(1), C(9)–C(10) 1.37(1), C(9)–C(11) 1.49(1); C(1)–S(1)– C(3) 99.1(5), C(2)–N(2)–C(10) 120.1(7), C(1)–N(3)–C(14) 123.3(8), S(1)– C(1)–N(1) 128.7(7), S(1)–C(1)–N(3) 113.1(7), N(1)–C(1)–N(3) 118.1(9), N(2)–C(2)–C(3) 118.5(8), N(2)–C(2)–C(7) 119.4(8), C(3)–C(2)–C(7) 122.1(8), S(1)–C(3)–C(2) 125.3(7), S(1)–C(3)–C(4) 118.5(7), C(2)–C(3)– C(4) 116.1(9), F(1)–C(4)–C(3) 116.4(9), F(1)–C(4)–C(5) 120.3(9), C(3)– C(4)–C(5) 123.2(9), F(2)–C(5)–C(4) 117.8(9), F(2)–C(5)–C(6) 123.2(9), C(4)–C(5)–C(6) 119.0(9), F(3)–C(6)–C(5) 116.0(8), F(3)–C(6)–C(7) 121.4(8), C(5)–C(6)–C(7) 122.5(9), C(2)–C(7)–C(6) 116.9(8), C(2)– C(7)–C(8) 122.4(8), C(6)–C(7)–C(8) 120.7(8), O(1)–C(8)–C(7) 122.1(9), O(1)–C(8)–C(9) 124.6(9), C(7)–C(8)–C(9) 113.3(8), C(8)–C(9)–C(10) 120.3(8), C(8)–C(9)–C(11) 125.7(8), C(10)–C(9)–C(11) 114.0(8), N(2)– C(10)–C(9) 124.5(8).Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) Evidence for the structure of compounds 3a–h is provided by 1H, 19F NMR and mass spectroscopic data, as well as by the X-ray analysis performed for the compound 3g.§ X-Ray analysis of compound 3g¶ revealed that it represents a fused tricyclic system bearing three fluorine atoms, ethoxycarbonyl and azacycloheptane substituents (Figure 1).The † General procedure for the synthesis of 9,10-difluoro-7-oxo- 7H-2-[pyridin-3(4)-yl]pyrido[1,2,3-d,e][1,3,4]-benzoxa(thia)diazine-6- carboxylic acid 3a–d: (a) A solution of ethyl 3-[(pyridin-4-yl)- hydrazido]-2-(tetrafluorobenzoyl)acrylate 1a (0.5 g, 1.2 mmol) in dry toluene (20 ml) was kept under reflux for 2 h.The reaction solution was filtered at the end of the reaction. The filtrate was evaporated and the precipitate obtained was recrystallized from propan-2-ol to yield 3a (0.25 g, 56%), mp 244–246 °C. 1H NMR ([2H6]DMSO) d: 1.30 (t, 3H, Me), 4.23 (q, 2H, OCH2CH3), 7.63 (dd, 1H, 8-H, 3J 11 Hz, 4J 7.5 Hz), 7.88 (dd, 2H, 2',6'-H, 3J 4.5 Hz, 4J 1.5 Hz), 8.56 (s, 1H, 5-H), 8.85 (dd, 2H, 3',5'-H, 3J 4.5 Hz, 4J 1.5 Hz); 19F NMR ([2H6]DMSO) d: 154.24 (dd, 1F, 10-F, 3JFF 22 Hz, 4JFH 7.5 Hz), 134.51 (dd, 1F, 9-F, 3JFF 22 Hz, 3JFH 11 Hz); m/z: 371 (50%, M+), 326 (51), 299 (100). 3b, mp 216–218 °C (propan-2-ol). 1H NMR ([2H6]DMSO) d: 1.30 (t, 3H, Me), 4.23 (q, 2H, OCH2CH3), 7.64 (dd, 1H, 8-H, 3J 10.4 Hz, 4J 7.6 Hz), 7.67 (ddd, 1H, 5'-H, 3J5'-H,6'-H 8.1 Hz, 3J5'-H,4'-H 4.9 Hz, 5J5'-H,2'-H 0.8 Hz), 8.32 (ddd, 1H, 6'-H, 3J6'-H,5'-H 8.1 Hz, 4J6'-H,4'-H 2.3 Hz, 4J6'-H,2'-H 1.5 Hz), 8.57 (s, 1H, 5-H), 8.85 (dd, 1H, 4'-H, 3J4'-H,5'-H 4.9 Hz, 4J4'-H,6'-H 2.3 Hz), 9.14 (dd, 1H, 2'-H, 5J2'-H,5'-H 0.8 Hz, 4J2'-H,6'-H 1.5 Hz); 19F NMR ([2H6]DMSO) d: 154.24 (dd, 1F, 10-F, 3JFF 22 Hz, 4JFH 7.6 Hz), 134.66 (dd, 1F, 9-F, 3JFF 22 Hz, 3JFH 10.4 Hz); m/z: 371 (82%, M+), 326 (73), 299 (100). 3c, mp 238–240 °C (acetonitrile). 1H NMR ([2H6]DMSO) d: 1.28 (t, 3H, Me), 4.22 (q, 2H, OCH2CH3), 7.85 (dd, 2H, 2',6'-H, 3J 4.6 Hz, 4J 1.5 Hz), 8.47 (s, 1H, 5-H), 8.84 (dd, 2H, 3',5'-H, 3J 4.6 Hz, 4J 1.5 Hz); 19F NMR ([2H6]DMSO) d: 160.59 (dd, 1F, 9-F, 3J 20.2 Hz, 3J 21.4 Hz), 151.43 (dd, 1F, 10-F, 3J 21.4 Hz, 4J 6.0 Hz), 146.19 (dd, 1F, 8-F, 3J 20.2 Hz, 4J 6.0 Hz); m/z: 389 (40%, M+), 344 (45), 317 (100), 240 (36), 213 (34), 185 (34). (b) A solution of 1d (0.5 g, 1.17 mmol) and KF (0.14 g, 2.33 mmol) in acetonitrile (10 ml) was kept under reflux for 2 h.The precipitate of 3d obtained after cooling the reaction solution to room temperature was filtered off, washed with water and recrystallized from ethanol (0.35 g, 76%), mp 226–228 °C. 1H NMR ([2H6]DMSO) d: 1.29 (t, 3H, Me), 4.23 (q, 2H, OCH2CH3), 7.65 (ddd, 1H, 5'-H, 3J5'-H,6'-H 8.1 Hz, 3J5'-H,4'-H 4.8 Hz, 5J5'-H,2'-H 0.9 Hz), 8.32 (ddd, 1H, 6'-H, 3J6'-H,5'-H 8.1 Hz, 4J6'-H,4'-H 2.3 Hz, 4J6'-H,2'-H 1.5 Hz), 8.50 (s, 1H, 5-H), 8.86 (dd, 1H, 4'-H, 3J4'-H,5'-H 4.8 Hz, 4J4'-H,6'-H 2.3 Hz), 9.12 (dd, 1H, 2'-H, 5J2'-H,5'-H 0.9 Hz, 4J2'-H,6'-H 1.5 Hz); 19F NMR ([2H6]DMSO) d: 160.77 (dd, 1F, 9-F, 3J 20.2 Hz, 3J 21.3 Hz), 151.42 (dd, 1F, 10-F, 3J 21.3 Hz, 4J 5.5 Hz), 146.31 (dd, 1F, 8-F, 3J 20.2 Hz, 4J 5.5 Hz); m/z: 389 (34%, M+), 344 (30), 317 (100), 240 (29), 213 (33), 185 (27).General procedure for the synthesis of 2R-substituted ethyl 9,10-difluoro-8-X-7-oxo-7H-pyrido[1,2,3-d,e][1,3,4]-benzothiadiazine- 6-carboxylates 3e–h.A solution of 1f (0.8 g, 1.9 mmol) in dry toluene (10 ml) was kept under reflux for 1 h. The precipitate of 3f obtained after cooling the reaction solution to room temperature was filtered off and recrystallized from DMSO (0.36 g, 48%), mp 250–251 °C. 1H NMR ([2H6]DMSO) d: 1.29 (t, 3H, Me), 1.85–2.10 (m, 4H, 3',4'-H), 3.40–3.65 (m, 4H, 2',5'-H), 4.24 (q, 2H, OCH2CH3), 7.80 (dd, 1H, 8-H, 3J 10.8 Hz, 4J 8.5 Hz), 8.37 (s, 1H, 5-H); 19F NMR ([2H6]DMSO) d: 137.8 (dd, 1F, 9-F, 3JFF 22.3 Hz, 3JFH 10.8 Hz), 132.2 (dd, 1F, 10-F, 3JFF 22.3 Hz, 4JFH 8.5 Hz); m/z: 379 (73%, M+), 334 (15), 308 (17), 307 (100), 238 (25). 3e, mp 172–175 °C (acetone). 1H NMR ([2H6]DMSO) d: 1.29 (t, 3H, Me), 1.69–1.73 (m, 4H, 4',5'-H), 1.73–1.90 (m, 4H, 3',6'-H), 3.56–3.70 (m, 4H, 2',7'-H), 4.24 (q, 2H, OCH2CH3), 7.78 (dd, 1H, 8-H, 3J 10.8 Hz, 4J 9.0 Hz), 8.37 (s, 1H, 5-H); 19F NMR ([2H6]DMSO) d: 137.8 (dd, 1F, 9-F, 3JFF 23.5 Hz, 3JFH 10.8 Hz), 132.1 (dd, 1F, 10-F, 3JFF 23.5 Hz, 4JFH 9.0 Hz); m/z: 407 (100%, M+), 362 (22), 335 (86), 265 (11), 238 (49). 3g, mp 171–173 °C (acetone). 1H NMR ([2H6]DMSO) d: 1.28 (t, 3H, Me), 1.61–1.75 (m, 4H, 4',5'-H), 1.75–1.90 (m, 4H, 3',6'-H), 3.56–3.70 (m, 4H, 2',7'-H), 4.22 (q, 2H, OCH2CH3), 8.33 (s, 1H, 5-H); 19F NMR ([2H6]DMSO) d: 162.41 (dd, 1F, 9-F, 3J9-F,8-F 20.2 Hz, 3J9-F,10-F 23.2 Hz), 140.93 (dd, 1F, 8-F, 3J8-F,9-F 20.2 Hz, 4J8-F,10-F 9.8 Hz), 129.63 (dd, 1F, 10-F, 3J10-F,9-F 23.2 Hz, 4J10-F,8-F 9.8 Hz); m/z 425 (100%, M+), 380 (15), 353 (67), 283 (11), 256 (57). 3h, mp 230–231 °C (ethanol). 1H NMR ([2H6]DMSO) d: 1.28 (t, 3H, Me), 1.85–2.01 (m, 4H, 3',4'-H), 3.40–3.57 (m, 4H, 2',5'-H), 4.22 (q, 2H, OCH2CH3), 8.24 (s, 1H, 5-H); 19F NMR ([2H6]DMSO) d: 163.69 (dd, 1F, 9-F, 3J9-F,8-F 20.4 Hz, 3J9-F,10-F 23.2 Hz), 142.12 (dd, 1F, 8-F, 3J8-F,9-F 20.4 Hz, 4J8-F,10-F 9.3 Hz), 131.05 (dd, 1F, 10-F, 3J10-F,9-F 23.2 Hz, 4J10-F,8-F 9.3 Hz); m/z 397 (63%, M+), 352 (12), 324 (100), 256 (24).tricyclic system is nearly planar, the dihedral angle between planes of the quinoline fragment and the fused six-membered thiadiazine ring being 3.1°. The azacycloheptane fragment adopts a chair conformation, with the N(3), C(14), C(16) and C(17) atoms almost coplanar and deviations of the C(15), C(18) and C(19) atoms from this average plane of –0.64, 0.89 and 1.17 Å, respectively. References 1 Quinolone Antibacterial Agents, eds.D. C. Hoope and J. S. Wolfson, ASM, Washington, 1993. 2 D. Bouzard, in Antibiotics and Antiviral Compounds, eds. K. Krohn, H. A. Rirst and H. Maag, VCH, Weinheim, 1993. 3 G. A. Mokrushina, V. N. Charushin and O.N. Chupakhin, Khim.- Pharm. Zh., 1995, 9, 5 (in Russian). 4 U. Petersen, S. Bartel, K.-D. Bremm, T. Himmler, A. Krebs and T. Schenke, Bull. Soc. Chim. Belg., 1996, 105, 683. 5 S. Schneider, M. Ruppelt, M. Schriewer, T. J. Schulze and R. Neumann, European Pat. 563,734, C07D (Chem. Abstr., 1994, 120, 134497x). 6 D. T. W. Chu, R. Hallas, J. J. Clement, J. J. Alder, E. McDonald and J.J. Platner, Drugs Expl. Clin. Res., 1992, 18, 275. 7 D. J. Dorgan and D. W. Gottschall, GB Pat., 27,201,C07D (Chem. Abstr., 1997, 127, 176444c). 8 G. N. Lipunova, G. A. Mokrushina, E. V. Nosova, L. I. Rusinova and V. N. Charushin, Mendeleev Commun., 1997, 109. 9 E. V. Nosova, G. N. Lipunova, G. A. Mokrushina, O. M. Chasovskikh, L. I. Rusinova, V. N. Charushin and G. G. Alexandrov, Zh.Org. Khim., 1998, 34, 436 (in Russian). ‡ Ethyl 1-(pyridin-4-carbonyl)amino-6,7,8-trifluoro-4-oxo-1,4-dihydroquinolin- 3-carboxylate 2a. A solution of ethyl 3-[2-(pyridin-4-carbonyl)- hydrazino-1]-2-(tetrafluorobenzoyl)acrylate 1a (0.8 g, 1.9 mmol) in dry toluene (12 ml) was refluxed for 1 h. The reaction solution was then immediately filtered, evaporated and the precipitate obtained recrystallized from propan-2-ol to yield quinolone 2a (0.3 g, 40%), mp 142–144 °C. 1H NMR ([2H6]DMSO) d: 1.30 (t, 3H, Me), 4.26 (q, 2H, OCH2CH3), 7.87 (dd, 2H, 2',6'-H, 3J 4.4 Hz, 4J 1.5 Hz), 8.04 (ddd, 1H, 5-H, 3JHF 10.2 Hz, 4JHF 8.0 Hz, 5JHF 2.1 Hz), 8.81 (s, 1H, 2-H), 8.87 (dd, 2H, 3',5'-H, 3J 4.4 Hz, 4J 1.5 Hz); 19F NMR ([2H6]DMSO) d: 151.13 (ddd, 1F, 7-F, 3J7-F,6-F 23.2 Hz, 3J7-F,8-F 19.2 Hz, 4JFH 8.0 Hz), 148.66 (ddd, 1F, 8-F, 3J8-F,7-F 19.2 Hz, 4J8-F,6-F 4.6 Hz, 5JFH 2.1 Hz), 136.32 (ddd, 1F, 6-F, 3J6-F,7-F 23.2 Hz, 3JFH 10.2 Hz, 4J6-F,8-F 4.6 Hz).§ The authors would like to thank Dr. G. Alexandrov for the X-ray analysis. ¶ Experimental X-ray crystallographic data for 3g were obtained on a Syntex-P21 diffractometer (l MoKa, graphite monochromator, q/2qscan, 2qmax = 60°). The structure was solved by a direct method and refined by a full-matrix least-squares method in an anisotropic approximation using programs SHELX-93 to R = 0.076 (wR2 = 0.187) for 2128 independent reflections with F2 > 3s(I); GOOF = 1.203. Empirical formula C19H18F3N3O3S, monoclinic crystals, space group P21/c, a = 6.913(5) Å, b = 12.532(8) Å, c = 21.32(2) Å, b = 91.06(6)°, V = 1847(3) Å3, dcalc = 1.530 g cm–3, Z = 4, m = 0.232mm–1. Full lists of bond angles, bond lengths and thermal parameters have been deposited at the Cambrige Crystallographic Data Centre (CCDC). For detail, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 1998. Any request to the CCDC should quote full literature citation and the reference number 1135/27. Received: Moscow, 19th May 1998 Cambridge, 18th June 1998; Com. 8/04513E

