摘要:

Mendeleev Communications Electronic Version, Issue 1, 2002 1 A cobalt(II)–porphyrin complex as a regulator of cross-linking radical copolymerization Svetlana V. Kurmaz,* Evgenia O. Perepelitsina, Maria L. Bubnova, Genrietta A. Estrina and Valentin P. Roshchupkin Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation. Fax: +7 096 524 9676; e-mail: skurmaz@icp.ac.ru 10.1070/MC2002v012n01ABEH001544 The additions of a porphyrin cobalt complex diminished the rate of cross-linking copolymerization of ethylene glycol dimethacrylate (EGDMA) and styrene, shifted the autoacceleration process towards higher degrees of monomer conversions and modified the structure and properties of resulting cross-linked copolymers owing to catalytic chain transfer reaction, catalytic inhibition reaction and chain regeneration as a result of the reversible breakdown of a Co–C bond. Control over the kinetics of cross-linking radical polymerization and copolymerization of multifunctional vinyl compounds and the structure of the resulting polymer networks is a complex problem.The cross-linking polymerization is characterised by autoacceleration early in the reaction due to the hindered mobility of growing radicals attached to hyperbranched macromolecules and microgel particles bearing pendant vinyl groups.1,2 As a result, intramolecular cyclization causes the polymer–monomer microphase separation.3 The vitrification of the reaction medium adds complexity to copolymerization reaction and copolymer structure development.It gives rise to diffusion control over the propagation chain constant and leads to a rate autoretardation. At this stage, distinctions between comonomers in mobility can lead to a deviation of local comonomer concentrations in the vicinity of growing macroradicals from global concentrations and thereby affect the copolymer composition.4 As a consequence, the resulting polymeric networks are always heterogeneous.This structural heterogeneity has a dramatic impact on the properties of the final cross-linked materials.1,5 Here, we propose the control of cross-linking radical copolymerization by the addition of the CoII tetramethyl hematoporphyrin IX complex [CoIIP], which is known as a catalytic chain transfer agent and a catalytic inhibitor in the linear radical polymerization of methyl methacrylate6 and styrene.7 The capabilities of CoIIP as a regulator of cross-linking copolymerization are evident from a comparison of conventional and CoIIPcontrolled copolymerization of ethylene glycol dimethacrylate (EGDMA) and styrene with respect to the kinetics of copolymerization and the structure and properties of the resulting copolymers. Commercial styrene was distilled in a vacuum after the removal of an inhibitor by a 10% NaOH solution.EGDMA (Aldrich) was used without further purification. The copolymerizations were conducted at 60 °C in glass ampoules sealed in a vacuum after freeze–pump–thaw cycles. The concentrations of CoIIP were 3.5×10–4 and 4.1×10–3 mol dm–3.The concentration of an initiator (AIBN) was 6.4×10–3 mol dm–3. The copolymerization kinetics of EGDMA and styrene was monitored by isothermal calorimetry. An equimolar monomer mixture feed was used. The computations of C=C bond conversion and copolymerization rate were described elsewhere.8 The final conversions of C=C bonds in EGDMA and styrene copolymers were determined by IR spectroscopy.9 The structure of copolymers was probed by the sorption of benzene and water vapour at atmospheric pressure and 20 °C. The mechanical properties of the copolymers were investigated in an uniaxial compression mode.A modernised Hepplers consistometer and cylindrical copolymer samples 5 mm in length and 3 mm in diameter were used to obtain the stress–strain plots. Figure 1 shows a significant difference in the kinetics between the conventional copolymerization of EGDMA and styrene and the copolymerization in the presence of CoIIP.On adding 3.5×10–4 mol dm–3 CoIIP, the beginning of a gel effect shifts to higher conversion and the rate of copolymerization at a maximum is lowered by a factor of 6. An increase in the concentration of the additive to 4.1×10–3 mol dm–3 eliminates the gel effect almost completely.Thus, CoIIP can be used as a regulator of cross-linking radical copolymerization. To understand how CoIIP affects cross-linking radical copolymerization of EGDMA and styrene, data on the impact of CoIIP upon linear homopolymerizations of methyl methacrylate (MMA) and styrene should be taken into account. It is known6 that in the course of MMA polymerization CoIIP catalyses chain transfer reaction from a tertiary propagating radical to a monomer via the consecutive steps producing unsaturated macromonomers Pn 10 In styrene polymerization, the chain transfer coefficient from a secondary propagating radical to a monomer is 10 times smaller than that in MMA polymerization.7 This decrease in chain transfer coefficient was attributed to the concurrent catalytic inhibition reaction and to the reversible cobalt–carbon bond formation The reversible dissociation of a cobalt–carbon bond can result in polystyrene growing chain regeneration,7 which gives rise to a ‘living’ polymerization mechanism.11–13 By analogy with the linear homopolymerization of MMA and styrene, a CoIIP additive will reduce the rate of cross-linking copolymerization of EGDMA and styrene because of reactions Figure 1 Effect of CoIIP on the (1)–(3) rate and (1')–(3') conversion of the copolymerization of EGDMA and styrene at 60 °C.[CoIIP] = (1), (1') 0; (2), (2') 3.5×10–4; (3), (3') 4.1×10–3 mol dm–3. [AIBN] = 6.4×10–3 mol dm–3. 60 40 12 8 4 1.0 0.8 0.6 0.4 0.2 500 1000 1500 2000 W/M×103, min–1 Conversion, C t/min 1 2 3 1' 2' 3' Rn* + CoIIP Pn + HCoIIIP, HCoIIIP +M CoIIP + R1 * (1) (2) H(–CH2–C–)n–CH2–C=CH2 Me COOMe COOMe (A) HCoIIIP + Rm* Pm + CoIIP (3) Rn* +CoIIP Rn–CoIIIP.(4)Mendeleev Communications Electronic Version, Issue 1, 2002 2 (3) and (4), and such a decrease was observed experimentally (Figure 1). At the same time, there is one more pathway unique to the polymerization of dimethacrylates whereby CoIIP transforms the kinetics of crosslinking copolymerization and the development of a polymer network structure.Unlike MMA, the polymerization and copolymerization of dimethacrylates produce multifunctional oligomers bearing pendant reactive methacrylic groups as an alternative to macromonomers A. Note that the multifunctional oligomers of type B are intermediate species synthesised in situ as a result of catalytic chain transfer reactions (1) and (2) on the way from the initial dimethacrylates to the resulting cross-linked copolymer.They radically alter the course of reaction in comparison to conventional copolymerization. The conventional reaction proceed through the formation and growing of microgel particles (C) Because of a hindered mobility of radicals R* attached to microgel particles, the rate of termination reaction diminishes, the gel effect arises, and the resulting cross-linked copolymer becomes heterogeneous.In the presence of CoIIP, the reaction medium has another structure (D) because catalytic chain transfer reaction prevents the formation of large microgel particles, suppresses the gel effect and produces a network copolymer of more homogeneous structure.The suggestion that catalytic chain transfer reactions (1) and (2) restrict the growth of copolymer chains producing mainly terminal C=C bonds of methacrylic groups was supported through the determination of the concentration of residual double bonds in resulting copolymers by calorimetry and IR spectroscopy.The total concentration of C=C bonds in the copolymers obtained in the presence of 4.1×10–3 mol dm–3 CoIIP determined from IR spectra was 10% higher than the value determined by calori-metry. This is because IR spectroscopy, contrary to calorimetry, detects not only C=C bond consumption in copolymerization but also the production of new terminal C=C bonds in oligomers B as a result of catalytic chain transfer reaction.In accordance with these data, the average concentration of methacrylic units in intermediate oligomers of type B may be evaluated as ~10%. The direct evidence for the formation of multifunctional oligo-mers B was obtained by the analysis of soluble products of the copolymerization of EGDMA and styrene in the presence of 20% of dimethylformamide.According to IR spectra, the products contain a lot of pendant methacrylic groups. The average molecular weights of these multifunctional oligomers were determined to be Mn = 2270 and Mw = 14350 by gel permeation chromatography using polystyrene as a standard. A considerable disadvantage of the conventional cross-linking polymerization is the incompleteness of shrinkage (contraction).The problem is that during the polymerization of multifunctional methacrylates the rate of volume shrinkage is lower than the rate of polymerization because the chemical reaction requires merely the single oligomer and growing macroradical to be mobile whereas shrinkage requires a concerted movement of the entire reactive medium.14 The incomplete shrinkage gives rise to undesirable results such as internal stresses, microporosity, micro-cracks, and poor mechanical properties.1 The additives of CoIIP solve the problem through the suppression of a gel effect and the increasing mobility of a reactive medium.The equalization of the rates of copolymerization and volume relaxation can lead to profound changes in the structure and properties of resulting copolymers.We found that the sorption and mechanical properties of EGDMA and styrene copolymers obtained in the presence of 3.5×10–4 and of 4.1×10–3 mol dm–3 CoIIP (samples II and III) (B) R * R R R R R R * * *R * * * * (C) (D) *R styrene EGDMA Figure 2 The kinetics of (a) water and (b) benzene vapour sorption by EGDMA and styrene copolymers (1) I, (2) II, (3) III.The final conversions of C=C bonds in copolymers I, II and III are 88.5, 88.3 and 89%, respectively. 2.0 1.5 1.0 0.5 20 40 60 80 100 1 2 3 (a) Swelling (%) Time/days 20 40 60 80 100 Time/days 15 10 5 1 2 3 Swelling (%) (b) Figure 3 The plots of strain vs. stress for EGDMA and styrene copolymers (1) I, (2) II, (3) III. The final conversions of C=C bonds in copolymers I, II and III are 88.5, 88.3 and 89%, respectively. 300 200 100 0.1 0.2 0.3 e s/MPa 1 2 3Mendeleev Communications Electronic Version, Issue 1, 2002 3 differ significantly from the properties of a conventional copolymer (sample I). It is known that the C=C bond conversion is of fundamental importance to the properties of network polymers. Because of this, we tried to match the copolymers with equal C=C bond conversions.For this purpose, the low conversions of copolymers I and II were brought up to the conversion of copolymer III by a stepwise change in temperature from 70 to 120° under IR-spectroscopic control. Figure 2(a) shows that the sorption of water by a conventional copolymer of EGDMA and styrene (I) occurs in two successive steps. We believe that the first step of sorption is determined by the formation of H-bonds between ester groups and H2O molecules and the second step, by water condensation in the micropores.The absence of this step of water sorption in case of copolymers II and III confirms that CoIIP contributes to the development of a more homogeneous copolymer structure in comparison to conventional copolymerization.Figure 2(b) shows benzene sorption curves. The sorption rate increases in copolymers arranged in a sequence I, II, III. The maximal sorption levels increase in the same sequence. Thus, the copolymers obtained in the presence of CoIIP have higher molecular mobility and elasticity as compared to a conventional copolymer. This is obviously a result of the fragmentation of copolymer chains due to catalytic chain transfer and catalytic chain inhibition reactions and formation of a specific network of short styrene–methacrylate chains (1) cross-linked by oligomer spacers (2) Note that a variation in CoIIP concentration allows us to vary the number and size of chains (1) over a wide range and thereby to control the contributions from components (1) and (2) to copolymer properties.An example of the effect of CoIIP concentration on the stress– strain properties of copolymers is presented in Figure 3. The addition of 3.5×10–4 mol dm–3 CoIIP has almost no effect on the properties. An increase in CoIIP concentration up to 4.1×10–3 mol dm–3 significantly diminishes the modulus of elasticity and forced elasticity. These data confirm the conclusion based on benzene sorption [Figure 2(b)] that a CoIIP additive is favourable to the production of more elastic copolymer networks. The copolymerization of triethylene glycol dimethacrylate and styrene was also studied.The influence of CoIIP on the kinetics of copolymerization and the properties of the resulting copolymers were generally the same as in the case of the EGDMA– styrene system.Thus, CoIIP is a promising regulator of cross-linking radical copolymerization and network structure development. It can be used as an effective tool for macromolecular design. This work was supported by the Russian Foundation for Basic Research (grant no. 01-03-33259) and a grant for young scientists (no. 144) from the Russian Academy of Sciences. References 1 V.P. Roshchupkin and S. V. Kurmaz, in Polymeric Materials Encyclopædia, Salamone, C., CRC Press, Boca Raton, 1996, vol. 7, p. 30. 2 J. E. Elliott and C. N. Bowman, Macromolecules, 1999, 32, 8621. 3 K.Dusek, Collect. Czech. Chem. Commun., 1993, 58, 2245. 4 S. V. Kurmaz and V. P. Roshchupkin, Vysokomol. Soedin., Ser. B, 1997, 39, 1557 [Polym. Sci. (Engl. Transl.), 1997, 39, 358]. 5 A.R. Kannurpatti, J. W. Anseth and C. H. Bowman, Polymer, 1998, 39, 2507. 6 B. R. Smirnov, I. M. Belgovskii, G. V. Ponomarev, A. P. Marchenko and N. S. Enikolopyan, Dokl. Akad. Nauk SSSR, 1980, 254, 127 [Dokl. Chem. (Engl. Transl.), 1980, 254, 426]. 7 B. R. Smirnov, V. D. Plotnikov, B. V. Ozerkovskii, V. P. Roshchupkin and N. S. Yenikolopyan, Vysokomol. Soedin., Ser. A., 1981, 23, 2588 [Polym. Sci. USSR (Engl. Transl.), 1981, 23, 2807]. 8 A. A. Berlin, T. Ya. Kefeli and G. V. Korolev, Poliefirakrilaty (Polyesteracrylates), Nauka, Moscow, 1967, p. 272 (in Russian). 9 S. V. Kurmaz and V. P. Roshchupkin, Plastmassy, in press. 10 B. V. Ozerkovskii and V. P. Roshchupkin, Dokl. Akad. Nauk SSSR, 1980, 254, 157 [Dokl. Phys. Chem. (Engl. Transl.), 1980, 254, 731]. 11 J. P. A. Heuts, D. J. Forster, T. P. Davis, B. Yamada, H. Yamazoe and M. Azukizawa, Macromolecules, 1999, 32, 2511. 12 T. E. Patten and K. Matyjaszewski, Acc. Chem. Res., 1999, 32, 895. 13 G. V. Korolev and A. P. Marchenko, Usp. Khim., 2000, 69, 447 (Russ. Chem. Rev., 2000, 69, 409). 14 J. G. Kloosterboer, Adv. Polym. Sci., 1988, 84, 1. 1 2 Received: 24th December 2001; Com. 01/1870

