摘要:

Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Photoisomerization of the perfluoroallyl radical: a FTIR matrix-isolation study Esfir G. Baskir,* Victor A. Korolev and Oleg M. Nefedov N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: bas@cacr.ioc.ac.ru 10.1070/MC2000v010n04ABEH001318 The perfluoropropen-2-yl radical was found to be the main product of photolysis of the perfluoroallyl radical.Free radicals are important intermediates in chemical reactions, as well as in atmospheric chemistry, catalysis and biochemistry. Matrix isolation provides an opportunity to detect these transient species and to study their transformations, including photochemical reactions. The allyl radical, which is the simplest conjugated system, is one of the best studied radicals.1–7 In particular, it was found by matrix IR spectroscopy that photoirradiation of the allyl radical results in both isomerization to the cyclopropyl radical and decomposition to allene or isomeric methylacetylene.4,5 Data on a perfluorinated analogue of the allyl radical are scanty. Radical C3F5 1 was first obtained photochemically by the interaction of the tributylsilyl radical with 3-bromopentafluoropropene and detected in a cyclopropane solution by EPR spectroscopy.8 More recently, we measured the matrix IR spectrum of radical 1 generated by pyrolysis of perfluorohexa- 1,5-diene.9 In this work, we examined perfluoroallyl radical 1 and its photoisomerization products in more detail using matrix IR spectroscopy and quantum-chemical calculations. The experimental procedure was described previously.10,11 Perfluorohexa-1,5-diene was pyrolysed at 1150–1300 K and a pressure of 10–4 Torr in a quartz reactor (50–120 mm in length and 5 mm in diameter) connected to an optical helium cryostat.The pyrolysis products with a high excess of argon (~1 : 1000) were frozen on the polished surface of a copper cube cooled to 10 K by a Displex 208R closed-cycle cryogenic system (Air Products & Chemicals).The IR spectra were recorded on a Bruker IFS-113v Fourier-transform spectrometer with a resolution of 0.5 cm–1 in the frequency range 4000–400 cm–1 using the beam reflection scheme. The photolysis was carried out with a high-pressure mercury lamp (1000 W), and the irradiation wavelength was varied using glass filters.The UV irradiation (260 < l < 400 nm) of an Ar matrix containing the pyrolysis products resulted in a synchronous decrease in the intensities of the IR bands belonging to radical 1 (Table 1, Figure 1). The intensities of some bands, among which were the absorption bands of perfluoroallene (2065.1, 1284.2, 1238.8, 1033.4 and 609.0 cm–1)12 and isomeric perfluoromethylacetylene (1373.8, 1164.8, 1102.6 and 766.2 cm–1),13 increased simultaneously.New bands at 1785.4, 1307.8, 1262.0, 1166.4, 1149.1, 1009.3, 698.3, 598.5 and 530.8 cm–1 were of special interest. The appearance of these bands was not associated with transformations of the starting perfluorohexa-1,5-diene, which was present in the mixture of pyrolysis products, because the intensities of its IR absorption bands remained unchanged after irradiation of the matrix.Moreover, a control experiment on the photolysis of the starting compound specially sputtered in the matrix also showed no changes in the spectrum. The absorption band intensities of pyrolysis by-products such as the CF3 radical and perfluoropropylene CF3CFCF2 did not decrease.Thus, the new bands can be attributed to the products of phototransformation of only radical 1. The heating of the matrix to a diffusion temperature (35 K) was accompanied by a decrease in the intensity of these bands and by the simultaneous appearance and growth of several IR bands (1743.3, 1380,8, 1221.8, 1131.6, 1110.0, 1045.3, 996.6 and 741.6 cm–1) belonging to stable molecules.Hence it follows that the new IR bands belong to an unstable species, whereas the bands appeared during the heating probably belong to recombination products. Moreover, the IR bands of the photoproduct 1 did not coincide with the bands of the known intermediates that can be formed in the decomposition of 1, namely, CF2=CF14 and CF3 15 radicals or difluorocarbene CF2.15 Therefore, the photoproduct from 1 is most likely a photoisomer of this species. To reveal the structure of the species formed, we compared the experimental data with the results of quantum-chemical calculations.The optimum geometry and vibrational spectrum were calculated by both the classical ab initio UHF method in the 3-21G, 6-31G and 6-311G* basis sets and the B3LYP density functional method (DFT) in the 6-311G* basis set using the GAUSSIAN-94 program system.16 Perfluoroallyl radical 1 was chosen as a model for the determination of the most appropriate calculation method.In the calculations of radical 1, the B3LYP method with the 6-311G* basis set gave the most plausible results, which showed the presence of aligned C–C bonds and a somewhat nonplanar geometry (symmetry C2).This method also gave the best agreement between the