摘要:

Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Cryochemical synthesis of bimetallic nanoparticles in the silver–lead–methyl acrylate system Boris M. Sergeev,*a Gleb B. Sergeeva and Andrei N. Prusovb a Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. E-mail: gbs@cryo.chem.msu.su b A. N. Belozerskii Institute of Physico-chemical Biology, M.V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 939 3181 Combined condensation of silver, lead and methyl acrylate vapours in a vacuum onto a glass reactor surface cooled by liquid nitrogen followed by melting and heating of the co-condensate results in the formation of organosols consisting of bimetallic particles capable of aggregation; the size of these particles does not exceed 5 nm.Bimetallic nanoparticles with a uniform or lamellar distribution of metals in the bulk attract attention due to their application in catalysis and as model objects in studies of alloy formation.1 Bimetallic nanoparticles are usually obtained by reduction of salts of two metals in solution or by condensation of metal and organic solvent vapours in a vacuum onto a cooled surface.2 The latter technique was also used in this work.The choice of the silver–lead–methyl acrylate system is based on the results of our previous studies3 and on a quantum-chemical estimation of the properties of bimetallic nanoparticles. The binding energies of mixed metal clusters (M1)m(M2)n (m + n £ 4) have been calculated.These values are obtained as the energy differences of the equilibrium structures of clusters and of all possible fragments in their equilibrium geometries. The silver–lead systems are found to be the most stable ones.4 We showed previously3 that combined condensation of methyl acrylate (MA) with silver is accompanied by initiation of methyl acrylate polymerisation by silver.The adsorption of the resulting macromolecules on the surface of the silver nanoparticles provides the high stability of the organosols and the possibility of concentrating them, to the extent of obtaining solid poly(methyl acrylate) films containing several percent of silver. In the present work, we describe the results of cryochemical synthesis of dispersions of Ag/Pb bimetallic particles in methyl acrylate. Vapours of silver and lead were obtained by means of two independent evaporators mounted in a semi-preparative reactor.The concentration of the metals in the organosols was determined by atomic emission spectroscopy with an inductively coupled plasma and by X-ray fluorescent analysis. The Ag/Pb/MA organosols formed by slow (ca. 1 h) heating of low-temperature co-condensates are reddish-brown and are stable for several days in an argon atmosphere.The Pb/MA system studied simultaneously behaves similarly. The methyl acrylate evaporated during the cryosynthesis of Pb/MA and Ag/Pb/MA organosols can be quantitatively removed from them, which indicates the absence of polymerisation under the experimental conditions. Thus, unlike silver, lead does not initiate the polymerisation of methyl acrylate.Moreover, as regards methyl acrylate polymerisation, the system containing both metals behaves as Pb/MA rather than as Ag/MA. In our opinion, such a behaviour is caused either by a non-additive change of nanoparticle properties on transition from binary systems, Pb/MA and Ag/MA, to a ternary system (Ag/Pb/MA), or by efficient inhibition by lead of MA polymerisation initiated by silver atoms.Methyl acrylate is obviously a less efficient stabiliser of nanoparticles than poly(methyl acrylate), which creates on their surface a polymeric shell preventing aggregation. For this reason, lead and lead/silver nanoparticles form aggregates in organosols. This is easily seen in the electron microscopic photographs shown in Figure 1.In both cases, the particle size does not exceed 5 nm, i.e. they are smaller than the diameter of the silver nanoparticles (7–15 nm) obtained previously under similar conditions.3 Figure 2 (curve 1) shows an absorption spectrum of cryochemically synthesised Pb/MA organosol. The spectrum shape is determined by the fact that the maximum of the lead plasmon absorption band is located at ca. 220 nm.5,6 As a result of oxidation of lead particles with air oxygen, organosol absorption in the visible range decreases rapidly, and opalescence appears. The Pb/C2H5OH system behaves similarly.5 The silver plasmon absorption band in the Ag/MA organosol has a maximum at 416–420 nm.3 In the spectrum of the freshly prepared Ag/Pb/MA organosol recorded immediately after it was transferred (in argon atmosphere) from the reactor chamber into a cylindrical ampoule (internal diameter d = 5 mm) and sealed (Figure 2, curve 2) this band is red-shifted (lmax = 438 nm). Figure 1 Microphotographs of nanoparticles in Pb/MA (a) and Ag/Pb/MA (b) organosols. (a) (b) 50 nm 50 nmMendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) When the ampoule was unsealed and the sample exposed to air and placed in a spectrophotometric cell (l = 1 mm) lmax sharply increased to 453 nm (Figure 2, curve 3). During the subsequent 1–1.5 h, lmax gradually approaches 466 nm (Figure 2, curve 4). At the same time, the intensity of the band decreases somewhat, possibly due to oxidation of lead involved in bimetallic particles.The interpretation of the absorption spectra of dispersions of metal colloidal particles is known to be a multifactor problem.7 Taking this into account, it is unlikely that an exhaustive explanation of the spectral changes occurring on transition from the Ag/MA and Pb/MA systems to Ag/Pb/MA can be given at present. On the other hand, the electron microscopic data presented in this work allow us to consider the aggregation of nanoparticles as the main, theoretically substantiated7,8 cause of the red shift (416–420 nm ® 438 nm) in an inert environment.The oxidation of lead with air oxygen can affect the stability of bimetallic nanoparticles. In this case, the long-wave shift of lmax, 438 nm ® 453 nm and 453 nm ® 465 nm (Figure 2, curves 2–3 and 3–4), indicates the development of the aggregation processes and, possibly, a change in the electronic state of the bimetallic particles due to lead oxidation.9 Further studies will make it possible to estimate how the composition of the bimetallic nanoparticles and the structure and properties of the surface layer of an organic ligand affect the optical and chemical properties of cryochemically synthesised nanoparticles and their organosols.The authors are grateful to A. V. Pukhovskii for his help in performing X-ray fluorescent analyses of organosols. The work was partially supported by the Russian Foundation for Basic Research (grant no. 96-03-33970) and INTAS (grant no. 94-4299). References 1 G. Schmid, Chem. Rev., 1992, 92, 1709. 2 K. J. Klabunde, Free Atoms, Clusters and Nanoscale Particles, Academic Press, New York, 1994. 3 B. M. Sergeev, G. B. Sergeev, Y. J. Lee, A. N. Prusov and V. A. Polyakov, Mendeleev Commun., 1997, 151. 4 A. Yu. Ermilov, A. V. Nemukhin and G. B. Sergeev, Izv. Ross. Akad. Nauk, Ser. Fiz., 1998 (in press). 5 K. Kimura and S. Bandow, Bull. Chem. Soc. Jpn., 1983, 56, 3578. 6 A. Henglein, E. Janata and A. Fojtic, J.Phys. Chem., 1992, 96, 4734. 7 Yu. I. Petrov, Klastery i malye chastitsy (Clusters and small particles), Nauka, Moscow, 1986 (in Russian). 8 U. Kreibig, Z. Phys. D. Atoms, Molecules and Clusters, 1986, 3, 239. 9 A. Henglein, A. Holzwarth and E. Janata, Ber. Bunsenges. Phys. Chem., 1993, 97, 1429. Figure 2 Absorption spectra of cryochemically synthesised organosols: 1, Pb/MA (recorded immediately after completion of the co-condensate melting and its transfer into a 1 mm spectrophotometric cell in air); 2, Ag/Pb/MA (sample in a sealed cylindrical ampoule, internal diameter 5 mm, in an argon atmosphere); 3–4, the same as 2 immediately after unsealing the ampoule in air and pouring the sample into a 1 mm spectrophotometric cell (curve 3) and 1–1.5 h later (curve 4). Metal content (mg ml–1): 1.12 lead in Pb/MA; 0.14 lead in Ag/Pb/MA; 0.09 silver in Ag/Pb/MA. 0.5 0.4 0.3 0.2 0.1 0.0 300 400 500 600 700 800 900 2.0 1.5 1.0 0.5 0.0 Absorption l/nm l2 max = 438 nm l3 max = 453 nm l4 max = 466 nm 1 2 3 4 Absorption Received: Moscow, 26th November 1997 Cambridge, 15th December 1997; Com. 7/08944I

ISSN:0959-9436     

出版商:RSC    

年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Photochemical reactions of dimethyl ether radical cations in freon matrices and SF6 at 77 K Michail Ya. Mel’nikov,* Dmitrii V. Baskakov, Irina A. Baranova, Vladilen N. Belevskii and Ol’ga L. Mel’nikova Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 939 1814; e-mail: melnikov@melnik.chem.msu.su It has been shown for the first time that under the action of light within the absorption band of dimethyl ether radical cations in freon matrices [lmax @ 436 nm, emax @ (2.5±0.5)×103 M–1 cm–1], the radical cations decay due to charge transfer to freon molecules, whereas in an SF6 matrix they undergo deprotonation with quantum yields F@(4–15)×10–2 and F@(2–6)×10–4, respectively, at 77 K.Radical cations are among the most important intermediates in many photochemical, radiation and oxidation processes. However, scant data are available on the reactivity of electronically excited radical cations.1 Recently, the quantum yields of phototransformations of some radical cations in various freon matrices were determined2–5 and the previously stated opinion on the significance of charge transfer processes from organic radical cations to freon molecules6 was confirmed.The SF6 matrix was used previously, e.g. for the stabilisation of some radical cations,7 but the phototransformations in this matrix have not been studied. However, the large difference between the ionisation potentials of SF6 and those of the majority of organic compounds (D � 5 eV) permits studies of the phototransformations of radical cations to be carried out in this matrix in the absence of charge transfer to matrix molecules.The purpose of this study was to obtain data on the mechanism and efficiency of dimethyl ether (DME) radical cations stabilised in freon and SF6 matrices at 77 K. In the experiments, DME solutions (0.1–0.5 vol.%) in a freon mixture containing 1:1, v/v, of CFCl3 (freon-11) and CF2BrCF2Br (freon-114B2), whose glass transition temperature is 77 K, as well as in freon-11 (0.5 vol.%), freon-114B2 (0.5 vol.%) and SF6 (0.02–4 vol.%) were evacuated to 10–4 Torr and irradiated with X-rays (E = 50 kV); the total absorbed dose was 0.5–2.0 kGr.EPR and optical absorption spectra of the intermediates formed were recorded on an E-3 Varian radiofrequency spectrometer and a Specord M-40 spectrophotometer (optical path 0.3 cm) using the same samples.The absolute error in the determination of the concentration of paramagnetic centres by EPR under the conditions used did not exceed ±20%. A high-pressure mercury lamp with a narrow-band glass filter (l = 436 nm, Dn1/2 @ 3000 cm–1) was used as the light source.The absolute intensity of light was determined by ferric oxalate actinometry (l = 436 nm); the light intensity was 1.6×10–4 einstein cm–3 s–1. The volume of each sample was 0.08–0.13 cm3. Since all of the matrices used in our experiments, except freon mixture, were polycrystalline, we used the monomolecular photochemical reaction of di-p-cresylnitroxyl (DCN), which was carried out in 10–4 M solutions in the same matrices, as a special standard for the evaluation of the effective optical path in these matrices.Assuming that the quantum yields of DCN phototransformation in various frozen freons and SF6 are nearly the same, we found that the effective optical path in various polycrystalline matrices is 1.5–4.0 times longer than that in glassy samples.The data obtained were in good agreement with the previous estimates3 made using the photochemical reaction of diphenyldiazomethane as the standard. The extinction coefficients and the quantum yields reported in the present study were obtained in 4 to 6 successive experiments; the error values are given for a confidence limit of 0.95.Upon exposure of DME solutions in individual freons and in their mixtures to X-ray irradiation at 77 K, their EPR spectra displayed a characteristic signal due to DME radical cations [a(6H) ª 43.0 G],9 which had the best resolution in freon-11. In freon-11 and freon-114B2, the DME radical cations account for 80% of the overall concentration of paramagnetic centres produced by irradiation.In the optical absorption spectra, the irradiation of DME solutions in freon mixtures at 77 K results in the appearance of absorption bands with lmax @ 370 and 590 nm, which can be assigned to radical cations of freons,8 and an absorption band with lmax @ 435 nm. The EPR spectra of irradiated DME solutions in freon mixtures contain a signal due to the DME radical cations and an overlapping signal which appears upon irradiation of pure freon mixture.The intensities of both absorption and EPR spectra of freon radical cations and radicals were comparable to those of DME radical cations. Because in this case the most high-field components of the EPR spectrum of DME radical cations were not distorted by any other overlapping signals, the determination of the concentration of radical cations was carried out using the shape factor of these components obtained in irradiated solutions in freon-114B2 (the shape of the EPR spectrum lines of DME radical cations is most similar to that observed for freon mixtures).When irradiated solutions of DME in freon mixtures are exposed to light with l = 436 nm, changes in intensity of the (a) (b) (c) 50 G Figure 1 EPR spectra of irradiated solutions of DME in freon-11 (a) and SF6 (0.02 vol.%) (b), (c), before (a), (b) and after the action of light with l = 436 nm, at 77 K.aThe proportion of radical cation with a relatively high reactivity F1. Table 1 Quantum yields of photochemical reactions of DME radical cations in freon-11, freon-114B2 and SF6 at 77 K. Matrix F1 F2 ba Freon-11 0.15±0.03 0.06±0.01 0.4±0.1 Freon-114B2 0.04±0.01 — — SF6 (6.1±0.4)×10–4 (3.4±0.4)×10–4 0.3±0.05Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) absorption band with lmax @ 435 nm correlate with changes in the concentration of DME radical cations determined by EPR. This allowed us to assign this absorption band to DME radical cations and to determine their extinction coefficient [emax @ (2.5±0.5)×103 M–1 cm–1] and the oscillator strength in the corresponding electron transition (f ª 0.07) (Figure 2).In all freon matrices used, the action of light with l = 436 nm at 77 K results in the decay of DME radical cations without the formation of any paramagnetic particles. This process has the same spectral dependence as the absorption spectrum of DME radical cations.Since the energy of a photon with l = 436 nm is higher than the difference between the ionisation potentials of freons and DME, it is natural to relate the changes observed to the photo-induced charge transfer from DME radical cations to matrix molecules. The dependence of the photo-induced decay kinetics of DME radical cations in a freon-11 matrix on the absorbed light dose has a bimodal shape, as in the cases reported previously;2,4,5 this may suggest a kinetic nonequivalence of reacting particles in the solid phase (Table 1).To eliminate the possibility of charge transfer to matrix molecules, we studied the photo-transformation of DME radical cations in an SF6 matrix. The EPR spectrum of irradiated solutions of DME in SF6 at 77 K displays a superposition of a well resolved signal of DME radical cations [a(6H) ª 43.0 G] and a signal due to ·CH2OCH3 radicals [a(2H) ª 18.0 G] [Figure 2(b)].† Computer simulation of experimental EPR spectra shows that a 200-fold increase in the concentration of DME in SF6 results in an increase in the relative yield of neutral radicals from just 0.4 to 0.6.This implies that at the concentration of DME in SF6 used for photochemical experiments (0.02 vol.%), the accumulation of ·CH2OCH3 radicals under X-ray irradiation is due to the decomposition of the DME radicacations which have not undergone relaxation, rather than to ion-molecular reactions in associates.The action of light with l = 436 nm on irradiated DME solutions (0.02 vol.%) results in a decrease in intensity of the EPR signal of radical cations and a synchronous increase in the signal of ·CH2OCH3 radicals, while the total concentration of paramagnetic particles remains unchanged [Figure 1(c)].The dependence of the photo-transformation kinetics of DME radical cations in SF6 on the absorbed light dose also has a bimodal shape (Table 1). The quantitative conversion of DME radical cations to ·CH2OCH3 radicals under the action of light could be interpreted with reasonable reliability as a result of photo-induced deprotonation of DME radical cations: † At high amplifications, the EPR spectra of irradiated Me2O solutions at 77 K display components of the SF6 – radical spectrum;10 on increasing the temperature of the samples to 135 K, the individual spectrum of SF5 · radicals is observed.11 The small quantum yield of this process explains why we were unable to detect it in freon matrices where it cannot compete with the highly efficient charge transfer to matrix molecules.Along with the conversion of DME radical cations, we observe that the intensity of the EPR signal assigned to SF6 – changes. We assume that these changes may be due to the reaction: Unfortunately, the wide extent of the EPR spectrum of SF6 – prevents us from making a quantitative comparison of DME and SF6 radical cations.It is important to note that the action of light with l = 436 nm on irradiated, pure SF6 does not cause such changes in the EPR spectra. The study was carried out with financial support from the Russian Foundation for Basic Research (RFBR) (grant no. 95-03-08110) and RFBR–INTAS (grant no. 95-0008). References 1 T. Bally, in Radical Ionic Systems, eds. A. Lund and M. Shiotani, Kluwer Academic Publishers, Dordrecht, 1991, p. 3. 2 M. Ya. Mel’nikov, E. N. Seropegina, V. N. Belevskii, S. I. Belopushkin and D. V. Baskakov, Mendeleev Commun., 1996, 183. 3 M. Ya. Mel’nikov, E. N. Seropegina, V.N. Belevskii, S. I. Belopushkin and O. L. Mel’nikova, Khim. Vys. Energ., 1997, 31, 281 [High Energy Chem. (Engl. Transl.), 1997, 31, 250]. 4 M. Ya.Mel’nikov, V. N. Belevskii, S. I. Belopushkin and O. L. Mel’nikova, Izv. Akad. Nauk, Ser. Khim., 1997, 1302 (Russ. Chem. Bull., 1997, 46, 1245). 5 M. Ya.Mel’nikov, O. L.Mel’nikova, V. N. Belevskii and S. I. Belopushkin, Khim. Vys. Energ., 1998, 32, 57 [High Energy Chem. (Engl. Transl.), 1998, 32, in press]. 6 N. Shida and Y. Takemura, Radiat. Phys. Chem., 1983, 21, 157. 7 K. Toriyama, K. Nunome and M. Iwasaki, J. Chem. Phys., 1982, 77, 5891. 8 R. Mehnert, in Radical Ionic Systems, eds. A. Lund and M. Shiotani, Kluwer Academic Publishers, Dordrecht, 1991, p. 231. 9 M. S. R. Symons and B. W. Wren, J. Chem. Soc., Perkin Trans. 2, 1984, 511. 10 R. W. Fessenden and R. H. Schuler, J. Chem. Phys., 1966, 45, 1845. 11 A. Hasegawa and F. Williams, Chem. Phys. Lett., 1977, 45, 275. 2500 2000 1500 1000 500 0 375 400 425 450 475 500 525 l/nm e/M–1 cm–1 Figure 2 Absorption spectrum of DME radical cations in irradiated solutions of DME (0.4 vol.%) in freon mixtures at 77 K. CH3OCH3 +· ·CH2OCH3 + H+ H+ + SF6 – HF + SF5 Received: Moscow, 23rd September 1997 Cambridge, 21st November 1997; Com. 7/07578B