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年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) One-step route to fluorinated furo[2,3-b]quinoxalines Valerii N. Charushin,* Galina A. Mokrushina, Galina M. Petrova, Grigori G. Alexandrov and Oleg N. Chupakhin Department of Organic Chemistry, Urals State Technical University, 620002 Ekaterinburg, Russian Federation. Fax: +7 3432 74 0458; e-mail: azine@htf.rcupi.e-burg.su The reaction of 6,7-difluoro-1-ethylquinoxalinium salts with 2,4-pentanedione, ethyl and bornyl acetoacetates and other b-keto esters results in the formation of 6,7-difluoro-3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxalines.In addition, asymmetric 6-fluoro-7- morpholino and 6-fluoro-7-thiomorpholino substituted 1-ethylquinoxalinium salts react with alkyl acetoacetates in a regio- and stereoselective manner, thus giving exclusively the corresponding alkyl 2-methyl-6-fluoro-7-substituted 3a,4,9,9atetrahydrofuro[ 2,3-b]quinoxalin-3-carboxylates. A common way to condensed azines is based on the use of displacement reactions in which electron-deficient azines bearing two halogen atoms or other leaving groups in the orthoposition to each other are allowed to react with bifunctional nucleophilic reagents (for a review see ref. 1). For instance, 2,3,5,6-tetrachloropyrazine has been found to react with ethyl acetoacetate to give ethyl 2-methyl-5,6-dichlorofuro[2,3-b]- pyrazine-3-carboxylate (Scheme 1).2 We have developed a new methodology for the synthesis of a variety of condensed heterocyclic systems based on diadditiontype cyclizations of bifunctional nucleophiles with quaternary 1-alkyl-1,4-diazinium salts, their aza and benzo analogues bearing no nucleofugal groups (Scheme 2).3–8 In this paper we describe the first examples of the ortho-cyclization reaction in the series of fluorinated 1-ethylquinoxalinium salts 1 and 2a,b. 6,7-Difluoroquinoxaline and 6,7-difluoro-1-ethylquinoxalinium tetrafluoroborate 1 became available very recently.9 It has also been shown that both fluorine atoms in these molecules can be replaced with nucleophiles.9 In particular, substitution of the fluorine atom at C(7) by amines in 1 occurs very easily at 10–15 °C, yielding the corresponding 6-fluoro-7-substituted 1-ethylquinoxalinium tetrafluoroborates 2a,b.7 Taking into account the good leaving ability of both fluorine atoms in 1, it might be expected that nucleophilic mono- or disubstitution reactions would have to take place in the reaction of 1 with b-dicarbonyl compounds.On the other hand, the 1,4-diazinium salts are capable of reacting with bifunctional nucleophiles to give condensed tetrahydropyrazines, due to the diaddition reaction of enolates on C(2) and C(3) of the pyrazine ring.3,4 We have found that in the reaction of 6,7-difluoro-1-ethylquinoxalinium tetrafluoroborate 1 with 2,4-pentanedione and alkyl acetoacetates, including ethyl, bornyl, isobornyl or structurally more complicated esters, the diaddition of these enolates at C(2) and C(3) of the pyrazine ring proceeds much faster than the displacement of fluorine atoms in the benzene ring, thus resulting in fluorinated derivatives of 3a,4,9,9a-tetrahydrofuro- [2,3-b]quinoxalines 3a–e in high yields (Scheme 3).†,‡ The cyclization reaction demonstrates high regio- and stereoselectivity.Even in those cases when asymmetric 6-fluoro- 7-morpholino 2a and 6-fluoro-7-thiomorpholino 2b substituted quinoxalinium salts 2a,b reacted with alkyl acetoacetates, no regio- or stereo-isomeric products, apart from furo[2,3-b]- quinoxalines 4a–d, were obtained.Evidence for the structure of compounds 3a–e and 4a–d is provided by their 1H‡ and 19F NMR spectra. The H(3a) signal can easily be assigned in the 1H NMR spectra of 3a–e and 4a–d since it is coupled to the N–H proton. Another specific feature is a long-range coupling constant between H(3a) and the C(2)–Me protons. The fact that H(3a) resonates at a higher field (4.7–5.0 ppm) than H(9a) (5.8–6.0 ppm) suggests that the H(9a) resonance is affected by the neighbouring electronegative oxygen atom.Also, X-ray crystallographic analysis performed for the acyl derivative of 3e, 1-(isopropyloxycarbonyl)ethyl 2-methyl-4-acetyl-9-ethyl-6,7-difluoro-3a,4,9,9a-tetrahydrofuro- [2,3-b]quinoxalin-3-carboxylate 5,§ gave unequivocal evidence for the structure.This revealed that the tetrahydropyrazine ring † A typical experimental procedure for the synthesis of fluorinated furo[2,3-b]quinoxalines 3a–e and 4a–d. Isobornyl 2-methyl-9-ethyl-6,7-difluoro-3a,4,9,9a-tetrahydrofuro[2,3-b]- quinoxalin-3-carboxylate 3d. Diethylamine (0.36 ml, 3.6 mmol) was added dropwise to a mixture of 6,7-difluoro-1-ethylquinoxalinium tetrafluoroborate 1 (1 g, 3.5 mmol) and isobornyl acetoacetate (1 ml, 3.7 mmol) in 4 ml of ethanol at ambient temperature with stirring until dissolving of the reactants was complete.In a few minutes, when colourless crystals of compound 3d started to appear, the reaction mixture was put into an ice-bath for 2–3 h and the crystalline product was filtered off, washed with cool ethanol and dried in air.Recrystallization from hexane gave colourless crystals of 3d with mp 125 °C. Yield 1.1 g (72%). Compounds 3a–c,e and 4a–d were obtained similarly. 1-(Isopropyloxycarbonyl)ethyl 2-methyl-4-acetyl-9-ethyl-6,7-difluoro- 3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxalin-3-carboxylate 5. Acetic anhydride (5 ml, 50 mmol) was added to 1-(isopropyloxycarbonyl)ethyl 2-methyl- 9-ethyl-6,7-difluoro-3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxalin-3-carboxylate 3e (0.5 g, 1.2 mmol).The reaction mixture was refluxed for 5 min and left to stand at room temperature for 24 h. The crystalline product obtained was filtered off and recrystallized from aqueous 80% ethanol. Yield 0.4 g (72%), mp 153 °C. ‡ 3a: yield 75%, mp 121–122 °C (decomp.); 1H NMR (CDCl3) d: 4.98 [H(3a)], 5.83 [H(9a)], 3JH(3a)–H(9a) 7.9 Hz. 3b: yield 78%, mp 129–130 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.65 [H(3a)], 5.85 [H(9a)], 3JH(3a)–H(9a) 8.2 Hz. 3c: yield 75%, mp 133–134 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.65 [H(3a)], 6.05 [H(9a)], 3JH(3a)–H(9a) 8.0 Hz. 3d: yield 72%, mp 125 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.90 [H(3a)], 5.87 [H(9a)], 3JH(3a)–H(9a) 7.9 Hz. 3e: yield 73%, mp 120 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.95 [H(3a)], 5.91 [H(9a)], 3JH(3a)–H(9a) 9.0 Hz. 4a: yield 84%, mp 125–126 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.70 [H(3a)], 5.98 [H(9a)], 3JH(3a)–H(9a) 8.2 Hz. 4b: yield 83%, mp 135 °C (decomp.); 1H NMR (CDCl3) d: 4.85 [H(3a)], 5.85 [H(9a)], 3JH(3a)–H(9a) 8.7 Hz. 4c: yield 80%, mp 134–135 °C (decomp.); 1H NMR ([2H6]DMSO) d: 4.68 [H(3a)], 5.96 [H(9a)], 3JH(3a)–H(9a) 8.0 Hz. 4d: yield 90%, mp 145–146 °C (decomp.); 1H NMR (CDCl3) d: 4.85 [H(3a)], 5.85 [H(9a)], 3JH(3a)–H(9a) 8.7 Hz. N N Cl Cl Cl Cl N N Cl Cl O Me COOEt Scheme 1 MeCOCH2COOEt Z N N R HX Y Z N N R H X Y H H R = alkyl; Z = N, CR, benzo; X and Y are N-, O- or C-nucleophilic centres Scheme 2Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) in 5 exists in a boat conformation with two nitrogen atoms deviating from the average plane of the other four carbons by –0.54 and –0.50 Å, respectively. The dihedral angle between the benzene ring A and the average plane of the four carbons of the tetrahydropyrazine ring B is 156.1°, while the dihedral § X-ray crystallographic data for 5 were obtained at 20 °C on a ‘CAD-4’ diffractometer (MoKa radiation, graphite monochromator, w-scan, 2qmax = 60°).The structure was solved by a direct method and refined by a full-matrix least-squares method in an anisotropic approximation (isotropic for hydrogen atoms) using programs SHELXL-93 to R = 0.0386 for 3040 independent reflections with F2 > 3s(I); F(000) = 476, largest diff. peak and hole are 0.172 and –0.175 Å–3, respectively.Empirical formula C22H26F2N2O6, triclinic crystals, space group P1, a = 8.755(1) Å, b = 10.382(2) Å, c = 12.418(2) Å, a = 80.61°, b = 87.96°, g = 78.96°, V = 1093.0(3) Å3, dcalc = 1.375 g cm–3, Z = 2. Bond angles, bond lengths and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details, see ‘Notice to Authors’, Mendeleev Commun., 1998, Issue 1.Any request to the CCDC for data should quote the full literature citation and the reference number 1135/26. angle between the rings B and C of the heterocyclic fragment is 98.7° (Figure 1). It is also worth noting that the ring junction hydrogen atoms are in a cis-orientation, thus forming a torsion angle H–C(7)–C(8)–H of 3.1°. References 1 V.N. Charushin, M. G. Ponizovsky and O. N. Chupakhin, Khim. Geterotsikl. Soedin., 1985, 1011 [Chem. Heterocycl. Compd. (Engl. Transl.), 1985, 839]. 2 Y. C. Tong and H. O. Kerlinger, J. Heterocycl. Chem., 1983, 20, 365. 3 V. N. Charushin, O. N. Chupakhin and H. C. van der Plas, Adv. Heterocycl. Chem., 1988, 43, 301. 4 V. N. Charushin, O. N. Chupakhin and A. I. Rezvukhin, Heterocycles, 1981, 16, 195. 5 V.N. Charushin, A. I. Chernyshev, N. N. Sorokin and O. N. Chupakhin, Org. Magn. Reson., 1984, 22, 775. 6 V. N. Charushin, N. N. Sorokin, A. I. Chernyshev, V. G. Baklykov, M. G. Ponizovsky and O. N. Chupakhin, Magn. Reson. Chem., 1986, 24, 777. 7 S. G. Alexeev, V. N. Charushin, O. N. Chupakhin and G. G. Alexandrov, Tetrahedron Lett., 1988, 29, 1431. 8 O.N. Chupakhin, B. V. Rudakov, S. G. Alexeev, S. V. Shorshnev and V. N. Charushin, Heterocycles, 1992, 33, 931. 9 G. A. Mokrushina, V. N. Charushin, A. M. Shevelin, O. M. Chasovskikh, A. A. Sherbakov, G. G. Alexandrov and O. N. Chupakhin, Zh. Org. Khim., 1998, 34, 123 (in Russian). C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) O(1) O(2) O(3) O(4) O(5) O(6) N(1) N(2) C(20) C(21) C(22) Figure 1 Molecular structure and numbering of atoms for compound 5.Enumeration of atoms does not correspond to IUPAC nomenclature. Selected bond lengths/Å and bond angles/° for compound 5: F(1)–C(2) 1.356(3), F(2)–C(3) 1.351(2), N(1)–C(12) 1.373(3), N(1)–C(6) 1.419(2), N(1)–C(8) 1.470(2), N(2)–C(5) 1.407(3), N(2)–C(7) 1.428(3), N(2)–C(14) 1.474(3), O(1)–C(10) 1.356(3), O(1)–C(7) 1.482(2), O(2)–C(12) 1.216(2), O(3)–C(16) 1.213(2), O(4)–C(16) 1.354(2), O(4)–C(17) 1.444(3), O(5)– C(19) 1.198(3), O(6)–C(19) 1.328(3), O(6)–C(20) 1.472(3), C(1)–C(2) 1.373(3), C(1)–C(6) 1.379(3), C(2)–C(3) 1.362(3), C(3)–C(4) 1.379(3), C(4)–C(5) 1.387(3), C(5)–C(6) 1.405(3), C(7)–C(8) 1.549(3), C(8)–C(9) 1.508(3), C(9)–C(10) 1.342(3), C(9)–C(16) 1.447(3), C(10)–C(11) 1.482(3), C(12)–C(13) 1.506(3), C(14)–C(15) 1.507(4), C(17)–C(19) 1.514(3), C(17)–C(18) 1.515(4), C(20)–C(21) 1.483(5), C(20)–C(22) 1.491(4); C(12)–N(1)–C(6) 125.6(2), C(12)–N(1)–C(8) 119.9(2), C(6)–N(1)–C(8) 113.7(2), C(5)–N(2)–C(7) 114.3(2), C(5)–N(2)–C(14) 117.3(2), C(7)– N(2)–C(14) 116.0(2), C(10)–O(1)–C(7) 108.7(2), C(16)–O(4)–C(17) 115.0(2), C(19)–O(6)–C(20) 118.4(2), C(2)–C(1)–C(6) 118.7(2), F(1)– C(2)–C(3) 119.5(2), F(1)–C(2)–C(1) 119.7(2), C(3)–C(2)–C(1) 120.8(2), F(2)–C(3)–C(2) 119.2(2), F(2)–C(3)–C(4) 119.2(2), C(2)–C(3)–C(4) 121.6(2), C(3)–C(4)–C(5) 118.7(2), C(4)–C(5)–C(6) 119.1(2), C(4)–C(5)– N(2) 124.6(2), C(6)–C(5)–N(2) 116.2(2), C(1)–C(6)–C(5) 120.9(2), C(1)– C(6)–N(1) 123.5(2), C(5)–C(6)–N(1) 115.5(2), N(2)–C(7)–O(1) 110.0(2), N(2)–C(7)–C(8) 113.5(2), O(1)–C(7)–C(8) 105.3(2), N(1)–C(8)–C(9) 114.9(2), N(1)–C(8)–C(7) 110.6(2), C(9)–C(8)–C(7) 102.3(2), C(10)– C(9)–C(16) 124.5(2), C(10)–C(9)–C(8) 109.8(2), C(16)–C(9)–C(8) 125.7(2), C(9)–C(10)–O(1) 113.9(2), C(9)–C(10)–C(11) 131.9(2), O(1)–C(10)– C(11) 114.1(2), O(2)–C(12)–N(1) 121.1(2), O(2)–C(12)–C(13) 121.3(2), N(1)–C(12)–C(13) 117.6(2), N(2)–C(14)–C(15) 112.1(2), O(3)–C(16)– O(4) 121.8(2), O(3)–C(16)–C(9) 126.7(2), O(4)–C(16)–C(9) 111.5(2), O(4)–C(17)–C(19) 111.5(2), O(4)–C(17)–C(18) 106.4(2), C(19)–C(17)– C(18) 111.1(2), O(5)–C(19)–O(6) 125.1(2), O(5)–C(19)–C(17) 122.3(2), O(6)–C(19)–C(17) 112.6(2), O(6)–C(20)–C(21) 108.7(3), O(6)–C(20)– C(22) 105.9(2), C(21)–C(20)–C(22) 113.4(3).F(1) F(2) A B C N N Et F F BF4 NH X N N Et F N BF4 X 1 2a,b MeCOCH2COR MeCOCH2COR N N Et F F H O Me COR H(3a) H(9a) 3a–e N N Et F N X O Me COR H H H 4a–d a R = Me b R = OEt c R = O-bornyl d R = O-isobornyl e R = OCHMeCOOCHMe2 a R = OEt, X = O b R = O-isobornyl, X = O c R = OEt, X = S d R = O-isobornyl, X = S Scheme 3 Received: Moscow, 27th April 1998 Cambridge, 4th June 1998; Com. 8/03518K