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年代:2002

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Difluorination ability of F-TEDA-BF4 in the transannular cyclization of bicyclo[3.3.1]nonane dienes in monoglyme Yurii A. Serguchev,* Lyudmila F. Lourie and Maxim V. Ponomarenko Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 02094 Kiev, Ukraine. Fax: +380 44 573 2643; e-mail: serg@mail.kar.net 10.1070/MC2002v012n01ABEH001531 The interaction of 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA-BF4) with 3,7-bismethylenebicyclo[ 3.3.1]nonane and its derivatives in monoglyme results in the transannular cyclization of the dienes to form 1-fluoro-3-fluoroalkyladamantanes.Electrophilic N.F reagents are widely used in the selective fluorination of organic, in particular, unsaturated, substrates.1 The reactions are usually conducted in nucleophilic or dissociating solvents because in aprotic media with low polarity and small nucleophilicity (CHCl3, CH2Cl2, Freon-113, THF etc.) they give a complex mixture of products.2 The side formation of difluorides was observed in the reactions of F-TEDA-BF4 with unsaturated substrates.3,4 For example, 1,2-difluorosaccharides were reported to form as by-products, in addition to monofluorinated carbohydrates, in the fluorination of glycals with F-TEDA-BF4 in nitromethane in the presence of alcohols.3 Side difluorination occurred in the transannular cyclization of 3,7-bismethylenebicyclo[3.3.1]nonane with F-TEDA-BF4 in protic solvents, where 1-fluoro-3-fluoromethyladamantane was detected as an impurity among the major products, 1-RO-3- fluoromethyladamantanes (R = H, Alk or Ac).4 Here, we report the unusual and intriguing finding: under certain conditions, F-TEDA-BF4 can act as an effective difluorinating agent in the transannular cyclization of 3,7-bismethylenebicyclo[ 3.3.1]nonane and its derivatives with a methyl or phenyl substituent at one of the exocyclic methylene groups.The starting substrates (3,7-bismethylenebicyclo[3.3.1]nonane 1a, 3-ethylidene-7-methylenebicyclo[3.3.1]nonane 1b and 3-benzylidene- 7-methylenebicyclo[3.3.1]nonane 1c) were prepared by the published procedures.4,5 When the reaction was carried out in monoglyme, difluoro-substituted adamantanes 2a.c were obtained in high yields.¢Ó It was of interest to elucidate whether monoglyme is a specific solvent promoting the difluorination.For this purpose, we conducted the reaction of 1a with F-TEDA-BF4 in a series of aprotic polar solvents. In low-polarity solvents such as CH2Cl2, C2H4Cl2 and THF, no cyclization was observed even at the stirring the reactants for many days. In polar nitromethane, the reaction occurred; however, the yield of difluoride 2a was very low.The major product in this solvent was tentatively identified as 1-fluoromethyladamantane with a TEDA-BF4 residue attached to the bridge-head atom 3-C (Scheme 2, compound 3). The formation of similar products was observed in the reactions of glycals with F-TEDA-BF4.3 We failed to isolate this adduct from the reaction mixture, but its formation was proved by the following transformations caused by ionogenic agents.Upon heating the reaction mixture under reflux for several hours in the presence of methanol, acetic acid, aqueous hydrobromic acid or hydrogen chloride, the TEDA-BF4 residue in compound 3 was replaced by the external nucleophile with the formation of fluoromethyladamantanes 4.7.¢Ô Thus, monoglyme is responsible for the high yield of difluorides 2a.c in the transannular cyclization of dienes 1a.c with F-TEDA-BF4.The reaction mechanism can be conceived as follows: at the first step, the ¡®electrophilic¡� fluorine in the F.N group of F-TEDA-BF4 adds to a double bond of the diene to give, after the transannular cyclization, a stable adamantyl cation,6 which recombines with a fluoride anion making part of BF4 ..The promoting role of monoglyme evidently consists in binding ¢Ó In a typical procedure, 1.2 mmol of appropriate diene 1 and 1.32 mmol of F-TEDA-BF4 in 10 ml of monoglyme were heated at reflux with stirring for 45.120 h. The reaction mixture was dissolved in 40 ml of water and extracted with CH2Cl2 [(4.5)¡¿15 ml]. The combined extracts were washed with water (2¡¿10 ml), dried (Na2SO4) and concentrated by evaporation. The products were purified by column chromatography on silica gel (eluent: hexane.diethyl ether, 25:1).Their yields, as determined by GLC, are indicated in Scheme 1. R N N F CH2Cl BF4 BF4 F F R monoglyme . 1a.c a R = H b R = Me c R = Ph 2a.c 2a, 93% 2b, 81% 2c, 95% Scheme 1 ¢Ô The reaction of 1a (0.1 g, 0.67 mmol) with F-TEDA-BF4 (0.263 g, 0.74 mmol) in anhydrous nitromethane (10 ml) was conducted at room temperature for 12 h, until 1a was completely consumed (TLC test).The yield of 2a under these conditions was about 21% (GLC). After the addition of 2 ml of absolute methanol to the reaction mixture and heating at reflux for 9 h, 1-fluoromethyl-3-methoxyadamantane 4 was formed in 75% yield (GLC), whereas the yield of difluoride 2a remained as before.In a similar way, by heating the reaction mixture with 2 ml of acetic acid for 5 h, 1-acetoxy-3-fluoromethyladamantane 5 was obtained in 75% yield (GLC). The 1H, 13C and 19F NMR spectra of products 4 and 5 are in agreement with published data.4 Refluxing the reaction mixture with 3 ml of aqueous 60% HBr for 2 h afforded 1-bromo-3-fluoromethyladamantane 6 in 54% isolated yield.By passing an HCl gas through the reaction mixture over 7 h at 80 ��C, 1-chloro-3-fluoromethyladamantane 7 was obtained in 50% isolated yield. N N CH2Cl F BF4 BF4 F F 25 ¡ÆC, 12 h 1a 2a (21%) Scheme 2 MeNO2 N N CH2 Cl BF4 BF4 3 OMe MeOH, . 9 h 4 (75%) F OAc 5 (75%) F 7 h AcOH, . Br 6 (54%) F aq 60% HBr, 2 h . Cl 7 (50%) F .HCl gas F 5 hMendeleev Communications Electronic Version, Issue 1, 2002 2 the liberated BF3 into a firm etherate complex, which assists in releasing the F – ion. This also facilitates the interaction of the fluoride anion at the step determining the reaction products and ensures thereby the high selectivity of the difluorination reaction. All of the new compounds were identified by elemental analysis, NMR spectroscopy and mass spectrometry.§ References 1 G.S. Lal, G. P. Pez and R. G. Syvret, Chem. Rev., 1996, 96, 1737. 2 D. D. DesMarteau, Z. Q. Xu and M. Witz, J. Org. Chem., 1992, 57, 629. 3 M. Albert, K. Dax and J. Ortner, Tetrahedron, 1998, 54, 4839. 4 Yu. A. Serguchev, L. F. Lourie and M. V. Ponomarenko, Mendeleev Commun., 2000, 121. 5 P.A. Krasutskii, N. S. Chesskaya, V. N. Rodionov, O. P. Baula and A. G. Yurchenko, Zh. Org. Khim., 1985, 21, 1677 [J. Org. Chem. USSR (Engl. Transl.), 1985, 21, 1533]. 6 O. V. Tishchenko, Yu. A. Serguchev, L. F. Lourie and M. V. Ponomarenko, Teor. Eksp. Khim., 2000, 36, 254 (in Russian). 7 A. A. Fokin, P. A. Gunchenko, N. I. Kulik, S. V. Iksanova, P. A. Krasutskii, I. V. Gogoman and A.G. Yurchenko, Tetrahedron, 1996, 52, 5857. § The 1H, 13C and 19F NMR spectra were recorded on a Varian VXR-300 instrument at 300, 75.4 and 282.2 MHz, respectively, in CDCl3 with TMS or CCl3F as internal standards. 2a: colourless oil. 1H NMR, d: 1.40–2.00 (m, 12H, Ad), 2.34 (m, 2H, Ad), 4.05 (d, 2H, CH2F, J 47.6 Hz). 13C NMR, d: 30.92 (d, C-5, C-7, J 9.0 Hz), 35.38 (s, C-6), 36.91 (d, C-4, C-10, J 4.5 Hz), 39.12 (dd, C-3, J1 18.3 Hz, J2 9.5 Hz), 42.31 (d, C-8, C-9, J 17.2 Hz), 43.42 (dd, C-2, J1 17.6 Hz, J2 4.1 Hz), 91.21 (d, CH2F, J 172.9 Hz), 92.41 (d, C-1, J 185.9 Hz). 19F NMR, d: –133.41 (s, CF), –230.77 (t, CH2F, J 47.6 Hz). MS, m/z: 186 (M+, 10%), 153 (100%), 133 (7%) (cf. ref. 4). 2b: colourless oil. 1H NMR, d: 1.24 (dd, 3H, Me, J1 24.9 Hz, J2 6.3 Hz), 1.35–1.95 (m, 12H, Ad), 2.33 (m, 2H, Ad), 4.24 (dq, 1H, CHF, J1 47.1 Hz, J2 6.3 Hz). 13C NMR, d: 14.9 (d, Me, J 24.2 Hz), 31.3 (d, C-5, C-7, J 9.0 Hz), 35.8 (s, C-6), 36.4 (d, C-4, C-10, J 4.5 Hz), 41.9 (dd, C-3, J1 19.6 Hz, J2 9.8 Hz), 42.71 (d, C-8, C-9, J 17.3 Hz), 42.9 (dd, C-2, J1 18.8 Hz, J2 4.5 Hz), 93.38 (d, C-1, J 183.1 Hz), 96.55 (d, CHF, J 171.1 Hz). 19F NMR, d: –132.66 (, –185.87 (dq, CHF, J1 45.0 Hz, J2 24.0 Hz). MS, m/z: 200 (M+, 11%), 153 (100%), 133 (%) (cf.ref. 7). 2c: white crystals, mp 53–54.5 °C. 1H NMR, d: 1.55–1.99 (m, 12H, Ad), 2.30 (m, 2H, Ad), 5.03 (d, 1H, CHF, J 45.3 Hz), 7.19–7.25 (m, 2H, Ph), 7.30–7.40 (m, 3H, Ph). 13C NMR, d: 30.66 (d, C-5, C-7, J 9.8 Hz), 35.08 (s, C-6), 36.0–36.22 (m, C-4, C-10), 42.05 (dd, C-3, J1 22.5 Hz, J2 9.2 Hz), 42.05 (d, C-8, C-9, J 17.0 Hz), 42.45 (dd, C-2, J1 19.2 Hz, J2 4.2 Hz), 92.79 (d, C-1, J 183.7 Hz), 100.12 (d, CHF, J 176.8 Hz), 126.86 (d, Ph, J 7.7 Hz), 127.67 (s, Ph), 128.09 (s, Ph), 136.23 (d, Ph, J 21.4 Hz). 19F NMR, d: –133.62 (s, CF), –190.69 (d, CHF, J 44.9 Hz). MS, m/z: 262 (M+, 52%), 242 (6%), 153 (100%), 133 (11%). Found (%): C, 78.00; H, 7.81. Calc. for C17H20F2 (%): C, 77.83; H, 7.68. 6: white crystals, mp 48.5–49.5 °C. 1H NMR, d: 1.45–1.84 (m, 6H, Ad), 2.15–2.4 (m, 8H, Ad), 3.99 (d, 2H, CH2F, J 47.9 Hz). 13C NMR, d: 31.67 (s, C-5, C-7), 34.86 (s, C-6), 36.26 (d, C-4, C-10, J 4.2 Hz), 39.16 (d, C-3, J 18.8 Hz), 48.48 (s, C-8, C-9), 49.59 (d, C-2, J 4.2 Hz), 64.45 (s, C-1), 91.03 (d, CH2F, J 172.7 Hz). 19F NMR, d: –231.51 (t, CH2F, J 48.0 Hz). MS, m/z: 227 (12%), 167 (100%). Found (%): C, 53.30; H, 6.40; Br, 32.01. Calc. for C11H16BrF (%): C, 53.46; H, 6.53; Br, 32.34. 7: colourless oil. 1H NMR, d: 1.45–1.75 (m, 6H, Ad), 1.96 (s, 2H, Ad), 2.10 (m, 4H, Ad), 2.25 (m, 2H, Ad), 4.01 (d, 2H, CH2F, J 47.7 Hz). 13C NMR, d: 30.94 (s, C-5, C-7), 34.92 (s, C-6), 36.36 (d, C-4, C-10, J 5.6 Hz), 38.55 (d, C-3, J 17.7 Hz), 46.99 (s, C-8, C-9), 48.17 (d, C-2, J 4.0 Hz), 67.60 (s, C-1), 91.15 (d, CH2F, J 172.4 Hz). 19F NMR, d: –231.00 (t, CH2F, J 48.0 Hz). MS, m/z: 202 (M+, 4%), 169 (39%), 167 (100%), 133 (16%). Found (%): C, 65.00; H, 7.70; Cl, 17.51. Calc. for C11H16ClF (%): C, 65.18; H, 7.96; Cl, 17.49. Received: 13th November 2001; Com. 01/1857

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年代:2002

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Iron-containing materials FeM (M = B, Cr, Ti or VN) prepared by self-propagating high-temperature synthesis Maxim V. Kuznetsov,*a Yury G. Morozov,a Inna P. Borovinskaya,a Yuri M. Maximov,b Ivan P. Parkinc and Quentin A. Pankhurstd a SHS Research Centre, Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax: +7 095 962 8025; e-mail: kvin@kuznetsov.home.chg.ru b Department of Structural Macrokinetics, Tomsk Scientific Centre, Siberian Branch of the Russian Academy of Sciences, 634050 Tomsk, Russian Federation. Fax: +7 3822 25 9838; e-mail: maks@fisman.tomsk.su c Department of Chemistry, University College London, London WC1H OAJ, UK.Fax: +44 (0) 20 7679 7463; e-mail: i.p.parkin@ucl.ac.uk d Department of Physics and Astronomy, University College London, London WC1E 6BT, UK. Fax: +44 (0) 20 7679 1360; e-mail: q.pankhurst@ucl.ac.uk 10.1070/MC2002v012n01ABEH001523 The title iron-containing compounds were prepared, and their structural, magnetic and Mossbauer characteristics were examined.Iron-containing alloys FeM are widely used as individual compounds or the components of cermets and composite materials because of their high wear resistance, thermal stability, hydrogen capacity etc.1.3 FeB and FeCr are components of hard refractory cermet materials [FeCr.TiC and FeAl.(30.90 vol.%) FeB], which have improved abrasive wear properties and can operate at elevated temperatures.4 Intermetallic compounds of titanium with iron group elements (FeTi) exhibit attractive construction properties, specific durability, plasticity, corrosion resistance and unique shape memory properties.5 Particular properties of FeV alloy are responsible for its use as protective coatings in sodium- and lithium-cooled nuclear reactors.6 For the additional protection and improvement of alloy surfaces, for example, nitridation in ammonia can be carried out at 700 K for 24 h. Metals (Fe, R-10; Cr, PCM and Ti, PTOM) and non-metal (B) powders of ©ø 98% purity and metals oxides of ©ø 99.5% purity were used.All manipulations were carried out in a box filled with argon to prevent oxidation. All self-propagating hightemperature synthesis (SHS) reactions were carried out in an inert atmosphere using dry powders pressed as cylindrical samples (d = 10 mm, h = 20 mm). Ignition operations were made by REKROW (RK-2060) (UK).X-ray powder diffraction was performed in a reflection mode on a Philips X-pert diffractometer (Netherlands) using unfiltered CuK¥á radiation (l1 = 1.5405 A, l2 = 1.5443 A). Phases were identified and indexed using the JCPDS database and the ASTM and Unit Cell programs.Pycknometric densities were measured by standard methods using toluene; magnetic characteristics were investigated using EG&G PARC 4500 (USA) at room temperature and applied fields up to 10 kOe. SEM/EDAX were determined on JEOL EMA instrument (Japan). 57Fe Mossbauer spectra were recorded on a Wissel MR-260 constant acceleration spectrometer with a triangular drive waveform. All FeM (M = Cr, Ti or V) compounds were synthesised using the same reaction scheme involving preparation of an initial mixture of individual powders in the ratio 1:1.The general reaction scheme is: The iron.boron alloy may be synthesised by different ways involving combustion in an appropriate mixture of iron(III) oxide and boron powder in an argon atmosphere: The iron.boron alloy can also be produced by parallel reactions in a mixture of iron(III) oxide, iron metal and boron: As found by SEM/EDAX and elemental analysis, all of the starting elements were distributed in the structure of SHS-prepared materials in an appropriate ratio.The EDAX spot analysis of the final products showed the expected Fe:M ratios without any additives.SEM showed micron-sized agglomerates of crystallites. X-ray analysis of all SHS samples showed that all of them were crystallised compounds which unit cell parameters are in full agreement with reference data (Table 1). The X-ray powder diffraction data for the SHS-prepared powders are consistent with that for materials prepared by conventional ceramic synthesis.Phase purity of all the samples was 92% or higher. The mean crystallite sizes d were calculated to be ~ 1000 A for all the samples (except for FeCr) using the Sherrer equation. FeB exhibited an orthorhombic symmetry while FeCr and FeTi were tetragonal and cubic, respectively. Unfortunately, there are no reference data on the unit cell parameters of FeVN at room temperature.In comparison with the FeV lattice parameters, there is evidence about its tetragonal symmetry with some distortions, especially, along the a-axis, and an increase in the unit cell volume due to nitrogen insertion into the structure. The c/a parameter for FeV and FeVN were 0.517 and 0.555, respectively. The same structural transformations were reported for the different iron alloys with transition (Fe.Ta) and nontransition metals (Fe.Ge) after nitridation. All the SHS-prepared FeM compounds have lower maximum (smax) and remanent (sr) magnetisation values, as compared with appropriate amorphous compounds, and are soft magnetic materials like many other transition-metal alloys.The FeTi compound was reported to be paramagnetic in the bulk;11 however, the SHSFe + M FeM (I) Fe2O3 + 4B 2FeB + B2O3 (II) Fe2O3 + 4Fe + 8B 6FeB + B2O3 Fe2O3 + 4B 2FeB + B2O3 Fe + B FeB (III) (IIIa) (IIIb) Table 1 Room-temperature X-ray and magnetic characteristics of FeM (M = B, Cr, VN and Ti) compounds produced by SHS in zero field.The parameters are maximum magnetisation smax (¡¾0.01 emu g.1) and remanent magnetisation sr (¡¾0.01 emu g.1) recorded in an external field of 10 kOe.The pycnometric densities d (g cm.3) are also given. Compound smax sr d Unit cell parameters/A of SHS products a, b and c (¡¾0.004 A); V/A3 (¡¾0.5 A3) Reference X-ray data FeB 61.90 3.55 4.9 a = 4.058 b = 5.510 c = 2.945 V = 65.85 a = 4.011 b = 5.470 c = 2.942 V = 64.557 FeCr 16.30 0.97 5.8 a = 8.815 c = 4.505 V = 350.06 a = 8.800 c = 4.544 V = 351.898 FeVN 2.03 0.52 5.2 a = 8.209 c = 4.562 V = 307.42 a = 8.943 c = 4.620 V = 369.499,a FeTi 0.42 0.04 5.2 a = 2.920 V = 24.90 a = 2.976 V = 26.3610 a Reference X-ray data for the FeV sample.Mendeleev Communications Electronic Version, Issue 1, 2002 2 prepared material exhibited a slightly ferromagnetic behaviour with a maximum magnetisation 0.42 emu g.1.Room-temperature transmission Mossbauer data were recorded on all four samples.FeB and FeVN gave magnetically split spectra (Figure 1), while FeTi gave a paramagnetic spectrum (Figure 2). Despite strenuous efforts, an unusable spectrum was obtained from FeCr because the extreme hardness of the material made it impossible to prepare a sufficiently thin Mossbauer absorber. The FeB, FeVN and FeTi spectra were analysed as a superposition of Lorentzian sextets, doublets and/or singlets, yielding the fit parameters given in Table 2.The FeB spectrum was modelled as three magnetic sextets and one paramagnetic doublet. The majority phase component, accounting for 63% of the total spectral area, has a hyperfine field, Bhf ¡í 117 kG, which is consistent with a reported value (118 kG) for stoichiometric crystalline FeB.12.14 The second sextet, with its smaller Bhf and larger isomer shift d, is probably due to some site disorder in the alloy, leading to Fe atoms encountering more than the usual number of near-neighbour interstitial B atoms.The minority phase doublet in the spectrum indicates that some Fe atoms are magnetically isolated in the sample. The FeVN spectrum was best fitted to three sextets plus a singlet. The component sextets correspond to statistical variations in the number of next-neighbour V and/or N atoms surrounding each Fe atom.Previous studies of FeAl alloys have shown three distinct sextets corresponding to 0, 3 and 4 next-neighbour Al atoms, with both the hyperfine field Bhf increasing and the isomer shift d decreasing as the number of Al neighbours increased. 12,15,16 This trend in Bhf and d is reflected in Table 2. The minority phase singlet also indicates that some Fe atoms are magnetically isolated in the sample. The paramagnetic FeTi spectrum was fitted as two singlets of approximately equal areas. The isomer shift of the left-hand singlet d ¡í .0.25 mms.1 is close to the reported value (.0.26 mms.1) for crystalline FeTi grown by arc melting.17 The presence of a second singlet in the spectrum indicates some site disorder, perhaps leading to some more iron-rich regions with isomer shifts closer to zero. References 1 S.Morris, S. B. Dodd, P. J. Hall, A. J. Mackinnon and L. E. A. Berlouis, J. Alloys Compd., 1999, 295, 458. 2 S. Tondu, T. Schnick, L. Pawlowski, B. Wielage, S.Steinhauser and L. Sabatier, Surf. Coat. Technol., 2000, 123, 247. 3 M. Xu, M. X. Quan, Z. Q. Hu and K. Y. He, J. Mater. Sci. Technol., 2001, 17, 260. 4 M. Jones, A. J. Horlock, P. H. Shipway, D. G. McCartney and J. V.Wood, Wear, 2001, 249, 246. 5 A. D. Bratchikov, A. G. Merzhanov, V. I. Itin and V. M. Maslov, Abstracts of II Conference on Technological Combustion, Chernogolovka, Russia, 1978, p. 75 (in Russian). 6 L. Dalessio, R. Teghil, A. Santagata, V. Marotta, D. Ferro and G. DeMaria, Surf. Coat. Technol., 1996, 80, 221. 7 W. B. Pearson, Handbook of Lattice Spacings and Structures of Metals, Pergamon Press, Oxford, 1967. 8 JCPDS . International Centre for Diffraction Data, File 05-0708. 9 JCPDS . International Centre for Diffraction Data, File 07-0383. 10 JCPDS . International Centre for Diffraction Data, File 19-0636. 11 S. V. Mankovsky, A. A. Ostroukhov, V. M. Floka and V. T. Cherepin, Vacuum, 1997, 48, 245. 12 N. N. Greenwood and T. C. Gibb, Mossbauer Spectroscopy, Chapman and Hall, London, 1971. 13 T. Shinjo, F. Itoh, H. Takaki, Y. Nakamura and N. Shikazono, J. Phys. Soc. Jpn., 1964, 19, 1252. 14 J. D. Cooper, T. C. Gibb, N. N.Greenwood and R. V. Parish, Trans. Faraday Soc., 1964, 60, 2097. 15 E. A. Friedman and W. J. Nicholson, J. Appl. Phys., 1963, 34, 1048. 16 M. B. Stearns and S. S. Wilson, Phys. Rev. Lett., 1964, 13, 313. 17 S. H. Liou and C. L. Chien, J. Appl. Phys., 1984, 55, 1820. 8.00 7.95 7.90 7.85 7.80 FeB FeVN 92.1 92.0 91.9 91.8 91.7 .4 .2 0 2 4 Velocity/mm s.1 Intensity (106 counts) Figure 1 Room-temperature Mossbauer spectra of SHS-produced FeB and FeVN. The solid lines show the least-squares fit of the data. 16.0 15.9 15.8 15.7 15.6 .3 .2 .1 0 1 2 3 Velocity/mm s.1 Intensity (106 counts) FeTi Figure 2 Room-temperature paramagnetic Mossbauer spectrum of SHSproduced FeTi. Table 2 Room-temperature Mossbauer data for SHS-produced FeM (M = = B, VN and Ti) alloys. The parameters are the isomer shift d, quadrupole shift 2e or quadrupole splitting ., hyperfine field Bhf, and relative spectral area R of the subcomponent spectra. Sample d/mms.1 2e or ./mms.1 Bhf/kG R (%) FeB 0.28(1) 0.31(1) 0.22(1) 0.12(1) 0.20(2) 0.45(1) 117(2) 90(1) . 63(2) 30(2) 7(1) FeVN 0.28(2) 0.30(2) 0.30(2) 0.31(1) 0.19(3) 0.17(3) 0.20(4) . 116(2) 101(2) 80(3) . 16(7) 20(11) 30(9) 34(4) FeTi .0.25(2) .0.04(2) .. .. 46(10) 54(10) Received: 5th October 2001; Com. 01/1849