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出版商:RSC    

年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Filament-like structure formation in vacuum thermally evaporated thin films of polyaniline during oxidation in nitric acid Victor F. Ivanov,* Oksana L. Gribkova, Aleksandr A. Nekrasov and Anatolii V. Vannikov A. N. Frumkin Institute of Electrochemistry, Russian Academy of Sciences, 117071 Moscow, Russian Federation. Fax: + 7 095 952 0846; e-mail: vanlab@glas.apc.org Oxidation of vacuum thermally evaporated thin films of polyaniline by aqueous nitric acid results in autocatalytic formation of filament-like heterogeneous dissipative structures in the oxidized areas due to non-equlibrium reactions between the reduced form of polyaniline and the oxidant.Thin films produced by vacuum thermal evaporation of polyaniline (PAN) comprise a structure whose degree of oxidation is several times less than that in the initial form (ca. 50%).1 Hydrolysis of imine fragments of the polymer chain by means of their interaction with strongly bonded water is the most probable cause of this.1 Considering the whole range of characteristics, the evaporated layers deposited in this way differ dramatically from native emeraldine.2 This is due to both differences in the degree of oxidation and changes in intermolecular organization.In regeneration processes of the evaporated PAN films (for example, during acid–base cyclic treatment in air), restoration of the initial degree of oxidation and initial three-dimensional intermolecular structure take place.2–4 In the present study we have studied the process of regeneration of vacuum thermally evaporated PAN thin films (0.3–0.5 mm) on glass substrates with and without a transparent conducting SnO2 layer (surface electrical resistivity ca. 20 Ohm/ ), using aqueous solutions of nitric acid. The vacuum deposited layers were prepared according to the method described in refs. 3 and 4. For the solution preparation nitric acid of ‘chemically pure’ grade and distilled water were used.Treatment of the vacuum deposited layers in 3.3 M aqueous nitric acid was carried out at room temperature after less than one day of storage in a vacuum. During this treatment the changes shown in Figure 1(a)–(e) were observed. Immediately upon contact of the layer with aqueous nitric acid protonation of the PAN occurs extensively [Figure 1(a)].The higher optical density in the central areas is due to the greater thickness of the film there. Further changes observed are due primarily to the oxidation process and filament-like structure formation in the film [Figure 1(b)–(d)]. Our earlier spectral investigations5 showed that colour formation in this system occurs due to the intense growth of a wide absorption band with a maximum at l ca. 800 nm, which is assigned to delocalized polarons.6 Microscopic examination of the film surface at a hundred-fold magnification in non-polarized light makes it possible to draw conclusions about the rather high homogeneity of the deposited evaporated layer. One may therefore expect the oxidation process to proceed uniformly on the whole area of the film.However, as can be seen in Figure 1(b)–(d), this is not the case. It should be noted that the uncoloured areas in the vacuum deposited layer are composed of non-oxidized species and the coloured of oxidized ones. Hence, the oxidation process proceeds at different rates in different areas of the film. It is interesting that major, confined areas of oxidation are formed in the early stages, and that the further course of the oxidation process is accompanied by preferential expansion of these oxidized areas.This expansion of the oxidized areas evidently has a fractal character. It should be noted that according to the results of Aoki and coworkers,7 the oxidation front in a conventional PAN film during electrochemical oxidation also has a fractal character.The results presented here testify to the fact that PAN oxidation is an autocatalytic process. Centres of oxidation formed in the early stages of the process initiate further oxidation in the adjacent areas. The whole film area gradually becomes involved in this process [Figure 1(e)]. However, some peculiarities of the process are still not clearly understood. In particular, it is not clear why generation of the oxidized areas proceeds preferentially in the early stage, after which their expansion primarily occurs.This process resembles well-known phase transition processes such as crystallization, condensation, etc.8 As distinct from these phase transitions, in our case the nuclei form filament-like structures. Such a character of the structure formation in PAN during its oxidation is possibly due to the existence of crystallites in the vacuum deposited layer, and the oxidation process is primarily initiated in boundary areas between the crystallites. These phenomena are obviously very interesting, because here we can observe visually for the first time the process of heterogeneous structure formation from an initially homogeneous one, which is essential for reduced PAN.It is generally accepted that it is the heterogeneous structure that is typical, according to the results of various investigation methods, for both PAN and other conducting polymers. The character of this heterogeneity may Figure 1 Vacuum evaporated PAN film deposited onto a glass substrate during treatment with aqueous nitric acid; time/s: (a) 120, (b) 170, (c) 190, (d) 230, (e) 1510.(a) (b) (c) (d) (e)Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) be due, in particular, to the low value of the percolation threshold for PAN. The results presented apparently testify to the fact that formation of a heterogeneous structure on a macroscopic scale of non-homogeneity is thermodynamically approved under certain non-equilibrium conditions.9 At the same time, one should account for the fact that, as we have found, if the vacuum evaporated film is deposited onto a transparent conducting substrate, the structural heterogeneities of the above-mentioned scale are not observed under the same oxidation conditions.This is evidently due to a levelling of the electrochemical potential in the PAN layer because of the presence of a conducting SnO2 layer which participates in the process of electron exchange with PAN.It is possible that the scale of the heterogeneities is essentially less in the latter case and can only be observed by using more sophisticated technical devices. This work was accomplished with financial support from the Russian Foundation for Basic Research (grants no. 96-15-97320 and 96-03-34315). The authors are thankful to S. G. Titov for his valuable help in carrying out this study. References 1 V. F. Ivanov, I. V. Gontar’, A. A. Nekrasov, O. L. Gribkova and A. V. Vannikov, Zh. Fiz. Khim., 1997, 71, 133 (Russ. J. Phys. Chem., 1997, 71, 125). 2 V. F. Ivanov, A. A. Nekrasov, O. L. Gribkova and A. V. Vannikov, Electrochim. Acta, 1996, 41, 1811. 3 A. A. Nekrasov, V. F. Ivanov, O. L. Gribkova and A. V. Vannikov, Synth. Met., 1994, 65, 71. 4 V. F. Ivanov, A. A. Nekrasov, O. L. Gribkova and A. V. Vannikov, Abstracts of the International Conference on Science and Technology of Synthetic Metals (ICSM’94), Seoul, Korea, 1994, p. 337. 5 A. A. Nekrasov, V. F. Ivanov, O. L. Gribkova and A. V. Vannikov, Abstracts of the Joint International Meeting of the Electrochemical Society and the International Society of Electrochemistry, Paris, France, 1997, p. 1472. 6 D. E. Stilwell and S.-M. Park, J. Electrochem. Soc., 1989, 136, 427. 7 K. Aoki and Y. Teragishi, Abstracts of the Joint International Meeting of the Electrochemical Society and the International Society of Electrochemistry, Paris, France, 1997, p. 1447. 8 H. E. Stanley, Introduction to Phase Transitions and Critical Phenomena, Clarendon Press, Oxford, 1971. 9 G. Nicolis and I. Prigogine, Self-organization in Non-equilibrium Systems, John Wiley, New York, 1977. Received: Moscow, 28th October 1997 Cambridge, 9th December 1997; Com. 7/07979F