experimental and calculated signals in both frequency (the average deviation did not exceed 2%) and intensity. A comparison between the calculated and experimental spectra of radical 1 allowed us to detect previously unobserved IR bands and to assign more adequately the IR bands to normal vibrations.According to this calculation, an intense absorption band at 1499.3 cm–1 corresponds to the antisymmetric stretching vibration of C–C, confirming electron delocalization in the allylic system of radical 1. The experience gained from the calculation of radical 1 was used in the consideration of isomeric structures.Five different isomers are plausible for a species with the molecular formula C3F5 (Scheme 1). We calculated the structures, energy parameters and vibrational spectra of these isomers by the B3LYP method in the 6-311G* basis set. The stability of these species was found to decrease in the following order: allylic structure 1 > propen-2-yl 2 > trans- and cis-propen-1-yl radicals 3, 4 > cyclopropyl radical 5 (Table 1).The photoisomerization of the allyl radical can proceed with the formation of a cyclopropyl structure.4,5 However, the experimental set of IR bands of the photoisomer was strongly different from that predicted by the quantum-chemical calculation for analogous perfluorinated species 5 (Table 1). Because the spectrum of the photolysis products exhibits a band at 1875.4 cm–1, which is characteristic of polyfluoroalkenes and indicates the presence of the C=C bond in the molecule, structures 2–4 can be attributed to the photoisomer. In our case, the best agreement between the experimental and calculated frequencies of the vibrational spectrum was observed for the structure of radical 2 F F F F F 1 F F F F 2 F F F F 3 F F F F 4 F F F F F F F F 5 C C C F F F F F 6 Scheme 1Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) (Table 1), whose formation can be explained by the 1,2-migration of a fluorine atom in radical 1 (Scheme 2). The potential barrier for this process calculated by the B3LYP/6-311G* method is equal to 18.1 kJ mol–1. Transition state 6 corresponding to the fluorine transfer from the allylic position to a terminal carbon atom is characterised by a negative frequency (–234 cm–1) related to the migration of a fluorine atom between the adjacent carbon atoms.Indeed, the calculation of the energy along the internal reaction coordinate (IRC) confirmed that 6 is a transition state, and a shift to one or another side along the potential-energy curve results in one of the two minima corresponding to the structures of 1 and 2.Moreover, the bands at 1307.8, 1262.0, 1166.4 and 1149.1 cm–1 attributed to radical 2 can also be observed as weak absorption bands in the spectrum of the primary products of pyrolysis along with the intense IR bands of radical 1. In fact, according to the quantum-chemical calculation, the difference between the energies of formation of radicals 1 and 2 is approximately equal to 1.3 kJ mol–1 in favour of 1, and its formation under conditions of high-temperature pyrolysis is the main process, whereas the concentration of 2 in the equilibrium mixture can be as high as several percent. Thus, the photolysis of perfluoroallyl radical 1 isolated in an argon matrix results in the formation of a new unstable species, which was identified as perfluoropropen-2-yl radical 2 on the basis of the data of matrix IR spectroscopy and quantum-chemical calculations.This work was supported by the Russian Foundation for Basic Research (grant nos. 98-07-90290, 99-15-78323 and 97-03-33740) and INTAS (grant no. 96-0866). References 1 A. K. Maltsev, V. A. Korolev and O. M. Nefedov, Izv.Akad. Nauk SSSR, Ser. Khim., 1984, 555 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1984, 33, 510). 2 E. Vajda, J. Tremmel, B. Rozsondai, I. Hargittai, A. K. Maltsev, N. D. Kagramanov and O. M. Nefedov, J. Am. Chem. Soc., 1986, 108, 4352. 3 R. Glaser and G.-C. Choy, J. Phys. Chem., 1994, 98, 11379. 4 K. Holtzhauer, C. Cometta-Morini and J. F. M. Oth, J. Phys. Org. Chem., 1990, 3, 219. 5 G. Maier and S. Senger, Angew. Chem., Int. Ed. Engl., 1994, 33, 558. 6 D. Uy, S. Davis and D. J. Nesbitt, J. Chem. Phys., 1998, 109, 7793 and references therein. 7 D. Stranges, M. Stemmler, X. Yang, J. D. Chesko, A. G. Suits and Y. T. Lee, J. Chem. Phys., 1998, 109, 5372. 8 B. E. Smart, F. J. Krusic, F. Meakin and R. C. Bingham, J. Am. Chem. Soc., 1974, 96, 7382. 9 A. K. Maltsev, E.G. Baskir, N. D. Kagramanov and O. M. Nefedov, Izv. Akad. Nauk SSSR, Ser. Khim., 1986, 1998 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1986, 35, 1817). 10 V. A. Korolev and E. G. Baskir, Izv. Akad. Nauk, Ser. Khim., 1995, 464 (Russ. Chem. Bull., 1995, 44, 448). 11 E. G. Baskir and O. M. Nefedov, Izv. Akad. Nauk, Ser. Khim., 1996, 109 (Russ. Chem. Bull., 1996, 45, 99). 12 J.R. Durig, Y. S. Li, J. D. Witt, A. P. Zens and P. D. Ellis, Spectrochim. Acta, 1977, 33A, 529. 13 W. Stuckey and J. Heicklen, J. Am. Chem. Soc., 1968, 90, 3952. 