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Kinetic resolution of (±)-2-methyl-1,2,3,4-tetrahydroquinoline and (±)-2-methylindoline Victor P. Krasnov,* Galina L. Levit, Irina N. Andreeva, Alexander N. Grishakov, Valery N. Charushin and Oleg N. Chupakhin Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation. Fax: +7 3432 74 1189; e-mail: ca@ios.uran.ru 10.1070/MC2002v012n01ABEH001545 The acylation of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2-methylindoline by (S)-naproxen acyl chloride resulted in their kinetic resolution with the predominant formation of (S,S)-diastereoisomeric amides (de 78–76%), recrystallisation of which followed by acid hydrolysis gave individual (S)-isomers of heterocyclic amines.The kinetic resolution of racemic compounds from various classes is an effective method for obtaining individual stereoisomers.1 We found previously that the kinetic resolution of 2,3-dihydro- 3-methyl-4H-1,4-benzoxazine derivatives by (S)-2-(6-methoxynaphthyl- 2)propionyl chloride [(S)-naproxen acyl chloride] gave (S)-2,3-dihydro-3-methyl-4H-1,4-benzoxazines of high optical purity.2 In this paper, we report on the use of the above resolving agent for the preparation of individual (S)-stereoisomers of 2-methyl-1,2,3,4-tetrahydroquinoline 1 and 2-methylindoline 2, close structural analogues of 2,3-dihydro-3-methyl-4H-1,4-benzoxazine.As the first step, the diastereomeric mixtures of amides 4a,b and 5a,b were obtained by the interaction of acyl chloride 3 with racemic amines 1 and 2 in the stoichiometric ratio in the presence of TEA (Scheme 1).† In both cases, the compositions of diastereoisomeric mixtures 4a,b (5a,b) were 1:1 according to the 1H NMR spectra‡ and HPLC data.§ When the molar ratio between starting amine 1 (or 2) and acyl chloride 3 was 2:1, without any tertiary amine present in the reaction mixture, the resulting products 4a,b (5a,b) were found to be significantly enriched with (S,S)-diastereoisomers 4a (5a).¶ In the case of amide 4a, de was 78%; in the case of 5a, de was 76%.The (S,S)-diastereoisomers 4a and 5a of high diastereoisomeric purity (de > 99%) were obtained after recrystallisation from hexane in yields about 75%.†† The (R)-isomers of amines 1 and 2 can be isolated from acidic solutions in ee 78 and 76%, respectively.‡‡ (S,S)-Amides 4a and 5a were hydrolysed on heating under reflux in a mixture of concentrated HCl and glacial acetic acid2 to give individual (S)-isomers of amines 1 and 2 (Scheme 2).§§ The yields of (S)-(–)-isomers of amines 1 and 2 were 30 and † To a stirred solution of amine 1 or 2 (1 mmol) and TEA (1 mmol) in dry benzene (5 ml) a solution of acyl chloride 3 (1 mmol) in dry benzene (5 ml) was added dropwise.The reaction mixture was stirred at room temperature for 24 h. Then, it was washed successively with 1 M HCl, water, 5% NaHCO3 and water and dried (MgSO4). The resulting solution was evaporated to dryness to give a yellow oily residue, which was treated with hexane to yield amides 4a,b (82%), 5a,b (86%) as yellow oil. 1+ ; 0H 20H &O 2 0H 7($ EHQ]HQH URRP WHPSHUDWXUH ; 1 2 0H 20H 0H DD ; 1 2 0H 20H 0H EE ; &+ ; &+ 6FKHPH ‡ 1H NMR spectra were recorded on a Bruker DRX 400 spectrometer, the spectra of amides 4a,b and 5a,b were measured in [2H6]DMSO at 100 °C; the spectra of amines S-1 and S-2 were measured in CDCl3 at ambient temperature.All signals are given in ppm (d) with TMS as an internal standard. 4a,b: 7.79–6.96 (m, 10H, arom.), 4.79 (m) and 4.66 (m) (1H, CH– quinoline), 4.42 (q) and 4.15 (q) (1H, CH–naproxen, J 6.9 Hz), 3.89 (s) and 3.84 (s) (3H, OMe), 2.63 (ddd) and 2.30 (ddd) (1H, C4–HA– quinoline, J 15.0, 5.3 and 5.2 Hz), 2.12 (dddd, 1H, C3–HA–quinoline, J 13.0, 7.6, 5.4 and 5.2 Hz), 1.79 (ddd) and ~1.29 (m) (1H, C4–HB– quinoline, J 15.0, 10.1 and 5.4 Hz), 1.47 (d) and 1.37 (d) (3H, Me– naproxen, J 6.9 Hz), ~1.29 (m) and 1.16 (dddd) (1H, C3–HB–quinoline, J 13.0, 10.1, 6.7 and 5.3 Hz), 1.04 (d) and 0.93 (d) (3H, Me–quinoline, J 6.6 Hz). 5a,b: 7.98–6.94 (m, 10H, arom.), 4.85 (dqd) and 4.66 (dqd) (1H, CH– indoline, J 8.8, 6.4 and 1.4 Hz), 4.35 (q) and 4.21 (q) (1H, CH–naproxen, J 6.8 Hz), 3.864 (s) and 3.858 (s) (3H, OMe), 3.38 (dd) and 3.12 (dd) (1H, C3–HA–indoline, J 15.9 and 8.7 Hz), 2.59 (dd) and 2.58 (dd) (1H, C3–HB–indoline, J 15.9 and 0.6 Hz), 1.53 (d) and 1.52 (d) (3H, Me– naproxen, J 6.8 Hz), 1.32 (d) and 0.97 (d) (3H, Me–indoline, J 6.5 Hz). § The de values of amides 4 and 5 were measured by HPLC on a Merck- Hitachi chromatograph with an L-4000A Intelligent Pump, an L-4000A UV Detector, and a D-2500A Chromato-Integrator [Hibar Pre-packed Column RT250-4, Lichrosorb Si-60]; mobile phase: hexane–PriOH, 200:1 (A), hexane–PriOH, 80:1 (B), flow rate of 1 cm3 min–1; UV detection at 230 nm; t4a 17.0 min, t4b 15.4 min (A); t5a 6.8 min, t5b 5.4 min (B).¶ To a stirred solution of amine 1 or 2 (1 mmol) in dry benzene (5 ml) a solution of acid chloride 3 (0.5 mmol) in dry benzene (3 mmol) was added.The reaction mixture was stirred for 24 h at room temperature; then, it was washed sequentially with 1 M HCl, water, 5% NaHCO3 and water and dried (MgSO4). The solution was evaporated to dryness to give (S,S)-diastereoisomer 4a (de 78%) in 90% yield or (S,S)-diastereoisomer 5a (de 76%) in 86% yield. †† 4a: mp 57–59 °C; [a]D +66.8° (c 1.3, CHCl3); de 99.0%.HPLC: tR 17.0 min (A). 1H NMR, d: 7.79–6.96 (m, 10H, arom.), 4.79 (ddq, 1H, CH–quinoline, J 7.6, 6.7 and 6.6 Hz), 4.42 (q, 1H, CH–naproxen, J 6.9 Hz), 3.84 (s, 3H, OMe), 2.30 (ddd, 1H, C4–HA–quinoline, J 15.0, 5.3 and 5.2 Hz), 2.12 (dddd, 1H, C3–HA–quinoline, J 13.0, 7.6, 5.4 and 5.2 Hz), 1.79 (ddd, 1H, C4–HB–quinoline, J 15.0, 10.1 and 5.4 Hz), 1.47 (d, 3H, Me–naproxen, J 6.9 Hz), 1.16 (dddd, 1H, C3–HB–quinoline, J 13.0, 10.1, 6.7 and 5.3 Hz), 0.93 (d, 3H, Me–quinoline, J 6.6 Hz). 5a: mp 106–107 °C; [a]D +82.8° (c 1.9, CHCl3); de 99.3%.HPLC: tR 6.8 min (B). 1H NMR, d: 7.98–6.94 (m, 10H, arom.), 4.85 (dqd, 1H, CH–indoline, J 8.7, 6.5 and 1.4 Hz), 4.35 (q, 1H, CH–naproxen, J 6.9 Hz), 3.864 (s, 3H, OMe), 3.38 (dd, 1H, C3–HA–indoline, J 15.9 and 8.7 Hz), 2.59 (dd, 1H, C3–HB–indoline, J 15.9 and 0.6 Hz), 1.53 (d, 3H, Me– naproxen, J 6.8 Hz), 0.97 (d, 3H, Me–indoline, J 6.5 Hz).‡‡The aqueous acid layers after preparing amide 4a or 5a were treated with NaOH up to pH 9–10 under ice cooling, extracted by chloroform, washed with brine, and dried (MgSO4). The solution was evaporated to dryness to give amines (R)-1 in 90% yield or (R)-2 in 86% yield as colourless oils.Optical purity was determined by HPLC with the pre-column derivatization of amines by acyl chloride 3.Mendeleev Communications Electronic Version, Issue 1, 2002 2 27%, respectively, relative to the starting racemic amines. The optical purity of the obtained stereoisomers was confirmed by HPLC after the derivatization of amines by acyl chloride 3.The stereochemical configuration of compound (S)-(.)-1 was determined by a comparison of the [a]D sign with published data3 for (R)-(+)-1. The absolute configuration of (S)-2 has not been determined before our study. Assignment of the absolute configuration for the 2-methylindoline fragment of amide 5a was performed by X-ray diffraction analysis, taking into account the known absolute configuration of the starting (S)-naproxen (Figure 1).In conclusion, note that the use of (S)-naproxen acyl chloride as a resolving agent in the kinetic resolution of racemic heterocyclic amines appears to be a good general procedure for obtaining individual stereoisomers of high optical purity. This work was supported by the Russian Foundation for Basic Research (grant nos. 00-03-32776, 01-03-96424 and 00-15-97390). References 1 R. Noyori, M. Tokunaga and M. Kitamuro, Bull. Chem. Soc. Jpn., 1995, 36. 2 V. N. Charushin, V. P. Krasnov, G. L. Levit, M. A. Korolyova, M. I. Kodess, O. N. Chupakhin, M. H. Kim, H. S. Lee, Y. J. Park and K.-Ch. Kim, Tetrahedron Asymmetry, 1999, 2691. 3 M. P. Paradisi and A.Romeo, J. Chem. Soc., Perkin Trans. 1, 1977, 596. ¡×¡×Amide 4a or 5a (1 mmol) was heated under reflux in a mixture of glacial acetic acid (5 ml) and conc. HCl (5 ml) for 15 h. The reaction mixture was evaporated to dryness. Water (10 ml) was added to the residue; the precipitate was filtered off and washed with water. The combined filtrates were made alkaline with 10 M NaOH to pH 10 at +5 ¡ÆC and extracted with CH2Cl2.The organic layer was washed with brine and dried (MgSO4). The solution was evaporated to dryness to give amines (S)-1 in 90% yield or (S)-2 in 85% yield as colourless oils. (S)-(.)-1: [a]D .85¡Æ (c 1.5, benzene). Lit.,3 (R)-1: [a]D +85¡Æ (c 2, benzene). 1H NMR, d: 6.96.6.92 (m, 2H, C5H, C7H), 6.58 (t, 1H, C6H, J 7.4 and 1.2 Hz), 6.44 (dd, 1H, C8H, J 8.3 and 1.2 Hz), 3.63 (br.s, 1H, NH), 3.38 (dqd, 1H, C2H, J 9.8, 6.3 and 2.8 Hz), 2.82 (ddd, 1H, C4.HA, J 16.4, 11.4 and 5.6 Hz), 2.71 (ddd, 1H, C4.HB, J 16.4, 5.4 and 3.7 Hz), 1.91 (dddd, 1H, C3.HA, J 12.8, 5.7, 3.5 and 2.9 Hz), 1.57 (dddd, 1H, C3.HB, J 12.8, 11.4, 9.9 and 5.4 Hz), 1.19 (d, 3H, Me, J 6.3 Hz). (S)-(.)-2: [a]D .12.2¡Æ (c 2.6, benzene). 1HNMR, d: 7.07 (dd, 1H, C4H, J 7.2 and 0.3 Hz), 7.00 (ddd, 1H, C5H, J 7.5, 7.4 and 0.4 Hz), 6.68 (ddd, 1H, C6H, J 7.5, 7.3 and 0.8 Hz), 6.59 (dd, 1H, C7H, J 7.8 and 0.3 Hz), 3.98 (ddq, 1H, C2H, J 8.5, 7.8 and 6.2 Hz), 3.62 (br. s, 1H, NH), 3.13 (dd, 1H, C3.HA, J 15.4 and 8.5 Hz), 2.62 (dd, 1H, C3.HB, J 15.4 and 7.8 Hz), 1.28 (d, 3H, Me, J 6.2 Hz). ; 1 2 0H 20H 0H DD 1+ ; 0H +&O $F2+ . ; &+ ; &+ 6FKHPH C(5) C(6) C(7) C(24) C(8) C(2) C(3) C(9) C(4) N(1) C(10) O(1) C(12) C(11) C(15) C(16) C(14) C(13) C(21) C(22) C(17) C(18) C(23) O(2) C(19) C(20) Figure 1 Crystal structure of (S,S)-amide 5a. Received: 25th December 2001; Com. 01/1871