ISSN:0959-9436     

出版商:RSC    

年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Photoacoustic detection of the spinodal decay of carbon Sergei I. Kudryashov,* Alexander A. Karabutov and Nikita B. Zorov Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 431 3063; e-mail: serg@laser.chem.msu.su The equivalence of the amplitudes of the thermoacoustic pressure and recoil pressure in a graphite surface layer laser vaporised during an irradiation pulse corresponds to reaching the critical point of carbon.Transition into the critical state has been considered in optothermodynamics since the early 1970s within the context of the problem of strong heating and compression of compounds under the action of laser irradiation; this problem had been defined and studied in the area of inertial laser thermonuclear synthesis.1 A transition of this type has been realised experimentally for readily boiling liquids (methanol, ethanol) heated with laser irradiation of millisecond duration; the instant at which the critical state was reached was detected by the effect of liquid opalescence in the critical state2,3 observed with resolution on the laser pulse time scale.Calculation of the energy deposited and photoacoustic pressure measurements at the instant of reaching the critical point made it possible to estimate the pressure of the substance in the critical state and the enthalpy of its formation. However, the necessity of using high-power and shorter irradiation pulses for heating, melting and evaporation of the compounds, the locality of heating and the opaqueness of the most of materials studied creates a real problem in studies of solids when the observation of the critical state is made by optical or photoacoustic methods; thus far, this problem has not been solved.In the present work, we studied the evaporation of polycrystalline graphite (PCG) by simultaneous photoacoustic monitoring of both components of the acoustic signal [thermoacoustic and evaporative (recoil) pressure].The resolution of these components, which is impossible in real time due to diffraction and dissipation of the high-frequency component of the Fourier spectrum of the acoustic signal in the lamellar structure of graphite, was achieved by suppressing the thermoacoustic wave of rarefaction (formed upon reflection of the thermoacoustic wave of compression from the free surface of the target) by the recoil pressure wave of compression.The photoacoustic study was performed on a set-up4 that enabled measurement of the mean crater depth during a pulse (X) as well as the thermoacoustic and recoil pressures. A portion of irradiation of the second harmonics of a pulse Nd:YAG laser [pulse energy 5 mJ in the TEM00 mode (stability 6%), pulse length (FWHM) 25 ns, pulse repetition rate 12.5 Hz] was fed to a photodiode and a pyroelectric in order to synchronise the system of recording and control of laser irradiation energy at each pulse.After reducing the main irradiation to a required magnitude and focusing, it was directed to a target normally to the surface. Absorption of irradiation in the graphite target created a surface source of ultrasonic waves, which were recorded at the rear side of the target in the idle mode by means of a ‘thick’ piezoelectric sensor and an oscilloscope.According to the optothermodynamics theory,5 during the evaporation of a material under the action of laser irradiation of nanosecond duration, there exists thermal equilibrium on the surface due to compensation of the flux of irradiation energy onto the surface from the environment by a reverse flux of energy transferred by the material removed by the thermal mechanism.However, equilibrium of mass transfer and mechanical equilibrium on the surface does not exist, since mass transfer is unidirectional.In this case, the first compression wave of the material, which corresponds to the thermoacoustic pressure Pta, is created by a change in the internal pressure of the condensed phase due to changes of its density and temperature and is accompanied by a rarefaction wave appearing upon reflection of the compression wave from the free surface of the target. The Figure 1 Shape of the acoustic signal: (1) synchronisation pulse; (2) thermoacoustic pulse of compression; (3) thermoacoustic pulse of rarefaction; (4) evaporation pulse of compression.(1) (2) (3) (4) 100 10 0.1 1 80 70 60 50 40 30 power density/GW cm–2 thermoacoustic and recoil pressure (a.u.) normalised themoacoustic and recoil pressure (a.u.) 0.1 1 power density/GW cm–2 Figure 2 (a) Dependences of Pta(I0) and Prec(I0) (light and dark squares) for PCG.(b) Dependences of normalised values Pta /I0 and Prec /I0. (a) (b)Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) experimentally recorded bipolar pulse of thermoacoustic pressure in the liquid corresponds to the existence of both waves upon laser generation of sound on a free surface (Figure 1) and is described for a thermally ‘thick’ absorbing layer by the following expression:6 where Vvib is the vibrational velocity; rl and Cl are the liquid density and sound speed for the liquid; a is the coefficient of optical absorption; b and Cp are coefficients of thermal expansion and isobaric specific heat of liquid carbon; A(Y) is the absorbance of a melted film at a given thickness Y; I0 is the amplitude of normal distribution of laser power density over the surface; and df/dt is the derivative of the time profile of a laser pulse (in our case, a Gaussian shape).In turn, the gasodynamic recoil pressure of products of target evaporation in a near-surface Knudsen layer, Prec, creates a compression wave on the target surface (Figure 1), whose pressure equals one half of the saturated vapour pressure under static evaporation conditions at the same instantaneous surface temperature5 where Vvap and rvap are the velocity and the density of the vapour; rs is the density of the graphite target; and the movement rate of the evaporation frontier in it, Vevap, equals7 where DevapH(P, T) is the heat of evaporation, and Ptr and Ttr are parameters of the triple point of carbon.In qualitative respects, the above expressions describe well the linear behaviour of experimental dependences X(I0), Pta(I0) and Prec(I0) in the region from 0.15 to 0.3 GW cm–2 (Figures 2,3) corresponding to the subcritical region of the carbon evaporation curve.7 At power density I0 > 0.3GWcm–2, an abrupt increase in efficiency of acoustic generation by the thermoacoustic and evaporation mechanisms is observed, while the recoil pressure increases considerably faster and becomes the same as the thermoacoustic pressure at 0.3–0.4 GW cm–2 (Figure 2), completely suppressing the thermoacoustic rarefaction wave.Previously, an analogous effect has been observed in low temperature boiling liquids8 and has been related to surface optical breakdown. We relate this fact to the following: at a certain moment during a laser pulse whose maximum power density is within 0.3–0.4 GW cm–2, the thermodynamic state of the carbon melt surface layer becomes unstable at the intersecting spinodal curve of carbon.The latter implies hydrodynamic expansion of material of the target into the environment instead of its evaporation.Therefore in this case thermoacoustic compression pressure is the stagnation internal pressure of the carbon melt before expansion and recoil pressure is the gasodynamic external pressure during expansion. Their amplitudes under these conditions become equal in accordance with the known Bernoulli equation. The non-linear increase in the velocity of movement of the evaporation frontier above 0.3 GW cm–2 observed for experimentally measured parameters of crater depth (X) and recoil pressure of destruction products Prec (Figures 2,3) correlates with the formation and spinodal decay of the labile state of carbon, and it can thus be explained by the abrupt decrease in the thermal effect of removal of target material in the vicinity of the spinodal curve on the state diagram.Thus, the new photoacoustic technique for identifying the spinodal decay of carbon upon laser evaporation of graphite based on Pta /Prec, as suggested in this paper, makes it possible to study near-critical phenomena for refractory and opaque materials upon local laser heating of the target. The authors are grateful to the Russian Foundation for Basic Research (grant no. 96-03-33324) for financial support. References 1 F. V. Bunkin and M. I. Tribelskii, Usp. Fiz. Nauk, 1980, 130, 193 (Sov. Phys. Usp., 1980, 23, 105). 2 F. V. Bunkin, V. M. Podgaetskii and M. I. Tribel’skii, Zh. Eksperim. Teor. Fiz., 1978, 75, 2309 (in Russian). 3 F. V. Bunkin, V. M. Podgaetskii, M. I. Tribel’skii and L. S. Mel’nikov, PZhTF, 1979, 5, 521 (in Russian). 4 S. I. Kudryashov, N. B. Zorov, A. A. Karabutov, S. V. Kuznetsov and Yu. Ya. Kuzyakov, Izv. Ross. Akad. Nauk, Ser. Fiz., 1996, 3, 5 (in Russian). 5 S. I. Anisimov, A. Ya. Imas, G. S. Romanov and Yu. V. Khodyko, Deistvie izlucheniya bol’shoi moshchnosti na metally (Effect of Highpower Radiation on Metals), Nauka, Moscow, 1970 (in Russian). 6 V. E. Gusev and A. A. Karabutov, Lazernaya Optoakustika (Laser Photoacoustics), Nauka, Moscow, 1991 (in Russian). 7 S. I. Kudryashov, A. A. Karabutov, V. I. Emel’yanov, M. A. Kudryashova, R. D. Voronina and N. B. Zorov, Mendeleev Commun., 1998, 27. 8 F. V. Bunkin, K. L. Vodop’yanov, L. A. Kulevskii and G. A. Lyakhov, Izv. Akad. Nauk SSSR, Ser. Fiz., 1985, 49, 558 (in Russian). 9 Dzh.Redi, Deistvie lazernogo izlucheniya bol’shoi moshchnosti (Effect of High-power Laser Irradiation), Nauka, Moscow, 1974 (in Russian). Pta(t) = rlClVvib(t) = I0 A(Y)b aCp df dt (1) Figure 3 Dependence of mean crater depth per irradiation pulse, X(I0) for PCG. crater depth/mm power density/GW cm–2 0.8 0.6 0.4 0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Prec(t) = rvap(t)[Vvap(t)]2 = rsVevap(t)Vvap(t) = 0.5Psat[T(t)] (2) Vevap(t) @ A(Y)I(t)Vm DevapH(p, T) + DH(Ptr, Ttr ® P, T) (3), Received: Moscow, 6th November 1997 Cambridge, 15th December 1997; Com. 7/08309B

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年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Lipase-mediated stereodivergent synthesis of both enantiomers of 4-(2,6-dimethylheptyl)benzoic acid Galina D. Gamalevich,a Edward P. Serebryakov*a and Alexei L. Vlasyukb a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328 b The Higher Chemical College, Russian Academy of Sciences, 125820 Moscow, Russian Federation (S)- and (R)-Enantiomers of methyl 4-(3-hydroxy-2-methylpropyl)benzoate, obtained by enzymatic kinetic resolution of the related racemic arene(tricarbonyl)chromium complex in the vinyl acetate–PPL/Et2O acylating system, have been converted in four steps into the (R)- and (S)-enantiomers of the title acid, respectively. Racemic 4-(2,6-dimethylheptyl)benzoic acid, (RS)-1 is known to effectively control the level of serum cholesterol in vivo,1 to inhibit accumulation of intracellular cholesterol in the culture of sclerotized human aortic cells2 and to activate cholesterol esterase in vitro.3 Hence, it appears to be a promising drug for the treatment of hypercholesterolemia and atherosclerosis.However, the biomedical properties of its enantiomeric components, (R)-1 and (S)-1 have not been so far reported, since the latter have remained unknown themselves. With a view to obtaining the hitherto unrecorded acids (R)-1 and (S)-1 we designed a stereodivergent scheme for their synthesis from a common precursor, enal 2 (see ref. 4), involving the stage of enzymatic kinetic resolution of the racemic alcohol (RS)-3 (see refs. 5 and 6) with the aid of porcine pancreatic lipase (PPL). Since neither partial enzymatic hydrolysis of the corresponding racemic acetate6 nor partial acylation of (RS)-3 using the vinyl acetate–PPL/Et2O system7 afforded the required products of high enantiomeric purity, we resorted to a hitherto unemployed device of sharply changing the size and polarity of the substrate upon its transformation into the respective arene(tricarbonyl)- chromium complex, (RS)-4 (see ref. 7). Partial acylation of racemic metal complex (RS)-4 using the vinyl acetate–PPL/Et2O system (20 °C, 47–51% conversion)† followed by column chromatography on SiO2 [hexane–Et2O (1:1) ® Et2O] afforded optically active acetate (S)-4a and alcohol (R)-4 in ca. 100% and 70% yield, respectively. Their decomplexing with an equimolar amount of I2 in THF (20 °C, 2.5 h) resulted in quantitative recovery of acetate (S)-3a and alcohol (R)-3, isolated as colourless oils with [a]D 20 +7.28° (CHCl3) and [a]D 20 +9.25° (CHCl3), respectively. By means of the Zempleén deacylation acetate (S)-3a was converted into a specimen of alcohol (S)-3 with [a]D 20 –9.80° (CHCl3). From the values of [a]D for alcohols (R)-3 and (S)-3 it followed that their enantiomeric purity was 89.5% and 96%, respectively.This seems to be a fair compromise between a short-path, good-yield approach to alcohols (R)-3 and (S)-3, on the one hand, and high values of ee sufficient to serve the purpose, on the other. Originally, it appeared that the safest route from alcohols (R)-3 and (S)-3 to acids (S)-1 and (R)-1 would be to transform the former successively into the corresponding tosylates, iodides and triphenylphosphonium salts, and then to extend the side chain by employing either organocopper reagents or Wittig olefination, either of which would proceed without affecting the stereogenic carbon atom in the chiral reactant.Unfortunately, the trial experiments, carried out starting from racemic alcohol (RS)-3, showed that neither the tosylate (RS)-5 nor iodide (RS)-6 gave satisfactory yields of the ester (RS)-1 upon interaction with various organocopper reagents derived from Me2CHCH2CH2Br. In all variants one observed the formation † Porcine pancreatic lipase used in this work (14.7 U mg–1) was purchased from ‘Serva’, Germany.Previously,6 the specimens of alcohols (R)-3 and (S)-3 with ca. 100% ee [as shown by the 1H and 19F NMR spectra of the (S)-MTPA esters of (R)-3 and (S)-3], were obtained by enzymatic hydrolysis of acetate (RS)-4a with 70% and 30% conversion, [a]D 20 +10.4° and –10.33°, respectively (both in CHCl3). of alternative products and recovery of the racemic substrate.‡ Attempts to obtain the olefinic ester (RS)-8 by successively treating racemic phosphonium salt (RS)-7 with base and 3-methylbutanal proved equally fruitless (Scheme 2).Swern oxidation of alcohol (RS)-3 turned out to be the best method among several tried for obtaining aldehyde (RS)-9 (95% yield). This aldehyde was immediately made to react with the phosphorane generated from 3-methylbut-2-enyl(triphenyl)- phosphonium chloride (MBTPC) by treating its suspension in THF with a 0.6 M solution of BunLi in hexane (–70 °C, 2 h, then 16 h at ~20 °C); the resulting diene ester (RS)-10 was isolated in 76% yield.The latter was hydrogenated over Pd/C to give the required ester (RS)-1a (84.5% yield). Its saponification ‡ A detailed account of this part of the work will be given in a subsequent communication.3 O CO2Me i (ref. 6) HO CO2Me ii HO CO2Me iii (C = 47–51%) Cr(CO)3 HO CO2Me Cr(CO)3 AcO CO2Me Cr(CO)3 AcO CO2Me HO CO2Me HO CO2Me iv v iv 2 (RS)-3 (RS)-4 (R)-4 (S)-4a (S)-3a (S)-3 96% ee (R)-3 89.5% ee Scheme 1 Reagents and conditions: i, H2–Ni/PriOH, 95 °C, 80 atm H2, 3 h (93%); ii, Cr(CO)6/Bu2O–THF (1:1, v/v), ca. 125 °C (Ar), 64 h (93%); iii, CH2=CHOAc–PPL/Et2O, room temperature, ~18 h [70% for (R)-4, ~100% for (S)-4a]; iv, I2 (1 equiv.)/THF, room temperature, 2.5 h (ca. 100%); v, NaOMe/MeOH, room temperature, 40 min (ca. 100%).Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) in aqueous MeOH (ca. 65 °C, 8 h) afforded in 90% yield the racemic acid (RS)-1 with mp 73–74 °C (from MeOH–H2O). Synthesis of the target acids (R)-1 and (S)-1 followed the same protocol, the only difference being that, in order to prevent the racemization of the stereogenic centre in aldehydes (R)-9 and (S)-9, the Wittig olefination was carried out using a small excess of MBTPC (1.2 equiv.) with respect to the aldehyde (1.0 equiv.) and BunLi (1 equiv.) and the contact of the aldehyde with the phosphorane at –70 °C was extended to 3–5 h.Under these conditions the yield of dienes (S)-10 and (R)-10 remained preparatively attractive (64–71%). The yields of acids (S)-1 and (R)-1 over four steps were 50.9% and 54.9%, based on alcohols (R)-3 and (S)-3, respectively. Accounting for ca. 50% conversion of racemic alcohol (RS)-4 at the partial acylation stage and the yields of compounds (S)-4a and (R)-4 thereof, the overall yields of acids (R)-1 and (S)-1 from the readily accessible enal 2 are within 12.5–14%.§ We are grateful to Dr.A. V. Ignatenko (N. D. Zelinsky Institute of Organic Chemistry, Moscow) for valuable assistance. This work was supported by the Russian Foundation for Basic Research (grant no. 96-03-33396) and the National Scientific & Technological Research Program ‘New methods of bioengineering: Engineering enzymology’ (grant no. 3-110). References 1 K. Nakamoto, T. Suzuki, S. Abe, K. Hayashi, A. Kajivara, I. Yamatsu, I. Otsuka and H. Shiojiri, Eur. Pat. Appl., EP 194693 (1986). 2 G. V. Kryshtal, G. M. Zhdankina and E. P. Serebryakov, Izv. Akad. Nauk, Ser. Khim., 1993, 2126 (Russ. Chem. Bull., 1993, 42, 2039). 3 E. P. Serebryakov, G.D. Gamalevich, A. V. Ignatenko, A. L. Vlasyuk, T. V. Filatova, V. V. Tertov and A. N. Orekhov (in preparation for Bioorg. & Med. Chem.). 4 G. V. Kryshtal, G. M. Zhdankina and E. P. Serebryakov, Zh. Org. Khim., 1994, 30, 732 (Russ. J. Org. Chem., 1994, 30, 777). 5 G. D. Gamalevich, A. V. Ignatenko, E. P. Serebryakov and N. E. Voishvillo, Izv. Akad. Nauk, Ser. Khim., 1995, 761 (Russ.Chem. Bull., 1995, 44, 743). 6 E. P. Serebryakov, G. D. Gamalevich, A. V. Strakhov and A. A. Vasil’ev, Mendeleev Commun., 1995, 175. 7 G. D. Gamalevich and E. P. Serebryakov, Izv. Akad. Nauk, Ser. Khim., 1997, 175 (Russ. Chem. Bull., 1997, 46, 171). 8 C.-S. Chen, Y. Fujimoto, G. Girdaukas and C. J. Sih, J. Am. Chem. Soc., 1982, 104, 7294. § Acid (R)-1: mp 76.5–77 °C (from MeOH–H2O), [a]D 20 +2.3° (c 1.0, CHCl3); acid (S)-1: mp 76–77 °C (from MeOH–H2O), [a]D 20 –2.3° (c 1.0, CHCl3).EI MS: m/z 248 (M+). All new compounds were characterised by their 1H and 13C NMR spectra. X CO2Me CO2R 3 5 (RS)-5 X = CH2OTs (RS)-6 X = CH2I (RS)-7 X = CH2P+Ph3I– (RS)-9 X = CHO (RS)-1a 3,4,5,6-tetrahydro (R = Me) (RS)-8 5,6-dihydro, D3, (R =Me) (RS)-10 D3,5 (R = Me) (RS)-1 3,4,5,6-tetrahydro (R = H) Scheme 2 (S)-3 CO2Me O i (> 95%) ii (71%) CO2Me iii (88%) CO2R (R)-1a R = Me (R)-1 R = H iv (92%) (R)-3 CO2Me O i (> 95%) ii (64%) iii (87%) CO2R (S)-1a R = Me (S)-1 R = H iv (89%) (S)-9 (S)-10 (R)-9 Scheme 3 Reagents and conditions: i, (a) COCl2–DMSO/CH2Cl2, –65 °C, (b) (S)-3 or (R)-3, –65 °C, 20 min, (c) NEt3, –65 ® 0 °C; ii, (a) [Me2C=CHCH2PPh3]I–BunLi/ THF–hexane, –70 °C, 2 h, (b) (S)-9 or (R)-9, –70 °C, 3–5 h (Ar) ® room temperature; iii, H2–Pd(10%)/C–MeOH, room temperature; iv, KOH/MeOH–H2O (95:5, v/v), 65 °C, 8 h. Received: Moscow, 22th October 1997 Cambridge, 4th December 1997; Com. 7/07977J