ISSN:0959-9436     

出版商:RSC    

年代:1998

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Novel synthesis of 4-aminofurazan-3-acetic acid Aleksei B. Sheremetev N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: sab@cacr.ioc.ac.ru The title compound 1 has been synthesized by a one-pot procedure starting from pyrrole; nitrosation and hydroxylamine treatment under basic conditions afford the target product in high yield.A number of substituted furazanic acids have been synthesized as potential pharmaceuticals. Thus, derivatives of the cephalosporin and penicillin class have been shown to be effective antibacterial agents,1 and the set of amides are vasodilators2 and anticonvulsants.3 Hydroxyfurazancarboxylic acid has been investigated as a drug active on bones.4 As part of our program on the synthesis and investigation of compounds containing the furazan ring, we are interested in 4-aminofurazan-3-acetic acid 1, which contains a carboxyl group at one end and an amino group at the other.These versatile groups allow us to perform selective linking reactions at either end of the furazan. Only one preparative method exists for 1, starting from 1,3-acetonedicarboxylic acid 2 and sodium nitrite to form 4-hydroxyimino-3-oxobutanoic acid 3 and subsequent treatment with hydroxylamine to give the target furazan (Scheme 1).5 The maximum overall yield in this synthesis is about 50%, being limited by a destructive mono-nitrosation step in which the yield is quite variable.Because of the interesting properties of the amino acid 1 a search for an efficient preparation of the compound was undertaken. A perusal of the literature had indicated few reasonable routes to furazan acetic acids.6 From our viewpoint, however, the most attractive approach seemed to involve a recentlydeveloped strategy,7 as well as related studies,8 which are based on the reactions of carbonyl compounds or their equivalents with hydroxylamine (being an oximating, aminating and redox reagent) and the capability of intermediate organic derivatives of hydroxylamine to undergo rearrangements.We have successfully adapted this strategy to the synthesis of the amino acid 1. As outlined in Scheme 2, pyrrole 4 was converted into the sodium salt of oxime 5 (quantitative yield) by nitrosation with alkyl nitrite in the presence of sodium alcoholate by a modified literature procedure.9 Subsequent treatment with excess hydroxylamine and KOH under reflux and with vigorous stirring gave the target amino acid 1 in 78% yield.Both stages are carried out as one-pot procedures. Based on (i), this result and our earlier observations and (ii), the knowledge that the reaction of 2,5-disubstituted 3-nitrosopyrroles and hydroxylamine is a method of synthesizing oximes of 3-acetonyl-4-alkyl(aryl)furazans,10 we suggested a plausible mechanism for the above transformation (Scheme 3).Thus, initial cleavage of the pyrrole ring by oximation could produce an open-chain trioxime 6, which then dehydrates to give an intermediate furazan 7.Subsequent base promoted furazan ring cleavage could generate cyanooxime 8.† This would react with hydroxylamine to yield compound 9 by addition to the CºN bond and hydrolysis with oxidation of the terminal oxime function. The dioxime 9 dehydrated to the target aminofurazan 1. To conclude, the first synthesis of aminofurazans has been achieved using a methodology based on the transformation of a pyrrole precursor. The novel experimental procedure is straightforward.Current efforts in this laboratory are focused on further applications of this methodology for the formation of aminofurazans from pyrrole derivatives. References 1 (a) L. B. Crast, US Pat., 3322750, 1967 (Chem. Abstr., 1967, 67, 100144); (b) L. B. Crast, US Pat., 3322751, 1967 (Chem.Abstr., 1967, 67, 64412); (c) G. A. Veinberg, A. M. Kac, L. N. Petrulyanis, L. I. Kononov, L. S. Gitlina, V. E. Golender, A. B. Posenblit and E. Lukevic, Khim. Geterotsikl. Soedin., 1989, 683 [Chem. Heterocycl. Compd. (Engl. Transl.), 1989, 571]. 2 (a) K. Schonafinger, R. Beyerle, A. Mogilev, H. Bohn, P. Martorana and R.-E. Nitz, German Pat., 3012862 A1, 1981; (b) K. Schonafinger, R.Beyerle, A. Mogilev, H. Bohn, P. Martorana and R.-E. Nitz, German Pat., 3047730 A1, 1982; (c) K. Schonafinger, R. Beyerle, P. Martorana and R.-E. Nitz, German Pat., 3134849 A1, 1983. 3 (a) A. Fundaro and M. C. Cassone, Farmaco Ed. Sci., 1975, 30, 891; (b) R. Calvino and A. Fundaro, Farmaco Ed. Sci., 1977, 32, 789. 4 T. M. Willson, P. S. Charifson, A. D. Baxter and N.G. Geddie, Bioorg. Med. Chem. Lett., 1996, 6, 1043. 5 I. V. Celinskii, S. F. Melnikova and M. P. Zelenov, Zh. Org. Khim., 1996, 32, 766 (Russ. J. Org. Chem., 1996, 32, 734). 6 (a) A. Hantzsch and J. Urbahn, Chem. Ber., 1895, 28, 753; (b) A. Quilico and M. Freri, Gazz. Chim. Ital., 1946, 76, 3; (c) A. R. Katritzky, B.Wallis, R. T. C. Brownlee and R. D. Topsom, Tetrahedron, 1965, 21, 1681; (d) R.G. Micetich, Can. J. Chem., 1970, 48, 2006; (e) A. E. Vasilvitskii, A. B. Sheremetev, T. S. Novikova, L. I. Khmelnitskii and O. M. Nefedov, Izv. Akad. Nauk SSSR, Ser. Khim., 1989, 2876 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1989, 38, 2640). † As shown earlier,11 reaction of the salt 5 with hydroxylamine without heating yields a product with the empirical formula C4H5N3O2, which corresponds to compound 8.COOH COOH O COOH O HON NaNO2/H+ N O N H2N COOH NH2OH 2 3 1 Scheme 1 N H N NONa N O N NH2 HO O i ii 4 5 1 Scheme 2 Reagents and conditions: i, AlkONO, AlkONa; ii, NH2OH·HCl, KOH, H2O, reflux, 4 h. 5 HON NOH NOH HON N N O HON CN NOH O2C NOH NOH H2N 6 7 8 9 1 Scheme 3Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) 7 (a) A.B. Sheremetev, V. O. Kulagina, L. V. Batog, O. V. Lebedev, I. L. Yudin, T. S. Pivina, V. G. Andrianov and I. B. Starchenkov, Proceedings of 22nd International Pyrotechnics Seminar, July 15–19, 1996, Colorado, USA, p. 377; (b) A. B. Sheremetev and E. V. Mantseva, Mendeleev Commun., 1996, 246; (c) A. B. Sheremetev and I. V. Ovchinnikov, Heteroatom Chem., 1997, 8, 7. 8 For a review of the chemistry of aminofurazans, see: V. G. Andrianov and A.V. Eremeev, Khim. Geterotsikl. Soedin., 1984, 1155 [Chem. Heterocycl. Compd. (Engl. Transl.), 1984, 937]. 9 (a) A. Angeli and M. Spica, Gazz. Chim. Ital., 1899, 29 (I), 500; (b) M. Spica and F. Angelico, Gazz. Chim. Ital., 1899, 29 (II), 49. 10 T. Ajello, Gazz. Chim. Ital., 1937, 67, 55. 11 F. Angelico and A. Angeli, Atti Real. Accad. Lincei, 1905, [5] 14 (I), 699. Received: Moscow, 18th May 1998 Cambridge, 5th June 1998; Com. 8/04239J