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Use of tandem AN-AN reactions for the synthesis of thiazolo[4,5-e]-1,2,4-triazines 1 1 1 1 +< 6 +1 <1 +2++ +1 1 1+D±F D $U 3K E $U S0H2&+ F $U S12&+ 6FKHPH Valery N. Charushin,*a Nataliya N. Mochulskaya,b Anatoly A. Andreiko,a Mikhail I. Kodessa and Oleg N. Chupakhina a Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation. Fax: +7 3432 74 5191; e-mail: charushin@prm.uran.ru b Department of Organic Chemistry, Urals State Technical University, 620002 Ekaterinburg, Russian Federation 3-Aryl-1,2,4-triazines react with thioamides in acetic anhydride to produce thiazolo[4,5-e]-1,2,4-triazine derivatives and this reaction represents a new method for the fusion of thiazole and 1,2,4-triazine rings based on the nucleophilic ortho-diaddition type (AN-AN) cyclization reactions.The ortho-diaddition type (AN-AN) cyclizations of �-deficient azaaromatics (pyridazines, pyrazines, 1,2,4-triazines, pyrido[2,3-b]- pyrazines, pteridines, their quaternary salts, aza and benzo analogues, etc.) with bifunctional nucleophiles are of interest as an effective methodology for the synthesis of condensed heterocyclic systems.1–7 A general scheme for the synthesis of condensed tetrahydropyrazines from pyrazinium cations is given below.5 5 + ; +; 0H 1 6 3K $U 1 :$U :1D±F 6FKHPH Several examples of the tandem AN-AN reactions between 1,2,4-triazinium salts and bifunctional nucleophiles have been reported;3–5,8–10 however, the patterns of heterocyclic fragments annelated to the 1,2,4-triazine ring are rather limited. Due to the relatively low stability of tetrahydrotriazines, only two types of condensed systems, i.e., pyrrolo[2,3-e]- and furo[2,3-e]-1,2,4- triazines, have so far been obtained by the reactions of 1,2,4- triazinium salts with acetoacetamides,3,8,9 ketene-N,N'-aminals,10 and other C,N- or C,O-dinucleophiles.5 It should be noted that all ring systems hitherto annelated in this way to 5,6-unsubstituted 1,2,4-triazines are heterocycles bearing one heteroatom, so that at least one of the two newly formed bonds in the fused tetrahydrotriazine systems is a C–C bond, enhancing the stability of the adducts.The ortho-diaddition reactions of 1,2,4- triazinium salts with bifunctional nucleophiles in which both reactive centres are heteroatoms have never, so far, resulted in the formation of stable adducts. In this paper, we report the first successful examples of the tandem ortho-diaddition type cyclization reaction between 1,2,4- triazines and N,S-dinucleophiles.We found that the reaction of 5,6-unsubstituted 3-aryl-1,2,4-triazines 1a–c with thiobenzamide 2 in acetic anhydride proceeds very smoothly at room temperature resulting in the formation of thiazolo[4,5-e]-1,2,4-triazines 3a–c in good yields.† The use of acetic anhydride as a solvent in this reaction is very important since the N-acetylation of adducts enhances their stabilty.$F2 3K Mendeleev Communications Electronic Version, Issue 1, 2002 10.1070/MC2002v012n01ABEH001547 The elemental analytical data and the molecular ion (M+) peaks in the mass spectra of compounds 3a–c are in full agreement with the 1:1 adduct formation. Evidence for the structure of 3a–c is provided by 1H and 13C NMR, including proton-coupled spectra, as well as HETCOR and HMBC two-dimensional heteronuclear experiments performed for compound 3b. In the 1H NMR spectra of thiazolotriazines 3a–c, the ring junction proton 7a-H appears as a doublet (d 6.36–6.46 ppm) with 3J7a-H, 3a-H 7.5–7.7 Hz, while the resonance signal of 3a-H (d 6.15–6.19 ppm) is a double doublet due to additional coupling with the adjacent NH proton: 3J3a-H, NH 2.1–2.2 Hz.The values of the vicinal coupling constants 3J7a-H, 3a-H 7.5–7.7 Hz correspond to the cis orientation of the ring junction protons, which is a common feature of tetrahydropyrazines and tetrahydro-1,2,4- triazines annelated with five-membered heterocycles.11 In the 13C NMR spectra of 3a–c, the ring junction carbon atoms 3a-C and 7a-C can easily be distinguished due to a considerable gap in their chemical shifts and the difference in onebond C–H coupling constants.According to the 13C NMR spectral data on the related system of 3a,4,9,9a-tetrahydrothiazolo- [4,5-b]quinoxalines, the ring junction carbon atom 3a-C adjacent to the C=N bond of the thiazole ring resonates at a lower field (93–97 ppm) and has a smaller one-bond coupling constant (1JC, H 154–157 Hz) relative to the corresponding parameters of the ring junction carbon 9a-C adjacent to sulfur (67–70 ppm, 1JC, H 164–167 Hz).11–13 Indeed, in the 13C NMR spectra of 3a–c, the resonance signal of 3a-C is observed at a lower field (d 80.71–80.79 ppm, 1J3a-C, 3a-H 160.8–162.1 Hz), while the 7a-C resonates at 61.29–62.06 ppm and is coupled with 7a-H (1J7a-C, 7a-H 166.8–168.9 Hz).These data provide unequivocal evidence for the regio-orientation of the thiazole ring. The position of NH (and therefore the site of the N-acetyl group) is clear from two vicinal couplings: 3J3a-H, NH and 3J3a-H, 5-C. Long-range couplings observed in the HMBC spectrum of 3b (Scheme 3, Table 1) are also in full correspondence with the structure.1 6 2+ D D 1 + 0H 0H2 0H + + 1 1+1 6 1 2+D D 1 1 + + 0H2 + Scheme 3 Indicative long-range interactions in the HMBC spectrum of 3b. 1Table 1 Long-range correlations observed in the HMBC spectrum of 3b.Cross-section along F2 Cross-section along F1 Carbon Correlated proton Proton Correlated carbon 4''-C, 5-C 2'-C 2-C, 4'-C 1'-C 4''-C, 1''-C 2-C 2-C, 5-C, 7a-C 4''-C C=O 2''-H 4'-H 2'-H 3'-H 3''-H 7a-H 3a-H OMe Me Me 2'-H, 7a-H, 3a-H 2''-H, 3''-H, OMe 2''-H, 3''-H, 3a-H 3'-H 2'-H, 3'-H 4'-H, 2'-H 4'-H, 3'-H 3''-H 2''-H 7a-H C=O 2-C 4''-C 5-C 1'-C 4'-C 3'-C 2'-C 1''-C 3''-C 3a-C † 3 The 1H NMR spectra in [2H6]DMSO were recorded on a Bruker WP-250 instrument (250 MHz for 1H).The 13C NMR spectra of 3a–c in CDCl were measured on a Bruker DRX-400 spectrometer (400 MHz for 1H and 100 MHz for 13C). Mass spectra were recorded using a Varian MAT 311A spectrometer.Typical procedure for the prepararion of 3a–c. Thiobenzamide (2.70 mmol) was added to a suspension of 3-aryl-1,2,4-triazines 1a–c (2.70 mmol) in 2 ml (in case of 1c, in 25 ml) of acetic anhydride. The reaction mixture was stirred at room temperature for 6 h (in case of 3c, for 3 days). The precipitate obtained was filtered off and washed with a small amount of acetic anhydride and hexane (in case of 3c, with isopropanol) and dried in air.3a-H, 7a-H 7.7 Hz, 3J3a-H, NH NH, 3a-H For 3b: yield 51%, mp 172–173 °C. 1H NMR (250 MHz, [2H For 3a: yield 58%, mp 206–207 °C. 1HNMR (250MHz, [2H6]DMSO) d: 2.28 (s, 3H, Me), 6.18 (dd, 1H, 3a-H, 3J 2.2 Hz), 6.46 (d, 1H, 7a-H, 3J7a-H, 3a-H 7.7 Hz), 7.4–7.6 (m, 6H, 2Ph), 7.7–7.8 (m, 2H, Ph), 7.8–7.9 (m, 2H, Ph), 8.48 (d, 1H, NH, 3J 2.2 Hz). 13C NMR (CDCl3) d: 21.37 (q, Me, J 129.2 Hz), 62.06 (dd, 7a-C, J 168.2 Hz, J 4.0 Hz), 81.00 (d, 3a-C, J 160.8 Hz), 126.41 (dt, J 160.8 Hz, J 6.7 Hz), 128.00 (dt, J 161.2 Hz, J 6.7 Hz), 128.45 (dd, J 161.3 Hz, J 7.5 Hz), 128.84 (dd, J 161.8 Hz, J 6.7 Hz), 130.30 (dt, J 161.0 Hz, J 8.3 Hz) and 132.08 (dt, J 161.5 Hz, J 8.4 Hz) (6 aromatic CH carbon atoms of two phenyl groups), 132.79 (t, 1'-C, Ph, J 7.9 Hz), 133.08 (t, 1''-C, Ph, J 6.9 Hz), 146.14 (m, 5-C), 167.31 (dt, 2-C, Jd » Jt 4.9 Hz), 170.48 (q, C=O, J 6.4 Hz).MS, m/z (%): 336 (83) [M+], 173 (33), 158 (22), 157 (43), 121 (34), 104 (100), 103 (23), 77 (28). Found (%): C, 64.27; H, 4.93; N, 16.87. Calc. for C18H16N4OS (%): C, 64.27; H, 4.79; N, 16.65.6]DMSO) d: 2.26 (s, 3H, Me), 3.80 (s, 3H, OMe), 6.15 (dd, 1H, 3a-H, 3J3a-H, 7a-H 7.7 Hz, 3J3a-H, NH 2.1 Hz), 6.46 (d, 1H, 7a-H, 3a-H, 3a-H 7.7 Hz), 7.00 (d, 2H, C6H4OMe, J 8.8 Hz), 7.4–7.6 (m, 3H, Ph), 7.7–7.8 (m, 2H, Ph), 7.80 (d, 2H, C 3a-H, 7a-H 7.6 Hz, 3J3a-H, NH 6H4OMe, J 8.8 Hz), 8.38 (d, 1H, NH, 3JNH, 3a-H 2.1 Hz). 13CNMR (CDCl3) d: 21.22 (q, Me, J 129.6 Hz), 55.27 (q, OMe, J 144.2 Hz), 61.29 (ddd, 7a-C, J 166.8 Hz, J 4.4 Hz, J 1.4 Hz), 80.71 (dd, 3a-C, J 162.1 Hz, J 0.9 Hz), 113.88 (dd, 3''-C, C6H4OMe, J 160.4 Hz, J 5.1 Hz), 125.12 (t, 1''-C, C6H4OMe, J 7.5 Hz), 127.20 (dd, 2''-C, C6H4OMe, J 159.9 Hz, J 7.0 Hz), 128.03 (ddd, 2'-C, Ph, J 160.6 Hz, J 7.4 Hz, J 6.4 Hz), 128.49 (dd, 3'-C, Ph, J 162.1 Hz, J 7.9 Hz), 132.01 (dt, 4'-C, Ph, J 164.5 Hz, J 7.2 Hz), 132.55 (t, 1'-C, Ph, J 7.8 Hz), 145.89 (dt, 5-C, J 3.7 Hz), 161.35 (dqt, 4''-C, C6H4OMe, J 4.8 Hz, J 6.8 Hz, J 2.4 Hz), 171.38 (dt, 2-C, Jd » Jt 5.2 Hz), 171.62 (qd, C=O, J 6.4 Hz, J 0.9 Hz).MS, m/z (%): 366 (100) [M+], 221 (25), 220 (28), 203 (32), 188 (25), 187 (36), 134 (80), 133 (34), 121 (37). Found (%): C, 62.56; H, 4.88; N, 15.16.Calc. for C19H18N4O2S (%): C, 62.28; H, 4.95; N, 15.29. For 3c: yield 15%, mp 236–238 °C. 1H NMR (250 MHz, [2H6]DMSO) d: 2.31 (s, 3H, Me), 6.12 (dd, 1H, 3a-H, 3J 2.2 Hz), 6.36 (d, 4H, 7a-H, 3J7a-H, 3a-H 7.6 Hz), 7.4–7.6 (m, 3H, Ph), 7.7–7.8 (m, 2H, Ph), 8.11 (d, 2H, C6H4NO2, J 9.2 Hz), 8.26 (d, 2H, C6H4NO2, J 9.2 Hz), 8.64 (d, 1H, NH, 3JNH, 3a-H 2.2 Hz). 13C NMR (CDCl3) d: 21.60 (q, Me, J 129.2 Hz), 61.95 (ddd, 7a-C, J 168.9 Hz, J 4.0 Hz, J 1.0 Hz), 80.79 (d, 3a-C, J 162.1 Hz), 124.20 (dd, 3''-C, C6H4NO2, J 172.4 Hz, J 4.4 Hz), 127.81 (dd, 2''-C, C6H4NO2, J 168.4 Hz, J 7.5 Hz), 128.29 (ddd, 2'-C, Ph, J 159.8 Hz, J 7.2 Hz), 129.49 (dd, 3'-C, Ph, J 161.6 Hz, J 7.2 Hz), 132.75 (t, 1'-C, Ph, J 7.8 Hz), 132.78 (dt, 4'-C, Ph, J 162.9 Hz, J 7.4 Hz), 139.09 (t, 1''-C, C6H4NO2, J 7.7 Hz), 143.71 (m, 5-C), 148.62 (tt, 4'-C, C6H4NO2, J 9.5 Hz, J 3.3 Hz), 167.25 (td, 2-C, Jt 5.4 Hz, Jd 4.9 Hz), 170.97 (d, C=O, J 6.4 Hz).MS, m/z (%): 381 (100) [M+], 339 (27), 236 (45), 218 (32), 203 (22), 202 (50), 149 (42), 121 (55), 104 (34), 103 (54). Found (%): C, 56.72; H, 3.87; N, 18.23. Calc. for C18H15N5O3S (%): C, 56.68; H, 3.96; N, 18.36.Mendeleev Communications Electronic Version, Issue 1, 2002 This work was supported by the US Civilian Research and Development Foundation (award no. REC-005) and the Russian Foundation for Basic Research (grant no. 01-03-96456a). References 1 V. N. Charushin, O. N. Chupakhin and H. C. van der Plas, Adv. Heterocycl. Chem., 1988, 43, 301. 2 V.N. Charushin, G. A. Mokrushina, G. M. Petrova, G. G. Alexandrov and O. N. Chupakhin, Mendeleev Commun., 1998, 133. 3 V. N. Charushin, S. G. Alexeev, O. N. Chupakhin and H. C. van der Plas, Adv. Heterocycl. Chem., 1989, 46, 73. 4 O. N. Chupakhin, B. V. Rudakov, S. G. Alexeev and V. N. Charushin, Heterocycles, 1992, 33, 931. 5 O. N. Chupakhin, G.L. Rusinov, D. G. Beresnev, V. N. Charushin and H. Neunhoeffer, J. Heterocycl. Chem., 2001, 38, 901. 6 D. V. Besedin, A. V. Gulevskaja and A. F. Pozharskii, Mendeleev Commun., 2000, 150. 7 A. V. Gulevskaja, D. V. Besedin, A. F. Pozharskii and Z. A. Starikova, Tetrahedron Lett., 2001, 42, 5981. 8 S. G. Alexeev, V. N. Charushin, O. N. Chupakhin and G. G. Alexandrov, Tetrahedron Lett., 1988, 29, 1431. 9 S. G. Alexeev, V. N. Charushin, O. N. Chupakhin, G. G. Alexandrov, S. V. Shorshnev and A. I. Chernyshev, Izv. Akad. Nauk SSSR, Ser. Khim., 1989, 1637 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1989, 38, 1501). 10 S. G. Alexeev, V. N. Charushin, O. N. Chupakhin, M. F. Gordeev and V. A. Dorokhov, Izv. Akad. Nauk SSSR, Ser. Khim., 1989, 494 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1989, 38, 438). 11 O. N. Chupakhin, V. N. Charushin and S. V. Shorshnev, Prog. Nucl. Magn. Reson. Spectrosc., 1988, 20, 95. 12 V. G. Baklykov, V. N. Charushin, O. N. Chupakhin and V. N. Drozd, Khim. Geterotsikl. Soedin., 1984, 686 [Chem. Heterocycl. Compd. (Engl. Transl.), 1984, 20, 554]. 13 V. N. Charushin, V. G. Baklykov, O. N. Chupakhin and V. N. Drozd, Khim. Geterotsikl. Soedin., 1984, 396 (in Russian). Received: 3rd January 2002; Com. 02/1873 2