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出版商:RSC    

年代:1998

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Synthesis of spacer-armed glycosides using azidophenylselenylation of allyl glycosides Andrei A. Sherman, Leonid O. Kononov, Alexander S. Shashkov, Georgij V. Zatonsky and Nikolay E. Nifant’ev* N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax:+7 095 135 8784; e-mail: nen@ioc.ac.ru Protected 3-aminopropyl spacer-armed glycosides that can be further used for the preparation of neoglycoconjugates have been prepared from allyl glycosides using azidophenylselenylation of the double bond as a key step.Neoglycoconjugates are synthetic compounds that emulate the behaviour of the natural glycoconjugates and are useful tools in glycobiology research.1,2 A prerequisite for the preparation of neoglycoconjugates is the accessibility of a spacer-armed glycoside, i.e.a glycoside with a functional group in the aglycon that can be used for coupling to a carrier. An amino function at the terminal position of an aglycon alkyl chain has been widely used for this purpose.2 For example, 3-aminopropyl glycosides3 have already been used for the preparation of various neoglycoconjugates.However, there still exists a need for the development of new approaches to the preparation of such spacer-armed glycosides from simple glycosides (so called pre-spacer glycosides) under mild conditions. Such an approach would be of special importance for long-chain oligosaccharides. Retrosynthetic analysis shows that 3-aminopropyl glycosides may be obtained by addition of a synthetic equivalent of the amino group to the double bond of allyl glycosides.We anticipated that azidophenylselenylation4 of allyl glycosides followed by subsequent reduction of the azido function and removal of the phenylselenyl moiety (Scheme 1, path A) could constitute a new approach to the preparation of 3-aminopropyl spacer-armed glycosides from allyl glycosides (for other methods of functionalization of allyl glycosides see refs. 5–7). Peracetylated allyl lactoside 1a8,9 was chosen as a model substrate for azidophenylselenylation which was performed under the conditions developed4 for aliphatic alkenes. Treatment of 1a (0.05 mmol) with NaN3 (2.4 equiv.), (PhSe)2 (0.6 equiv.) and PhI(OAc)2 (1.4 equiv.) in CH2Cl2 (0.5 ml) at 20 °C (18 h) PhI(OAc)2 + 2N3 + N3 Path A Path B [PhI(N3)2] [PhI(OAc)(N3)] – PhI – N3 2N3 [PhI(OAc)] RO – PhI RO N3 RO OAc 2 7 RO N3 SePh 3a,b RO N3 10b + CH2N3 RO 11b + (PhSe)2 RO NHX SePh RO OAc SePh 4b X = H 5b X = Boc 8a,b RO NHBoc RO OAc 6b 9b O AcO AcO OAc OAc O O OAc AcO OAc O AcO AcO OAc OAc a R = b R = 1a,b Scheme 1 – (a) (b) H-1 H-1' H-3,3' H-1 –584.0 –582.0 –580.0 –578.0 –576.0 –574.0 4.4 4.0 3.6 3.2 ppm H-1' H-3,3' ppm ppm H-3 H-3' H-1 H-1' H-3,3' 4.8 4.4 4.0 3.6 –590.0 –588.0 –586.0 –584.0 –582.0 –580.0 H-1 H-1' ppm Figure 1 2D 1H–77Se NMR spectra of compounds 3b (a) and 8b (b) (Bruker AM-300, 303 K, C6D6). Numeration of atoms in the aglycon: sugar-1-2-3.Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) unexpectedly afforded two adducts 3a (31%, 1.2:1 ratio of diastereoisomers) and 8a (23%, 1.3:1 ratio of diastereoisomers) rather than a single product (cf.ref. 4). Unidentified products possessing neither allyl nor aromatic fragments (1H NMR data) were also isolated in ca. 20% yield. The presence of PhSe groups in both adducts 3a and 8a, seven AcO groups in 3a and eight AcO groups in 8a was evident from 1H, 13C and 77Se NMR data (Table 1).Compound 3a has an absorption band at 2108 cm–1 in the IR spectrum which is characteristic of an azido group whereas in 8a this band was absent. The spectral data obtained allowed us to surmise that 3a and 8a were the products of azidophenylselenylation and acetoxyphenylselenylation of 1a, respectively. The overlap of signals of five aglycon protons and four H-6 protons of glucose and galactose residues in the 1H NMR spectra of 3a and 8a complicated the determination of the exact substitution pattern of the aglycon. In order to simplify interpretation of the spectra, azidophenylselenylation of allyl galactoside 1b6 was performed under the same conditions.The reaction afforded the desired azido adduct 3b (23%, 1.1:1 ratio of diastereoisomers) together with the acetoxy derivative 8b (42%, 1.4:1 ratio of diastereoisomers). The structures of the adducts 3b and 8b were determined similarly by a combination of NMR and IR spectroscopies.However, in this case it was possible to prove unambigously by 2D 1H–77Se NMR spectroscopy the position of the phenylselenyl moiety at C-2 of the aglycon in both 3b and 8b.Thus, the spectra (Figure 1) of both compounds 3b and 8b contained correlation cross-peaks between the selenium signals and the signals of all methylene protons of the aglycon. This is possible only if the PhSe moiety is attached to the C-2 carbon. 2D 1H–77Se HMQC experiments10 were optimized for the observation of couplings with JH–Se 5 Hz, hence the spectra do not contain correlation cross-peaks between selenium and the proton at C-2 of the aglycon since the geminal 2JH–Se is known11 to be ca. 10 Hz. The competitive acetoxyphenylselenylation observed can be rationalised as follows. The azidophenylselenylation reaction (Scheme 1, path A) is thought4 to involve oxidation of two azide anions by PhI(OAc)2 into azide radicals followed by their addition to alkene 1 and subsequent trapping of the resulting carbon-centered azido radical 2 with (PhSe)2.Apparently, oxidation of azide anion by PhI(OAc)2 proceeds (Scheme 1, path A) via an exchange reaction leading to PhI(N3)2, which decomposes rapidly into two azide radicals and PhI. When the concentration of azide anion is low (due to the poor solubility of NaN3 in CH2Cl2), substitution of only one AcO group in PhI(OAc)2 may occur (path B) leading to the mixed species PhI(OAc)(N3), which decomposes into azide and PhI(OAc)• radicals.The latter can react with alkene 1 by transfer of an AcO radical and liberation of PhI. Subsequent trapping of the resulting carbon-centered acetoxy radical 3 with (PhSe)2 completes the acetoxyphenylselenylation. Thus, it is likely that the low concentration of azide anion in the reaction medium is responsible for the formation of the acetoxy adducts 8a,b.In order to increase the effective concentration of azide anion we performed the reaction in other solvents. In MeCN the ratio of the adducts 3b and 8b was similar to that obtained in CH2Cl2, but in pyridine or in tetramethylurea the formation of 3b prevailed over 8b (TLC data).Addition of water did not influence the 3b/8b ratio, but decreased the reaction rate significantly. In N,N-dimethylformamide (DMF) the reaction was slow, however, it resulted in the exclusive formation of 3b. We reasoned that the addition of a crown ether would further increase the effective concentration of azide anion and hence accelerate the reaction. Portion-wise addition of PhI(OAc)2 (2 equiv.in total) to a solution of 1b (0.41 mmol), (PhSe)2 (0.6 equiv.) and NaN3 (3 equiv.) in anhydrous DMF (2 ml) containing 18-crown-6 (1 equiv.) at 20 °C (72 h) yielded 86% of azidophenylselenylation adduct 3b as the only product. Formation of acetoxyphenylselenylation by-product 8b was totally suppressed under high effective concentration of azide anion.Further transformation of the azidophenylselenylation adduct 3b into the target 3-aminopropyl glycoside required removal of the phenylselenyl residue and reduction of the azido moiety, which could be accomplished either simultaneously or in a step-wise manner (in any order). However, attempted reduction of azide and simultaneous deselenation of 3b with Bu3SnH and AIBN in refluxing toluene failed leading to complex mixtures resulting probably from competitive reactions of the amine initially formed from azide (cf.ref. 12). Deselenation of 3b using elimination of PhSeOH from the corresponding selenoxide formed in situ by oxidation (H2O2) of 3b afforded nearly quantitatively the corresponding cis and trans vinyl azides 10b together with cis vinyl ether 11b in a 2:4:1 ratio.Hydrogenation (H2, 10% Pd/C, AcOEt, AcOH, 20 °C) of the mixture of 10b and 11b resulted in decomposition. These results suggested that the phenylselenyl moiety should be cleaved only after reduction of the azide. Thus, 3b was first converted into 5b in 62% overall yield in a one-pot reduction/protection sequence: reaction of azide 3b (0.066 mmol) with Ph3P (1.5 equiv.) in refluxing THF (3 ml) and hydrolysis of the phosphimine thus formed by addition of aNMR spectra were recorded with a Bruker AM-300 instrument at 303 K in CDCl3 unless otherwise stated.Acetone was used as an external standard in 1H (2.225 ppm) and 13C NMR (31.45 ppm) and (PhSe)2 in 77Se NMR (–460 ppm11). In all compounds the chemical shifts of the protons and carbons of the sugar moiety were very close to the published6,8,9 ones and thus are not presented.bNumeration of atoms in the aglycon: sugar-1-2-3. c 1H, 13C and 77Se NMR spectra were recorded in C6D6. d 1H and 77Se NMR spectra were recorded in C6D6. eC6H5Se 6.93–7.47 (5H). fC6H5Se 7.03–7.62 (5H). gC6H5Se 7.29–7.61 (5H); (CH3)3C 1.41 (9H). h(CH3)3C 1.43 (9H). iC6H5Se 6.91–7.53 (5H); CH3CO 1.52–1.96 (24H).jC6H5Se 7.01–7.55 (5H); CH3CO 1.62–1.98 (15H). kCH3CO 1.98–2.16 (15H). Table 1 1H, 13C and 77Se NMR data (d/ppm)a,b for aglycons in compounds 3a,b, 5b, 6b, 8a,b, 9b, 10b and 11b. Compound H-1 H-1' H-2 H-3 H-3' C-1 C-2 C-3 Se Other 3ac 3.63 4.07 3.12 3.27 3.35 70.2 43.3 52.5 –575 e 43.7 –580 3bd 4.09 3.60 3.11 3.35 3.29 69.7 43.4 52.4 –576 f 4.01 3.65 3.14 3.35 3.28 69.9 42.9 52.5 –583 5b 3.65–3.80 4.11–4.17 3.42–3.47 3.34 3.44 70.7 44.2 42.4 g 44.5 6b 3.58 3.94 1.88 3.19 3.19 67.9 29.8 37.8 h 8ac 4.39–4.53 4.39–4.53 3.37 3.58–3.70 4.04–4.16 69.5 42.4 64.3 i 42.7 8bd 4.21 3.64 3.40 4.52 4.38 69.4 41.8 64.1 –588 j 4.12 3.69 3.38 4.37 4.27 69.9 42.3 64.2 –585 9b 3.56 3.96 1.90 4.12 4.12 70.7 28.8 61.1 k 10b (E) 4.15 4.32 5.41 6.15 63.2 131.1 115.2 10b (Z) 4.17 5.03 6.33 66.7 129.1 114.6 11b 6.33 5.01 4.17 101.8 129.1 68.1Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) H2O (1.7 ml) to give free amine 4b which was transformed into 5b by treatment with N-(tert-butyloxycarbonyloxy)succinimide (7 equiv.). Reductive deselenation of 5b (0.032 mmol) was effected with Bu3SnH (6 equiv.) and AIBN (0.1 equiv.) in refluxing toluene (1 ml) to give in 15 min the target 3-N-(tertbutyloxycarbonylamino) propyl glycoside 6b {[a]D 29 –15° (c 0.25, CHCl3)} in 93% yield.Similarly, deselenation (Bu3SnH–AIBN, toluene) of 8b afforded 3-acetoxypropyl glycoside 9b {[a]D 30 –5° (c 1, CHCl3)} in 83% yield. The terminal position of the NHBoc and AcO groups in the aglycons of 6b and 9b, respectively, was evident from their NMR spectra (Table 1).This fact served as unambiguous proof of the terminal position of the N3 and AcO moieties in the adducts 3b and 8b, and hence of the penultimate position of the phenylselenyl group in 3b and 8b, thus proving the ascribed regioselectivity of azido- and acetoxy-phenylselenylation. In conclusion, the described sequence of reactions (azidophenylselenylation –reduction of azide–deselenation) is a useful approach for the transformation of allyl glycosides into protected 3-aminopropyl glycosides.This work was supported by the President of the Russian Federation (grant no. 96-15-96991) and the Russian Foundation for Basic Research (grant no. 97-03-33037a). The authors are grateful to Yurii V. Mironov (The Higher Chemical College, Moscow) for technical assistance.References 1 Methods in Enzymology (Neoglycoconjugates, parts A and B), eds. Y. C. Lee and R. T. Lee, Academic Press, San Diego, California, 1994, vols. 242, 247. 2 G. Magnusson, A. Ya. Chernyak, J. Kihlberg and L. O. Kononov, in Neoglycoconjugates: Preparation and Application, eds. Y. C. Lee and R. T. Lee, Academic Press, San Diego, California, 1994, p. 53. 3 N. V. Bovin, E. Yu. Korchagina, T. V. Zemlyanukhina, N. E. Byramova, O. E. Galanina, A. E. Zemlyakov, A. E. Ivanov, V. P. Zubov and L. V. Mochalova, Glycoconj. J., 1993, 10, 142. 4 M. Tingoli, M. Tiecco, D. Chianelli, R. Balduci and A. Temperini, J. Org. Chem., 1991, 56, 6809. 5 M. A. Bernstein and L. D. Hall, Carbohydr. Res., 1980, 78, c1. 6 R. T. Lee and Y. C. Lee, Carbohydr. Res., 1974, 37, 193. 7 M. A. Nashed, Carbohydr. Res., 1983, 123, 241. 8 K. Okamoto, T. Kondo and T. Goto, Tetrahedron, 1987, 43, 5919. 9 L. O. Kononov, A. V. Kornilov, A. A. Sherman, E. V. Zyryanov, A. S. Shashkov, G. V. Zatonsky and N. E. Nifant’ev, Bioorg. Khim., 1998, 24, in press. 10 A. Bax and S. Subramanian, J. Magn. Reson., 1986, 67, 565. 11 W. McFarlane and R. J. Wood, J. Chem. Soc., Dalton Trans., 1972, 1397. 12 T. Ercegovic and G. Magnusson, J. Org. Chem., 1996, 61, 179. Received: Moscow, 15th October 1997 Cambridge, 28th November 1997; Com. 7/07604E