14 A. Thoma, B. E.Wurfel, R. Schlachta, G. M. Lask and V. E. Bondybey, J. Phys. Chem., 1992, 96, 7231. 15 D. E. Milligan and M. E. Jacox, J. Phys. Chem., 1968, 48, 2265. 16 J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B.G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J.Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian 94, Revision D.1, Gaussian, Inc., Pittsburgh PA, 1995. 1.0 0.5 0.0 –0.5 2000 1800 1600 1400 1200 1000 800 600 Intensity n/cm–1 2 A MA MA 2 A 2 MA MA 2 2 2 A 2 A 1 1 1 1 1 2 1 Figure 1 Difference IR spectrum of the products of pyrolysis of 1,5-perfluorohexadiene in an argon matrix at 10 K before photolysis (bands directed down: 1 is the perfluoroallyl radical) and after photolysis (bands directed up: 2 is the perfluoropropen-2-yl radical, MA is perfluoromethylacetylene and A is perfluoroallene). 2 F F F F F 1 F F F F 2 F Ar matrix, 10 K hn Scheme 2 Table 1 Experimental and calculated (B3LYP/6-311G*) vibrational frequencies (n) in the range 4000–400 cm–1, total (E) and relative (DE) energies of the perfluoroallyl radical and its isomers.n/cm–1 Assignment n/cm–1 Assignment Calculateda Experimental Calculateda Experimental 1 5 3 4 2 1596.5 (5) aCalculated intensities in km mol–1 are given in parentheses. ns(C–C) 1515.0 (20) 1784.1 (40) 1790.0 (116) 1838.8 (419) 1785.4 s n(C=C) 1531.7 (262) 1499.3 s nas(C–C) 1272.7 (111) 1341.0 (141) 1363.9 (133) 1303.5 (101) 1307.8 m ns(CF2), n(C–C) 1360.6 (311) 1350.9 s nas(CF2) 1216.3 (461) 1238.7 (390) 1230.0 (46) 1253.3 (382) 1262.0 vs nas(CF2) 1305.8 (46) 1301.2 w nas(CF2) 1205.8 (266) 1198.9 (198) 1181.9 (434) 1156.1 (333) 1166.4 s nas(CF3), 1212.4 (191) 1215.1 s n(CF) 1177.2 (48) 1158.9 (305) 1159.5 (309) 1126.9 (230) 1149.1 m nas(CF3), n(C–C) 1009.6 (269) 1007.7 s ns(CF2), ns(C–C) 856.7 (123) 1106.4 (195) 1067.5 (263) 1010.8 (305) 1009.3 m ns(CF2), ns(CF3) 729.7 (0) ns(CF2), ds(CF2) 819.2 (39) 778.9 (2) 843.6 (12) 808.4 (5) d(CCC), ns(CF2) 575.4 (2) 581.2 vw das(CF2) 760.9 (4) 636.7 (0) 718.2 (26) 688.9 (14) 698.3 w ds(CF3), d(CCC) 572.2 (0) rr(CF2) 750.6 (1) 625.6 (2) 637.1 (0) 633.0 (17) rr(CF2) 451.4 (12) rw(CF) 568.3 (1) 575.9 (13) 577.6 (1) 599.1 (7) 598.5 w ds(CF2), ds(CF3) 397.7 (4) rw(CF2) 541.9 (15) 513.1 (6) 494.1 (2) 577.9 (0) das(CF3), rw(CF2) 381.1 (1) rr(CF2) 439.6 (3) 484.7 (2) 408.7 (1) 523.5 (3) 530.8 vw rr(CF3) E (hartrees) –613.5879 –613.5386 –613.5692 –613.5707 –613.5828 DE/kJ mol–1 12.9 4.9 4.5 1.3 Received: 25th April 2000; Com. 00/1644

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Synthesis of selenoesters Irina P. Beletskaya,*a Aleksandr S. Sigeev,a Aleksandr S. Peregudovb and Pavel V. Petrovskiib a Department of Chemistry, M. V. Lomonosov Moscow State University, 199899 Moscow, Russian Federation. Fax: +7 095 938 1844; e-mail: beletska@org.chem.msu.su b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 117813 Moscow, Russian Federation 10.1070/MC2000v010n04ABEH001317 Tributyltin phenyl selenide, which was prepared from Bu3SnSnBu3 and PhSeSePh upon irradiation, easily reacts with acid halides to form selenoesters in very high yields.Previously,1 Bu3SnSePh was found to form upon irradiation of a mixture of the distannane Bu3SnSnBu3 and the diselenide PhSeSePh with daylight.This compound can be used as a source of the phenylseleno group, in particular, in situ, in crosscoupling reactions with aryl iodides or aryl triflates, catalysed by transition metal complexes, and with aryldiazonium salts.2 Tributyltin phenyl selenide is more convenient in handling than commonly used selenols because of its stability to atmospheric oxygen and the absence of intense unpleasant odours.We found that tributyltin phenyl selenide readily reacts with acid chlorides to form corresponding phenylselenoesters in almost quantitative yields. The rather general character of this reaction provides an opportunity to prepare selenoesters of aromatic, aliphatic and a,b-unsaturated acids (Table 1). The reaction was performed in chloroform at room temperature.The course of reaction was followed using 119Sn and 77Se NMR spectroscopy by monitoring the disappearance of signals due to the starting tributyltin phenyl selenide (119Sn, d 60 ppm; 77Se, d –489 ppm)† and the appearance of signals due to reaction products (Bu3SnCl: 119Sn, d 145 ppm; 77Se d values for RCOSePh are given in Table 1). In a typical procedure, a solution of 1 mmol of an acid chloride and 1 mmol of tributyltin phenyl selenide‡ in 2 ml of dry chloroform was stirred at room temperature for 1 h.After completion of the reaction, the reaction mixture was treated with an aqueous KF solution to precipitate tin compounds, the solvent was evaporated, and the residue was recrystallised from hexane.