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年代:2002

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Synthesis of functionalised bipyridines by sequential nucleophilic substitution of hydrogen and cycloaddition in 1,2,4-triazine rings Dmitry N. Kozhevnikov,a Valery N. Kozhevnikov,a Tatiana V. Nikitina,a Vladimir L. Rusinov,*a Oleg N. Chupakhina and Hans Neunhoefferb a Urals State Technical University, 620002 Ekaterinburg, Russian Federation.Fax: +7 3432 74 0458; e-mail: rusinov@htf.ustu.ru b Darmstadt University of Technology, D-64287, Darmstadt, Germany. Fax: +49 615 116 3574; e-mail: di88@hrzpub.tu-darmstadt.de 10.1070/MC2002v012n01ABEH001548 A new methodology for the synthesis of functionalised bipyridines by the direct cyanation of 3-(2-pyridyl)-1,2,4-triazine 4-oxide through nucleophilic substitution for hydrogen followed by the transformation of the 1,2,4-triazine ring into the pyridine ring by the Diels–Alder reaction and, finally, the chemical conversion of the cyano group is described.The 2,2'-bipyridine system is a well-known ligand for the design of supramolecular metal complex systems.1 In spite of the large number of publications, methods for the synthesis of asymmetric bipyridines and terpyridines bearing different functional groups are scantily known.2 Here, we describe a new methodology for the design of asymmetrically substituted bipyridines involving the synthesis of 3-(2'-pyridyl)-1,2,4-triazine 4-oxides, their functionalization by nucleophilic substitution for hydrogen and finally, formation of the bipyridine system by an inverse electron demand Diels– Alder reaction.The high reactivity of 1,2,4-triazines towards nucleophiles and dienophiles allows oligopyridines bearing different types of substituents (the residues of the nucleophiles and products of their chemical transformation) to be prepared. A modified method3 was used to form the 1,2,4-triazine ring. Thus, the condensation of pyridine-2-carbaldehyde with isonitrosoacetophenone hydrazone followed by aromatization of the intermediate by oxidation with KMnO4 in acetone results in the formation of 6-phenyl-3-(2'-pyridyl)-1,2,4-triazine 4-oxide 1.† The N-oxide group makes the 1,2,4-triazine ring more susceptible towards nucleophilic substitution for hydrogen.We chose the cyanide anion as a nucleophile for two main reasons. One of them is the high electron-withdrawing property of the cyano group, which increases the reactivity of a heterocycle in the inverse electron demand Diels–Alder reaction with electron-rich dienophiles. The other is the easy conversion of the cyano group into other functional groups, which opens a way to substituted ligands.Thus, the treatment of compound 1 with acetone cyanohydrin in the presence of triethylamine leads to 5-cyano- 6-phenyl-3-(2'-pyridyl)-1,2,4-triazine 2 (Scheme 1).In this case, the cyanide anion formed in situ adds at the 5-position of the 1,2,4-triazine ring resulting in the intermediate ó-adduct, the dehydration of which forms aromatised product 2. The reaction proceeds very smoothly in 91% yield. Cyano-1,2,4-triazine 2 was found to accelerate the Diels– Alder reaction.In our case, a enamine and bicyclo[2.2.1]hepta- 2,5-diene were used as electron-rich dienophiles. Thus, 5-cyano- 1,2,4-triazine 2 reacts with 1-pyrrolidino-1-cyclopentene at room temperature forming two isomeric cycloadducts 3 and 4 as a result of cycloaddition of the dienophile to the C-3 and C-6 atoms of the 1,2,4-triazine ring followed by the elimination of nitrogen.The formation of an isomer mixture does not play a crucial role because the refluxing of cycloadducts 3 and 4 in acetic acid leads to their aromatization via the elimination of pyrrolidine to give 6-cyano-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 5 in almost 100% yield (Scheme 1). Similarly, 5-cyano-1,2,4-triazine 2 reacts with bicyclo[2.2.1]- hepta-2,5-diene.However, in this case, more severe conditions are required, at least refluxing in toluene. The reaction proceeds with the elimination of nitrogen and cyclopentadiene yielding 6-cyano-5-phenyl-2,2'-bipyridine 6. In the reaction with bicyclo- [2.2.1]hepta-2,5-diene, the cyano group facilitates the reaction significantly in comparison with unsubstituted pyridyl-1,2,4- triazine.4 The presence of a cyano group in bipyridine 5 allows the further functionalization, which opens way to new building blocks for the bipyridine series.Thus, the hydrolysis of the cyano group in cyanobipyridine 5 in 95% sulfuric acid leads to 6-carbamoyl-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 7. Further hydrolysis of amide 7 in concentrated hydrochloric acid forms 5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine-6- carboxylic acid 8.The esterification of acid 8 via the intermediate formation of an acid chloride yields 6-ethoxycarbonyl- 5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 9. The reduction of ester 9 with sodium borohydride results in 6-hydroxymethyl- 5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 10 (Scheme 2). Thus, the sequential use of nucleophilic substitution for Scheme 1 Reagents and conditions: i, Py-2-CHO, EtOH, room temperature, 12 h; ii, KMnO4–acetone, 0 °C; iii, NEt3, CH2Cl2, reflux; iv, benzene, reflux, 1 h; v, AcOH, reflux, 0.5 h; vi, toluene, reflux, 4 h.Ph N N OH NH2 N N N N O Ph N N N N Ph NC 1 2 Me HO CN Me i, ii iii 2 N N Ph NC 6 N N Ph NC 4 H N N N Ph NC 5 N N Ph NC 3 H N N iv v viMendeleev Communications Electronic Version, Issue 1, 2002 2 hydrogen and the Diels–Alder reaction in the 1,2,4-triazine series is a convenient route for the synthesis of a wide range of functionalised bipyridines.References 1 J.-M.Lehn, Supramolecular Chemistry – Concepts and Perspectives, VCH, Weinheim, 1995. 2 D. S. Lawrens, T. Jiang and M. Levett, Chem. Rev., 1995, 95, 2229. 3 D. N. Kozhevnikov, V. N. Kozhevnikov, V. L. Rusinov and O. N. Chupakhin, Mendeleev Commun., 1997, 238. 4 (a) O. Pfuller and J. Sauer, Tetrahedron Lett., 1998, 39, 8821; (b) G. Pabst, O. Pfuller and J. Sauer, Tetrahedron, 1999, 55, 5047. † 6-Phenyl-3-(2-pyridyl)-1,2,4-triazine-4-oxide 1. Pyridine 2-carboxaldehyde (1.07 g, 10.0 mmol) was added to a stirred solution of isonitrosoacetophenone hydrazone (1.63 g, 10.0 mmol) in ethanol (10 ml).The reaction mixture was kept at room temperature for 12 h. The resulting precipitate was filtered off, washed with ethanol, dried and then dissolved in acetone (100 ml). Potassium permanganate (1 g, 6.3 mmol) in acetone (50 ml) was added dropwise to this solution at 0 °C in 30 min. The reaction mixture was additionally stirred at 0 °C for 30 min. The precipitated MnO2 was removed by filtration and washed with acetone (3×10 ml).Filtrates were combined, the solvent was evaporated at a reduced pressure and the residue was recrystallised from ethanol to give 1 (1.28 g, 57%): mp 173–174 °C. 1H NMR ([2H6]DMSO) d: 7.54–7.61 (m, 4H), 7.94–8.06 (m, 2H), 8.20–8.26 (m, 2H), 8.77–8.79 (m, 1H), 9.32 (s, 1H).EI-MS, m/z (I, %): 250 (M+, 23). Found (%): C, 67.14; H, 4.13; N, 22.42. Calc. for C14H10N4O (250.26) (%): C, 67.19; H, 4.03; N, 22.39. 5-Cyano-6-phenyl-3-(2-pyridyl)-1,2,4-triazine 2. To a solution of 1,2,4-triazine-4-oxide 1 (1 g, 4 mmol) in dichloromethane (30 ml) acetonecyanohydrin (0.73 ml, 8 mmol) and triethylamine (0.56 ml, 4 mmol) were added with stirring, and the solution was refluxed for 30 min.The solvent was evaporated in vacuo, and the residue was treated with diethyl ether (10 ml). The precipitate obtained was filtered off and washed with isopropanol (2 ml) and diethyl ether (5 ml) to give 2 (0.94 g, 91%). No further purification was required; mp 128–129 °C. 1HNMR ([2H6]DMSO) d: 7.60–7.71 (m, 4H), 8.03–8.15 (m, 3H), 8.55–8.60 (m, 1H), 8.85–8.88 (m, 1H).EI-MS, m/z (I, %): 259 (M+, 4), 231 (M – N2, 21). Found (%): C, 69.35; H, 3.47; N, 27.14. Calc. for C15H9N5 (259.27) (%): C, 69.49; H, 3.50; N, 27.01. 6-Cyano-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 5. 1-Pyrrolidino- 1-cyclopentene (0.32 ml, 2.2 mmol) was added to a solution of 5-cyano-6-phenyl-3-(2-pyridyl)-1,2,4-triazine 2 (0.52 g, 2 mmol) in benzene (10 ml).As a result, immediate nitrogen evolution took place. The reaction mixture was stirred at room temperature for 1 h and then refluxed for 1 h. The solvent was evaporated in vacuo, and the residue was refluxed in acetic acid (3 ml) for 30 min. Crystals of 5 were filtered off and washed with acetic acid (2 ml). Yield of 5 as a colourless needles: 0.58 g, 97%; mp 192–193 °C. 1H NMR ([2H6]DMSO) d: 2.02–2.20 (m, 2H), 2.86–2.93 (m, 2H), 3.53–3.60 (m, 2H), 7.42–7.58 (m, 6H), 7.90– 7.97 (m, 1H), 8.30–8.33 (m, 1H), 8.66–8.69 (m, 1H).EI-MS, m/z (I, %): 297 (M+, 100). Found (%): C, 80.74; H, 4.98; N, 14.27. Calc. for C20H15N3 (297.36) (%): C, 80.78; H, 5.08; N, 14.13. 6-Cyano-5-phenyl-2,2'-bipyridine 6. A mixture of 5-cyano-6-phenyl- 3-(2-pyridyl)-1,2,4-triazine 2 (0.52 g, 2 mmol) and bicyclo[2.2.1]hepta- 2,5-diene (0.86 ml, 8 mmol) was refluxed in toluene (10 ml) for 4 h.The solvent was removed on a rotary evaporator, and the residue was recrystallised from ethanol to give 6 (0.47 g, 92%); mp 194–195 °C. 1HNMR ([2H6]DMSO) d: 7.44–7.70 (m, 6H), 7.74–8.00 (m, 1H), 8.17 (d, 1H, J 8.1 Hz), 8.43–8.47 (m, 1H), 8.68–8.75 (m, 1H), 8.73 (d, 1H, J 8.1 Hz).EI-MS, m/z (I, %): 257 (M+, 100). Found (%): C, 79.52; H, 4.41; N, 16.31. Calc. for C17H11N3 (257.30) (%): C, 79.36; H, 4.31; N, 16.33. 6-Carbamoyl-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 7: mp 197– 198 °C. 1H NMR ([2H6]DMSO) d: 1.96–2.10 (m, 2H), 2.72 (t, 2H, J 7.7 Hz), 3.50 (t, 2H, J 7.7 Hz), 7.12 (br. s, 1H, amide), 7.22–7.41 (m, 6H), 7.72 (br. s, 1H, amide), 8.845–8.93 (m, 1H), 8.42–8.47 (m, 1H), 8.63–6.67 (m, 1H).EI-MS, m/z (I, %): 315 (M+, 36). Found (%): C, 76.19; H, 5.54; N, 13.30. Calc. for C20H17N3O (315.38) (%): C, 76.17; H, 5.43; N, 13.32. 6-Carboxy-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine hydrochloride 8: mp 209–210 °C. 1H NMR ([2H6]DMSO) d: 2.04–2.19 (m, 2H), 2.84 (t, 2H, J 7.3 Hz), 3.48 (t, 2H, J 7.3 Hz), 7.29–7.49 (m, 5H), 7.78–7.86 (m, 1H), 8.33–8.50 (m, 2H), 8.86–8.92 (m, 1H).EI-MS, m/z (I, %): 316 (M+, 11), 272 (M+ – CO2). Found (%): C, 68.07; H, 4.56; N, 7.73. Calc. for C20H16N2O2·HCl (%): C, 68.08; H, 4.86; N, 7.94. 6-Ethoxycarbonyl-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 9: mp 126–127 °C. 1H NMR ([2H6]DMSO) d: 0.97 (t, 3H, J 7.5 Hz), 1.98– 2.16 (m, 2H), 2.82 (t, 2H, J 7.5 Hz), 3.53 (t, 2H, J 7.5 Hz), 4.03 (q, 2H, J 7.5 Hz), 7.25–7.46 (m, 6H), 7.82–7.92 (m, 1H), 8.30–8.36 (m, 1H), 8.64–8.67 (m, 1H).Found (%): C, 76.67; H, 5.90; N, 8.17. Calc. for C22H20N2O2 (344.42) (%): C, 76.72; H, 5.85; N, 8.13. 6-Hydroxymethyl-5-phenyl-2-(2'-pyridyl)-3,4-cyclopentenopyridine 10: mp 140–141 °C. 1H NMR ([2H6]DMSO) d: 1.98–2.09 (m, 2H), 2.70 (t, 2H, J 7.4 Hz), 3.46 (t, 2H, J 7.4 Hz), 4.38 (br. s, 2H), 4.69 (br. s, 1H), 7.30–7.50 (m, 6H), 7.84–7.93 (m, 1H), 8.38–8.43 (m, 1H), 8.63–8.66 (m, 1H). EI-MS, m/z (I, %): 302 (M+, 100). Found (%): C, 79.44; H, 5.94; N, 9.40. Calc. for C20H18N2O (302.38) (%): C, 79.44; H, 6.00; N, 9.26. N N Ph O NH2 7 5 i 92% ii 83% N N Ph O OH 8 N N Ph O OEt 9 iii, iv 87% v 75% N N Ph OH 10 Scheme 2 Reagents and conditions: i, H2SO4 (95%), 100 °C, 6 h; ii, HCl (conc.), reflux, 7 h; iii, SOCl2, reflux, 7 h; iv, EtOH, reflux, 1 h; v, NaBH4, EtOH, reflux, 5 h. Received: 8th January 2002; Com. 02/1874

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Synthesis of 3-spiroannulated hexahydro-6,8a-epoxyisoquinolines Alexey V. Varlamov, Evgenia V. Nikitina, Fedor I. Zubkov,* Olga V. Shurupova and Alexei I. Chernyshev Department of Organic Chemistry, Peoples¡� Friendship University of Russia, 117419 Moscow, Russian Federation. Fax: +7 095 952 0745; e-mail: fzubkov@sci.pfu.edu.ru 10.1070/MC2002v012n01ABEH001535 The title compounds were synthesised by the intramolecular [4+2]-cycloaddition of 1-N-furfurylamino-1-allylcyclanes in the presence of acetic anhydride.The intramolecular [4+2]-cycloaddition of 1-N-alkenylfurfurylamines is widely used for building hexahydro-3a,6-epoxyindole and hexahydro-3a,6-isoindole systems. The intramolecular Diels. Alder reaction in the furan series is more rarely used to synthesise hexahydro-6,8a-epoxyquinolines1.3 and hexahydro-6,8aisoquinolines3 .7 because the parent compounds are inaccessible and the cycloaddition occurs ambiguously.The synthesis of analogous spiroannulated structures was not described previously.8 Here, we propose a facile synthetic route to 3-spiroannulated 6,8a-epoxyisoquinolines 2a.e based on the intramolecular [4+2]- cycloaddition of 1-allyl-1-N-furfurylaminocycloalkanes 1a.e.Starting homoallylamines 1 are formed in high yields in the reaction of the appropriate Schiff bases with allylmagnesium bromide.9,10 Compound 1e (X = CHBut) is formed as a mixture of two isomers with different arrangements of the tert-butyl and allyl groups, the major isomer being a diequatorial derivative.According to the 1H NMR data, the ratio between e-1-allyl-e-4- tert-butyl and a-1-allyl-e-4-tert-butyl is approximately 1.5:1. The refluxing of amines 1 in an excess of acetic anhydride¢Ó is accompanied by easy intramolecular exo-[4+2]-cyclization of intermediate N-acetyl derivatives. In this case, 3-spiroannulated hexahydro-6,8a-epoxyisoquinolines 2a.e are formed in moderate yields.These compounds are colourless crystalline substances stable in storage. The reaction of an isomeric mixture of 1e with an excess of acetic anhydride leads to the formation of isomeric bicyclic compounds 2e, the fractional crystallization of which gave major diequatorial derivative 2e (maj). Note that a mixture of isomeric tert-butyl-substituted allylamines 1e slowly undergoes cyclization even at room temperature to form an isomer mixture of 2f.Both isomers were chromatographically separated in moderate yields. Their structure will be reported elsewhere. The structures of synthesised epoxyisoquinolines 2a.f were found from spectroscopic data.¢Ô The mass spectra exhibited the peaks of molecular ions in accordance with the empirical formulae.The pyrilium ion (m/z 81), which is formed by the retrodiene decomposition of an oxabicyclo[2.2.1]heptene unit, exhibited maximum peak intensities in the mass spectra of all of the compounds. The IR spectra exhibited characteristic bands ¢Ó Typical procedure for the synthesis of 4-annulated 11-oxa-3-azatricyclo[ 6.2.1.01,6]undec-9-enes 2a.e: 0.1 mol of homoallylamine 1 with a 20-fold molar excess of acetic anhydride was refluxed for 3.6 h.An excess of the anhydride was distilled in a vacuum. The residue was added to 200 ml of water, and the solution was alkalified with sodium carbonate to pH 9.10. The mixture was extracted with ethyl acetate (3¡¿70 ml), and the extract was dried with MgSO4. The residue after the distillation of the solvent was recrystallised from hexane.ethyl acetate.Bicyclic compounds 2 were obtained as colourless crystals. O NH X X N O Me O N O H N O H 1a.e 2a. e Ac2O ., 3.6 h X = CHBut two weeks room temperature 2f 2 abcd e (maj) fa X . CH2 (CH2)2 NEt CHBut CHBut Yield (%) 48 68 66 48 44 25 aThe overall yield of the isomer mixture. 2 4 8 9 10 ¢Ô 2a: mp 88.89 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.36 (dd, 1H, J 6.0 and 1.3 Hz), 6.09 (d, 1H, J 6.0 Hz), 4.91 (dd, 1H, J 4.0 and 1.3 Hz), 4.03 (d, 1H, J 15.4 Hz), 3.94 (d, 1H, J 15.4 Hz), 2.10 (s, 3H, Me), 2.22.1.95 and 1.79.1.42 (m, 13H).IR (KBr, n/cm.1): 1630 (C=O and C=C). MS (EI, 70 eV), m/z (%): 247 (M+, 18), 206 (10), 204 (6), 164 (6), 126 (15), 122 (9), 82 (7), 81 (100), 53 (6), 43 (11), 41 (5). Found (%): C, 72.62; H, 8.24; N, 5.81.Calc. for C15H21NO2 (%): C, 72.87; H, 8.50; N, 5.67. 2b: mp 134.135 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.35 (dd, 2H, J 1.8 and 5.8 Hz), 4.92 (dd, 1H, J 4.3 and 1.8 Hz), 3.97 (d, 1H, J 15.3 Hz), 3.80 (d, 1H, J 15.3 Hz), 2.17 (s, 3H, Me), 1.42 (m, 1H), 1.92 (dd, 1H, J 12.8 and 4.6 Hz), 1.6.1.2 (m, 13H). IR (KBr, n/cm.1): 1630 (C=O and C=C). MS (EI, 70 eV), m/z (%): 261 (M+, 63), 220 (19), 218 (13), 204 (34), 176 (12), 140 (40), 122 (14), 121 (29), 81 (100), 43 (25), 40 (26).Found (%): C, 73.36; H, 8.79; N, 5.24. Calc. for C16H23NO2 (%): C, 73.56; H, 8.81; N, 5.36. 2c: mp 135.136 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.32 (s, 2H), 4.90 (d, 1H, J 4.3 Hz), 4.04 (d, 1H, J 15.0 Hz), 3.47 (d, 1H, J 15.0 Hz), 2.14 (s, 3H, Me), 1.96 (dd, 1H, J 11.3 and 3.1 Hz), 1.41 (dt, 1H, J 11.3 and 4.3 Hz), 1.2.2.0 (m, 15H).IR (KBr, n/cm.1): 1623 (C=O and C=C). MS (EI, 70 eV), m/z (%): 275 (M+, 45), 234 (12), 204 (24), 176 (11), 154 (41), 135 (18), 122 (11), 81 (100), 53 (10), 43 (18), 41 (11). Found (%): C, 74.27; H, 9.15; N, 5.26. Calc. for C17H25NO2 (%): C, 74.18; H, 9.10; N, 5.10. 2d: mp 113.114 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.38 (dd, 1H, J 1.5 and 5.8 Hz), 6.08 (d, 1H, J 5.8 Hz), 4.93 (d, 1H, J 1.5 and 3.7 Hz), 4.04 (d, 1H, J 15.0 Hz), 3.89 (d, 1H, J 15.0 Hz), 2.16 (s, 3H, Me), 2.65.2.22 and 1.9.1.34 (m, 14H), 1.43 (dt, 1H, J 11.3, 3.7 and 8.2 Hz), 1.08 (t, 3H).IR (KBr, n/cm.1): 1674 (C=O). MS (EI, 70 eV), m/z (%): 290 (M+, 27), 275 (10), 248 (14), 247 (100), 152 (42), 150 (18), 124 (14), 123 (13), 122 (21), 110 (64), 108 (14), 85 (14), 84 (25), 58 (12), 56 (11), 43 (17), 41 (8).Found (%): C, 70.52; H, 8.78; N, 9.55. Calc. for C17H26N2O2 (%): C, 70.31; H, 9.02; N, 9.65. 2e: mp 154.154.5 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.38 (dd, 1H, J 1.5 and 5.8 Hz), 6.05 (d, 1H, J 5.8 Hz), 4.91 (dd, 1H, J 1.5 and 4.6 Hz), 4.10 (d, 1H, J 15.9 Hz), 3.52 (d, 1H, J 15.9 Hz), 2.16 (s, 3H), 2.5.2.2 and 1.95.0.95 (m, 13H), 0.85 (s, 9H). IR (KBr, n/cm.1): 1637 (C=O and C=C).MS (EI, 70 eV), m/z (%): 317 (M+, 5), 260 (11), 218 (10), 196 (13), 177 (12), 176 (16), 122 (10), 107 (10), 91 (12), 81 (100), 79 (13), 57 (56), 54 (15), 43 (50), 41 (34). Found (%): C, 75.58; H, 9.83; N, 4.26. Calc. for C20H31NO2 (%): C, 75.70; H, 9.78; N, 4.41. 2f (maj): mp 127.129 ¡ÆC. 1H NMR (200 MHz, CDCl3) d: 6.37 (dd, 1H, J 5.8 and 1.8 Hz), 5.97 (d, 1H, J 5.8 Hz), 4.92 (dd, 1H, J 1.8 and 4.6 Hz), 3.52 (d, 1H, J 15.3 Hz), 3.32 (d, 1H, J 15.3 Hz), 2.3.2.15 and 1.8.1.0 (m, 14H), 0.86 (s, 9H).IR (KBr, n/cm.1): 3320 (NH), 1610 (C=C). MS (EI, 70 eV), m/z (%): 275 (M+, 8), 176 (47), 154 (16), 83 (13), 81 (100), 79 (10), 77 (10), 57 (47), 53 (23), 41 (54), 39 (12). Found (%): C, 78.72; H, 10.70; N, 5.21.Calc. for C18H29NO (%): C, 78.49; H, 10.61; N, 5.09.Mendeleev Communications Electronic Version, Issue 1, 2002 2 due to the stretching vibrations of the amide C=O group at 1623–1674 cm–1. The 1H NMR spectra of compounds 2a–f contained no signals of allylic protons (4.8–5.3 ppm), which are present in the spectra of starting amines 1a–e. At the same time, the spectra exhibited the proton systems H-8 (dd) and H-9 (dd), and H-10 (dd) at 4.90–4.93 and 5.97–6.32 ppm, respectively, with the vicinal constants J8,9 1.3–1.8 and J9,10 5.8–6.0 Hz, respectively.These systems are typical of 7-oxabicyclo[2.2.1]heptenes.3 The exo-configuration of adducts 2a–e was established on the basis of J7-exo,6-endo 2.8–3.2 Hz values compared with published data.3,11 This work was supported by the Russian Foundation for Basic Research (grant no. 01-03-32 844). References 1 A. Padwa, M. A. Brodney, B. Liu, K. Satake and T. Wu, J. Org. Chem., 1999, 64, 3595. 2 A. Padwa, M. A. Brodney, B. Liu, K. Satake and C. S. Straub, J. Org. Chem., 1999, 64, 4617. 3 A. Padwa and T. S. Reger, Can. J. Chem., 2000, 78,49. 4 M. S. Bailey, B. J. Brisdon, D. W. Brown and K. M. Stark, Tetrahedron Lett., 1983, 24, 3037. 5 T. Hudlicky, G. Butora, S. P. Fearnley, A. G. Gum, P. J. Persichini, M. R. Stabile and J. S. Merola, J. Chem. Soc., Perkin Trans. 1, 1995, 2393. 6 C.Andrés, J. Nieto, R. Pedrosa and M. Vicente, J. Org. Chem., 1998, 63, 8570. 7 K. A. Parker and M. R. Adamchuk, Tetrahedron Lett., 1978, 1689. 8 T. Ghoch and H. Hart, J. Org. Chem., 1989, 54, 5073. 9 V. V. Kouznetsov, N. Ocal, Z. Turgut, F. I. Zubkov, S. Kaban and A. V. Varlamov, Monatsh. Chem., 1998, 129, 671. 10 A. V. Varlamov, V. V. Kouznetsov, F. I. Zubkov, A. I. Chernyshev, G. G. Alexandrov, A. Palma, L. Vargas and S. Salas, Synthesis, 2001, 849. 11 C. Rogers and B. A. Keay, Can. J. Chem., 1992, 70, 2929. Received: 26th November 2001; Com. 01/1861