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年代:1998

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) A new route for the synthesis of 5,6-dihydropyridin-2(1H)-ones, 2-pyridones and (4-hydroxy-2-oxopiperid-3-yl)pyridinium chlorides by intramolecular cyclization of N-3-oxoalkylchloroacetamide derivatives Alexandr S. Fisyuk,*a Nicolai V. Poendaeva and Yuri G. Bundel’b a Department of Chemistry, Omsk State University, 644077 Omsk, Russian Federation.E-mail: fis@univer.omsk.su b Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation The intramolecular cyclization of triphenylphosphonium and pyridinium derivatives of N-3-oxoalkylchloroacetamides leads to 5,6-dihydropyridin-2(1H)-ones, 2-pyridones and (4-hydroxy-2-oxopiperid-3-yl)pyridinium chlorides. We have recently reported1 on the intramolecular cyclization of N-3-oxoalkylphenylacetamides into 5,6-dihydropyridin-2-ones under the influence of bases.The presence of active hydrogen at the a-carbamoyl position is a necessary condition for the reaction to proceed. The N-3-oxoalkylamides are very promising precursors for the synthesis of pyridine derivatives, due to both the wide range of preparative synthetic methods2–6 available and the convenience of these methods.Increasing a-carbamoyl position acidity can be achieved either by transformation of the a-carbamoyl group into a a-thiocarbamoyl group,7 or by placing an electron-attracting group in that position, e.g. pyridinium or triphenylphosphonium cations. In order to investigate the synthesis of 5,6-dihydropyridin- 2(1H)-ones and 2-pyridones based on N-3-oxoalkylchloroacetamides we have prepared the appropriate 1-(3-oxoalkylcarbamoylmethyl) pyridinium and -(triphenyl)phosphonium chlorides.Reactions of pyridinium ylides leading to formation of a variety of heterocyclic compounds are well known.8–12 Most of the pyridinium ylide heterocyclizations investigated proceed via an intermolecular Michael addition followed by cyclization of the intermediate into a heterocycle.The intramolecular cyclization of pyridinium ylides is also known,13 but its application for the synthesis of heterocycles is not widespread. We have obtained 1-(3-oxoalkylcarbamoylmethyl)pyridinium chlorides 2a–d† by interaction of N-3-oxoalkylchloroacetamides 1a–d with pyridine. Compounds 2a–c with triethylamine in DMF at room temperature give 1-(4-hydroxy- 2-oxopiperid-3-yl)pyridinium chlorides 4a–c‡ in high yields.Heating of both N-3-oxoalkylchloroacetamides 1c,d in a mixture of pyridine with DMF and compounds 2c,d with triethylamine in methanol leads to 2-pyridones 8c,d.§ By contrast, 1-(1-methyl-3-oxobutylcarbamoylmethyl)pyridinium chloride 2b under the same conditions does not form the corresponding 4,6-dimethyl-2-pyridone, but (4-hydroxy-4,6-dimethyl-2-oxopiperid- 3-yl)pyridinium chloride 4b does (Scheme 1).Apparently, the mechanism of transformation of 2a–c into 4a–c involves the formation of the corresponding pyridinium ylides 3a–c (Scheme 1). The degree of conversion of 2a–d depends on both electronic and structural factors. Transformation of 2 into 8 will be promoted by increasing both the effective † 1-(3-Oxoalkylcarbamoylmethyl)pyridinium chlorides 2a–d: a solution of 2 mmol of N-3-oxoalkylchloroacetamide 1 in 3 ml of pyridine was allowed to stand at room temperature for 24 h and then the reaction mixture was diluted with 10 ml of diethyl ether.The resulting precipitate was filtered off and washed with an additional 5 ml of dry diethyl ether to give 88–96% of 2a–d. 1H NMR data for compounds 2a–c (200 MHz, CD3OD, TMS, d): 2a: 9.64 (s, 1H, NH), 8.12–8.92 (m, 5H, Py), 5.40 (s, 2H, CH2–Py), 3.01 (s, 2H, OC–CH2), 2.10 (s, 3H, CH3–CO), 1.40 (s, 6H, CH3–C–CH3). 2b: 9.44 (s, 1H, NH), 9.03–9.21 (m, 5H, Py), 5.59 (s, 2H, CH2–Py), 4.12–4.31 (m, 1H, CH3–CHx–NH), 3.46 (A of ABX, 1H, CHAHB-CO, 2JAB 16.8 Hz, 3JBX 6.8 Hz), 3.25 (B of ABX, 1H, CHAHB–CO, 2JAB 16.8 Hz, 3JAX 6.8 Hz), 2.10 (s, 3H, CH3–CO), 1.16 (d, 3H, CH3–CHx–NH, 3 J 6.6 Hz). 2c: 9.97 (s, 1H, NH), 7.96–8.90 (m, 5H, Py), 7.24–7.61 (m, 10H, 2Ph), 5.56 (X of ABX, 1H, Ph–CHx–NH), 5.49 (s, 2H, CH2–Py), 3.74 (A of ABX, 1H, CHAHB–CO, 2JAB 17.4 Hz, 3JBX 8.1 Hz), 3.56 (B of ABX, 1H, CHAHB–CO, 2JAB 17.4 Hz, 3JAX 5.8 Hz). ‡ 1-(4-Hydroxy-2-oxopiperid-3-yl)pyridinium chlorides 4a–c: 4 mmol of 1-(3-oxoalkylcarbamoylmethyl)pyridinium chloride 2 was dissolved in the minimum amount of DMF (3–4 ml) and treated with 0.05 ml of triethylamine at 0–5 °C.The resulting mixture was allowed to stand at room temperature for 48 h. The resulting precipitate was separated and washed with dry diethyl ether (5 ml) to give 88–90% of 4a–c. 1H NMR data for compounds 4a,b (200 MHz, CD3OD, TMS, d): 4a: 8.13–9.00 (m, 5H, Py), 5.89 (s, 1H, 3-CH), 1.29 [s, 3H, 6-(CH3)a], 1.54 (s, 3H, 4-CH3), 2.18 (s, 2H, 5-CH2), 1.13 [s, 3H, 6-(CH3)e]. 4b: 9.18–10.00 (m, 5H, Py), 5.90 (s, 1H, CH–Py), 3.92–4.03 (m, 1H, CH3–CHx–NH), 2.21 (A of ABX, 1H, CHAHB–CHx–CH3, 2JAB 14.3 Hz, 3JAX 4.5 Hz), 1.99 (B of ABX, 1H, CHAHB–CHx–CH3, 2JAB 14.3 Hz, 3JAX 11.2 Hz), 1.33 (d, 3H, CH3–CHx–NH, J 7.3 Hz), 1.20 (s, 3H, CH3–C–OH).R2 O R1 N O Cl R3 R4 R2 O R1 N O Py+Cl– R3 R4 1a–d Py 2a–d NEt3 room temperature R2 O R1 N O Py+Cl– R3 R4 3a–c N OH R1 R2 R3 R4 O Py+Cl– 4a–c –H2O +H2O H H H H N R2 O Py+Cl– H R1 Ph N R2 O Py+Cl– H R1 Ph 5c,d 6c,d N R2 O Py+Cl– H R1 Ph 7c,d N R2 O H R1 Ph 8c,d – PyHCl NEt3, D Py D a R1 = R3 = R4 = Me, R2 = H b R1 = R4 = Me, R2 = R3 = H c R1 = R4 = Ph, R2 = R3 =H d R1, R2 = (–CH2–)4, R3 = H, R4 = Ph Scheme 1Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) volume of the R1 substituent, which decreases 4-hydroxy- 2-piperidone stability, and the acidity of the C6 position which eases isomerisation of dihydropyridin-2(1H)-ones 5,6 into intermediate 7. The elimination of pyridinium hydrochloride from pyridinium salts such as intermediate 7 has already been described.12,14 5,6-Dihydropyridin-2(1H)-ones are widely employed in the synthesis of alkaloids and aza sugars and possess significant biological activity.15–18 However, there are some restrictions on their synthesis such as inaccessibility of the starting reagents, low applicability of the preparation methods and difficult reaction conditions.1,16,19,20 Therefore, it may be interesting to develop new, flexible methods which allow 5,6-dihydropyridin- 2(1H)-ones to be obtained under mild conditions.We have studied the possibility of synthesising 5,6-dihydropyridin- 2(1H)-ones by means of an intramolecular Wittig reaction based on N-3-oxoalkylchloroacetamides.Cyclization of 1,1-dimethyl-3-oxobutylcarbamoylmethyl(triphenyl) phosphonium chloride 9a¶ by treatment with sodium ethylate at room temperature leads to 5,6-dihydro-4,6,6-trimethylpyridin- 2(1H)-one 10a†† in 90% yield (Scheme 2). Thus, we have shown that 5,6-dihydropyridin-2(1H)-ones, 2-pyridones and (4-hydroxy-2-oxopiperid-3-yl)pyridinium chlorides can be obtained by cyclization of the pyridinium and triphenylphosphonium derivatives of available N-3-oxoalkylchloroacetamides. This work was performed with financial support from the Russian Foundation for Basic Research (grant no. 97-03-33119a). § 4,6-Diphenylpyridin-2(1H)-one 8c and 4,5,6,7-tetrahydro-8-phenyl- 2-isoquinolone 8d: Method A. 4 mmol of N-3-oxoalkylchloroacetamide 1 was dissolved in a mixture of 0.5 ml pyridine with 0.5 ml DMF and refluxed for 3 h.After the reaction time had elapsed, the resulting mixture was poured into 30 ml of water. The resulting precipitate was filtered off, washed with an additional portion of water and dried in vacuo to give 42% of 8c and 24% of 8d. Method B. To a solution of 4 mmol of 1-(3-oxoalkylcarbamoylmethyl) pyridinium chloride 2 in 3 ml of methanol was added 0.15 ml of triethylamine.The resulting mixture was refluxed for 1 h. Methanol was removed under reduced pressure and the residue was washed with water, filtered off and dried in vacuo to give 79% of 8c and 58% of 8d. 1H NMR data for compounds 8c,d (200 MHz, [2H6]DMSO, TMS, d): 8c: 7.28–7.80 (m, 10H, 2Ph), 6.84 (d, 1H, 3-CH, 4J35 1.6 Hz), 6.50 (d, 1H, 5-CH, 4J35 1.6 Hz). 8d: 7.41–7.45 (m, 5H, Ph), 6.13 (s, 1H, 3-CH), 2.65 (m, 2H, 7-CH2), 1.57–1.65 (m, 4H, 5-CH2 and 6-CH2), 2.31 (m, 2H, 4-CH2). Mp 8c 211–212 °C, in agreement with the literature.21 ¶ 1,1-Dimethyl-3-oxobutylcarbamoylmethyl (triphenyl) phosphonium chloride 9a: N-(1,1-dimethyl-3-oxobutyl)chloroacetamide 1a (3.21 g, 16.7 mmol) and triphenylphosphine (4.84 g, 18.4 mmol) in dry dioxane (20 ml) were refluxed for 16 h.The resulting mixture was cooled and the resulting precipitate was filtered off, dried in vacuo and recrystallized from benzene–ethanol (5:1) to give 7.60 g (65%) of 9a. 1H NMR (200 MHz, CDCl3, TMS,) d: 9.68 (s, 1H, NH), 7.67–7.91 (m, 15H, 3Ph), 1.28 (s, 6H, CH3–C–CH3), 5.07 (d, 2H, CH2–+PPh3, 2JHP 14.4 Hz), 2.79 (s, 2H, OC–CH2), 2.04 (s, 3H, CH3–CO).References 1 A. S. Fyssiuk, M. A. Vorontsova and R. S. Sagitullin, Mendeleev Commun., 1993, 249. 2 I. D. Gridnev, A. V. Shastin and E. B. Balenkova, Tetrahedron, 1991, 47, 5577. 3 M. Lora-Tamayo, R. Madroñero, G. G. Muñoz and H. Leipprand, Chem. Ber., 1964, 97, 2234. 4 K. Ikeda, Y. Terao and M. Sekiya, Chem. Pharm. Bull., 1981, 29, 1156. 5 R.Schmidt, A ngew. Chem., 1965, 77, 218. 6 A. D. Synitsa, B. S. Drach and A. A. Kyslenko, Zh. Org. Khim., 1973, 9, 685 [J. Org. Chem. USSR (Engl. Transl.), 1973, 9, 706]. 7 A. S. Fissyuk, M. A. Vorontsova and D. V. Temnikov, Tetrahedron Lett., 1996, 37, 5203. 8 F. Krohnke, Synthesis, 1976, 1, 3. 9 V. P. Litvinov, Zh. Org. Khim., 1995, 31, 1441 (Russ. J. Org. Chem., 1995, 31, 1301). 10 L. A. Summers, Advances in Heterocyclic Chemistry, ed.A.R. Katritzky, Academic Press, New York, 1984, vol. 35, p. 281. 11 R. K. Bausal and J. K. Jain, Synthesis, 1986, 10, 840. 12 A. M. Shestopalov, Yu. A. Sharanin and V. P. Litvinov, Khim. Geterotsikl. Soedin., 1990, 363 [Chem. Heterocycl. Compd. (Engl. Transl.), 1990, 26, 311]. 13 K. Gewald, H. Muller, D. Lohman, G. Laban and P. Bellmann, German Patent 287030 (Chem. Abstr., 1991, 115, 29136). 14 J. Thesing and A. Muller, Chem. Ber., 1957, 90, 711. 15 P. M. Boll, J. Hansen and O. Simonsen, Tetrahedron, 1984, 40, 171. 16 T. Fujii, H. Kogen, Sh. Yoshifuji and K. Iga, Chem. Pharm. Bull., 1979, 27, 1847. 17 L. Micouin, A. Diez, D. López and M. Rubiralta, Tetrahedron Lett., 1995, 36, 1693. 18 H.-J. Altenbach and K. Himmeldirk, Tetrahedron: Asymmetry, 1995, 6, 1077. 19 M. Ch. Marson, U. Grabowska, A. Fallah, T. Walsgrove, D. S. Eggleston and P. W. Baures, J. Org. Chem., 1994, 59, 291. 20 M. Schamma and R. D. Rosenstock, J. Org. Chem., 1961, 26, 718. 21 T. Akiyama, N. Urasato, T. Imagava and M. Kawanisi, Bull. Chem. Soc. Jpn., 1976, 49, 1105. 22 H. K. Hall, Jr., J. Am. Chem. Soc., 1957, 79, 5444. †† 5,6-Dihydro-4,6,6-trimethylpyridin-2(1H)-one 10a: Compound 9a (1.400 g, 3.2 mmol) was dissolved in absolute ethanol (20 ml).To this solution was added, dropwise and with stirring over 5 min at room temperature, a solution of sodium ethylate which was first prepared by dissolving 0.074 g of sodium in absolute ethanol (5 ml). The reaction mixture was stirred for 1 h and filtered from the precipitated NaCl. The filtrate was evaporated and the residue was treated with 10 ml of pentane–ether (1:1) and filtered again. The pentane–ether filtrate was evaporated and from the resulting residue after column chromotography (SiO2, CHCl3–AcOEt 3:1) 0.125 g (90% yield) of 5,6-dihydro-4,6,6-trimethylpyridin- 2(1H)-one 10a was obtained. 1H NMR (200 MHz, CDCl3, TMS) d: 6.33 (s, 1H, NH), 5.72 (m, 1H, 3-CH), 2.23 (s, 2H, 5-CH2), 1.91 (s, 3H, 4-CH3), 1.28 [s, 6H, 2(6-CH3)]. Mp 10a 117–118 °C, in agreement with the literature.22 1a Me O N O Me Me PPh3Cl H EtONa N Me Me Me O H 9a 10a PPh3 Scheme 2 Received: Moscow, 23rd September 1997 Cambridge, 15th December 1997; Com. 7/07577D