§ The presence of electron-acceptor substituents in the acid chloride molecule accelerates the reaction.Thus, in the case of 4-nitrocinnamic acid chloride (Table 1, entry 8), the corresponding selenoester was formed almost immediately after mixing the reactants, whereas the reaction with cinnamic acid chloride (Table 1, entry 9) was completed in 1 h. Terephthaloyl dichloride also readily reacts with two equivalents of Bu3SnSePh under the specified conditions (Table 1, entry 5) to give a double substitution product.The reaction can also be performed step-by-step to isolate a monosubstitution product in a high yield (Table 1, entries 6 and 7). Although we did not examine the reaction mechanism in detail, the most probable mechanism is shown in Scheme 2. Commonly used methods for the synthesis of selenoesters are based on the reactions of acid chlorides with selenols in the presence of bases.3 Recently,4 it was proposed to use Hg(SePh)2 in this reaction in the presence of Bu4NX; however, only one of the two phenylseleno groups was involved in this reaction.Carboxylic acids can also be converted into corresponding selenoesters by the treatment with arylselenocyanates in the presence of equivalent amounts of tributylphosphine.5 † The 77Se and 119Sn NMR spectra were measured on a Bruker WP-200 SY spectrometer at 38.19 and 74.6 MHz, respectively, in chloroform; Me4Sn and PhSeSePh were used as external standards.‡ Tributyltin phenyl selenide can be prepared in situ by irradiation of a mixture of 0.5 mmol of diphenyl diselenide and 0.5 mmol of hexabutyldistannane with daylight for 1 h.An acid chloride was added to the resulting solution. In this case, the selenoester yield remained unchanged. R C Cl O + Bu3SnSePh R C SePh O CHCl3, 25 °C 1a–h 3a–h 2 a R = Ph b R = 4-FC6H4 c R = 4-ClC6H4 d R = 4-BrC6H4 e R = 4-(COCl)C6H4 f R = (E)-PhCH=CH g R = (E)-4-NO2C6H4CH=CH h R = Me Scheme 1 § 3b: 1H NMR (400 MHz, CDCl3) d: 7.17 (t, 2H, o-H in 4-FC6H4), 7.45 (m, 3H, Ph), 7.60 (m, 2H, Ph), 7.97 (dd, 2H, m-H in 4-FC6H4, 3JH–F 3.66 Hz, 3JH–H 8.66 Hz). 13C NMR (100 MHz, CDCl3) d: 116.11 (m-CH in 4-FC6H4, 2JC–F 22 Hz), 125.52 (Ph), 129.17 (p-CH in Ph), 129.41 (Ph), 129.89 (o-CH in 4-FC6H4, 3JC–F 9.5 Hz), 134.85 (1-C in 4-FC6H4, 4JC–F 2.9 Hz), 136.31 (Ph), 166.12 (p-C in 4-FC6H4, 1JC–F 255 Hz), 191.79 (C=O).MS, m/z: 280 [M+]. 3e: 1H NMR (CDCl3) d: 7.45 (m, 6H, Ph), 7.61 (m, 4H, Ph), 8.02 (s, 4H, C6H4). 13C NMR (CDCl3) d: 125.43 (C), 127.71 (CH), 129.29 (CH), 129.47 (CH), 136.12 (CH), 142.32 (C), 189.11 (CO). Found (%): Se, 36.21. Calc. for C20H14O2Se2 (%): Se, 35.55. MS, m/z: 446 [M+]. 3g: 1H NMR (CDCl3) d: 6.88 (d, 1H, CH=CHCO, J 15.8 Hz), 7.45 (m, 3H, Ph), 7.57 (m, 2H, Ph), 7.61 (d, 1H, CH=CHCO, J 15.8 Hz), 7.71 (d, 2H, 4-O2NC6H4, J 8.4 Hz), 8.25 (d, 2H, 4-NO2C6H4, J 8.4 Hz). 13C NMR (CDCl3) d: 124.01, 125.47, 128.86, 129.06, 129.29, 129.54, 135.48, 137.18, 139.80, 148.38, 190.43. Found (%): Se, 22.94. Calc. for C15H11NO3Se (%): Se, 23.77. MS, m/z: 333 [M+]. Table 1 Synthesis of selenoesters. Entry RCOCl RCOSePh 77Se, d/ppm Yielda (%) aAccording to 77Se NMR data.The yields of isolated compounds are given in parentheses. b2 equiv. of Bu3SnSePh. c1 equiv. of Bu3SnSePh. 1 PhCOCl PhCOSePh7 168.6 99 (96) 2 4-FC6H4COCl 4-FC6H4COSePh 170.5 99 (97) 3 4-ClC6H4COCl 4-ClC6H4COSePh5 174.5 98 (96) 4 4-BrC6H4COCl 4-BrC6H4COSePh7 174.7 99 (97) 5 1,4-C6H4(COCl)2 b 1,4-C6H4(COSePh)2 185.2 95 (93) 6 1,4-C6H4(COCl)2 c 4-(ClOC)C6H4COSePh 191.1 92 (89) 7 4-PhSeOCC6H4COCl 1,4-C6H4(COSePh)2 185.2 99 8 PhCH=CHCOCl PhCH=CHCOSePh10 154.3 97 (94) 9 4-NO2C6H4CH=CH– COCl 4-NO2C6H4CH=CH– COSePh 165.2 (96) 10 MeCOCl MeCOSePh9 203.1 97 (90) Bu3SnSePh RCOCl + R C SePh Cl O SnBu3 R C SePh O + Bu3SnCl Scheme 2Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) The procedure proposed for the synthesis of selenoesters has a number of advantages over previous methods due to the more convenient reagent Bu3SnSePh.In contrast to tributyltin phenyl selenide, silicon organoselenides do not directly react with acid chlorides. Thus, the reaction of tris(trimethylsilyl)silicon phenyl selenide with chlorocarbonic acid esters is catalysed by palladium complexes,6 and the reaction of trimethylsilyl phenyl selenide with RCOCl was performed in the presence of equimolar amounts of SmI2.7 However, trimethylsilyl phenyl telluride can directly react with ArCOCl to form corresponding telluroesters in good yields.Analogous tellurium derivatives directly react with acid chlorides. 8 This work was supported by the Russian Foundation for Basic Research and INTAS (grant no. 95-0126), the Programme ‘Leading Scientific School’ (grant no. 00-15-97406), and the Programme ‘Integration of the Higher School and the Academy of Sciences’ (grant no. AO-115). References 1 I. P. Beletskaya, A. S. Sigeev, A. S. Peregudov, P. V. Petrovskii, S. V. Amosova, V. A. Potapov and L. Hevesi, Sulf. Lett., 2000, 23, 145. 2 I. P. Beletskaya, A. S. Sigeev, A. S. Peregudov and P. V. Petrovskii, J. Organomet.Chem., 2000, 605, 96. 3 (a) M. Renson and C. Draguet, Bull. Soc. Chim. Belg., 1962, 71, 260; (b) H. Rheinboldt, in Houben-Weyl. Methoden der organischen Chemie, ed. E. Muller, Georg Thieme Verlag, Stuttgart, 1955, vol. IX, p. 1205. 4 C. C. Silveira, A. L. Braga and E. L. Larghi, Organometallics, 1999, 18, 5183. 5 P. A. Grieco, Y. Yokoyama and E. Williams, J. Org. Chem., 1978, 43, 1283. 6 C. H. Schiesser and M. A. Skidmore, J. Chem. Soc., Perkin Trans. 1, 1997, 2689. 7 S. Zhang and Y. Zhang, Synth. Commun., 1998, 28, 3999. 8 K. Sasaki, Y. Aso, T. Otsubo and F. Ogura, Chem. Lett., 1986, 977. 9 M. Baiwir and G. Llabres, Spectrochim. Acta, Part A, 1982, 38A, 575. 10 T. Jayachandran, T. Manimaran and V. T. Ramakrishnan, Indian J. Chem., Ser. B, 1984, 23B, 328. Received: 21st April 2000; Com. 00/1643