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Transition from isothermal to chain-thermal flame-propagation regimes in the branching-chain decomposition of nitrogen trichloride Nikolai M. Rubtsov*a and Vyacheslav D. Kotelkinb a Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation. Fax: +7 095 962 80 25; e-mail: ab3590@mail.sitek.ru b Department of Mechanics and Mathematics, M.V. Lomonosov Moscow State University, 119992 Moscow, Russian Federation. Fax: +7 095 939 2090; e-mail: kotelkin@mech.math.msu.su 10.1070/MC2002v012n01ABEH001497 The title transition has been detected in a mixture of nitrogen trichloride (4%) with helium. The occurrence of a non-linear branching step in the branched-chain reaction shortens the time interval of the development of a chain-thermal flame.Two general types of the propagation of subsonic flames are known in the theory of combustion: an isothermal regime and a thermal1 (or, more precisely, chain-thermal) regime. The velocity of isothermal flames is determined by the diffusion of the active centres (atoms and radicals) of a branched-chain reaction (BCR) into an unreacted mixture.1 The BCR mechanism must include non-linear chain branching (in this reaction, an increase in the number of free valences is due to the interaction of active centres).2,3 The area of isothermal flame propagation (IFP) (I in Figure 1) is broader than self-igniton area II.The structure of the ignition area in BCR (a pressure–temperature plot) is shown in Figure 1.Chain-thermal flame propagation (CTFP), as distinct from IFP, is due to heat evolution in the front of a developing BCR. The non-Arrhenius dependence5 of the branching on temperature is the positive feedback, which provides the occurrence of the stationary front of combustion. Chain-thermal flames have been widely investigated in BCR, including only linear branching. 4,6,7 The self-ignition area of these linear BCR II includes isothermal area IIa and chain-thermal explosion area IIb, which corresponds both to developing chain avalanche and accelerating heat accumulation.4 The stationary flame propagation in linear BCR in the vicinity of the lower self-ignition limit (IIa) is ruled out because the warming-up is missing.At pressures close to the lower boundary of IIa, the warming-up is reasonably large to warm the nearest layers of an unreacted gas up to the selfignition temperature (arrows 1 in Figure 1; in this case, the stationary combustion wave, namely CTFP, occurs). Therefore, in order that a stationary flame may develop, linear BCR must be initially in self-ignition area, or the initiating impulse (e.g., a spark) must provide the warming-up that is sufficient to transfer the BCR to the area close to IIb (arrow 0 in Figure 1).However this limitation does not take place for non-linear BCR, in which the stationary flame propagation may occur in both areas I and II. In this work, the transition of the flame propagation regime from area I to II (arrows 2 in Figure 2), which is possible only in non-linear BCR, is studied.IFP can be observed in dilute mixtures of CS2 with O2,2,3 thermal decomposition of NCl3,8 fluorination of difluoromethane,9 and oxidation of silane and dichlorosilane.10,11 Since IFP occurs at very low fuel contents (> 0.03%2,3), the interest in IFP is connected directly with explosion safety problems: NCl3 is formed in the commercial production of Cl2,12 and silanes are widely used in microelectronics.13 Therefore, a topical problem is to study flame propagation in non-linear BCR, namely the transition from IFP to CTFP.Thermal decomposition of gaseous nitrogen trichloride (NCl3) is an example of low temperature BCR. The BCR is convenient for attacking the problem because both linear and non-linear chain branching play an important role in this BCR.The kinetics and mechanism of the BCR were considered previously.8,14–17 The aim of this work was to detect and study the transition from IFP to CTFP by the example of the decomposition of nitrogen trichloride in a gaseous phase. The regularities obtained 0 1 2 I IIa IIb P T Figure 1 The ignition areas in BCR.(I) IFP area; (IIa) isothermal selfignition area and (IIb) chain-thermal explosion area. Arrows: (0) initiated ignition in linear BCR; (1) transition of a chain self-ignition to a chainthermal one (or to CTFP); (2) transition of an isothermal flame propagation to a chain-thermal one. The lengths of the arrows correspond to the warming-up. 6 5 4 3 2 1 0 20 40 60 80 100 P/Torr V/m s–1 100 50 0 50 (a) (b) 1 2 P/Torr V/m s–1 Figure 2 Dependence of the flame propagation velocity on total pressure in the mixtures of NCl3 with He. (a) Isothermal flame,9 (1) points (experiment); NCl3, 0.38%; curve indicates numerical simulation for 0.38% NCl3 in He; (2) circles (experiment); NCl3, 0.11%, curve indicates numerical simulation for 0.11% NCl3 in He; (b) chain-thermal flame, points (experiment), 4% NCl3 in He; curves indicate numerical simulation, solid line: Q1 = 17 kcal mol–1, Q2 = 34 kcal mol–1, dotted line: Q1 = 0, Q2 = 34 kcal mol–1.Mendeleev Communications Electronic Version, Issue 1, 2002 2 were applied to develop a one-dimensional model of flame propagation. The experiments were carried out under static conditions at 293 K, total pressures of 2.100 Torr and [NCl3] = 1.4%.A cylindrical quartz reactor (80 cm in length and 6 cm in diameter) had inlets for gas evacuation and optical windows. A rapidly heated small furnace placed on the butt end of the reactor provided ignition. After the ignition, a flame propagated into the cool part of the reactor (at 293 K). The velocity of flame travelling was recorded by three photomultiplier tubes equipped with light guides placed 20 cm apart using an oscilloscope. The inner surface of the reactor was covered with magnesium oxide, which provides the diffusive area of chain termination.8,14 The total pressure was measured with a sensitive pressure gauge (10.3 Torr).The concentration of NCl3 in helium was determined from a change in the total pressure after ignition by the stoichiometry of the reaction 2NCl3 ¢ç N2 + 3Cl2.17 Liquid NCl3 was obtained and gaseous mixtures were prepared by the published procedures.14 The reactor was evacuated to 4¡¿10.4 Torr before each experiment.It was found8 that a pressure range in which an isothermal flame propagation occurs [Figure 2(a)] expands with an increase in the NCl3 concentration.As this takes place, the flame propagation area expands in such a way that the upper limit of the flame propagation no longer exists over a certain concentration of NCl3 in He [Figure 2(b), points]. This means that the role of warming-up markedly increases over certain ranges of total pressures and concentrations of NCl3. Let us consider this phenomenon. The kinetic mechanism of the chemical decomposition of NCl3 can be represented as follows:8,14.17 It should be noted that the set of reactions (1).(9) is identical to that considered previously.15,16 The results16 of numerical calculations of IFP in dilute mixtures of NCl3 with He, CO2 and Cl2 based on reactions (1).(9) are in good agreement with experimental data. The reaction of termolecular chain termination is unclear.18 However, step (9) can explain the occurrence of the upper limit of IFP.16 Thus, the value of k9 can be considered only as its upper limit, i.e., both deactivation and termolecular termination are approximated by properly choosing k9.As is known, the stationary propagation of a reaction wave must be considered with no regard for a chain origination reaction. 27 The one-dimensional problem was examined. We determine the dimensionless variables and parameters similarly to ref. 16: t = k1[NCl3]0t, Y0 = [Cl]/[NCl3]0, Y1 = [Cl2 3¥�ou + ] / [NCl3]0, Y2 = [NCl2]/[NCl3]0, Y3 = [NCl3]/[NCl3]0b = k2/k1, f = k3/k1, g = = k8/(k1[NCl3]0), l = k4/(k1[NCl3]0), y = k5/k1, r = k7/(k1[NCl3]0), m = k6/k1, c = k9/(k1[NCl3]0); t is time (s), the total pressure (Torr) is designated as P, i.e., [NCl3]0 = sP, where s is the mole fractionf NCl3 in the initial mixture.The dimensionless velocity and coordinate of a propagating flame were defined in terms of the diffusivity of NCl3 (D3): v = U/(D3k1[NCl3]0)1/2, x = x/(D3/ k1[NCl3]0)1/2, where U and x are the corresponding dimensional values. The dimensionless diffusivities (Di /D3, i = 0.4) d0, d1, d2 in helium correspond to chlorine atoms, Cl2 3¥�ou + , NCl2 radicals, respectively.The system of non-linear second-order differential equations for the above kinetic mechanism is the following: As heat evolution takes place in the chain unit, the last equation corresponds to a heat balance, where Q1 and Q2 are the specific heats, cp is the heat capacity at a constant pressure (1.25 cal g.1 K.1 for He19), a is the temperature conductivity, L is the surface-to-volume ratio (cm.1), T is the temperature (K), a = Ldle/r2,1 where r is the reactor radius (cm), e = 2.718..., d is a critical parameter (2.0),1 the thermal conductivity l = = D(He.He) ¡í D(He.He) in dilute mixtures,28 d4 = D(He.He)/(D3cpr), r is the density of helium (g cm.3).28 The set of equations (I) was solved numerically as described previously.16 As the heterogeneous chain termination was considered to occur in a diffusive area,8 the rate constants k7 and k8 were calculated by the equation k = 23.2Di/(d2P),3 where d = 2r.The values of Di in He (cm2 s.1, 293 K, 760 Torr) were taken from refs. 23 and 28. The results of the numerical calculation of the evolution of system (I) at [NCl3] = 4% are shown in Figures 3(a) and 3(b) for total pressures of 5 and 35 Torr.As can be seen, the stationary velocities of flame propagation correspond to different BCR regimes: at a pressure of 5 Torr, the calculated warming-up is small (~10¡Æ in agreement with experimental data14) and the maximum [Cl2 3¥�ou + ]/ [NCl3] ratio is as high as 0.07. It is evident that this regime of the flame propagation is practically isothermal.At a pressure of 35 Torr, the calculated value of maximum warming-up is about 200¡Æ; in this case, [Cl2 3¥�ou + ] / [NCl3] << 0.07. The latter regime is already chain-thermal. Therefore, system (I) at [NCl3] = 4% admits at least two auto-wave solutions, which describe the stationary front of a propagating flame: one of them corresponds to CTFP, and the other corresponds to IFP.It was shown29 that the dependence of the integral chemiluminescence intensity of Cl2 3¥�ou + on total pressure increases from 0.1 to 2 Torr (at [NCl3] = 15%) and then sharply decreases with a further increase in pressure. This fact is consistent with the calculations performed [cf. Cl2 3¥�ou + concentrations in Figures 3(a) and 3(b)] and is evidently due to the transition from the isothermal to the chain-thermal regime of flame propagation.The upper limit of flame propagation at 4% NCl3 is missing in experiments, as well as in calculations. It is easy to verify that two auto-wave regimes corresponding to chain-thermal and isothermal flame propagations hold for different concentrations of NCl3 at similar pressures [cf.Figures 2(a) and 2(b) at total pressures > 35 Torr]. Actually, at [NCl3] = 0.4%, a chain-thermal regime of flame propagation is missing at the studied pressures in both experiments and calculations. It means that the transition to a chain-thermal regime is determined by both the initial pressure and the initial concentration of NCl3 in the mixture.The transition shows a critical character in total pressure, as is seen in Figure 2(b). IFP occurs at low pressures; an increase in the pressure causes the transition to CTFP in the pressure range (about 20 Torr) where calculated isothermal and chain-thermal solutions become separated. Note that the inclusion of heat evolution in only the linear chain branching reaction [step (2), Q2 = = 34 kcal mol.1 (ref. 21)] does not cause the transition to a chainthermal flame at pressures up to 100 Torr (Figure 2, dotted line).Therefore, the heat evolution in step (1) was also taken into account. The dependence of the calculated wave solution on the total pressure is shown in Figure 2(b) (solid line). However, a NCl3 NCl2 + Cl, k0 = 10.3.10.5 s.1,18 chain origination; Cl + NCl3 NCl2 + Cl2 + Q1, k1 = 1.6¡¿10.12 cm3 s.1,18 chain propagation; NCl2 + NCl3 N2 + Cl2 + 3Cl + Q2, k2 = 3.4¡¿10.11 exp(-e1/T) cm3 s.1, e1 = 3050/R [K],19,20 linear chain branching, specific heat Q1 was varied in a range of 0.17 kcal mol.1 in order to reveal the contribution of step 1 to heat evolution.The range of Q2 (20.34 kcal mol.1) is determined by the accuracy of the N.Cl bond energies in the molecule of NCl3;21 NCl2 + NCl2 N2 + Cl2 3¥�ou + + 2Cl, k3 = 6.0¡¿10.13 cm3 s.1,22,23 non-linear branching; Cl2 3¥�ou + 2Cl, k4 = 4.8¡¿102 s.1;24 Cl2 3¥�ou + + NCl3 NCl2 + Cl2 + 2Cl, k5 = 1.6¡¿10.12 cm3 s.1;15,16 Cl2 3¥�ou + + Cl Cl2 1¥Òg .+ Cl, k6 = 1.6¡¿10.10 cm3 s.1,25,26 non-linear chain termination; NCl2 reactor wall, k7, chain termination in a diffusive area; Cl reactor wall, k8, chain termination in a diffusive area Cl2 3¥�ou + + M Cl2 1¥Òg .+ M, k9 = 8¡¿10.13.10.13 cm3 s.1,25 deactivation.(see below); dY0/dt = d0d2Y0/dx2 + 2f(Y2)2 + yY1Y3 + 3Y2Y3 bexp(.3050/T) + + 2lY1 . Y0Y3 . gY0 dY1/dt = d1d2Y1/dx2 + 2f(Y2)2 . yY1Y3 . lY1 . cPY2 dY2/dt = d2d2Y2/dx2 . 2f(Y2)2 + yY1Y3 . rY2 . Y2Y3 bexp(.3050/T) dY3/dt = d2Y3/dx2 .yY1Y3 . Y0Y3 . Y2Y3 bexp(.3050/T) dT/dt = d4d2T/dx2 + sb[k2Y2Y3exp(.3050/T)Q1 + Y0Y3Q2]/ (cpr) . aL(T . 298)/(cp r) (I) Cl 0.73 NCl2 0.44 Cl2 3¥�ou + 0.55 NCl3 0.41 He 1.62Mendeleev Communications Electronic Version, Issue 1, 2002 3 wide range of parameters dealing with heat evolution (Q1, Q2, a, e1) is responsible for only qualitative agreement between calculated and experimental data because the accuracy of these parameters is inadequate. Moreover, the above one-dimensional problem does not allow us to investigate the occurrence of spatial regimes inherent in BCR as non-linear dynamic systems.30 Numerical calculations allowed us to establish whether the occurrence of non-linear branching in the mechanism of BCR has an effect on the transition to a chain-thermal regime of flame propagation.For this purpose, in solving system (I) under conditions of Figure 3(b), the value of k3 was taken equal to zero, i.e., non-linear chain branching was eliminated from system (I). The results are shown in Figure 3(c). It can be seen that the transition to an auto-wave chain-thermal regime occurs within a larger time interval than that in Figure 3(a).Thus the occurrence of non-linear branching enhances the inflammability of BCR. As would be expected, an auto-wave regime is missing under conditions of Figure 3(a) (at 5 Torr): neither IFR (k3 = 0) nor CTFP (low warming-up) can occur. The numerical calculations can also illustrate the fact that the rate of the linear branching influences the kinetics of BCR to a greater extent than the specific heat of this reaction.Actually, the occurrence of CTFP, with k3 taken 10 times lower and with Q2 taken 10 times higher than in previous calculations [in this case, the fifth equation of system (I), which describes heat evaluation, remains unchanged] is realized in the time interval that is four times larger than that presented in Figure 3(c). We are grateful to Professor V.V. Azatyan for helpful discussions. This work was supported by the Russian Foundation for Basic Research (grant no. 00-03-32979a). References 1 D. A. Frank-Kamenetskii, Diffuziya i teploperedacha v khimicheskoi kinetike (Diffusion and Heat Transfer in Chemical Kinetics), Nauka, Moscow, 1967, p. 491 (in Russian). 2 V. G. Voronkov and N. N. Semenov, Zh.Fiz. Khim., 1939, 13, 1695 (in Russian). 3 N. N. Semenov, O nekotorych problemakh khimicheskoi kinetiki i reaktsionnoi sposobnosti (On Some Problems of Chemical Kinetics and Reactivity), Akad. Nauk SSSR, Moscow, 1968, p. 686 (in Russian). 4 V. V. Azatyan, Kinet. Katal., 1999, 40, 818 [Kinet. Catal. (Engl. Transl.), 1999, 40, 720]. 5 V. V. Azatyan and A. A. Shavard, Izv. Akad. Nauk, Ser.Khim., 1977, 2460 (Bull. Chem. Sci., 1977, 26, 2279). 6 Ya.B.Zel’dovich, G. I. Barenblatt, V. B. Librovich and G. M.Machviladze, Matematicheskaya teoriya goreniya i vzryva (Mathematical Theory of Combustion and Explosion), Nauka, Moscow, 1980 (in Russian). 7 P. Gray, J. F. Griffiths and S. K. Scott, Proc. Roy. Soc. Lond., 1985, A397, 21. 8 V. V. Azatyan, R.R. Borodulin and N. M. Rubtsov, Fiz. Gorenia Vzryva, 1980, 5, 34 (in Russian). 9 V. P. Bulatov, V. I. Vedeneev, A. N. Kitaygorodskii and O. M. Sarkisov, Izv. Akad. Nauk SSSR, Ser. Khim., 1975, 1881 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1975, 24, 1763). 10 V. V. Azatyan, V. A. Kalkanov and A. A. Shavard, React. Kinet. Catal. Lett., 1980, 15, 367. 11 S. S. Nagorny, N. M. Rubtsov, S.M. Temchin and V. V. Azatyan, in Proc. of the Zel’dovich Memorial. International Conference on Combustion, Moscow, 1994, vol. 2, p. 54. 12 F. Baillou, R. Lisbet and G. Dupre, in Proc. of 7th Int. Symp. on Loss Prevention and Safety Promotion in the Process Industries, Taormine, Italy, 1992, p. 43. 13 C. Cze, VLSI Technology, Wiley, New York, 1981, vol. 1, p. 905. 14 V.V. Azatyan, R. R. Borodulin, E. A. Markevich, N. M. Rubtsov and N. N. Semenov, Izv. Akad. Nauk SSSR, Ser. Khim., 1976, 1459 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1976, 25, 1396). 15 N. M. Rubtsov, Mendeleev Commun., 1998, 173. 16 N. M. Rubtsov and V. D. Kotelkin, Mendeleev Commun., 2001, 61. 17 V. V. Azatyan, R. R. Borodulin, E. A. Markevich and N. M. Rubtsov, Fiz. Gorenia Vzryva, 1978, 14, 20 (in Russian). 18 N. M. Rubtsov, V. V. Azatyan and R. R. Borodulin, Izv. Akad. Nauk SSSR, Ser. Khim., 1980, 1234 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1980, 29, 1165). 19 V. V. Azatyan, R. R. Borodulin, E. A. Markevich, N. M. Rubtsov and N. N. Semenov, Dokl. Akad. Nauk SSSR, 1975, 224, 1096 [Dokl. Chem. (Engl. Transl.), 1975, 224, 1059]. 20 N. M. Rubtsov and R. R. Borodulin, in Kinetika i mekhanizm fizikokhimicheskikh protsessov (Kinetics and Mechanism of Physical and Chemical Processes), Chernogolovka, 1981, p. 14 (in Russian). 21 T. C. Clark and M. A. A. Clyne, Trans. Faraday Soc., 1970, 66, 372. 22 V. V. Azatyan, R. R. Borodulin and N. M. Rubtsov, Dokl. Akad. Nauk SSSR, 1979, 249, 1375 [Dokl. Chem. (Engl. Transl.), 1979, 249, 1223]. 23 Z. I. Kaganova and B.V. Novozhilov, Khim. Fiz., 1982, 1110 (in Russian). 24 M. A. A. Clark and H.W. Cruse, J. Chem. Soc., Faraday Trans. 2, 1972, 68, 1281. 25 M. A. A. Clyne and D. H. Stedman, Trans. Faraday Soc., 1968, 64, 2698. 26 T. C. Clark and M. A. A. Clyne, Trans. Faraday Soc., 1970, 66, 372. 27 V. S. Posvyanski, Skorost’ i predely rasprostraneniya izotermicheskikh plamen (Velocity and Limits of the Propagation of Nonthermal Flames), Ph. D. Thesis, Institute of Chemical Physics RAS, 1976, p. 134 (in Russian). 28 Tablitsy fizicheskikh velichin (Tables of Physical Values), ed. I. K. Kikoin, Atomizdat, Moscow, 1976, p. 1007 (in Russian). 29 N. M. Rubtsov, R. R. Borodulin and S. S. Saidchanov, Khim. Fiz., 1984, 521 (in Russian). 30 G. Nicolis and I. Prigogine, Self-organisation in Nonequilibrium Systems. From Dissipative Structures to Order through Fluctuations, Wiley- Interscience, New York, London, Sydney, Toronto, 1977, p. 512. Dimensionless concentration Warming-up/° 200 100 NCl3 T Cl2 3�ou + NCl2 Cl 1 0 V (arbitrary units) V0.8 V0.2 V0.5 1.0 0.5 NCl3 T Cl NCl2 400 200 Dimensionless concentration Warming-up/° 1 0 V0.8 V0.5 V0.2 V (arbitrary units) 1.0 0.5 400 200 Dimensionless concentration Warming-up/° 1 0 NCl3 T Cl NCl2 V0.8 V0.5 V0.2 V (arbitrary units) 1.0 0.5 (a) (b) (c) Figure 3 Evolution of system (I) upon calculation, 4% NCl3 in He, initial temperature of 300 K, Q1 = 17 kcalmol–1, Q2 = 34 kcalmol–1. (a) P = 5 Torr; (b) P = 35 Torr; (c) P = 35 Torr, k3 is assumed to be zero. Received: 9th July 2001; Com. 01/18