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) An efficient synthesis of symmetrical 2,5-diaryl-1,3,4-oxadiazoles Sergei I. Luiksaar, Leonid I. Belen’kii* and Mikhail M. Krayushkin N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: l030@suearn2.bitnet The interaction of trichloromethylarenes with excess hydrazine hydrate in alcohols leads to symmetrical 2,5-diaryl-1,3,4-oxadiazoles in 68–98% yields.In previous papers1,2 some factors governing the direction of the reaction of trichloromethylarenes (TCMA) with acylhydrazines and thioacylhydrazines were studied. In alcohols as solvents benzotrichloride 1a and its substituted derivatives give predominantly alkyl arenecarboxylates formed as the result of alcoholysis while target 1,3,4-oxadiazoles (thiadiazoles) are minor products.In pyridine solutions the products of reductive condensation, viz. the respective N-substituted aromatic aldohydrazones are formed preferentially or exclusively. For heterocyclization leading to 1,3,4-oxadiazole 2 or thiadiazole derivatives carrying out the reaction in a mixture of pyridine with methanol or ethanol appeared to be optimal conditions. At the same time, in reactions of TCMA with an equimolar amount of hydrazine hydrate in a pyridine–methanol mixture, symmetrically-substituted 2,5-diaryl-1,3,4-oxadiazoles were obtained in low yields (20%) and, additionally, methyl esters and hydrazides of the corresponding arenecarboxylic acids were isolated.2 In the present work we found unexpectedly that the yield of 2,5-diphenyl-1,3,4-oxadiazole 2a became near to quantitative when pyridine was excluded and the reaction was carried out by refluxing for 40 min in ethanol and using excess hydrazine as an HCl acceptor. 4-Chlorobenzotrichloride 1b and 3-bromobenzotrichloride 1c reacted with hydrazine in a similar fashion to benzotrichloride; yields of compounds 2b,c were 81% and 68%, respectively.† 2-Chlorobenzotrichloride and 2,4-dimethylbenzotrichloride, as well as mesitotrichloride, which gives only products of reductive condensation in alcohol–pyridine mixtures, failed to undergo heterocyclisation since they almost completely transform to the alcoholysis products, the corresponding aromatic carboxylates.Our attempts to prepare diphenyl-1,3,4-oxadiazole 2a from benzotrichloride and benzohydrazide using an excess of the latter as an HCl acceptor gave the target product in only ~15% yield. It is possible that benzotrichloride interacts with benzo- † 2,5-Diphenyl-1,3,4-oxadiazole 2a was obtained from benzotrichloride (2.7 ml, 19.2 mmol) and hydrazine hydrate (3.82 g, 76.4 mmol) in 10 ml of ethanol (reflux, 40 min).The resulting crystals were filtered off, washed with aqueous ethanol, recrystallised from ethanol and dried in a vacuum dessicator. Yield 2.04 g (96%), mp 139.5–141 °C (cf. refs. 1,2). 2,5-Bis(4-chlorophenyl)-1,3,4-oxadiazole 2b was obtained according the same procedure from 4-chlorobenzotrichloride in 81% yield, mp 243–245 °C (from DMF, cf.ref. 9). 1H NMR (Bruker AC-200, 200 MHz, [2H6]DMSO) d: 7.23 (s, 8H). 2,5-Bis(3-bromophenyl)-1,3,4-oxadiazole 2c was prepared in a similar way from 3-bromobenzotrichloride in 68% yield, mp 178–180 °C (from DMF, cf. ref. 10). 1H NMR (Bruker AC-200, 200 MHz, [2H6]DMSO) d: 7.75 (d, 2H, p-H, J 8 Hz), 7.54 (br., 2H, m-H), 7.35 (t, 4H, o-H, J 8 Hz). hydrazide slower than with hydrazine hydrate and the process of heterocycle formation cannot compete with the undesirable reaction of benzotrichloride alcoholysis.TCMA reactions with O-nucleophiles, and hydrolysis and alcoholysis in particular, probably proceed according to an SN1 mechanism, the reaction rate being independent of alkali or acid additives. The limiting stage involves elimination of a Cl– anion with the formation of an ArC+Cl2 cation and further transformations which proceed faster.3–5 One can suppose that on benzotrichloride alcoholysis the intermediate 3 forms, which can transform either to aroyl chloride 4 by RCl elimination (cf.ref. 6) or to hydrazonoate 5 by reaction with the hydrazine present. It is possible, as we proposed,2 that TCMA reacts first with hydrazine and then the hydrazonoyl chloride 6 formed converts to the ester 5.The latter on interaction with trichloride 1, aroyl chloride 4 or dichloroacetal 3 gives N-acylhydrazonoate 7 that transforms readily to 2,5-diaryl-1,3,4-ozadiazole 2. It should be noted that esters such as 7 were isolated in 30–50% yields in reactions of benzotrichloride with acylhydrazines7 as well as with N-phenylsemicarbazide,8 and on heating esters 7 converted almost quantitatively to heterocyclisation products, oxadiazoles of the type 2.One can suppose that sterically hindered O-chlorobenzotrichloride, 2,4-dimethylbenzotrichloride and mesitochloride mainly react not with alcohol or hydrazine molecules but with water molecules to give aroyl chlorides that transform on further interaction with alcohol to esters, which, as we have shown, cannot undergo reaction with hydrazine under the conditions employed here.References 1 I. S. Poddubnyi, L. I. Belen’kii and M. M. Krayushkin, Khim. Geterotsikl. Soedin., 1994, 686 [Chem. Heterocycl. Compd. (Engl. Transl.), 1994, 30, 602]. 2 I. S. Poddubnyi, L. I. Belen’kii and M. M. Krayushkin, Izv. Akad. Nauk, Ser. Khim., 1996, 1246 (Russ.Chem. Bull., 1996, 45, 1185). 3 F. Quemeneur, B. Bariou and M. Kerfanto, Compt. Rend. (C), 1971, 272, 497. 4 F. Quemeneur, B. Bariou and M. Kerfanto, Compt. Rend. (C), 1974, 278, 299. 5 G. F. Dvorko, N. Yu. Evtushenko and V. N. Zhovtyak, Zh. Obshch. Khim., 1987, 57, 1157 [J. Gen. Chem. USSR (Engl. Transl.), 1987, 57, 1035]. ArCCl3 + H2NNHCOR Py–AlkOH N O N Ar R 1 2 ArCCl3 H2NNH2 EtOH N O N Ar Ar 1a–c 2a–c a Ar = Ph b Ar = 4-ClC6H4 c Ar = 3-BrC6H4 1 ROH H2NNH2 ArCCl2 OR ArC N NH2 Cl ArC N NH2 OR ArC N NH OR CAr O ROH 3 H2NNH2 ArCOCl 4 6 5 7 2Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) 6 T. Ishigami, Y. Kinoshita and A. Sugimori, Chem. Lett., 1974, 149. 7 M. Golfier and R. Milcent, Synthesis, 1979, 946. 8 H. M. Hassanein, A. H. Shetta and N. M. Elwan, Heterocycles, 1982, 19, 1477. 9 F. N. Hayes, B. S. Rogers and A. D. G. Ott, J. Am. Chem. Soc., 1955, 77, 1850. 10 C. I. Chiriac, Rev. Roum. Chim., 1987, 32, 223. Received: Moscow, 15th May 1998 Cambridge, 18th June 1998; Com. 8/04510K