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Generalization of the Laplace equation for non-spherical interfaces in external fields Anatoly I. Rusanov* and Aleksandr K. Shchekin Mendeleev Center, St. Petersburg State University, 199034 St. Petersburg, Russian Federation. Fax: +7 812 428 6939; e-mail: rusanov@rus.usr.pu.ru 10.1070/MC2000v010n04ABEH001276 A general form of the Laplace equation has been derived using non-diagonal tensors for pressure and surface tension typical of non-spherical interfaces in external fields.The Laplace equation, the principal relationship of colloid science, is well known for a non-spherical interface with the scalar surface tension g as where p is the pressure (a and b indicate the adjacent phases) and Ri (i = 1, 2) are the principal curvature radii of the interface.Since surface tension depends on curvature, the interfacial nonsphericity itself leads to the anisotropy of surface tension, so that equation (1) can be written in the form where g1 and g2 are the surface tensions along the principal directions on the interface. There were many attempts to generalise the Laplace equation, but the results (see, e.g., refs. 1–9) mostly referred to the case when the pressure tensor and(or) the tensor of surface tension (defined as excess surface stress) are of a diagonal form. The latter, however, not always exists and is scarcely attainable if an interface is subjected to an arbitrarily directed external field. Using the total pressure and surfacetension tensors (including the field), the only problem remains to formulate the Laplace equation in terms of the non-diagonal pressure and surface-tension tensors, and this is the goal of this paper.First, we have to choose a co-ordinate system. Studying the interface shape, it is most convenient to use such curvilinear coordinates as reflecting the interface shape. In the mathematical language, this means that we use an orthogonal curvilinear coordinate system (u1, u2, u3) diagonalising the metric tensor of the interface, so that any co-ordinate surface (u1, u2) inside or near the interface can play a role of the Gibbs dividing surface, the u3 co-ordinate corresponding to the direction perpendicular to the interface.9 In contrast with the metric tensor, the pressure and surface-tension tensors are assumed to maintain (e.g., due to an external field) their non-diagonal form even in the above co-ordinate system.As the Laplace equation is a condition of mechanical equilibrium, it may be derived from the condition that the total force acting on any part of the system is zero. This can be formulated as where is the local pressure tensor, dA is the vector of a surface element (i.e., an elementary surface area multiplied by the vector n of the unit normal to the surface), and P = n is the vector of force applied to the elementary unit surface. The integration in (3) is carried out over the whole closed surface of a system part selected.Let us select an element at the interface between the phases a and b, the interphase thickness being so chosen as to attain bulk phases on both sides of the interface.Introducing a dividing surface inside the interphase divides the interface element into the a-layer (adjacent to the phase a and depicted as opaque in Figure 1) and the b-layer (adjacent to the phase b and depicted as transparent in Figure 1). Within the boundaries of the element, the dividing surface area is A0 = = l10l20, where l10 and l20 are the lengths of the dividing surface in directions 1 and 2 (Figure 1).Let us apply, as the first step, equation (3) to the a-layer filled (in mind) with the matter of the bulk phase a (extrapolated to the a-layer). As the second step, we similarly apply equation (3) to the b-layer filled with the matter of the bulk phase b. Then, we subtract both of the relationships obtained from equation (3) applied to the real interface element under consideration as a whole.In this way, we arrive at the mechanical equilibrium condition in the vector form where the first term represents the pressure-force difference at the dividing surface on its opposite sides, and the second and third terms represent the tension-force differences on the opposite edges of the dividing surface in directions 1 and 2, respectively.Note that, according to the above procedure, the vectors g1' and g2'' correspond to the force definition of the surface-tension vector (which is equivalent to the definition by integration of the excess strain over the cross-sections for directions 1 and 2, respectively10). Equation (4) implies