ISSN:0959-9436     

出版商:RSC    

年代:2002

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Dichlorosilane chlorination in the presence of propylene as an inhibitor at low pressures and 293 K Nikolai M. Rubtsov,* Georgii I. Tsvetkov and Victor I. Chernysh Institute for Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation. Fax: +7 095 962 8025; e-mail: ab3590@mail.sitek.ru 10.1070/MC2002v012n01ABEH001537 The strong inhibiting effect of C3H6 on the self-ignition of dichlorosilane–chlorine mixtures points to silylenes as chain carriers of the reaction.A critical concentration of chemically inert SF6 (> 45%) drastically improves the inhibiting action of C3H6 indicating the occurrence of energy branching. The chlorination of inorganic hydrides [monosilane,1 dichlorosilane (DCS),2 phosphine,3 germane4] and hydrocarbons,5 the reaction of monosilane with nitrogen trichloride6 and the thermal decomposition of NCl3 7 show special features of branched-chain processes (BCP).These are the existence of self-ignition isothermal limits and their dependence on the state of contacting surfaces, as well as the sensitivity of the kinetics to small additives of promoters and inhibitors.8,9 The energy branching (EB, the participation of excited intermediates in chain branching) plays an important role in chain chlorination because the material branching, e.g., ·H + O2 ® ·OH + ·O·, is evidently ruled out.EB in the reactions of electronically excited particles was established for NCl3 decomposition.7 EB in the reactions of vibrationally excited particles was detected in the fluorination of H2 and fluorinated hydrocarbons.11 In fact, fluorination reactions differ from those of chlorination in that they are more exothermic.Moreover, HF has a higher first vibrational level than that of HCl. In fluorination, EB occurs if the energy released in a certain step is enough for unimolecular decomposition of the product of this step, e.g., for the CH2F2 + F2 reaction the following branching process is suggested: CF2H + F2 ® CHF3 * + ·F; CHF3 * ® :CF2 + HF.11 Related reactions were proposed for 1,1- difluoroethane5 and SiH4 1 chlorination.In these mechanisms, carbenes and silylenes, respectively, participate in the EB process. Ab initio calculations were used to construct a mechanism for the pyrolysis of chlorinated silanes.12 The insertion reactions of chlorinated silylenes into chlorinated silanes, which yield chlorinated disilanes, were examined.It was assumed that DCS decomposition could be accelerated by a chlorosilylene-catalysed cycle including EB [its energetics is shown in Figure 1 (ref. 12)]: It is known that olefins react very rapidly with silylenes.13 The rate constants vary from 10–10 (for SiH2) to 10–11 cm3 s–1 (for SiHCl and SiCl2).Since SiHCl (A1B1–X1A1) was detected in DCS chlorination,2 the inhibiting action of olefins (e.g., propylene) will indicate that the reactions of silylenes as chain carriers are of considerable importance in the BCP. If inhibition takes place, the uniform self-ignition over the reactor volume can be studied because the self-ignition of pure DCS and Cl2 at 293 K occurs immediately after mixing (induction period ti is < 300 ms).2 This work is aimed at the establishment of the important role of silylenes as chain carriers, as well as energy factors, in the chain branching in BCP of DCS chlorination in the presence of propylene as an inhibitor and chemically inert sulfur hexafluoride (SF6) as a deactivator.The method of ignition delay was used.14,15 The basis for this method is an expansion of self-ignition area in the time of consumption of an inhibitor. The dependence of self-ignition limits on the fraction of an inhibitor is shown in Figure 1.16 As is seen, a combustible mixture enters the self-ignition area when the inhibitor concentration attains a certain critical value zcrit.The time tC it takes for the mixture to enter the self-ignition area and then to ignite is combined from the time t required to reach the boundary of the self-ignition area (ignition delay) and induction period ti, that is, tC = t + ti. Subsequent calculations hold for t >> ti, or tC @ t. In case of the participation of excited intermediates in chain branching, the addition of an effective deactivator will provide an additional pathway of chain termination and affect t.Let us demonstrate that the dependence of t on the concentrations of initial reactants in the presence of both an inhibitor and a deactivator differs markedly from that in the presence of a single inhibitor by an example of the generalized kinetic model of BCP with EB.The mechanism of DCS chlorination is unknown; therefore, the qualitative model of BCP must include chain origination, propagation, EB and termination via both an inhibitor (In) and a deactivator (M). Here, Y1 and Y2 are the initial reactants, for instance fuel and an oxidizer; Y0 and Y3 are active centres, Y4 * is the excited species that causes branching via unimolecular decomposition.Since the lower limit of the DCS + Cl2 reaction is low,2 the heterogeneous chain termination is not taken into account.14 The amounts of initial reactants consumed and intermediates formed during ignition delay may be considered as negligibly small.14,15 Therefore, dYi/dt (i = 0,3,4) may be put equal to zero and [Y1]0 = [B] and [Y2]0 = [A].Then, by entering new variables y = Y0/[B], x = Y3/[B], u = Y4/[B], A = Y2/[B], z = [In]/[B], p = [M]/[B] into the corresponding equations for the kinetic mechanism (II), for the stationary concentrations of Y0, Y3 and SiHCl + SiH2Cl2 HCl2SiSiH2Cl*; HCl2SiSiH2Cl* HCl2SiSiCl + H2; HCl2SiSiCl Cl2SiSiHCl SiCl2 + SiHCl; HCl2SiSiH2Cl* deactivation. (I) Y1 2Y0 Y1 + Y3 Y0 + products Y0 + Y2 Y4 * + products Y3 + In chain termination Y4 * 2Y3 Y4 * + M deactivation Y0 + In chain termination (k0) (k1) (k2) (k3); (k4) (k5); (k6). chain origination; chain propagation; chain propagation; linear chain branching (EB); (II) PI PII 0 zcrit Fraction of inhibitor / z Total pressure / P Figure 1 The dependence of self-ignition limits of a combustible mixture on the concentration of an inhibitor (g).16Mendeleev Communications Electronic Version, Issue 1, 2002 2 Y4 we obtain: Equation (3) can be solved with respect to u.Substituting this value in equation (2) and inserting h = k4/(k4 + k5p[B]) we obtain: It is no doubt that parameter h changes from 1 to 0 with an increase in the dimensionless amount of deactivator p.Equation (4) suggests that if in certain experiment p amounts up to the partial pressure enough for h to take the value 0.5 chain branching is completely terminated. Therefore, at h > 0.5, ignition delays are not liable to exist. Let us consider that the initial mixture always contains 8% In with respect to A. Then, [A] = z/0.08. Solving equation (1) and equation (4) for x and y, we derive If the denominator of these latter equations is equal to 0, x and y increase infinitely, i.e., self-ignition occurs.Therefore, zcrit is determined by the equality We divide the equation d[In]/dt = –k6Y0[In] – k3Y3[In], which determines the rate of inhibitor consumption, by [B]2: Let us substitute x and y into equation (5) and integrate equation (5) numerically with respect to z between the limits z and zcrit and with respect to t between 0 and t for obtaining the dependence of t on z and h.The results of numerical calculation are shown in Figure 2(a). The chosen values of the rate constants are close to those of silylenes13 being considered as chain carriers in the process. It can be seen that the linear dependence of t on [In]/[B] is expected, the shape of this dependence is determined significantly by the value of k0.It can be seen in Figure 2(a) (curve 1) that at h < 0.5 there are no ignition delays in the presence of the deactivator in the wide range of the ratios [In]/[B], whereas for h = 1 (no deactivation), i.e., in the absence of EB [Figure 2(a), curve 2] this effect is missing. To simplify the treatment, the possible occurrence of material branching along with EB was ignored.However, there are also no ignition delays at h < 0.25 if material branching, e.g., Y0 + Y3 ® 3Y1 (km ~ k2), is included, i.e., the critical character of the dependence of t on h also occurs. The result was tested by the numerical solution of a nonstationary system of kinetic equations for mechanism (II) using the forth-order Runge–Kutta method.It was shown that there are no ignition delays at h < 0.5: the system does not tend to self-ignite at all. Therefore, the qualitative calculations predict a drastic change in the dependence of t on the amount of a deactivator in the presence of both an inhibitor and the deactivator. The experiments were carried out under static conditions at 293 K and total pressures of 0.27–2 kPa.Two cylindrical quartz reactors (15 cm long, 3 cm in diameter, reactor I and 15 cm long, 12 cm in diameter, reactor II) had inlets for gas evacuation and optical windows. Chlorine was initially allowed to bleed into a reactor up to a necessary pressure (0.07–0.4 kPa). Then, the mixture containing DCS + C3H6 + SF6 or Kr (if necessary) was admitted up to a total pressure of 0.4–2 kPa; t was taken as an interval from this moment up to that of a severe decrease in Cl2 concentration.Mixtures containing SF6 were investigated in parallel with mixtures containing the same amount of Kr instead of SF6. The mixtures of DCS + 3–8% C3H6 + 20–80% SF6 or 20–80% Kr, as well as analogous mixtures without C3H6, were prepared before experiments.The concentration of Cl2 was measured by the absorption at 300 nm using a VM-25 monochromator (Germany), a FEY-39 photomultiplier and a Hg–He lamp. The emission and absorption spectra of self-ignition were recorded with an OSA-500 optical spectra analyser (Germany) with a resolution of 0.2 nm per channel. The required number of scans (1 scan = 500 channels per 32 ms) was stored in a computer.The change in total pressure P during self-ignition in reactor II was measured by a mechanotrone. It was shown that self-ignition occurs immediately after the mixing of pure DCS and Cl2 (see ref. 2). However, the addition of > 4% C3H6 caused ignition delays more than 5 s pointing to the fact that C3H6 acts as an inhibitor, i.e., t >> ti. By this means that the reactants may be considered mixed well; therefore, the uniform self-ignition over the reactor volume occurs in the presence of C3H6.Moreover, the strong inhibiting action of C3H6 suggests that linear chain branching gives rise to short ti rather than chain initiation. The only known very rapid step silylene + C3H6 ® chain termination (10–10–10–11 cm3 s–1) is responsible for this inhibiting action.An example of the simultaneous recording of chemiluminescence (470 nm) and absorption (300 nm) is shown in Figure 3. As can be seen from the absorption curve, two intermediates form in self-ignition. The long-lived species has a structureless spectrum at 270–480 nm; it is observed only at [DCS]/[Cl2] £ 1. There is no evidence for the assignment of this spectrum in the literature. The spectra of the short-lived intermediate are shown in Figure 3.The emission bands are due to SiHCl (A1B1–X1A1)17 and the absorption bands, due to SiCl2.18 The silylenes detected are chain carriers of the BCP because C3H6, which reacts rapidly with silylenes, has a marked inhibiting effect on this BCP. It was shown that t increases linearly with an increase in [C3H6]/[DCS] at constant [Cl2].It was also shown that t does not depend on the total pressure, but it depends on the ratio ([DCS] + [C3H6])/[Cl2]. This dependence is almost linear. Since in each set of experiments [DCS]/[C3H6] = const, t depends only on the ratio between an inhibitor and Cl2 [Figure 2(b)]. The data 2k0/(k1[B]) + x – k2y[A]/k1 – k6yz/k1 = 0 –x + 2k4u/(k1[B]) – k3xz/k1 = 0 k2y[A]/k1 – k4u/(k1[B]) – k5up/k1 = 0 (1) (2) (3) –x + 2k2hy[A]/k1 – k3xz/k1 = 0 (4) x = –4k0(2k1 + k3z)/{z[B](50hk1k2 – 25k1k2 – 25zk2k3 – 2k6k1 – 2zk6k3)} y = –2k0(50hk2 + 25k2 + 2k6)/{[B](50hk1k2 – 25k1k2 – 25zk2k3 – – 2k6k1 – 2zk6k3)} zcrit = k1(50hk2 + 25k2 + 2k6)/[k3(25k2 + 2k6)].dz/dt = –[B](k6yz + k3xz). (5) 140 120 100 80 60 40 20 0 0.4 0.3 0.2 0.1 0 1 0.8 0.6 0.4 0.2 1 2 t/s z h 1 2 3 4 5 6 - Kr (%) 7 200 150 100 50 0 0.5 0.4 0.3 0.2 0.1 0 0 20 40 60 80 SF6 (%) [C3H6]/[Cl2] t/s (a) (b) Figure 2 (a) Calculated dependence of ignition delays t on the concentration of inhibitor z and deactivator h.B = 5×1016 cm–3, k0 = 2×10–3 s–1, k1 = = 10–12 cm3 s–1, k2 = 10–14 cm3 s–1, k3 = 10–12 cm3 s–1, k6 = 10–11 cm3 s–1. (1) generalized model (II), EB occurs; (2) generalized model (II), EB does not occur, h = 1 (no deactivation); (b) experimental dependences of ignition delays t on the ratio between an inhibitor and Cl2 and concentration of SF6 (closed circles) and Kr (open circles) Reactor I.(1) 0.20 kPa Cl2 + mixture of DCS + 8% C3H6; (2) 0.28 kPa Cl2 + mixture of DCS + 8% C3H6; (3) 0.12 kPa Cl2 + mixture of DCS + 8% C3H6; (4) 0.20 kPa Cl2 + mixture of DCS + 6.4% C3H6 + 20% SF6; (5) 0.20 kPa Cl2 + mixture of DCS + 5.4% C3H6 + 32% SF6; (6) 0.20 kPa Cl2 + mixture of DCS + 8% C3H6 + 20%, 50%, 60% Kr; 0.20 kPa Cl2 + mixture of DCS +80% Kr; (7) 0.20 kPa Cl2 + mixture of DCS + 4.5% C3H6 + 45% SF6.Mendeleev Communications Electronic Version, Issue 1, 2002 3 shown in Figure 2(b) were obtained from the time dependence of [Cl2] in the Cl2 + DCS + C3H6 + SF6 (or Kr) system.Typical data are shown in Figure 4. In the presence of 8% C3H6 and 50% SF6, t > 30 min whereas t in the presence of 8% C3H6 and 50% Kr is no longer than 110 s. As is expected, the deactivating action of Kr, if any, is markedly weaker than that of SF6. Actually, as can be seen in Figure 2(b), ignition delays are observed at 80% Kr (open circles), i.e., in the context of our qualitative consideration, hKr is close to 1.However [Figure 2(b), closed circles], the critical amount (~45%) of SF6 exists such as the dependence of t on [SF6] undergoes a drastic change. A comparison of Figures 2(a) and 2(b) shows that the result can be qualitatively rationalised on the basis of the generalized model of BCP with EB; in this case, in the context of kinetic mechanism (II), hSF6 ¡í 0.5.The self-ignition in reactor II at [Cl2] > 0.03 kPa and P > > 0.20 kPa is always followed by a sharp sound. The time dependence of the total pressure during self-ignition is shown in Figure 3. As can be seen, an almost three-fold increase in P during the self-ignition is observed. It means that the BCP at low surface to volume ratios occurs in a chain-thermal explosion regime,19 and the warming-up makes up .T = 293..P/P ¡í ¡í 1000¡Æ. Therefore, the set of reactions (I) of a chlorosilylenecatalysed cycle may occur.In a series of experiments, H2 was added into a reactor before Cl2 (Figure 4). It was shown that t in the presence of H2 slightly increases (Figure 4, curve 2).Note that t does not depend on the total pressure in our conditions. SiHCl and SiCl2 do not react with H2,13 the reaction Cl + H2 ¢ç H + Cl2 is chain propagation, and it cannot cause an increase in t. However, the rapid chain termination SiH2 + H2 ¢ç SiH4 (10.13 cm3 s.1, ref. 13) can give rise to an increase in t. It may serve as indirect evidence for SiH2 formation in DCS chlorination.Then, a heat emission can take place in the fast reactions (rate constant of the reaction SiH2 + Cl2 is 1.4¡¿10.10 cm3 s.1, ref. 13): Note that the energy released in (III) is enough to obtain excited SiHCl (A1B1). SiH2 can result from the steps12 SiCl2 + SiH2Cl2 ¢ç ¢ç Cl3SiSiH2Cl* ¢ç SiH2 + SiCl4. The set of reactions (I), (III) and (IV) represents possible steps of DCS chlorination including silylenes as chain carriers and formation of SiHCl (A1B1) and EB.This presumption is still to be refined by the establishment of the composition of reaction products, especially, detection of H2. We are grateful to Professor V. V. Azatyan for many useful discussions. This work was supported by the Russian Foundation for Basic Research (grant no. 00-03-32979a). References 1 E. N. Chesnokov and V. N. Panfilov, Dokl. Akad. Nauk SSSR, 1981, 261, 925 [Dokl. Chem. (Engl. Transl.), 1981, 261, 865]. 2 N. M. Rubtsov, S. M. Temchin, V. I. Chernysh and G. I. Tsvetkov, Kinet. Katal., 1997, 38, 495 [Kinet. Catal. (Engl. Transl.), 1997, 38, 441]. 3 V. V. Azatyan, S. G. Gagarin, V. I. Zakharyin, V. A. Kalkanov and Yu.A. Kolbanovskii, Khim. Fiz., 1983, 2, 201 (in Russian). 4 R. G. Aivazyan and V. V. Azatyan, Khim. Fiz., 1997, 16, 621 [Chem. Phys. Reports (Engl. Transl.), 1997, 16, 599]. 5 I. R. Begishev, O. L. Gromovenko and V. A. Poluektov, Zh. Fiz. Khim., 1994, 68, 1099 (Russ. J. Phys. Chem., 1994, 68, 992). 6 V. V. Azatyan and E. A. Markevich, Kinet. Katal., 1988, 27, 1291 [Kinet. Catal.(Engl. Transl.), 1988, 27, 1191]. 7 V. V. Azatyan, R. R. Borodulin, E. A. Markevich, N. M. Rubtsov and N. N. Semenov, Izv. Akad. Nauk SSSR, Ser. Khim., 1976, 1459 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1976, 25, 1396). 8 N. N. Semenov, O nekotorykh problemakh khimicheskoi kinetiki i reaktsionnoi sposobnosti (On Some Problems of Chemical Kinetics and Reactivity), Akad. Nauk SSSR, Moscow, 1958, p. 685 (in Russian). 9 E. T. Denisov and V. V. Azatyan, Ingibirovanie tsepnykh reaktsii (Inhibition of Chain Reactions), Ross. Akad. Nauk, Chernogolovka, 1997, p. 265 (in Russian). 10 V. V. Azatyan, R. R. Borodulin and N. M. Rubtsov, Fiz. Gorenia Vzryva, 1980, 5, 34 (in Russian). 11 V. I. Vedeneev and A. E. Shilov, in Fizicheskaya khimiya, Sovremennye problemy (Physical Chemistry, Contemporary Problems), Khimiya, Moscow, 1985, p. 7 (in Russian). 12 M. T. Swihart and R. W. Carr, J. Phys. Chem., A, 1998, 102, 1542. 13 I. Safarik, V. Sandhu, E. M. Lown, O. P. Strauss and T. M. Bell, Research Chem. Intermed., 1990, 14, 108. 14 A. V. Parijskaya and V. I. Vedeneev, Kinet. Katal., 1973, 14, 1116 [Kinet. Catal. (Engl. Transl.), 1973, 14, 981]. 15 N. M. Rubtsov, V.V. Azatyan and R. R. Borodulin, Izv. Akad. Nauk SSSR, Ser. Khim., 1980, 1234 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1980, 29, 1165). 16 V. V. Azatyan, Kinet. Katal., 1975, 16, 567 [Kinet. Catal. (Engl. Transl.), 1975, 16, 487]. 17 C. P. Conner and E. W. Stewart, J. Am. Chem. Soc., 1977, 99, 2544. 18 F.-T. Chau, D. C. Wang, E. P. F. Lee, J. M. Dyke and D. K. W. Mok, J. Phys. Chem., A, 1999, 103, 4925. 19 V. V. Azatyan, Kinet. Katal., 1999, 40, 818 [Kinet. Catal. (Engl. Transl.), 1999, 40, 791]. 20 L. V. Gurvich, G. V. Karachentsev and V. N. Kondratiev, Energii razryva khimicheskikh svyazei. Potentsialy ionizatsii (Chemical Bonds Energies. Ionization Potentials), Nauka, Moscow, 1976 (in Russian). 1 2 3 SiHCl SiCl2 P/Torr 2 6 10 10 30 50 t/ms t/s Chemiluminescence Absorbance 6 4 2 4 8 (arb.units) (arb. units) 310 315 320 325 Absorbance SiCl2 A.X 13 12 11 10 9 8 7 6 5 9 8 7 6 5 4 l/nm Intensity 450 460 470 480 490 500 l/nm 013-010 012-010 011-010 010-010 030-000 020-000 010-000 000-000 000-010 SiHCl (A1B1.X1A1) Figure 3 The time dependences of (1) chemiluminescence at 400 nm, (2) absorption at 300 nm and (3) total pressure in the self-ignition of 0.13 kPa Cl2 + 0.13 kPa (DCS + 8% C3H6) and experimental spectra of SiHCl (A1B1.X1A1) and SiCl2 [10 scans, 10 accumulations, 0.20 kPa Cl2 + 0.20 kPa (DCS + 8% C3H6)]. Reactor II. Curve 3 demonstrates the inherent vibrations of a mechanothrone (300 Hz) under the impact of an expanding gas. 10 1 20 n 20 n SiH2 + Cl2 SiHCl + HCl + 363 kJ mol.1 (ref. 20) SiH2 + Cl2 SiH2Cl + Cl + 221 kJ mol.1 (ref. 20) (III) (IV) 10 5 1 2 3 4 5 0 20 40 60 80 100 18000 10 5 10 5 t/s bleeding-up self-ignition pumping out self-ignition DCS-additives bleeding-up DCS-additives self-ignition bleeding-up DCS-additives Absorption at 300 nm (%) Figure 4 The experimental time dependences of Cl2 concentration: (1) 0.20 kPa Cl2 + 0.56 kPa (DCS + 8% C3H6); (2) 0.13 kPa H2 + 0.20 kPa Cl2 + 0.56 kPa (DCS + 8% C3H6); (3) 0.20 kPa Cl2 + 0.20 kPa (DCS + 8% C3H6 + 50% Kr); (4) 0.20 kPa Cl2 + 0.20 kPa (DCS + 8% C3H6 + 50% SF6); (5) 0.20 kPa Cl2 + 0.18 kPa (DCS + 80% SF6). Received: 5th December 2001; Com. 01/1863