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年代:1998

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) An unexpected reaction of 3-aryl-2-pyrazolin-5-ylacetohydrazides with chlorine: formation of 3-aryl-4-chloro-5-trichloromethylpyrazoles Sergei A. Voznesenskii, Leonid I. Belen’kii,* Arkady A. Dudinov, Marina I. Struchkova and Mikhail M. Krayushkin N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation.Fax: +7 095 135 5328 In attempting to synthesize 3-aryl-2-pyrazolin-5-ylacetyl chlorides by chlorination of the respective hydrazides, 3-aryl-4-chloro- 5-trichloromethylpyrazoles have been obtained; a probable mechanism for the transformation is discussed. Previously we described the preparation of 3-aryl-2-pyrazolin- 5-ylacetohydrazides 1 from 1-aryl-5,5-dichloropenta-2,4-dien- 1-ones through 6-aryl-2-pyrones.1 It seemed interesting to study the possibility of using hydrazides 1 in the synthesis of other derivatives of 3-aryl-2-pyrazolin-5-ylacetic acids, in particular, of their halides, which can be used for the preparation of modified b-lactam antibiotics. A direct transformation of hydrazides to acid chlorides upon chlorination in nitromethane,2,3 as well as the preparation of acid bromides when employing bromination under similar conditions,3 are described.We have carried out the chlorination of hydrazides 1† under the conditions described in ref. 2 (suspension of hydrazide hydrochloride in nitromethane, room temperature, stirring). However, instead of the anticipated acid chlorides, 3-aryl-4-chloro- 5-trichloromethylpyrazoles 2‡ were isolated (Scheme 1).When considering a possible mechanism for the transformation observed one should take into account some properties of pyrazolines and pyrazoles. It is known that pyrazolines can be readily oxidized to pyrazoles by bromine.4,5 Chlorination of methylpyrazoles in the ring and side chain is also described, the methyl groups being transformed to trichloromethyl groups.6 Based on these data one may suppose that in our case the oxidation and halogenation of the pyrazoline ring take place in an initial step of the reaction to give 3-aryl-4-chloro- 5-pyrazolylacetohydrazides 3. Under the reaction conditions employed an aryl substituent can undergo chlorination. The latter, however, requires the presence of a group such as OMe, which strongly activates the benzene ring towards electrophilic substitution.Simultaneously or after ring chlorination cleavage of the hydrazide fragment takes place, and the chloropyrazolyl- † 3-Aryl-2-pyrazolin-5-ylacetohydrazides 1a, 1c, 1d were described by us previously (ref. 1), and compounds 1b, 1e were prepared analogously. 3-(4-Chlorophenyl)-2-pyrazolin-5-ylacetohydrazide 1b: mp 155–156 °C (ethanol), yield 77%. 1H NMR, d: 2.25 (m, 2H, CH2CO), 2.70 and 3.05 (dd, 1H, CH2 pyrazoline), 4.10 (m, 1H, CHpyrazoline), 7.40 and 7.60 (d, 2H, HAr), 9.00 (s, 1H, NH). 13C NMR: 36.9 (CH2), 38.5 (C(4)), 57.2 (C(5)), 126.9 (CAr-ipso), 128.4 (CAr-meta), 132.2 (CAr-para), 132.4 (CAr-ortho), 148.0 (C(3)), 169.0 (CO). Found (%): C 52.45, 52.33; H 5.28, 5.11; Cl 14.33, 13.90.Calc. for C11H11ClN4O (%): C 52.28; H 5.19; Cl 14.03. 3-(4-Methoxyphenyl)-2-pyrazolin-5-ylacetohydrazide 1e: mp 173–174 °C (ethanol), yield 68%. 1H NMR, d: 2.22 (m, 2H, CH2CO), 2.65 and 3.04 (dd, 1H, CH2 pyrazoline), 3.75 (s, 3H, OCH3), 3.95 (m, 1H, CHpyrazoline), 6.93 and 7.52 (d, 2H, HAr), 9.00 (s, 1H, NH). 13C NMR: 37.4 (CH2), 55.1 (C(4)), 56.8 (CH3), 113.8 (CAr-ipso), 126.0 (CAr-meta), 126.8 (CAr-para), 159.3 (CAr-ortho), 149.4 (C(3)), 169.5 (CO).Found (%): C 58.09, 58.22; H 6.29, 6.36. Calc. for C12H14N4O (%): C 58.05; H 6.49. acetyl chloride 4 formed undergoes chlorination of the methylene group. Finally, chlorinolysis of the CCl2–COCl bond in the intermediate 3-aryl-4-chloro-5-pyrazoledichloroacetyl chloride 5 proceeds to form trichloromethylpyrazole 2 (Scheme 2).However, the proposed sequence of aromatization, chlorination and chlorinolysis steps requires additional investigation. It should be noted that phenylacetohydrazide readily transforms to the respective acid chloride.2 Since in ref. 2 the reaction of this hydrazide with chlorine was carried out under considerably milder conditions than for the majority of other subjects we performed an experiment with phenylacetohydrazide under the standard conditions used for hydrazides 1, phenylacetyl chloride also being obtained.Thus, the transformation found is specific for pyrazolinylacetohydrazides. ‡ Typical procedure for the preparation of 3-aryl-4-chloro-5-trichloromethylpyrazoles 2. Hydrazide 1 (1 g) was dissolved with heating (50–70 °C) in 30–35 ml of nitromethane and HCl was bubbled through until precipitation of sediment ceased.After cooling to room temperature a slow stream of chlorine was bubbled with stirring through the suspension formed until complete dissolution of the precipitate (1.5–2.5 h) and then the mixture was left to stand overnight at room temperature. The solvent was removed on a rotary evaporator, and the residue was recrystallized from nitromethane or heptane. 4-Chloro-3-phenyl-5-trichloromethylpyrazole 2a: mp 201–202 °C, yield 67%. 1H NMR, d: 7.5–7.8 (m, 5H, Ph), 14.1 (br., 1H, NH). 13C NMR, d: 103.4 (C(4)), 126.8 (CAr-ipso), 127.1 and 127.3 (CAr-meta), 128.8 and 129.0 (CAr-para), 129.1 and 129.6 (CAr-ortho), 141.7 (C(3)), 148.0 (C(5)). Found (%): C 40.46, 40.41; H 2.10, 2.15; Cl 47.69, 47.54; N 9.56, 9,48.Calc. for C10H6Cl4N2 (%): C 36.35; H 1.53; Cl 53.65; N 8.48. 4-Chloro-3-(4-chlorophenyl)-5-trichloromethylpyrazole 2b, mp 188– 189 °C, yield 73%. 1H NMR, d: 7.60 (d, 2H, m-H), 7.77 (d, 2H, o-H), 14.1 (br., 1H, NH). 13C NMR, d: 89.5 (CCl3), 103.6 (C(4)), 125.6 (CAripso), 128.7 (CAr-meta), 129.0 and 129.1 (CAr-ortho), 133.3 and 134.3 (CArpara), 140.6 (C(3)), 148.0 (C(5)).Found (%): C 36.75, 36.45; H 1.60, 1.64; Cl 53.61, 53.21; N 8.60, 8.61. Calc. for C10H5Cl5N2 (%): C 36.35; H 1.53; Cl 53.65; N 8.48. 3-(4-Bromophenyl)-4-chloro-5-(trichloromethyl)pyrazole 2c, mp 199.5– 201.5 °C, yield 58%. 1H NMR, d: 7.62 (d, 2H, m-H), 7.8 (d, 2H, o-H), 14.1 (br., NH). 13C NMR, d: 89.9 (CCl3), 103.8 (C(4)), 123.1 (CAr-para), 126.0 (CAr-ipso), 129.0 and 129.2 (CAr-meta), 131.7 and 132.1 (CAr-ortho), 140.6 (C(3)), 148.1 (C(5)).Found (high resolution MS, Varian MAT- 311A): M = 371.84096. Calc. for C10H5BrCl4N2: M = 371.83903. 4-Chloro-3-(3-nitrophenyl)-5-trichloromethylpyrazole 2d: mp 164 °C, yield 63%. 1H NMR, d: 7.87 (t, 1H, 5'-H), 8.23 (d, 1H, 4'-H), 8.35 (d, 1H, 6'-H), 8.62 (s, 1H, 2'-H). 13C NMR, d: 89.6 (CCl3), 104.4 (C(4)), 121.2 and 121.8 (C(4')), 123.2 and 124.1 (C(6')), 128.2 (C(1')), 130.5 and 130.8 (C(5')), 133.1 and 133.3 (C(2')), 133.5 (C(3')), 139.7 (C(3)), 148.0 (C(5)). Found (%): C 35.89, 35.53; H 1.58, 1.49; Cl 40.91, 40.60; N 12.60, 12.51. Calc. for C10H5Cl4N3O2 (%): C 35.22; H 1.48; Cl 41.59; N 12.32. 4-Chloro-3-(3-chloro-4-methoxyphenyl)-5-trichloromethylpyrazole 2e, mp 191–192 °C, yield 68%. 1H NMR, d: 7.33 (d, 1H, 5'-H), 7.75 (d, 1H, 6'-H), 7.85 (s, 1H, 2'-H). 13C NMR, d: 56.3 and 56.4 (OCH3), 86.4 (CCl3), 103.1 (C(4)), 113.0 and 113.2 (C(5')), 119.9 (C(1')), 121.3 and 121.6 (C(3')), 127.5 and 127.9 (C(6')), 128.2 and 128.5 (C(2')), 154.8 and 155.4 (C(4')), 140.3 (C(3)), 147.9 (C(5)). Found (%): C 36.83, 36.85; H 2.06, 1.89; Cl 49.02, 48.90.Calc. for C11H7Cl5N2O (%): C 36.65; H 1.96; Cl 49.18. N H N Ar CONHNH 2 Cl2 CH3NO2 N H N Ar' CCl3 Cl 1 2 aAr = Ar' = Ph d Ar = Ar' = 3-NO2C6H4 b Ar = Ar' = 4-ClC6H4 c Ar = Ar' = 4-BrC6H4 e Ar = 4-MeOC6H4 Ar' = 3-Cl-4-MeOC6H3 Scheme 1 H HMendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) The structures of compounds 2 obtained were supported by 1H and 13C NMR spectra.§ 1H NMR spectra contain only signals due to the protons of aryl substituents and broad NH signals (for compounds 2d,e the broadening is so strong that the signals were impossible to identify).In the 13C NMR spectra signals due to the CCl3 group at 86.5–90 ppm are present (for compound 2a this signal could not be identified). Obtaining and interpretating the 13C NMR spectra are difficult since most carbon atoms in the molecules of the compounds 2 are quaternary and give signals of low intensity.In addition, carbon atoms bearing hydrogen atoms, and in some cases selected quaternary atoms, are also represented by double sets of signals of unequal intensity. Similar peculiarities are characteristic of the 13C NMR spectrum of methyl 4-chloro-3-(4-chlorophenyl)- pyrazole-5-carboxylate¶ that was obtained from trichloride 2b.In this ester the NH proton manifests itself as two broadened signals when the 1H NMR spectrum is obtained at a § NMR spectra (in [2H6]DMSO) were recorded on Bruker AM-300 and Bruker AC-200 instruments. Assignments of the spectra were made taking into account the values of the chemical shifts and increments summarized in ref. 7. ¶ Methyl 4-chloro-3-(4-chlorophenyl)pyrazole-5-carboxylate. A solution of trichloride 2b (0.2 g, 0.6 mmol) in 8 ml of absolute methanol was refluxed for 5 h and left for 2 days. Excess methanol was removed and the residue recrystallized from methanol. Mp 193–195 °C, yield 0.16 g (nearly quantitative). 