the vectors P3, g1' and g2'' not to be directed, by necessity, along the normal or the tangent to the dividing surface, respectively.Dividing (4) by l10l20 with the subsequent transitions l10 ® 0 and l20 ® 0, we proceed to the rigorous local formulation of the mechanical equilibrium condition Equation (5), the main result of this work, is a generalization of the Laplace equation valid for any (diagonal or non-diagonal) forms of the pressure and surface-tension tensors.Surprisingly, the Laplace equation exhibits an extremely compact form even in the general and complicated case. Vector equation (5) comprises three scalar equations, which can be deduced as described below. There are the identities [with ei (i = 1, 2, 3) as unit vectors along the co-ordinate line directions] where g'i1 and g'' i2 are the components of the surface-tension tensors as excess stress tensors over the cross-sections for direcp a – pb= , g R1 +R2 (1) pa – pb= + , g1 R1 (2) g2 R2 (pdA) = PdA = 0 ^ ò ò (3) p^ p^ 1 2 n a b l10 l20 R10 R20 Figure 1 Element of a non-spherical interface.(P3 a – P3 b)l10l20 + Dg1 ' l20 + Dg2''l10 = 0, (4) ¶ ¶ P3 a – P3 b = – – . g1 ' l10 (5) g 2'' l20 ¶ ¶ P3 a – P3 b= (Pi3 a – Pi3 b )ei , g1 ' = gi1 ' ei , g2'' = gi2'' ei .(6) Si = 1 3 Si = 1 3 Si = 1 3Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) tions 1 and 2, respectively. Using (6), we can write equation (5) in the form Now, we have to account for the standard Serret–Frenet equations of differential geometry where t, n and b are the unit vectors of the line tangent, the line principal normal and the line binormal, respectively; c and T are the line curvature and the line torsion, respectively. According to the above choice of the co-ordinate system, T = 0 in our case. Then, applying (8) to the co-ordinate lines on the dividing surface (we have t = e1, n = –e3, b = –e2 with L = l10 and t = e2, n = –e3, b = –e1 with L = l20), we obtain Putting now (9) in (7), we can pass to separate scalar components of equation (7).In particular, multiplying (7) scalarly by e3, we have Equation (10) was derived by Evans and Skalak11 for a curved membrane. In the case when the surface-tension tensor is diagonal (g31 = g32 = 0), equation (10) is identical to equation (2). Multiplying now equation (7) by e1 and e2, we obtain, respectively, Nobody seems to consider these equilibrium conditions so far. Passing to the diagonal form of the pressure and surface-tension tensors, equations (11) and (12) change to the known conditions that means the conservation of the principal surface-tension components along the corresponding co-ordinate lines.This work was supported by the Russian Foundation for Basic Research (grant no. 98-03-32009a). References 1 F. P. Buff, J. Chem. Phys., 1955, 23, 419. 2 F. P. Buff, in Handbuch der Physik, ed. S. Fluegge, Springer, Berlin, 1960, vol. 10, p. 281. 3 V. V. Krotov, A. I. Rusanov and A. Blinowski, Kolloidn. Zh., 1982, 44, 471 [Colloid J. USSR (Engl. Transl.), 1982, 44, 420]. 4 P. A. Kralchevsky, J. Colloid Interface Sci., 1990, 137, 217. 5 T. D. Gurkov and P. A. Kralchevsky, Colloids Surf., 1990, 47, 45. 6 P. A. Kralchevsky, J. C. Eriksson and S. Ljunggren, Adv. Colloid Interface Sci., 1994, 48, 19. 7 M. Pasandideh-Fard, P. Chen, J. Mostaghimi and A. W. Neumann, Adv. Colloid Interface Sci., 1996, 63, 151. 8 P. Chen, S. S. Susnar, M. Pasandideh-Fard, J. Mostaghimi and A. W. Neumann, Adv. Colloid Interface Sci., 1996, 63, 179. 9 A. I. Rusanov and A. K. Shchekin, Kolloidn. Zh., 1999, 61, 437 [Colloid J. (Engl. Transl.), 1999, 61, 403]. 10 A. I. Rusanov, A. K. Shchekin and V. B. Warshavsky, Kolloidn. Zh., 2000, in press. 11 A. E. Evans and R. Skalak, CRC Crit. Rev. Bioeng., 1979, 3, 181. ¶ gi1 ' (Pi3 a – Pi3 b )ei = – ei – gi1 ' – ei – gi2 '' . (7) Si = 1 3 Si = 1 3 Si = 1 3 ¶l10 ¶ ¶l10 ei Si = 1 3 ¶gi2'' ¶l20 Si = 1 3 ¶ ¶l20 ei dt/dL = cn, dn/dL = –ct + Tb, db/dL = –Tn, (8) ¶ ¶l10 e1 = – , R10 e3 ¶ ¶l10 e2 = 0, ¶ ¶l10 e3= , R10 e1 ¶ ¶l20 e2 = – , R20 e3 ¶ ¶l20 e1 = 0, ¶ ¶l20 e3= . R20 e2 (9) P33 a – P33 b = – + – + ¶g31 ' ¶l10 g11 ' R10 ¶g32 '' ¶l20 g22 '' R20 (10) P13 a – P13 b = – – – , ¶g11 ' ¶l10 g31 ' R10 ¶g12 '' ¶l20 (11) P23 a – P23 b = – – – . ¶g21 ' ¶l10 g22 '' R20 ¶ g32 '' ¶l20 (12) ¶ g11 ' ¶l10 g22 '' ¶l20 = 0, = 0 (13) ¶ Received: 7th February 2000; Com. 00/1602