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Cascade and stepwise oxidation of 4-phenyl- and 4-( -pyridyl)tetrahydropyridines Anatoly T. Soldatenkov,* Ayalew W. Temesgen, Ives A. Bekro, Svetlana A. Soldatova and Boris N. Anissimov Peoples’ Friendship University of Russia, 117198 Moscow, Russian Federation. Fax: + 7 095 433 1511 A general cascade and stepwise oxidation scheme for 4-aryl-substituted 1,2,3,6-tetrahydropyridines with KMnO4 is described, which includes the consecutive oxidative transformation of the carbon triad in the substrate allylamine fragment, yielding tetrahydropyridin-2-ones, 3,4-dihydroxypiperidin-2-ones and, finally, 1-formylamino-3-arylpropan-3-ones. The ability of 1,2,3,6-tetrahydropyridines (THP) to react with aqueous KMnO4 was reported1 to depend considerably on the nature of the substituent present at the 4-position of the pyridine ring.For example, the 4-methyl-substituted THPs are easily hydroxylated under the classical conditions of the Vagner reaction (cooling, water–alcohol solution), whereas their 4-phenyl analogues appeared to be completely inert.1 This latter fact appears to be connected with the coplanarity of the phenyl and tetrahydropyridine moities which increases steric hindrance to permanganate anion attack on the double bond.Nevertheless, we have recently found2,3 that 4-phenylTHP 1a and 4-(g-pyridyl)THP 1b can be readily polyfunctionalised by a one-pot oxidation protocol, making available a high-yield synthetic method for the preparation of 3,4-dihydroxypiperidin- 2-ones 3a,b under slightly modified conditions (20–35 °C, water–acetonitrile solution).Our subsequent investigation4 of the one-pot oxidations has demonstrated the possibility of 2-oxo-4-phenylTHP 2a and 1-formylamino-3-phenylpropan- 3-one 4a formation starting in each case from 1a. The data thus obtained have prompted us to pose two important questions: are the compounds 2a–4a recovered in the different experiments formed as a result of a gradual elevation of the degree of oxidation in one reaction sequence; and, if so, can this cascade reaction be considered as a general one, at least for the 4-arylsubstituted THP series? In order to answer these questions it was decided to use the same one-pot procedures4 to afford new 2-oxo-THP 2b and aminopropanone 4b from 1b. Their successful repetition together with the separate oxidation of the lactam 2a into the lactamdiol 3a, the separate oxidative conversion of the latter through ring cleavage into the aminoketone 4a, and repeating the same experimental sequence with 2b and 3b, would provide supporting evidence for generalising both the cascade and the stepwise routes for the THP oxidative transformations. All the reactions were carried out in the presence of KMnO4 in water– acetonitrile solutions and afforded unambiguously the expected results.It was therefore established that oxidation of 4-pyridyl- THP 1b into 2b and 4b proceeded well, though with lower yields (27% and 58%, respectively) in comparison with the analogous reactions of 4-phenylTHP.2,4 The lactams 2a,b were readily hydroxylated at < 0 °C (in contrast to the inert 4-aryl THP 11) into the cis-diol lactams 3a,b with yields 54% and 45%, respectively.However, at room temperature the yield of 3a was increased to 76%. Apart from the importance of the 1 ® 2 ® 3 conversions, it is worth pointing out the decisive role of the amide group in the 2 ® 3 reaction.The presence of the electron-accepting amide group seems likely to significantly polarize the C=C bond in lactams 2 thus leading (even < 0 °C) to successful dihydroxylation of the 4-aryl THP system. The final stage in the oxidative transformation study consisted of proving the fact that the lactam diols 3 were intermediate products in the formation of amidoketones 4. On treatment of 3 with KMnO4 under elevated temperatures (up to 50 °C), TLC showed complete conversion to compounds 4.On work-up a colourless, thick oil of 4 was obtained in 34% to 58% yield. In the case of one-pot oxidation of 1b hydrochloride at room temperature the amide 4b was chromatographically separated in 43% yield. The structures of new compounds 2b and 4b were confirmed spectroscopically.† The data thus obtained allow us to conclude that a general cascade and stepwise scheme for the transformation of 4-arylsubstituted THP can be elaborated, based on the gradual elevation of the degree of oxidation of the triad of carbon atoms present in the allylamine moiety of the initial THP.These schemes can be useful in understanding certain azine oxidation mechanisms and can also serve as new, effective laboratory methods for the synthesis of three important groups of compounds.We thank the Russian Foundation for Basic Research (grant no. 96-03-33432a) for supporting the investigation. † 1H NMR spectra were recorded at 300 MHz in CDCl3, standard TMS. Compound 2b was prepared by oxidation of 1b with KMnO4 (1a:KMnO4 = 1:1.5) in MeCN at 20 °C, 1.5 h; yield 27%, mp 84–85 °C. 1H NMR, d: 2.78 and 3.58 (t, 2×2H, 5-CH2 and 6-CH2, 2J 7.0 Hz, 3J 7.0 Hz), 3.03 (s, 3H, Me), 6.43 (s, 1H, 3-H), 7.37 and 8.64 (dd, 2×2H, AA'BB', 2J 5.0 Hz, 3J 1.5 Hz); MS (EI, 70 eV, 80 °C), m/z (%): 188 (100) [M+]; IR (KBr, n/cm–1): 1650 (NC=O), 1600 (C=C). Found (%): C, 69.86; H, 6.83; N, 14.82. Calc. for C11H12N2O (%): C,70.21; H, 6.38; N, 14.89. Compound 2a was obtained similarly from 1a (1a:KMnO4 = 1:1.5, 0.75 h); yield 65%, mp 78–80 °C.4 Compound 3a was obtained by hydroxylation of 2a in aqueous MeCN (2a:KMnO4 = 1:1.5) at 0 °C, 1.5 h; yield 54%, mp 117 °C.2 The yield of 3a was increased to 76% at 20 °C, 2 h.One-pot oxodihydroxylation of 1a in aqueous MeCN (1a:KMnO4 = 1:1.5) at 20 °C, 2 h gave 3a in 76% yield.2 Compound 3b was prepared by hydroxylation of 2b in aqueous MeCN (2b:KMnO4 = 1:1.5) at 0 °C, 2 h; yield 45%, mp 220–222 °C.3 One-pot oxodihydroxylation of 1b in aqueous MeCN (1b:KMnO4 = 1:1.5) at 20 °C yielded 65% of 3b in 2 h.3 Compound 4a was obtained from one-pot oxidation of 1a·HCl in acetone (1a·HCl:KMnO4 = 1:1.5) at 20 °C, 2 h; yield 85%, colourless oil, Rf 0.73 in acetone.4 4a was also obtained from oxidation of 3a in MeCN (3a:KMnO4 = 1:1.5) at 50 °C, 0.5 h; yield 34%.Compound 4b was prepared by oxidation of 3b in MeCN (3b:KMnO4 = 1:1.5) at 50 °C, 0.5 h; yield 58%, colourless thick oil (purified by chromatography on silica gel column, eluent diethyl ether, Rf 0.41 in acetone). Compound 4b was also prepared by one-pot 1b·HCl oxidation (1b·HCl:KMnO4 = 1:1.5) in acetone at 20 °C, 2 h; yield 43%.In the 1H NMR spectrum of the amide 4b a double set of N(Me)CHO group signals are observed. 1H NMR, d: 2.92 and 3.12 (s, 2×1.5H, Me), 3.3 (t, 2H, 1-CH2, 2J 6.0 Hz, 3J 6.0 Hz), 3.8 (t, 2H, 2J 6.0 Hz, 3J 6.0 Hz), 7.75 and 8.85 (dd, 2×2H, AA'BB', 2J 4.5 Hz, 3J 1.5 Hz), 8.01 and 8.2 (s, 2×0.5H, NCHO); MS (100 °C), m/z (%): 192 (80) [M+], 107 (36), 106 (81), 86 (100), 78 (74), 72 (59), 58 (44); IR (paraffin oil, n/cm–1): 1676 and 1646 (C=O).Found (%): C, 61.96; H, 6.47; N, 14.21. Calc. for C10H12N2O2 (%): C, 62.50; H, 6.25; N, 14.58. g N Ar Me N Ar Me O N Me O OH Ar OH N CHO O Ar Me a Ar = Ph b Ar = 4-Py 1a,b 2a,b 3a,b 4a,b Scheme 1Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) References 1 T. N. Maksimova, V. B. Mochalin and B. V. Unkovskii, Khim. Geterotsikl. Soedin., 1980, 783 [Chem. Heterocycl. Compd. (Engl. Transl.), 1980, 604]. 2 A. T. Soldatenkov, I. A. Bekro, J. A. Mamyrbekova, S. A. Soldatova, A. W. Temesgen, N. D. Sergeeva, L. N. Kuleshova and V. N. Khrustalev, Khim. Geterotsikl. Soedin., 1996, 222 [Chem. Heterocycl. Compd. (Engl. Transl.), 1996, 197]. 3 A. T. Soldatenkov, I. A. Bekro, S. A. Soldatova, E. Glover, A. Temesgen, L. N. Kuleshova, V. N. Khrustalev and N. D. Sergeeva, Izv. Akad. Nauk, Ser. Khim., 1997, 2020 (Russ. Chem. Bull., 1997, 46, 1916). 4 A. T. Soldatenkov, A. W. Temesgen, I. A. Bekro, T. P. Khristoforova, S. A. Soldatova and B. N. Anissimov, Mendeleev Commun., 1997, 243. Received: Moscow, 14th May 1998 Cambridge, 23rd June 1998; Com. 8/03650K

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Ab initio study of the structure of, and double proton exchange in, 1,4-dihydroxy-2,3-diformylbuta-1,3-diene Tatyana N. Gribanova, Ruslan M. Minyaev* and Vladimir I. Minkin Institute of Physical and Organic Chemistry, Rostov State University, 344090 Rostov-on-Don, Russian Federation. Fax: +7 8632 28 5667; e-mail: minyaev@ipoc.rnd.runnet.ru Concerted low-energy barrier (3.7 kcal mol–1) double proton exchange in 1,4-dihydroxy-2,3-diformylbuta-1,3-diene has been predicted using ab initio [MP2(fc)/6-31G**] calculations.Particular attention has been given to the study of the kinetics and mechanism of the intramolecular two proton migration in oxalic acid,1 oxalamidine,2 azophenine,3,4 2,2'-bipyridyl- 3,3'-diole5,6 and other similar compounds.7,8 Both theoretical and experimental investigations1–8 showed that all the dyotropic rearrangements studied follow a two-step mechanism involving sequential proton transfer with inclusion of a zwitterionic intermediate.No unambiguous experimental or theoretical evidence for the realization of the concerted (one-step) double proton transfer within a molecule have hitherto been presented.In the present work we report on ab initio [MP2(fc)/6-31G**]9 calculations of a concerted low-energy barrier (3.7 kcal mol–1) degenerate rearrangement of 1,4-dihydroxy-2,3-diformylbuta- 1,3-diene 1 due to intramolecular double proton transfer. According to the MP2(fc)/6-31G** calculations, a planar structure 1 (l = 0; hereafter l designates the number of negative eigenvalues at a given stationary point) with C2h-symmetry corresponds to the most stable form of the 1,4-dihydroxy- 2,3-diformylbuta-1,3-diene. A possible cis-(Z)-conformer 3 is 2.6 kcal mol–1 less favourable than 1.Unlike 1, the isomer 3 is acoplanar (C2-symmetry) with the dihedral C=C–C=C angle equal to 61.6°. Calculated molecular structures, geometry and energy parameters of the structures 1–3 are given in Figure 1 and Table 1.The symmetric structure 2 of D2h-symmetry corresponds to a true saddle point (l = 1) on the potential energy surface (PES) of C6H6O4. A possible zwitterionic intermediate 4 that would result from single-proton transfer does not correspond to a stationary point. Optimizations starting from the zwitterionic configuration 4 with C2v and C1 symmetries lead to structures 2 and 1, respectively.Thus, there exists only the concerted proton exchange pathway 1a 2 1b in 1,4-dihydroxy- 2,3-diformylbuta-1,3-diene which implies occurrence of the multicentered transition state structure 2 with a very low energy of 3.7 kcal mol–1 relative to 1. The three-centre hydrogen bridges in 2 are nearly linear (deviation from linearity is ca. 12°). The H···O=C angle of 112.6° lies within the limits of the optimal values for proton transfer along the hydrogen bond.10 Accounting for zero-point energy corrections in 1 and 2 leads to the conclusion that the bicyclic structure 2 with hydrogen atoms centered in the middle of the O···O bridge possesses lower total energy as compared with 1.A similar phenomenon of the vibrational stabilisation of the structure with symmetrical hydrogen bridges has been discussed11 recently with reference to experimental data for the IHI system.12 Thus, our calculations corroborate the assumption about the crucial influence of the stereochemical conditions on the proton transfer mechanism. Structure 1,4-dihydroxy-2,3-diformylbuta- 1,3-diene appears to be the first example of a dyotropic molecule in which one-step low-barrier double proton exchange confirmed at the MP2-level is possible.This work was supported by the Russian Foundation for Basic Research (grant nos. 98-03-33169a and 96-15-97476). O O O O H H H H H H O O O O H H H H H H O O O O H H H H H H 1a 2 1b O O H O H O O OH OH O 3 4 1, C2h (l = 0) C O 1.017 1.495 1.247 1.310 1.385 1.488 1.448 124.0 126.9 1.098 129.0 131.4 1.085 108.9 167.9 2, D2h (l = 1) C C C C C C C C C C C O O O O O O O 1.194 1.275 1.091 1.487 1.410 124.7 129.1 109.8 172.7 1.247 1.327 1.474 1.450 1.371 118.3 123.9 124.9 147.5 0.994 1.689 Dihedral angle CCCC 61.6° C C C C C C O O O O 3, C2 (l = 0) Figure 1 Geometry parameters of structures 1–3 calculated by the MP2(fc)/6-31G** method.Bond lengths and angles are given in angströms and degrees, respectively. Table 1 Total energies (Etot in hartree), relative energies (DE in kcal mol–1), the number of negative hessian eigenvalues (l), harmonic zero-point correction (ZPE in hartree), relative energy including harmonic zero-point correction (DEZPE in kcal mol–1), reaction enthalpy (DH in kcal mol–1) and the smallest or imaginary vibration frequency (w1/iw in cm–1) for the structures 1–3 calculated by the MP2(fc)/6-31G** method.Structure Etot DE l ZPE DEZPE DH (w1/iw) 1, C2h –531.63149 0 0 0.11877 0 0 22.7 2, D2h –531.62561 3.68 1 0.11193 –0.60 –0.91 i1189.5 3, C2 –531.62732 2.62 0 0.11813 2.21 2.47 46.1Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) References 1 C. W. Bock, J. Chem. Phys., 1986, 85, 5391. 2 G. Scherer and H.-H. Limbach, J. Am. Chem. Soc., 1994, 116, 1230. 3 M. K. Holloway, C. H. Reynolds and M. K. Merz, J. Am. Chem. Soc., 1989, 111, 3466. 4 H. Rumpel and H.-H. Limbach, J. Am. Chem. Soc., 1989, 111, 5429. 5 V. Barone and C. Adamo, Chem. Phys. Lett., 1995, 241, 1. 6 A. L. Sobolewski and L.Adamovicz, Chem. Phys. Lett., 1996, 252, 33. 7 V. I. Minkin, B. Ya. Simkin and R. M. Minyaev, Quantum Chemistry of Organic Compounds. Mechanisms of Reactions, Springer, Heidelberg, 1990, p. 270. 8 V. I. Minkin, L. P. Olekhnovich and Yu. A. Zhdanov, Molecular Design of Tautomeric Compounds, D. Reidel, Doldrecht–Boston–Tokyo, 1988, p. 271. 9 M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S. Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. J. Su, T. L. Windus, M. Dupuis and J. A. Montgomery, J. Comput. Chem., 1993, 14, 1347 (package of ab initio programs, ‘GAMESS’, Version 1996). 10 S. Scheiner, Acc. Chem. Res., 1994, 27, 402. 11 J. Manz, R. Meyer, E. Pollak and J. Römelt, Chem. Phys. Lett., 1982, 93, 184. 12 J. Manz and J. Römelt, Chem. Phys. Lett., 1981, 81, 179. Received: Moscow, 14th May 1998 Cambridge, 8th June 1998; Com. 8/03649G