1H NMR, d: 3.90 (s, 3H, Me), 7.59 (d, 2H, o-H), 7.83 (d, 2H, m-H), 14.3 (br., 1H, NH); 13C NMR, d: 52.1 (OCH3), 109.5 (C(4)), 125.5 (C(1')), 127.3 (C(4')), 130.4 and 130.5 (C(2') and C(6')), 135.0 (C(4')), 138.7 (C(3)), 146.3 (C(5)), 158.3 and 160.9 (C(CO)). Found (%): C 48.64, 48.46; H 3.10, 3.21; Cl 26.48, 26.18; N 10.31.Calc. for C11H8Cl2N2O2 (%): C 48.73; H 2.97; Cl 26.16; N 10.33. temperature close to the freezing point of [2H6]DMSO.The phenomena mentioned can be explained by either hindered rotation around the C–C bond of the bound aryl group and pyrazole ring or by the presence of two tautomeric forms with an H atom at different nitrogen atoms of the heterocycle. The true origin of the ‘duplication’ of the signals requires additional investigation. The authors are very grateful to B. V. Lichitskii for helpful discussions and to A.V. Ignatenko for recording some of the NMR spectra. Partial financial support by the Russian Foundation for Basic Research (grant no. 95-03-09748) is gratefully acknowledged. References 1 A. A. Dudinov, S. A. Voznesenskii, I. S. Poddubnyi, B. I. Ugrak, L. I. Belen’kii and M. M. Krayushkin, Khim. Geterotsikl. Soedin., 1995, 1511 [Chem. Heterocycl. Compd. (Engl. Transl.), 1995, 1311]. 2 L. A. Carpino, J. Am. Chem. Soc., 1957, 79, 96. 3 L. A. Carpino, Chem. Ind., 1956, 123. 4 T. Jacobs, in Geterotsiklicheskie Soedineniya (Heterocyclic Compounds), ed. R. Elderfield, Inostrannaya Literatura, Moscow, 1961, vol. 5, p. 84 (in Russian). 5 J. Elguero, in Comprehensive Heterocyclic Chemistry, eds. A. R. Katritzky and C. W. Rees, Pergamon Press, Oxford, 1984, vol. 5, p. 254. 6 R. Hüttel, O. Schäfer and G. Welzel, Lieb. Ann., 1956, 598, 186. 7 E. Pretsch, T. Clerc, J. Seibl and W. Simon, Tables of Spectral Data for Structure Determination of Organic Compounds, Springer–Verlag, Berlin, 1983. N H N Ar CONHNH2 Cl2 CH3NO2 N H N Ar Cl Cl 1 2 3 4 5 COCl N H N Ar Cl COCl Scheme 2 H H H Received: Moscow, 31st October 1997 Cambridge, 9th December 1997; Com. 7/07983D

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Electrochemical transformation of malonate and alkylidenemalonates into 3-substituted cyclopropane-1,1,2,2-tetracarboxylates Michail N. Elinson,*a Sergey K. Feducovich,a Sergey G. Bushuev,a Alexander A. Zakharenkov,a Denis V. Pashchenkob and Gennady I. Nikishina a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation.Fax: + 7 095 135 5328 b The Higher Chemical College, Russian Academy of Sciences, 125820 Moscow, Russian Federation Electrolysis of malonate and alkylidenemalonates in an undivided cell in methanol in the presence of sodium bromide or sodium iodide as mediators leads to substituted 1,1,2,2-cyclopropanetetracarboxylates in 80–95% substance and 60–75% current yield.Cyclopropane derivatives occupy a significant place in synthetic organic chemistry.1 Their structural and reactivity features have found widespread applications in the synthesis of natural products. Cyclopropanecarboxylic acid derivatives play an important role as effective agents in agriculture and medicine.2 Insecticidal pyrethrins (derivatives of cyclopropanoid chrysanthemic acid) are perhaps the best known example of their use.3 A well-known method of synthesis of cyclopropanes involves addition of halogenosubstituted C–H acid anions A, generated by the action of base on the corresponding C–H acid AH, to the conjugated activated olefin followed by cyclization with elimination of halogen anion:4 In recent years the method of anion A generation and its reactions with activated olefins have been achieved in doublephase systems in the presence of phase-transfer catalysts.5 Electrochemical reduction of dihalogeno-substituted malonates and further successful addition of anion (A X = Y = COOR) to the activated double bond was the next step in the development of this reaction scheme.6 We now wish to report a new approach to the substituted cyclopropanes by the electrolysis of malonate (but not halogenosubstituted malonate) and alkylidenemalonates in an undivided cell in the presence of halides as mediators (Table 1).Special experiments have been used to check the mechanism of the process. Decreasing the quantity of electricity passed from 2.5 F mol–1 to 1.0 and 0.5 F mol–1 (experiments 3 and 4) resulted in a decreasing yield of 2a from 95% (experiment 2) to 36% and 19%, respectively. Under these conditions 2-methyl- 1,1,3,3-propanetetracarboxylate 3a was obtained as the main product in 56% and 77% yield, respectively.Electrochemical cyclization of 2-substituted-1,1,3,3-propanetetracarboxylates 3 have already been observed under conditions of indirect electrochemical oxidation mediated by halides:7 Thus, the first step in the process of indirect electrochemical transformation of alkylidenemalonates and malonates into substituted cyclopropanes 2 involves the electrochemicallyinduced addition of malonate anion A to the activated double bond of alkylidenemalonate with the formation of anion B.Further halogenation of anion B with halogen generated at the anode and cyclization induced by interaction with MeO–anion result in the formation of the end product of the process, cyclopropane 2 (Scheme 1).It has been found previously that sodium iodide is a more effective mediator for the indirect electrochemical cyclization of 2-substituted-1,1,3,3-propanetetracarboxylates 3.7 This is connected with the higher selectivity of iodine as an oxidant of anion B in the presence of MeO– anions compared to bromine.R R C C Y X R2 R1 Y X Y X 1 2 + CHalXY Hal– X = COOR Y = COOR, CN, C(O)NR2 Hal = Br, I A – R R C C COOMe COOMe R2 R1 MeOOC MeOOC COOMe COOMe 1 2 –e NaHal, MeOH + H2C COOMe COOMe 1 2 R2 R1 MeOOC MeOOC COOMe COOMe –e NaHal, MeOH R1 R2 COOMe COOMe MeOOC MeOOC 2 3 CH2(COOMe) 2 + MeO– CH(COOMe) 2 + MeOH R2 R1 COOMe COOMe + CH(COOMe)2 COOMe COOMe MeOOC MeOOC R1 R2 COOMe COOMe MeOOC MeOOC R1 R2 + Hal2 COOMe COOMe MeOOC MeOOC R1 R2 Hal + Hal– COOMe COOMe MeOOC MeOOC R1 R2 Hal COOMe COOMe MeOOC MeOOC R1 R2 Hal MeO– –Hal– R2 R1 MeOOC MeOOC COOMe COOMe cathode: 2MeOH + 2e 2MeO– + H2 anode: 2Hal– – 2e Hal2 (Hal = Br, I) in solution: B 2 Scheme 1Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) In the present investigation we have found that sodium bromide is more effective as a mediator for the process of indirect electrochemical transformation of alkylidenemalonates and malonate into substituted cyclopropanes 2. Thus, when using NaBr as a mediator the best substrate and current yields of substituted cyclopropanes 2 were obtained.This unusual result is most likely associated with the opening up of a new pathway for the process when using NaBr as a mediator (Scheme 2). The higher efficiency of NaBr as a mediator (Scheme 2) is directly related to the fact that bromomalonate is a stronger C–H acid compared to iodomalonate. That is why the stage of proton abstraction (2) by MeO– anion in the case of bromomalonate is faster than in the case of iodomalonate.Another reason may be that addition of bromomalonate to alkylidenemalonates is more rapid than the analogous addition of iodomalonate anion. The main side reactions of the process are cathodic hydrogenation and cathodic hydrodimerisation of alkylidenemalonates. Nevertheless, in all experiments the total yield of these two by-products was less than 10%.For the reaction of benzylidenemalonate the corresponding hydrodimer, 2,3-diphenyl- 1,1,4,4-butanetetracarboxylate 4, was isolated in 9% yield. The process of alkylidenemalonate hydrodimerization becomes the main reaction pathway on cathodes with a high hydrogen overvoltage (lead, glassy carbon, graphite).8 The sufficient yield of 4 when using benzylidenemalonate as the activated olefin is connected with the higher stability of the intermediate anion-radical because of conjugation in the anion-radical centre with the electrons of the aromatic ring.The authors gratefully acknowledge the financial support of the Russian Foundation for Basic Research (grant no. 97-03-33165a). References 1 T. Tsuji and S. Nishida, The Chemistry of the Cyclopropyl Group, J.Wiley, New York, 1987. 2 L. A. Yanovskaya, V. A. Dombrovsky and A. Kh. Khusid, Tsiklopropany s funktsional’nymi gruppami. Sintez i primenenie (Cyclopropanes with functional groups. Synthesis and application), Nauka, Moscow, 1980 (in Russian). 3 J. Crosby, Tetrahedron, 1991, 47, 4789. 4 G. Bonavent, M. Causse, M. Guittard and R. Fraisse-Julien, Bull. Soc. Chim. Fr., 1964, 2462. 5 G. V. Kryshtal’, N. I. Shtemenko and L. A. Yanovskaya, Izv. Akad. Nauk SSSR, Ser. Khim., 1980, 2420 (in Russian). 6 J.-C. Le Menn, J. Sarrazin and A. Tallec, Electrochim. Acta, 1990, 35, 563. 7 M. N. Elinson, S. K. Feducovich and G. I. Nikishin, Izv. Akad. Nauk SSSR, Ser. Khim., 1990, 2783 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990, 39, 2523). 8 M. N. Elinson, S. K. Feducovich, A.A. Zakharenkov, B. I. Ugrak, G. I. Nikishin, S. V. Lindeman and Yu. T. Struchkov, Tetrahedron, 1995, 51, 5035. aAlkylidenemalonate 14 mmol, malonate 14 mmol, mediator 7 mmol, 20 ml of methanol, Fe-cathode, C-anode, current density 100 mA cm–2, 30 °C. bCurrent yield in parentheses. cTemperature 50 °C. Table 1 Electrochemical synthesis of 3-substituted cyclopropane-1,1,2,2-tetracarboxylates.a N Alkylidenemalonate R1 R2 Mediator Electricity passed/ F mol–1 Product, yield (%)b 1 1a Me H NaI 3.0 2a, 92 (61) 2 1a Me H NaBr 2.5 2a, 95 (76) 3 1a Me H NaBr 1.0 2a, 39; 3a, 56 4 1a Me H NaBr 0.5 2a, 16; 3a, 77 5 1b Pr H NaI 4.0 2b, 83 (42) 6 1b Pr H NaBr 3.0 2b, 94 (63) 7 1c n-C5H11 H NaBr 4.0 2c, 83 8 1d Ph H NaBr 4.0 2d, 75 9c 1e COOMe COOMe NaBr 4.0 2e, 58 Br COOMe COOMe CH(COOMe)2 + Br2 + Br– Br COOMe COOMe + MeO– Br COOMe COOMe + MeOH Br COOMe COOMe + R1 R2 COOMe COOMe R2 R1 MeOOC MeOOC COOMe COOMe + Br– 2 Scheme 2 (1) (2) (3) – Received: Moscow, 28th October 1997 Cambridge, 4th December 1997; Com. 7/07980J