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Mendeleev Communications Electronic Version, Issue 1, 2002 1 Isokinetic relationship for nucleophilic substitution reactions with a participating thiosulfate ion in aqueous-organic media: a special reaction mechanism Vladimir E. Bel’skii 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: vos@iopc.kcn.ru 10.1070/MC2002v012n01ABEH001499 For 72 nucleophilic substitution reactions at a saturated carbon atom with the participation of the S2O3 2– anion in aqueous-organic media, an isokinetic relationship with Tiso =1130 K and lgkiso =5.949 was found.For a series reactions, the isokinetic relationship (IKR) reflects a linear relationship between the activation energy Ea and the logarithm of the pre-exponential factor A of the Arrhenius equation.1 A search of IKR and systematization of kinetic data on this basis represent an urgent problem.These IKR, which are applicable to a wide variety of reactions, are very useful. They can be applied to the quantitative prediction of the reactivity of chemical compounds using computer expert systems.2 The existence of an IKR for a series of reactions suggests that they occur by identical mechanisms.3 Therefore, statistically significant deviations from a general IKR for particular reactions indicate that they occur by a special mechanism.Previously, the fulfilment of a general IKR4,5 for nucleophilic substitution reactions at a saturated carbon atom with the participation of anionic nucleophiles N–z (z is the charge of the anion) was established, where X and X– are the leaving group and its anion, respectively: Y is the substituent at a saturated carbon atom.The rate constants k (dm3 mol–1 s–1) of 165 reactions like (1) in protondonor and polar aprotic solvents and their mixtures at various temperatures T were described by a general IKR with the parameters Tiso = 6103K and lg kiso = 10.402.5 It was found that this IKR is applicable to many reactions like (1) in different solvents.The exception is provided by reactions with the participation of the S2O3 2– anion in the mixtures of water with organic solvents. In contrast to reactions (1) with the S2O3 2– anion in water, which exhibit no special behaviour,4 the above reactions are not described by the general IKR.5 In this work, the applicability of IKR to nucleophilic replacement reactions at saturated carbon with the participation of the S2O3 2– anion in mixed solvents is analysed.If an IKR is fulfilled for a series of reactions, the relations lg k = f(1/T) for the members of this series should statistically satisfy the equations of straight lines that pass through an isokinetic point with the coordinates lg kiso, 1/(2.303RTiso)3 According to equation (2), each member of the series has its own isokinetic activation parameters Eiso and lg Aiso = lg kiso + + Eiso/(2.303RTiso).The values of Tiso and lg kiso and the array of Eiso and lg Aiso values for the series of reactions are calculated using the leastsquares method by varying the values of Tiso and lg kiso until the minimum sum S = Ó(lg k – lg k')2 was achieved.Here, lg k' are the logarithms of rate constants calculated for the members of the series by equations (3) The calculations were performed using the ISOKIN program.4 The program made it possible to calculate the values of Eiso and lg Aiso at fixed values of Tiso and lg kiso; this calculation is necessary for testing the applicability of IKR to different kinetic data.In the calculations of IKR, rate constants should be corrected for the statistical factors F,4,5 which take into account the number of identical nucleophilic atoms in anions and the number of identical reaction centres in substrates. In this work, the statistical factor F = 1 was used for the S2O3 2– anion because one negatively charged sulfur atom of the S–S– bond participates in the reaction.6 An analysis of the rate constants of reactions (1) with the participation of the S2O3 2– anion in aqueous-organic mixtures6–10 demonstrated that cannot be described by a general IKR.5 The calculation of Eiso for these reactions using the parameters Tiso, and lg kiso from ref. 5 gives the values of Eiso higher than experimental Ea by 12–17 kJ mol–1. In contrast, the values of lg k for reactions (1) with the S2O3 2– anion in water were described by a general IKR.4 The values of lg k (n = 234) were analysed for 72 nucleophilic substitution reactions at a saturated carbon atom with the participation of the S2O3 2– anion in the mixtures of water with ethanol,6–9 acetone,9,10 dimethyl sulfoxide,10 and dioxane,10 as well as in the mixtures of water (40 vol%) with dimethoxyethane, 9 diglyme9 and butyrolactone.9 The water content of the mixtures was lower than 64 wt%.Substituted benzyl chlorides, alkyl chlorides and alkyl bromides participated in reactions. For each member of a series, the number of k values at different temperatures was no lower than 3, and the temperature range in which they were measured was not narrower than 20 K.The test series was described by an IKR with the parameters Tiso = 1130 K and lg kiso = 5.949 at s = [S/(n – 2)]0.5, which is equal to 0.025. This fact is indicative of the occurrence of a special mechanism for analysed reactions. The quality of the obtained IKR is characterised by a regression between the values of lg k included in the series and the values of lg k' calculated by equation (3) at a minimum S for all members of the series The regression coefficient equal to 1, the absence of a constant from the equation, a low value of s and a high value of r confirm the fulfilment of IKR for reactions (1) with the participation of the S2O3 2– anion in the test aqueous-organic media.As expected, the values of lg k for similar reactions in water4 cannot be described by the found IKR. The following compensation relationship between the parameters Eiso and lg Aiso for the members of a test series was calculated: A similar compensation relationship between Arrhenius parameters (Ea and lg A) for the members of a test series is approximate because the parameters Ea and lg A are characterised by high values of s.The values of lg k for the reactions of substituted benzyl chlorides with the S2O3 2– ion in the water–N-methylacetamide system (60 vol%, permittivity D = 101)9 are adequately described by a general IKR;5 therefore, they are not included in the analysed series. YCH2X + N–z = YCH2N–z + 1 + X–, (1) lg k – lg kiso = –Eiso[(2.303RT)–1 – (2.303RTiso)–1] (2) lg k' = lg Aiso – Eiso(2.303RT)–1 (3) lg k = (1.000±0.002)lg k' + (0.000±0.005) n = 234, s = 0.025, r = 0.9995 Eiso = (21.639±0.003)lg Aiso – (128.731±0.024) n = 72, r = 0.9999, s = 0.007 Ea = (7.69±0.68)lg A – (4.1±6.2) n = 72, r = 0.804, s = 4.6Mendeleev Communications Electronic Version, Issue 1, 2002 2 As mentioned above, the observed values of Ea in these media for the test reactions are lower by 12–17 kJ mol–1 than those estimated by a general IKR.This fact can be explained by the occurrence of a catalytic reaction path. In the water–ethanol (44 wt%) system, sodium thiosulfate forms ion pairs with smaller radii in comparison with ion pairs in water,11 namely, contact ion pairs. Probably, they are also formed in other aqueous-organic media with permittivities lower than that of water, in which solvent-separated ion pairs are formed.11 It should be noted that in the calculation of a general IKR reactions in aqueous-organic media with the participation of singly charged anions, which form solvent-separated ion pairs in these media,12 were included in the test series.5 On this basis, it is possible to assume that the formation of contact ion pairs by sodium thiosulfate in aqueous-organic media with low values of D is promoted by the large charge (–2) of S2O3 2– anions. Probably, the structure of the contact ion pairs of sodium thiosulfate allows the interaction of the cation of an ion pair with the leaving anion to cause the electrophilic catalysis of reactions.The test reactions may occur by two parallel mechanisms.In this connection, it is interesting to note the kinetic data for the reactions with the participation of the S2O3 2– anion in the water– acetonitrile (60 vol%, D = 52.3) system.9 The observed values of Ea for reactions in this system are much higher than Eiso calculated by the IKR for the test series (this system was not included in the calculation of IKR).This system has a high value of D, and solvent-separated ion pairs reacting by the general mechanism can prevail here. The values of Ea for nucleophilic substitution reactions at a saturated carbon atom with the participation of the S2O3 2– anion in aqueous-organic media are reduced. This fact can be explained by the ability of cations in the contact ion pairs of sodium thiosulfate to electrophilic catalysis.It is believed that nucleophilic substitution reactions with the participation of other doubly and multiply charged anions in similar media can occur by analogous mechanisms. This work was supported by the Russian Foundation for Basic Research (grant no. 02-03-32257a). References 1 W.Linert, Chem. Soc. Rev., 1994, 23, 430. 2 H. Sato, Chem. and Chem. Ind., 1999, 52, 146. 3 W. Linert and R. F. Jameson, Chem. Soc. Rev., 1989, 18, 477. 4 V. E. Bel’skii, Izv. Akad. Nauk, Ser. Khim., 2000, 809 (Russ. Chem. Bull., Int. Ed., 2000, 49, 806). 5 V. E. Bel’skii, Izv. Akad. Nauk, Ser. Khim., 2000, 2000 (Russ. Chem. Bull., Int. Ed., 2000, 49, 1968). 6 P. H. Dunbar and L. P. Hammett, J. Am. Chem. Soc., 1950, 72, 109. 7 T. I. Crowell and L. P. Hammett, J. Am. Chem. Soc., 1948, 70, 3444. 8 K. Akagi, S. Oae and M. Murakami, J. Am. Chem. Soc., 1956, 78, 4034. 9 R. Fuchs and A. Nisbet, J. Am. Chem. Soc., 1959, 81, 2371. 10 K. Kalliorinne and E. Tommila, Acta Chem. Scand., 1969, 23, 2567. 11 J. R. Bevan and C. B. Monk, J. Chem. Soc., 1956, 1392. 12 S. Elshazly, M. Grigo and J. Einfeldt, Z. Phys. Chem., 1983, 264, 1041. Received: 12th July 2001; Com. 01/1825

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年代:2002

数据来源: RSC