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Synthesis of some novel water-soluble chiral phosphines Andrei A. Karasik,* Igor O. Georgiev, Roman I. Vasiliev and Oleg G. Sinyashin 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: karasik@glass.ksu.ras.ru Two individual (RR)- and (SS)-isomers of dipotassium 1,3-di[phenyl(carboxylato)methyl]-5-phenyl-1,3,5-diazaphosphorinane have been synthesized in the reaction of bis(hydroxymethyl)phenylphosphine, paraformaldehyde and the potassium salt of (R)- or (S)-a-phenylglycine.In the last decade a rapid development of catalytic reactions in aqueous/organic biphasic systems, especially enantioselective processes,1–3 has focused the attention of chemists on synthetic routes to the chiral water-soluble phosphine ligands.The functionalisation of well-known optically active phosphines: BINAP, BDPP, DIOP, CHIRAPHOS and cyclobutaneDIOP with highly polar sulfonate,4–6 carboxylate7,8 or ammonium9 groups is a general route to such compounds. Reactions of hydroxymethylphosphines with primary and secondary amines are a powerful method for constructing numerous classes of air-stable linear and cyclic aminomethylphosphine ligands.10–12 A number of water soluble13–14 and some optically active aminomethylphosphines10 have already been obtained.We suggest using the reactions of hydroxymethylphosphines with derivatives of amino acids to obtain water-soluble chiral heterocyclic phosphine precursors of catalysts for aqueous/ organic biphasic catalytic reactions.Amino acids have been used in the construction of chiral phosphine ligands as a source of asymmetric carbon atoms, but their highly polar carboxylic and amine groups have usually been displaced.15 Both enantiomers of amino acids are accessible. We now introduce the synthesis of two individual (RR)- and (SS)-isomers of dipotassium 1,3-di[phenyl(carboxylato)methyl]-5-phenyl-1,3,5- diazaphosphorinane 1.It has been shown in previous investigations that crystalline, air-stable, non bulky 1,3-di-R-5-phenyl-1,3,5-diazaphosphorinane ligands12 are obtained in high yields from bis(hydroxymethyl)- phenylphosphine, paraformaldehyde and primary aryl- or benzylamine in benzene or acetone.We used the potassium salt of (S)- or (R)-phenylglycine and methanol as a solvent in this reaction, because the reactivity of free amino acids in the nucleophilic substitution reactions are low due to their betaine structure and all reagents are soluble in methanol.† In both cases white, highly water soluble, crystalline compounds with identical physical characteristics‡ (except specific rotation) were obtained.The values of specific rotation ([a]20 546 ) for the isomers show that S-(+)- and R-(–)-amino acid salts give SS-(+)- and RR-(–)-isomers of phosphine, respectively. The IR spectra of the compounds exhibit absorption bands due to Ph and CO2 – groups and H2O. In the 31P NMR spectra only one signal shifted to higher fields corresponding to initial hydroxymethylphosphine was observed.The 31P NMR data show that one isomer of heterocyclic phosphine11 was formed. The 1H NMR data are not informative, because of the overlapping of the signals of methylene and methyne protons. The 13C NMR spectra are consistent with the structure of heterocyclic phosphine.16 In the 13C NMR spectra signals of two types of methylene groups from P–CH2–N and N–CH2–N fragments were recorded.The methylene carbon signal of the P–CH2–N fragment was located to low field and revealed the direct coupling constant 1JP–C. Only one asymmetric carbon atom signal was observed, confirming the formation of an individual enantiomer. The NMR data of the phosphine obtained, dissolved in water and methanol, are similar.(RR)- and (SS)-isomers of dipotassium 1,3-di[phenyl(carboxylato) methyl]-5-phenyl-1,3,5-diazaphosphorinane show high water solubility, and a 1 M solution in water can be obtained. This phosphine concentration in water is therefore in the range practical for catalytic applications. The authors are grateful for financial support of this work by INTAS (grant no. 93-2011-ext.). References 1 D. Sinou, Bull. Soc. Chim. Fr., 1987, 480. 2 V. V. Dunina and I. P. Beletskaya, Zh. Org. Khim., 1992, 28, 1929 (Russ. J. Org. Chem., 1992, 28, 1547). 3 V. V. Dunina and I. P. Beletskaya, Zh. Org. Khim., 1992, 28, 2368 (Russ. J. Org. Chem., 1992, 28, 1913). 4 F. Alario, Y. Amrani, Y. Colleuille, T. P. Dang, J. Jenck, D. Morel and D. Sinou, J. Chem. Soc., Chem.Commun., 1986, 202. † General procedure for the synthesis of (RR)- and (SS)-dipotassium 1,3-di[phenyl(carboxylato)methyl]-5-phenyl-1,3,5-diazaphosphorinanes. Paraformaldehyde (0.215 g, 7.2 mmol) was dissolved in bis(hydroxymethyl) phenyl phosphine (1.23 g, 7.2 mmol) with mild heating and the mixture was diluted with 5 ml of dry methanol. A solution of S-(+)- or R-(–)-a-phenylglycine (2.19 g, 14.5 mmol) and KOH (0.81 g, 14.5 mmol) in 10–15 ml methanol {[a]20 546 = ±125° for potassium salts (H2O, c = = 2.86)} was prepared separately. The two mixtures were combined at room temperature with good mixing.The mixture became absolutely transparent and was noticeably warm. After no later than 2 h the reaction mixture was filtered through filter paper and the filtrate was concentrated to about 3–4 ml.After 0.5–1 h the white fine solid which formed was filtered on a thick glass filter, washed twice with MeOH– Et2O (1:1), then Et2O, and dried in vacuo. The resulting white fine crystals are hygroscopic and decompose in air. ‡ (RR)- and (SS)-potassium 1,3-di[phenyl(carboxylato)methyl}-5-phenyl- 1,3,5-diazaphosphorinanes. Global yields about 75–80%, mp 244–246 °C (decomp.). 13C NMR (100.6 MHz, D2O) d: 48.72 (d, 2C, C*H, JCH 142.2 Hz), 72.26 (t, 1C, N–CH2–N, JCH 145.9 Hz), 74.11 (dt, 2C, P– CH2–N, JCH 135.9 Hz, JPC 74.37 Hz), 127.28 (d, 1C, P–C6H5-p, JCH 156.0 Hz), 128.04 (d, 2C, C*H–C6H5-p, JCH 161.0 Hz), 128.13 (d, 4C, C*H–C6H5–m, JCH 161.3 Hz), 128.30 (d, 4C, C*H–C6H5-o, JCH 161.0 Hz), 128.74 (s, 2C, C*H–C6H5-ipso), 128.76 (dd, 2C, P–C6H5-m, JCH 145.5 Hz, JPC 5.0 Hz), 130.79 (dd, 2C, P–C6H5-o, JCH 162.0 Hz, JPC 14.7 Hz), 137.74 (d, 1C, P–C6H5-ipso, JPC, 46.1 Hz), 177.97 (s, 2C, COOK); 31P NMR (162.5 MHz, MeOH) d: –59.84; 31P NMR (162.5 MHz, H2O) d: –60.35; IR (Nujol, KBr, n/cm–1) 1580 (CO), 1590 (Ph), 1620, 3300–3360 (H2O).[a]20 546: (RR) –38.8° (MeOH, c = 7.13), (RR) –107.8° (H2O, c = 7.15); (SS) +38.7° (MeOH, c = 7.15); (SS) +107.8° (H2O, c = 7.14).Found (%): C, 52.97; H, 4.92; N, 5.06; P, 5.24. Calc. for C25H27K2N2O6P (%): C, 53.57; H, 4.82; N, 5.00; P, 5.54. PhP OH OH Ph CO2 H2N H 2 K CH2 O N N P H Ph CO2 Ph CO2 H Ph MeOH 2K 2H2O 1Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) 5 W. A. Herrmann, G. P. Albanese, R. B. Manetsberger, P. Lappe and H.Bahrmann, Angew. Chem., Int. Ed. Engl., 1990, 29, 391. 6 Y. Amrani, L. Lecomte, D. Sinou, J. Bakos, I. Toth and B. Heil, Organometallics, 1989, 8, 542. 7 R. Benhamza, Y. Amrani and D. Sinou, J. Organomet. Chem., 1985, 288, C37. 8 T. Malmstrom and C. Andersson, J. Chem. Soc., Chem. Commun., 1996, 1135. 9 I. Toth and B. E. Hansson, Tetrahedron: Asymmetry, 1990, 1, 895. 10 K. Keller and A. Tzschach, Z. Chem., 1984, 24, 365. 11 B. A. Arbuzov and G. N. Nikonov, in Advances in Heterocyclic Chemistry, ed. A. R. Katritzky, Academic Press, New York, 1994, 61, 60. 12 A. A. Karasik and G. N. Nikonov, Zh. Obshch. Khim., 1993, 63, 1921 (Russ. J. Gen. Chem., 1993, 63, 2775). 13 T. Bartik, B. Bartik, I. P. Guo and B. E. Hanson, J. Organomet. Chem., 1994, 480, 15. 14 I. O. Georgiev, A. A. Karasik, F. F. Nigmadzyanov and G. N. Nikonov, Koord. Khim., 1995, 21, 210 (Russ. J. Coord. Chem., 1995, 21, 222). 15 H-U. Blaser, Chem. Rev., 1992, 92, 935. 16 V. A. Zagumennov, A. A. Karasik, E. V. Nikitin and G. N. Nikonov, Izv. Akad. Nauk, Ser. Khim., 1997, 1202 (Russ. Chem. Bull., 1997, 46, 1154). Received: Moscow, 14th May 1998 Cambridge, 18th June 1998; Com. 8/03648I