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Synthesis of series 2 trioxilins from trioxilin B3 by selective hydrogenation Margarita A. Lapitskaya, Ljudmila L. Vasiljeva, Georgy V. Zatonsky and Kasimir K. Pivnitsky* N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: li@ioc.ac.ru 10.1070/MC2000v010n04ABEH001297 Trioxilins (as methyl esters) (10S,11S,12S)-TrXB2 and its (8E)-isomer were obtained by selective hydrogenation of the 5,6-double bond in (10S,11S,12S)-TrXB3 11,12-acetonide followed by deprotection. Hepoxilins and their immediate metabolites, trioxilins (TrX)1 of series 3† (i.e., with three double bonds at the 5,6-, 8,9- or 9,10-, and 14,15-positions), are metabolites formed from arachidonic acid via a 12-lipoxygenase pathway.1 During the last years, hepoxilins attracted significant attention of biochemists mainly because of their regulatory role in an insulin secretion and hence in connection with diabetes.However, these studies were limited to series 3 hepoxilins, although series 4 hepoxilins, derived from (all-Z)-5,8,11,14,17-eicosapentaenoic acid were identified as endogenous metabolites.2 Other eicosanoids, prostaglandins (PG), are biosynthesised not only from the two above polyunsaturated fatty acids (PGs of series 2 and 3), but to the same extent from bis-homo-g- linolenic acid (PGs of series 1).3 Therefore, the occurrence of the corresponding series 2 hepoxilins and trioxilins in organisms seems to be very probable.To identify these potential endogenous 12-lipoxygenase eicosanoids, an independent chemical synthesis is desirable. The total syntheses of prostaglandins of different series were accomplished by different, frequently independent, synthetic procedures. 3 However, the conversion of PG2 into PG1 was described. 4 This conversion is based on the selective hydrogenation of the 5,6(Z)-double bond in protected PG2 derivatives, which is possible because of a diminished reactivity of the 13,14-double bond resulting from the (E)-configuration and steric hindrances from protective groups.Such a situation is not characteristic of series 3 hepoxilins/trioxilins, in which 5,6(Z)- and 14,15(Z)- double bonds together with their surroundings are very similar, and the third 8,9(Z)-double bond is present.Nevertheless, we have found a new means to differentiate these three double bonds thus making possible a direct conversion of series 3 trioxilins into series 2. In the recent total synthesis of (10S,11S,12S)-TrXB3 we observed5 a striking selectivity in catalytic hydrogenation of 5,8,14-triacetylenic precursor 11,12-acetonide 1 into corresponding triene 2 (Scheme 1).The ease of hydrogenation of triple bonds in this triacetylene decreased in the order 5,6 > > 8,9 >> 14,15. The selectivity was explained by a hairpin conformation of the molecule due to the presence of a cis-substituted acetonide ring (as evident from the semi-empirical PM3 calculations). The C9,10-fragment of molecule 1 in this conformation screens the 14,15-triple bond to reduce its reactivity.We surmised that the same selectivity could be held in some extent in triene 2 as well, thus opening the way to corresponding eicosanoids of series 2. This assumption has happened to be the case. The catalytic hydrogenation of triene 2 over Pd/CaCO3 ‡ in the presence of pyridine produced a product mixture, which was separated by high-performance flash chromatography6 (HPFC).The main products were desired 5,6-dihydro derivative 3, isolated in 31% yield, and 8,9-dihydro derivative 5 (19%). Two minor products were unexpected (8E)-5,6-dihydro derivative 4 (11%) and tetrahydro derivative 6 (4.5%).§ The positions of double bonds in hydrogenation products 3–6 were determined from single- and two-dimensional (H–H COSY) 1H NMR data,¶ because the mass spectra provided information on the number rather than the position of double bonds because of the complexity of skeletal fragmentation.†† The NMR spectra of all compounds do not contain a multiplet of the C7H2 group separating 5,6- and 8,9-double bonds, which is characteristic of starting triene 2; therefore, one (or both) of these double bonds was hydrogenated.The presence of the 8,9-double bond in 3 † Trivial names and abbreviations: arachidonic acid is (all-Z)-5,8,11,14- eicosatetraenoic acid; bis-homo-g-linolenic acid is (all-Z)-8,11,14-eicosatrienoic acid; eicosanoids of series 1, 2, 3 or 4 are eicosanoids with 1, 2, 3 or 4 double bonds in a molecule, respectively; hepoxilins (of types A3/B3) are stereoisomers of 8/10-hydroxy-11,12-epoxyeicosa-5(Z),9(E)/ 8(Z),14(Z)-trienoic acids; PG is prostaglandin; TrXB3 are stereoisomers of 10,11,12-trihydroxyeicosa-5(Z),8(Z),14(Z)-trienoic acid (each compound can occur as a free acid or its methyl ester).‡ Hydrogenation over the Lindlar catalyst proceeded very slowly. § Triene 2 (23 mg) in a benzene solution (2.2 ml) containing pyridine (0.2% v/v) was hydrogenated over a prereduced 5% Pd/CaCO3 catalyst (5 mg, Aldrich) at 20 °C and 1 atm until all starting material was converted (5 h, TLC).The mixture was filtered and evaporated to dryness, and the residual oil was separated by HPFC on a Kieselgel 60 (Fluka) column (24×2 cm, over 2000 theoretical plates; gradient elution with EtOAc–hexane, 5:95 ® 20:80). In the order of elution, the following compounds were isolated: 1 mg (4.5%) of 6 [Rf 0.67, silica gel plates (Merck), quadruple development by EtOAc–hexane, 20:80, for starting triene 2 Rf 0.43], 2.5 mg (11%) of a 5 + 6 mixture, 4.4 mg (19%) of 5 {Rf 0.63, [a]D 31 –11° (c 0.29, CHCl3)}, 2.5 mg (11%) of 4 (Rf 0.52) and 7.1 mg (31%) of 3 {Rf 0.48, [a]D 31 –2.5° (c 0.47, CHCl3)}.O O COOMe Me Me Me HO 1 5 6 8 9 10 14 15 20 O O Me Me Me HO COOMe 1 5,6; 8,9 and 