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Mendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) Oxiranes in the Ritter reaction: synthesis of 6,7-(or 5,8-)dimethoxy- 3,4-dihydroisoquinolines by a tandem alkylation–cyclization procedure Vladimir A. Glushkov and Yurii V. Shklyaev* Institute of Technical Chemistry, Urals Branch of the Russian Academy of Sciences, 614600 Perm, Russian Federation. Fax: +7 3422 924 375; e-mail: cheminst@mail.psu.ru Treatment of 1,2- (or 1,4)-dimethoxybenzene with isobutylene oxide and an appropriate nitrile RCN in concentrated sulfuric acid leads to 1-R-6,7-(or 5,8-)dimethoxy-3,3-dimethyl-3,4-dihydroisoquinolines. Numerous syntheses of the isoquinoline ring are known to date.1 Most of them include formation of C4–C4a or C1–C8a bonds as a crucial stage.Here we describe a method for the preparation of substituted 3,4-dihydroisoquinolines via the convergent formation of these bonds step by step in a one-pot procedure.† Traditional syntheses of 3,4-dihydroisoquinolines using the Ritter reaction need styrenes2 or benzylcarbinols3 as precursors of the carbocation.To the best of our knowledge, until the present time the use of oxiranes in this reaction has not been documented.We examined an application of substituted epoxide, namely isobutylene oxide, in the acid-catalysed alkylation of activated aromatic compounds, involving generation of the carbonium ion in the first stage of the Ritter reaction, with subsequent electrophilic attack on the appropriate nitrile, giving the immonium salt, which is susceptible to cyclization to 3,3-dimethyl-3,4-dihydroisoquinolines 3a–d, 4a–c.The structure of compounds 3a–d, 4a–c was confirmed by elemental analysis, NMR and IR spectroscopy.‡ It should be † A typical experimental procedure was as follows. A mixture of veratrole (or 1,4-dimethoxybenzene, 13.82 g, 0.1 mol), isobutylene oxide (9.94 ml, 0.11 mol) and the appropriate nitrile (0.1 mol) in 120 ml of toluene was added, dropwise with vigorous stirring, to concentrated sulfuric acid (40 ml, 0.75 mol) for 20 min (temperature runs from 20 to 55 °C; for syntheses of 3a and 4a the temperature was maintained in the range 20–25 °C).After 1 h of stirring the reaction mixture was poured on to 300 g of crushed ice. The organic layer was separated and washed with 50 ml of water, the combined water layers were washed twice with 40 ml of toluene and made basic with ammonium carbonate up to pH 8, extracted with ether and dried over magnesium sulfate.Products were isolated and purified by vacuum distillation (3b,c, 4b), recrystallization (3a,d, 4c) or column chromatography on silica gel (4a). Compound 3a was isolated from the residue after ether extraction by treatment with methanol and recrystallization from hexane.Hydrochlorides of 3a,d were obtained by passing dry HCl through ether solutions of 3a,d and recrystallization from ethanol–ether. In the case of compounds 3b, 4b the water layer was made basic up to pH ~1 and refluxed for 3 h, cooled, treated with ammonium carbonate (pH ~8) and worked-up as described above. noted that the 1H NMR spectra of these substances after typical work-up show only one set of signals, i.e.the isobutylene oxide ring opens regioselectively under the reaction conditions. The mode of its opening is confirmed unambiguously by an independent synthesis of compounds 3b–d by the traditional method.3 Substance 3c was described earlier.4 The low yields of 3b, 4b (37% and 25%) are due to the fact that these compounds are obtained after hydrolysis and decarboxylation of 3a, 4a in dilute sulfuric acid during the workup, and partial demethylation of 3b, 4b takes place.The reaction described provides a simple and convenient one-pot procedure for preparing 1-substituted 3,3-dimethyl- 3,4-dihydroisoquinilines with electron-donating groups. The value of this protocol lies in the ability to obtain analogues of naturally occurring 6,7-dimethoxy-3,4-dihydroisoquinilines, as well as 5,8-dimethoxy substituted ones, which can be readily oxidized to the corresponding quinones, structural moieties of antimicrobial substances.5 References 1 S.Andreae, Isochinoline, in Houben-Weyl, Methoden der Organischen Chemie, Bd. E7a, Hetarene-II, Teil 1, ed. R. P. Kreher, Georg Thieme Verlag, Stuttgart, New York, 1991, p. 571. ‡ 3a: mp 104–105 °C (hexane), yield 80%; 1H NMR (80 MHz, CDCl3) d: 1.21 (s, 6H, 3-Me), 1.24 (t, 3H, Me, J 9.0 Hz), 2.69 (s, 2H, 4-CH2), 3.83 (s, 6H, 6,7-OMe), 4.10 (q, 2H, OCH2, J 10.0 Hz), 4.98 (s, 1H, CH=), 6.55 (s, 1H, 5-H), 7.06 (s, 1H, 8-H). (Compound exists in the form of enamine3). IR (Nujol, n/cm–1): 3260 (N–H), 1725 (C=O), 1645 (C=N), 1600, 1570, 1510, 1405, 1295, 1265 (nas C–O–C), 1235, 1210, 1185, 1150, 1090, 1040 (ns C–O–C), 1005, 950, 870. 3a·HCl: mp 184–186 °C (decomp.). 1H NMR (80 MHz, CDCl3) d: 1.16 (t, 3H, Me), 1.51 (s, 6H, 3-Me), 3.03 (s, 2H, 4-CH2), 3.81 (s, 3H, OMe), 3.86 (s, 3H, OMe), 4.13 (q, 2H, OCH2), 4.56 (s, 2H, CH2), 6.88 (s, 1H, 5-H), 7.09 (s, 1H, 8-H), 14.50 (wide s, 1H, NH) (enamine is protonated by b-C atom). 3b: bp 148–150 °C (12 mmHg), mp 75–76 °C (hexane), yield 37%, 1H NMR (80 MHz, CDCl3) d: 1.13 (s, 6H, 3-Me), 2.28 (s, 3H, 1-Me), 2.55 (s, 2H, 4-CH2), 3.84 (s, 6H, 6,7-OMe), 6.58 (s, 1H, 5-H), 6.93 (s, 1H, 8-H); IR (Nujol, n/cm–1): 1620 (C=N), 1595, 1570, 1510, 1345, 1290, 1265 (nas C–O–C), 1225, 1205, 1150, 1060 (ns C–O–C), 980, 965, 835. 3c·HCl: mp 199–203 °C (decomp.). 3d: mp 139–141 °C (acetone–ether), yield 55%, 1H NMR (80 MHz, CDCl3) d: 1.21 (s, 6H, 3-Me), 2.66 (s, 2H, 4-CH2), 3.63 (s, 3H, 7-MeO), 3.87 (s, 3H, 6-MeO), 6.60 (s, 2H, 5,8-H), 7.28–7.48 (m, 5H, H arom.); IR (Nujol, n/cm–1): 1600 (C=N), 1555, 1510, 1270 (nas C–O–C), 1210, 1030 (ns C–O–C). 4a: oil, yield 72%, 1H NMR (80 MHz, CDCl3) d: 1.15 (s, 6H, 3-Me), 1.20 (t, 3H, Me), 2.69 (s, 2H, 4-CH2), 3.67 (s, 3H, OMe), 3.70 (s, 3H, OMe), 4.05 (q, 2H, OCH2), 5.69 (s, 1H, HC=), 6.72 (s, 2H, 6,7-H), 9.21 (s, 1H, NH); IR (neat, n/cm–1): 3250 (NH), 1730, 1600, 1505, 1305, 1270, 1175, 1090. 4b: oil, bp 147–150 °C (7 mmHg), yield 25%, 1H NMR (80 MHz, CDCl3) d: 1.09 (s, 6H, 3-Me), 2.36 (s, 3H, 1-Me), 2.50 (s, 2H, 4-CH2), 3.68 (s, 6H, 5,8-MeO), 6.68 and 6.72 (2s, 2H, 6,7-H); IR (neat, n/cm–1): 1610 (C=N), 1590, 1580, 1330, 1270 (nas C–O–C), 1250, 1200, 1150, 1090, 1055 (ns C–O–C), 1035, 970, 910, 800. 4c: mp 82–83 °C (methanol–water), 1H NMR (80 MHz, CDCl3) d: 1.19 (s, 6H, 3-Me), 2.28 (s, 3H, MeS), 2.53 (s, 2H, 4-CH2), 3.72 (s, 3H, MeO), 3.79 (s, 3H, MeO), 6.75 (d, 2H, 6,7-H); IR (Nujol, n/cm–1): 1590, 1555, 1325, 1275, 1200, 1080, 1020, 1005, 980. R1 R1 + O Me Me H2SO4 R1 R1 Me Me +N C R2 R1 R1 Me Me N R2 R1 R1 Me Me N R2 1a 2R1 = 1,2-(MeO)2 1b 2R1 = 1,4-(MeO)2 a R2 = CH2COOEt b R2 = Me c R2 = SMe d R2 = Ph 3a–d 2R1 = 6,7-(MeO)2 4a–c 2R1 = 5,8-(MeO)2 2a–dMendeleev Communications Electronic Version, Issue 1, 1998 (pp. 1–42) 2 H. Wollweber and R. Hiltman, Angew. Chem., 1960, 72, 1001. 3 V. S. Shklyaev, B. B. Aleksandrov, G. I. Legotkina, M. I. Vakhrin, M. S. Gavrilov and A. G. Mikhailovskii, Khim. Geterotsikl. Soedin., 1983, 1560 [Chem. Heterocycl. Compd. (Engl. Transl.), 1983, 1242]. 4 B. B. Aleksandrov, V. A. Glushkov, E. N. Glushkova, A. A. Gorbunov, V. S. Shklyaev and Yu. V. Shklyaev, Khim. Geterotsikl. Soedin., 1994, 511 [Chem. Heterocycl. Compd. (Engl. Transl.), 1994, 449]. 5 (a) J. M. Frincke and D. J. Fualkner, J. Am. Chem. Soc., 1982, 104, 265; (b) M. Croisy-Delcey, C. Huel and E. Bisagni, J. Heterocycl. Chem., 1988, 25, 655. Received: Moscow, 30th September 1997 Cambridge, 6th November 1997; Com. 7/07583I

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