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Saturated vapour pressure and enthalpy of sublimation of C84 Olga V. Boltalina,*a Vitaliy Yu. Markov,a Andrey Ya. Borschevskii,a Vladimir Ya. Davydov,a Lev N. Sidorov,a Valery N. Bezmelnitsin,b Alexander V. Eletskiib and Roger Taylorc a Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation.Fax:+7 095 939 1240; e-mail: ovb@thermo.chem.msu.su b Institute of Applied Chemical Physics, Russian Research Centre ‘Kurchatov Institute’, 123182 Moscow, Russian Federation c The Chemistry Laboratory, CPES School, Sussex University, Brighton, BN1 9QJ, UK The vapour pressure and sublimation enthalpy of HPLC-purified C84 have been determined by Knudsen cell mass spectrometry in the temperature range 658–980 K; the temperature–pressure equation is ln(p/Pa) = (–24337±539)/(T/K) + (25.15±0.64), and the mean sublimation enthalpy at 853 K is 202±4 kJ mol–1.There has been considerable interest in the thermodynamic properties of pure C60 and C70. The enthalpies of formation, heat capacity, enthalpies of sublimation and the saturated vapour pressures have been reported.1–7 However, separation and purification of higher fullerenes Cn (n > 70) still remains a complicated and time- and labourconsuming procedure, and this hinders investigations of their physical and chemical properties. Only a few papers have been published on the thermodynamic studies of higher fullerenes and their mixtures.8,9 Here we report our determination of the sublimation enthalpy of pure C84 and partial-mole sublimation enthalpies of C76, C78 and C84 determined from a mixture of higher fullerenes.Sample preparation. Two samples were investigated. Sample 1 was prepared as follows. The crude fullerenes were Soxhletextracted with chloroform from the fullerene-containing soot. The extract was then dissolved in toluene and purified directly by HPLC (without pre-separation of C60 and C70) using a 10 mm×25 cm Cosmosil Buckyprep column, toluene eluent, operated at 4.5 ml min–1 flow rate.The retention time of C84 was 24.95 min (C60 elutes at 7.8 min under the same conditions). The product from the initial separation was recycled (same conditions) to remove traces of other fullerenes present due to tailing during the initial run.The re-purified material showed (HPLC) complete absence of other fullerenes (except that traces of C82 may be present since it is well-known to co-elute with C84 using this column and conditions, which are now the universal standard for separation of this fullerene). Sample 2 was obtained after HPLC removal of C60 and C70 from the fullerene-containing soot extract.Knudsen cell mass spectrometry study. A magnetic sector MI-1201 mass spectrometer (Russia) equipped with a high temperature ion source (electron impact ionization, EI) was used in the sublimation studies; details of the instrumentation are described elsewhere.10 A weighed amount (3–4 mg) of the sample was placed into the first chamber of the twin effusion cell. Both Ni and Pt effusion cells were incorporated in different series, the hole diameters being 0.5 and 0.25 mm, respectively.The evaporation/effusion surface ratios were estimated to be not less than 400 and 100, respectively. Prior to our experiments with the twin cells, they were checked for the equivalence of flows from the two chambers. [60]Fullerene was placed into both chambers, and C+ 60 ion currents were measured and found to be equal. Either [60]fullerene or caesium iodide, used as standards in the experiments with samples 1 and 2, respectively, were placed into the second chamber of the twin cell.The cell was resistively heated and the temperature was measured with a Pt/Pt–Rh thermocouple. The EI mass spectra of samples 1 and 2 are presented in Figures 1 and 2, respectively.The composition of sample 2 was estimated from the HPLC data, assuming equivalence of the extinction coefficients of C76, C78 and C84 (Table 1). The amount of residue after completion of the vapour pressure measurements comprised 10–15% of the starting sample (5–8 mg). The residue dissolved partially in toluene and the solution obtained was analysed by HPLC, which showed a relative increase in C60 and C70 contents compared to the initial composition.This contradicts expectation based on their higher volatilities and arises in part due to the known thermal degradation of higher fullerenes to lower ones, and possibly also from differential solubilities in the toluene- Figure 1 Electron impact mass spectrum of sample 1 at T = 980 K. Mass range 700–1030 amu. 250 200 150 100 50 700 750 800 850 900 950 1000 m/z Intensity (arbitrary units) C+ 60 C+ 82 C+ 84 Figure 2 Electron impact mass spectrum of sample 2 at T = 822 K. Mass range 700–1030 amu. 700 750 800 850 900 950 1000 m/z Intensity (arbitrary units) C+ 60 C+ 70 C+ 76 C+ 78 C+ 82 C+ 84 1.0 0.8 0.6 0.4 0.2 Table 1 Composition of sample 2 before and after evaporation. Fullerene Mole fraction Before evaporation After evaporation C60 0.05 0.10 C70 0.12 0.24 C76 0.19 0.14 C78 0.23 0.16 C84 0.41 0.36Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) insoluble carbonaceous residue. This residue, widely observed in fullerene thermolysis, is believed to be composed of degraded or polymerised material. The temperature dependence of C+ 84 ion current for sample 1 was measured in the temperature interval 658–980 K.The partial pressure values of C84 were obtained from comparison of the intensities of C+ 84, and of C+ 60 of the standard, using the known vapour pressure of C60.6 The correction for ionisation cross section was made using the additivity rule.11 The recommended temperature variation of the saturated vapour pressure of C84 in the temperature range 658–980 K, and the corresponding value of the sublimation enthalpy, are presented in Table 2.We consider the pressure equation already mentioned and the sublimation enthalpy to describe the thermodynamic characteristics of pure C84 and disregard the influence of 10% of C82 (always present unless a two-stage HPLC secondary Buckylutcher column is used).For sample 2 the temperature dependence was measured in the temperature range 700–862 K. The partial pressures were determined from the measured ion currents of C+ 84 and Cs2I+ of the standard (CsI) using the known vapour pressure of Cs2I2.12 The correction for ionisation cross sections was made using the additivity rule.11 The temperature dependence of the partial pressure of C84 and the corresponding partial molar enthalpy of sublimation are also presented in Table 2.The error values were taken from the least square correlation as t0.95s, where t0.95 is the Student coefficient and s is the standard deviation. The plots of ln[p(C84)/Pa] versus 1/T for samples 1 and 2 are presented in Figure 3. The values of the enthalpies of sublimation of C84 obtained from the pure sample and from the higher fullerene mixture were compared with the sublimation enthalpy of Moalem et al.8 and that of Piacente et al.9 (Table 2). The former result was determined in the study of a mixture of higher fullerenes [the composition estimated from surface analysis by laser-induced desorption (SALI) mass spectrometry was as follows: C60, 0.05%; C70, 13%; C78, 5.7%; C84, 44% and C96, 5.8%].This mixture was assumed to behave as an ideal solution and the value obtained was regarded as the sublimation enthalpy of pure C84. Our result for the sublimation enthalpy of separated C84 differs considerably from the values obtained for the mixture (see Table 2). This suggests that the higher fullerene mixture cannot be considered as an ideal solution.Using the data on the composition at the end of the experiment, the activity coefficient of C84 in sample 2 at 741 K was determined as g(C84) = 0.05±0.02 (Table 1). These results roughly satisfy a regular solution equation (1): where is the partial molar enthalpy of dissolution. We also determined the saturated vapour pressures and partial molar sublimation enthalpies of C76 and C78 for the higher fullerene mixture (see Table 2).Results for C60 and C70 were rather unexpected. Values of their activities were ca. 10–3, but the sublimation enthalpies were very close to the values obtained for pure substances.6,7 This can be ascribed to diffusion in the solid phase, i.e. the diffusion process controls the evaporation rate of the volatile component.It results in the decrease in concentration of volatile components C60 and C70 in the surface layer and leads, subsequently, to underestimated values of the activities of these components and underestimation of the partial molar sublimation enthalpies of C60 and C70. This effect would appear not to influence the results on the vapour pressure and sublimation enthalpy of the major components of the mixture, i.e.C84, C78 and C76, which are less volatile than C60 and C70. We are grateful to the Russian Foundation for Basic Research (grant nos. 97-03-003391a and 97-03-33682a) and the Russian Research Program ‘Fullerenes and Atomic Clusters’ for the partial financial support of this work. References 1 C.K.Mathews, M. Sai Baba, T. S. LakshmiNarasimhan, R.Balasubramanian, N. Sivaraman and P. R. Vasudeva Rao, J. Phys. Chem., 1992, 96, 3566. 2 M. Sai Baba, T. S. Lakshmi Narasimhan, R. Balasubramanian, N. Sivaraman and C. K. Mathews, J. Phys. Chem., 1994, 98, 1333. 3 J. Abrefah, D. R. Olander, M. Balooch and W. J. Siekhaus, Appl. Phys. Lett., 1992, 60, 1313. 4 A. Popovic, G. Drasic and J. Marsel, Rapid Commun. Mass Spectrom., 1994, 985. 5 E. V. Skokan, O. V. Boltalina, P. A. Dorozhko, L. M. Khomich, M. V. Korobov and L. N. Sidorov, Mol. Mat., 1994, 4, 221. 6 V. Piacente, G. Gigli, P. Scardala, A. Gustini and D. Ferro, J. Phys. Chem., 1995, 99, 14052. 7 V. Piacente, G. Gigli, P. Scardala, A. Gustini and P. Bardi, J. Phys. Chem., 1996, 100, 9815. 8 M. Moalem, M. Balooch, A. V. Hamza and R. S. Ruoff, J.Phys. Chem., 1995, 99, 16736. 9 V. Piacente, C. Palchetti, G. Gigli and P. Scardala, J. Phys. Chem., 1997, 101, 4303. 10 N. S. Chilingarov, M. V. Korobov, L. N. Sidorov, V. N. Mit’kin, V. A. Shipachev and S. V. Zemskov, J. Chem. Thermodyn., 1984, 16, 965. 11 J. W. Otwos and D. P. Stevenson, J. Am. Chem. Soc., 1956, 78, 536. 12 Termodinamicheskie Svoistva Individual’nykh Veshchestv (Thermodynamic Properties of Individual Substances), ed.V. P. Glushko, Nauka, Moscow, 1978–1982 (in Russian). aThe parameter of the temperature equation was estimated without errors. Table 2 Vapour pressures and sublimation enthalpies of C60, C70 and higher fullerenes. Work Fullerene System Temperature interval/K lg(p/Pa) = –B/T + A T/K DsubH0T /kJ mol–1 B/K A This C76 mixture 700–862 11586±913 10.32±1.21 756 222±17 This C78 mixture 700–862 11588±842 10.25±1.12 756 222±16 8 C84 mixture 800–950 12902±1306 15a — 247±25 9 C84 pure 920–1190 10950±300 10.92±0.30 950 210±6 This C84 pure 658–980 10570±234 10.92±0.28 853 202±4 This C84 mixture 700–862 12101±949 11.15±1.26 756 231±18 2 0 –2 –4 –6 –8 –10 –12 –14 1.0 1.1 1.2 1.3 1.4 1.5 1.6 ln[p(C84)/Pa] T–1/103 K–1 Figure 3 The plots of ln(p/Pa) versus 1/T for C84 over sample 1 ( ) and over sample 2 ( ). DsolH0 T(C84)m=RTln[g(C84)] (1) DsolH0 T(C84)m Received: Moscow, 7th May 1998 Cambridge, 8th June 1998; Com. 8/03647K

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Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) Formation of stable -aryliron(III) complexes from the reaction of chloroiron(III) octaphenyltetraazaporphyrinate with aryl Grignard reagents Pavel A. Stuzhin,*a Ol’ga V. Mal’chugina,a Stanislaw Wolowiec,b Lechoslaw Latos-Grazynskib and Boris D. Berezina a Department of Organic Chemistry, Ivanovo State Academy of Chemical Technology, 153460 Ivanovo, Russian Federation.Fax: +7 0932 37 7743; e-mail: stuzhin@icti.ivanovo.su b Department of Chemistry, University of Wroclaw, 50383 Wroclaw, Poland Chloro(octaphenyltetraazaporphyrinato)iron(III) [(Cl)FeIIIOPTAP] reacts with aryl Grignard reagents (ArMgBr; Ar = phenyl or p-tolyl) forming stable low-spin s-aryliron(III) complexes [(Ar)FeIIIOPTAP]. The inactivation of hemoproteins by arylhydrazines includes formation of aryl–iron s-bonded complexes of heme as intermediates.1 The structure, physico-chemical properties and reactivity of s-aryliron(III) complexes of synthetic porphyrins [(Ar)FeIIIP; P = OEP (octaethylporphine) or TPP (tetraphenylporphine)] which form in the reaction of iron(III) porphyrins with aryl Grignard reagents under strictly anaerobic conditions2,3 have been extensively investigated.4,5 The preparation of s-aryliron(III) phthalocyanines [(Ar)FeIIIPc] has also been demonstrated,6–8 but no full report on their synthesis and characterization has appeared since then.Thus s-phenyliron(III) phthalocyanine (Ph)FeIIIPc was prepared7,8 by oxidation of s-phenyliron(II) complex Li[(Ph)FeIIPc] which in turn forms in the reaction of BrFeIIIPc (or Py2FeIIPc) with phenyllithium.6 Grignard reagents can not be used in the synthesis of (Ar)FeIIIPc because they reduce iron(III) phthalocyanines to the iron(0) complex ([Fe0Pc]2–).6 Unlike s-phenyliron(III) phthalocyanine, which was reported to be a stable compound,7 s-aryliron(III) porphyrins are easily oxidized in the presence of dioxygen forming m-oxodiiron(III) or aryloxoiron(III) complexes [m-O(FeIIIP)2 or (PhO)FeIIIP]9 and give upon addition of acids HX acidoiron(III) complexes [(X)FeIIIP].2 Thus the stability of the Ar–Fe bond depends strongly on the properties of the macrocyclic ligand.In order to throw some more light on the factors determining the stability of the C–Fe bond we have obtained the s-phenyliron(III) complex of octaphenyltetraazaporphine, a macrocyclic ligand having an intermediate structure between common porphyrins and phthalocyanine.s-Phenyl(octaphenyltetraazaporphyrinato)iron(III) [(Ph)FeIIIOPTAP 2] was obtained by addition of phenylmagnesium bromide (PhMgBr) to a solution of chloro(octaphenyltetraazaporphyrinato) iron(III) [(Cl)FeIIIOPTAP 1]10 in dry benzene in aerobic conditions (Scheme 1). The colour of the solution changed immediately from red-brown to dark blue and then to green.Excess PhMgBr was hydrolyzed with water and the benzene layer (after drying with Na2SO4) was chromatographed on neutral Al2O3. s-Phenyliron(III) complex 2 was obtained from the second greenish-blue fraction (yield 14%)† while the first green fraction contained mostly m-oxodiiron(III) complex [m-O(FeIIIOPTAP)2]. In a similar manner using various aryl Grignard reagents other s-aryliron(III) complexes (Ar)FeIIIOPTAP (Ar = p-MePh, p-MeOPh etc.) can be obtained.Complex 2 is air-stable in the solid for several weeks, but in a solution in neutral solvents such as benzene or toluene it converts after several days to m-O(FeIIIOPTAP)2.Addition of † Analysis for 2: 1H NMR (300 MHz, [2H8]toluene, 293 K) d: 1.25 (o-Phb), 7.40 (m-Phb) and 3.53 (p-Phb) (OPTAP); 84.34, 8.00 and –30.85 (o-Phax, m-Phax and p-Phax). UV/VIS [benzene, lmax/nm (log e)]: 344 (4.45), 440sh, 458 (4.17), 489sh, 555sh, 607 (4.45). IR (KBr, n/cm–1): 536m, 608m, 640w, 696vs, 744s, 776m, 832s, 888w, 916w, 992vs, 1064w, 1152s, 1204w, 1296w, 1372s, 1440m, 1460m, 1484s.Found (%): C, 79.5; H, 4.4; N, 10.4. Calc. for C70H45N8Fe (%): C, 79.77; H, 4.30; N, 10.63. FAB-MS m/z: (Ph)FeOPTAP+ (1053, 14%; 1052, 28%; 1051, 35%; 1050, 44%; 1049, 39%; 1048, 29%); FeOPTAP+ (976, 46%; 975, 57%; 974, 100%; 973, 86%; 972, 71%; 971, 38%; 970, 28%). acid HX (X = Cl, CCl3COO) to a solution of 2 results in slow formation of the corresponding acidoiron(III) complex (X)FeIIIOPTAP and dissolution of 2 in pure pyridine leads to (py)2FeIIOPTAP.The CHN elemental analysis data for 2 are in agreement with the formula (Ph)FeIIIOPTAP. The mass spectrum of 2 obtained by a fast atom bombardment method contains mass peaks corresponding to the molecular ion [(Ph)FeOPTAP]+ and to the dephenylated fragment [FeOPTAP]+. In the IR spectrum of (Ph)FeIIIOPTAP the vibrations of the axially coordinated phenyl (Phax) coincide with that of the eight equatorial phenyls (Phb) attached to the b-pyrrole positions of the macrocyclic ligand, but some structural information can be obtained from the skeleton vibrations of the latter.Thus the band at 1296 cm–1 is characteristic of the five-coordinated (X)FeIIIOPTAP complexes10 and the position of the oxidation-state sensitive band at 1152 cm–1 is typical of the iron(III) complexes.11 Conversion of the chloride complex 1 to the s-phenyl complex 2 is accompanied by strong changes in the UV/VIS spectra (Figure 1).This is not unusual because the oxidation and spin states of the iron(III) ion have a large impact on the energies of the p ® p* transitions of the OPTAP macrocycle and on the appearance of the charge-transfer transitions.10,11 The spectrum of (Ph)FeIIIOPTAP [Figure 1(b)] differs greatly from the spectrum of the initial intermediate-spin (IS) FeIII complex (Cl)FeIIIOPTAP10 [Figure 1(a)] and is typical of complexes with low-spin (LS) FeIII.However, all known LS FeIII complexes of OPTAP2– are six-coordinate {e.g. [(CN)2FeIIIOPTAP] –, [(N3)2FeIIIOPTAP]–, [(HIm)(N3)FeIIIOPTAP] or s Figure 1 UV/VIS spectra of (a) (Cl)FeIIIOPTAP, (b) (Ph)FeIIIOPTAP in toluene (2.1×10–5 M) and (c)–(f) spectral changes observed after addition of 1-methylimidazole (2.55×10–4, 8.90×10–4, 3.56×10–3, 2.09×10–2 M, respectively) to a solution of (Ph)FeIIIOPTAP.A 0.8 0.6 0.4 0.2 0.0 400 500 600 700 800 l/nm a b c d e f b b fMendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129-168) [(HIm)2FeIIIOPTAP]+}.11,12 Five-coordinate complexes even with axial ligands possessing a stronger field than the halogenide [e.g. (N3)FeIIIOPTAP or even (CN)FeIIIOPTAP] usually have UV/VIS spectra typical of IS FeIII complexes. Evidently the s-Ar carbanion forming the strong s-bond with the iron atom raises the energy of the dz2 orbital and makes favourable the LS state of FeIII even in the five-coordinate complex.s- Aryliron(III) porphyrins and phthalocyanine are also LS complexes.2,7 Addition of small amounts of N-bases L (L = pyridine, imidazole) to a solution of 2 in neutral solvents results in spectral changes that are indicative of coordination of L in the trans-position to the s-phenyl anion with formation of (L)(Ph)FeIIIOPTAP 3 and under certain conditions an equilibrium between five- and six-coordinate complexes 2 and 3 can be observed [Figure 1, spectra (b)–(f)]. Formation of the six-coordinate complex 3 from 2 is accompanied by a strong bathochromic shift of the B-band [a2u(p) ® eg(p*) transition] from 344 to 397 nm, whereas the position of the Q-band [a1u(p) ® eg(p*) transition] at 607 nm remains practically unchanged.This is well explained by the different symmetry properties of the two highest occupied molecular orbitals. The a2u(p) orbital destabilizes upon coordination of the p-donor ligand in the sixth position, in contrast to the a1u(p) orbital which, having nodes on the coordinating pyrrole N-atoms of the OPTAP macrocycle, is much less sensitive to the changes in the coordination state of the Fe atom.In the 1H NMR spectra of (Ph)FeIIIOPTAP [Figure 2(a)] the paramagnetically-shifted phenyl protons of the macrocycle are observed at 1.25 (o-Phb), 7.40 (m-Phb) and 3.53 ppm (p-Phb) ([2H8]toluene, 293 K). The pattern of three singlets suggests fast rotation of the b-phenyl rings with respect to the Cb–Cphenyl bond.The signals of the axial phenyl protons are located at –84.34, 8.00 and –30.85 ppm for o-Phax, m-Phax and p-Phax, respectively. An identical 1H NMR spectrum has been obtained in the course of titration of (Cl)FeIIIOPTAP with PhMgBr in [2H8]toluene. The strong isotropic shift of the axial phenyl proton resonances is dominated by the contact contribution. The analysis indicates the large p-spin density at the axial ligand as the contact shift decreases in the characteristic order ortho > para > meta and can be accounted for by the spin delocalization from the dp orbitals to the p-type orbitals of the axially-coordinated phenyl ligand (although some contribution of the s-contact mechanism should be considered as well).14,15 In the relevant case of s-phenyliron(III) porphyrins the resonances of the axial phenyl protons were observed in the same region [for (Ph)FeIIITPP at 294 K by –81, 13.6 and –27 ppm for o-Phax, m-Phax and p-Phax, respectively].3 Coordination of a strong p-donor ligand such as 1-methylimidazole (1MeIm) in the trans-position to phenyl [(1MeIm)- (Ph)FeIIIOPTAP] decreases the range of paramagnetic shifts found for the Phax protons (–57.46, 14.30 and –14.42 ppm for o-Phax, m-Phax and p-Phax, respectively) [Figure 2(b)].The effect is comparable with that demonstrated for (1MeIm)(Ph)- FeIIITMP (TMP = meso-tetramesitylporphyrin dianion).13 The 1H NMR data suggest that (Ph)FeIIIOPTAP and (1MeIm)- (Ph)FeIIIOPTAP present the (dxy)2(dp)3(dz2)0(dx2 – y2)0 ground electronic state, as previously shown for the corresponding iron(III) porphyrin species.13,15 Tetraazasubstitution in the meso-positions of the porphyrin ligand endows the macrocyclic ligand with stronger p-acceptor and s-donor properties.These factors determine the strengthening of the Fe � Phax p-bonding and Fe � OPTAP s-bonding which can explain the higher oxidation stability observed for the s-aryliron(III) complexes of tetraazaporphyrins (and phthalocyanine as well).Further study of s-aryliron(III) octaphenyltetraazaporphyrin complexes using Mössbauer, NMR and EPR spectroscopy which are now in progress will reveal the details of their formation mechanism. We thank Professor B. Floris (Università di Roma ‘Tor Vergata’, Italy) for help in obtaining the mass spectra.References 1 K. L. Kunze and P. R. Ortiz de Montellano, J. Am. Chem. Soc., 1983, 105, 1380. 2 H. Ogoshi, H. Sugimoto, Z.-I. Yoshida, H. Kobayashi, H. Sakai and Y. Maeda, J. Organomet. Chem., 1982, 234, 185. 3 P. Cocolios, G. Lagrange and R. Guilard, J. Organomet. Chem., 1983, 253, 65. 4 P. Doppelt, Inorg. Chem., 1984, 23, 4009. 5 R. Guilard and K. M. Kadish, Chem. Rev., 1988, 88, 1121 and references therein. 6 R. Taube and H. Drevs, Z. Anorg. Allg. Chem., 1977, 429, 5. 7 R. Taube, H. Drevs and D. Steinborn, Z. Chem., 1978, 18, 425. 20 10 0 –10 m-Phax m-Phb o-Phb p-Phb m-Phax p-Phax o-Phax (a) (b) 4-H + 2-H 5-H m-Phax + 1-Me o-Phb p-Phax o-Phax 40 20 0 –20 –40 –60 –80 d/ppm Figure 2 300 MHz 1H NMR spectra of (a) (Ph)FeIIIOPTAP (293 K) and (b) (1MeIm)(Ph)FeIIIOPTAP (253 K) in [2H8]toluene. Inset in trace (a) presents details of the –10 to +20 ppm region (spectrum recorded at 180 K).Resonance assignments: o-Ph, m-Ph and p-Ph, resonances of ortho, meta and para phenyl protons (axial and b-phenyl signals are marked by subscripts Phax or Phb, respectively); 2-H, 4-H, 1-Me, 5-H resonances of coordinated 1-MeIm. N N N N N N N N Ph Ph Ph Ph Ph Ph Ph Ph Fe Cl 1 PhMgBr benzene (Cl)FeOPTAP N N N N N N N N Ph Ph Ph Ph Ph Ph Ph Ph Fe 2 (Ph)FeOPTAP Scheme 1Mendeleev Communications Electronic Version, Issue 4, 1998 (pp. 129–168) 8 E.-Ch. Müller, R. Kraft, G. Etzold, H. Drevs and R. Taube, J. Prakt. Chem., 1978, 320, 49. 9 R. D. Arasasingham, A. L. Balch, R. L. Hart and L. Latos-Grazynski, J. Am. Chem. Soc., 1990, 112, 7566. 10 P. A. Stuzhin, M. Hamdush and U. Ziener, Inorg. Chim. Acta, 1995, 236, 131. 11 P. A. Stuzhin, Koord. Khim., 1995, 21, 125 (Russ. J. Coord. Chem., 1995, 21, 117). 12 P. A. Stuzhin and M. Hamdush, Koord. Khim., 1998, 24, 330 (Russ. J. Coord. Chem., 1998, 24, 309). 13 A. L. Balch and M. W. Renner, Inorg. Chem., 1986, 25, 303. 14 P. J. Chmielewski and L. Latos-Grazynski, Inorg. Chem., 1992, 31, 5231. 15 P. J. Chmielewski, L. Latos-Grazynski and K. Rachlewicz, Magn. Reson. Chem., 1993, 31, 47. Received: Moscow, 28th April 1998 Cambridge, 18th June 1998; Com. 8/03

ISSN:0959-9436     

出版商:RSC    

年代:1998

数据来源: RSC