14,15 are triple bonds 2 5,6; 8,9 and 14,15 are double bonds 3 8,9: Z; 31% 4 8,9: E; 11% O O Me Me Me HO 5 5,6 is double bond; 19% 6 5,6 is single bond; 4.5% COOMe HO OH HO Me COOMe 7 5,6 is single, 8,9 is double bonds; TrXB2 8 5,6 is double, 8,9 is single bonds H2, Pd/CaCO3 AcOH, 55 °C 99% AcOH, 55 °C 97% Scheme 1Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) and 4 is evident from the chemical shifts and multiplicities of C10HOH signals, as well as their COSY correlations with the signal of a vinylic proton in each case. In 4, this signal (=C8H) is shifted to low field and splitted with the coupling constant 3J8–9 = 15.5 Hz so this double bond has (E)-configuration.Compounds 5 and 6 do not possess 8,9-double bonds, as evident from a significant (Dd –0.8 ppm) shift of non-allylic C10HOH signals to high field. The intactness of 14,15-double bonds in all hydrogenation products 3–6 follows from the similarity of C13H2 signals (multiplet centered at near 2.4 ppm) in their spectra. Some other features of the NMR spectra also support the conclusions that dihydro compounds 3 and 4 are formed by hydrogenation of the 5,6-double bond of 2; dihydro compound 5 is the result of 8,9-double bond hydrogenation, and both hydrogenations simultaneously lead to tetrahydro compound 6.It follows from the yields of hydrogenation products 3 + 4 and 5 that the hydrogenation reactivities of 5,6- and 8,9-double bonds in triene 2 are in a ratio of 2.2 : 1.The 14,15-double bond is not hydrogenated at all under the conditions used. All these findings are in a qualitative agreement with expectations based on the reactivity of triyne 1. The formation of (8E)- product 4 may be understood as the possibility of (Z) ® (E) isomerization of disubstituted double bonds in the course of Pdcatalyzed hydrogenations is long known.7 Dobson et al.7 found that the extent of this isomerization is unpredictable and depends (for Pd/C) on the origin of the catalyst.The acetic acid hydrolysis of acetonides 3 and 5 cleanly produced trioxilins (10S,11S,12S)-TrXB2 7‡‡ and 8,9-dihydro- (10S,11S,12S)-TrXB3 8§§ (as methyl esters). Although the total yield of series 2 trioxilin 7 is not high, this straightforward method of partial synthesis is much simpler and gives higher yields than any independent total synthesis.The similar protocol, e.g., hydroxyl group protection to shield the neighbouring double bonds — partial catalytic hydrogenation — deprotection, seems to be applicable to the synthesis of other less unsaturated 12-lipoxygenase eicosanoids from the corresponding series 3 congeners already obtained by total synthesis.This work was supported by the Russian Foundation for Basic Research (grant no. 98-03-32996) and by the Noncommercial Partnership programme ‘ASGL — Development of New Biologically Active Compounds for Medical Purposes’. References 1 C. R. Pace-Asciak, D. Reynaud and P. M. Demin, Lipids, 1995, 30, 107. 2 (a) D. L. Holland, J. East, K.H. Gibson, E. Clayton and A. Oldfield, Prostaglandins, 1985, 29, 1021; (b) C. R. Pace-Asciak, Prostaglandins, Leukotrienes and Medicine, 1986, 22, 1. 3 J. S. Bindra and R. Bindra, Prostaglandin Synthesis, Academic Press, New York, 1977. 4 (a) E. J. Corey and R. K. Varma, J. Am. Chem. Soc., 1971, 93, 7319; (b) E. J. Corey, R. Noyori and T. K. Schaaf, J. Am. Chem. Soc., 1970, 92, 2586. 5 M. A. Lapitskaya, L. L. Vasiljeva, D. M. Kochev and K. K. Pivnitsky, Izv. Akad. Nauk, Ser. Khim., 2000, 545 (Russ. Chem. Bull., 2000, 49, 549). 6 K. K. Pivnitsky, Aldrichim. Acta, 1989, 22, 30. 7 N. A. Dobson, G. Eglinton, M. Krishnamurti, R. A. Raphael and R. G. Willis, Tetrahedron, 1961, 16, 16. ¶ 1H NMR spectra were measured in CDCl3 on a Bruker DRX500 spectrometer at 500.13 MHz for 3, 4 and Bruker AC-200 at 200.13 MHz for 5, 6 (d/ppm).For 3: 0.89 (t, 3H, C20H3), 1.26–1.43 (m, 12H, C4–6,17–19H2), 1.38 and 1.52 (2s, 2×3H, O2CMe2), 1.58–1.66 (m, 2H, C3H2), 1.99–2.07 (m, 2H, C16H2), 2.10 (dqd, 1H, C7HaHb), 2.21 (dq, 1H, C7HaHb), 2.27–2.42 (m, 2H, C13H2), 2.31 (t, 2H, C2H2), 3.68 (s, 3H, COOMe), 4.00 (t, 1H, C11H), 4.14 (ddd, 1H, C12H), 4.45 (ddd, 1H, C10H), 5.38–5.45 (m, 2H, C9,14H), 5.48–5.56 (m, 1H, C15H), 5.63 (dt, 1H, C8H); 3J2–3 7.5 Hz, 3J6–7a 7.5 Hz, 3J6-7b 7.5 Hz, 2J7a–7b 15.0 Hz, 3J7a–8 7.5 Hz, 4J7a–9 2.0 Hz, 3J7b–8 7.5 Hz, 3J8–9 11.0 Hz, 3J9–10 9.2 Hz, 3J10–11 5.9 Hz, 3J10–OH 3.5 Hz, 3J11–12 5.9 Hz, 3J12–13a 5.2 Hz, 3J12–13b 8.9 Hz, 3J19–20 6.4 Hz. For 4: 0.89 (t, 3H, C20H3), 1.26–1.42 (m, 12H, C4–6,17–19H2), 1.38 and 1.51 (2s, 2×3H, O2CMe2), 1.62 (quintet, 2H, C3H2), 2.01–2.09 (m, 4H, C7,16H2), 2.29–2.44 (m, 2H, C13H2), 2.31 (t, 2H, C2H2), 3.68 (s, 3H, COOMe), 3.99 (t, 1H, C11H), 4.11–4.16 (m, 2H, C10,12H), 5.42 (ddt, 1H, C14H), 5.47 (ddt, 1H, C9H), 5.52 (dtt, 1H, C15H), 5.81 (dt, 1H, C8H); 3J2–3 7.6 Hz, 3J3–4 7.6 Hz, 3J7–8 6.5 Hz, 4J7–9 1.5 Hz, 3J8–9 15.5 Hz, 3J9–10 7.5 Hz, 3J10–11 6.2 Hz, 3J11–12 6.2 Hz, 3J13–14 6.8 Hz, 4J13–15 1.5 Hz, 3J14–15 10.7 Hz, 4J14–16 1.5 Hz, 3J15–16 7.3 Hz, 3J19–20 6.5 Hz.For 5: 0.89 (t, 3H, C20H3), 1.23–1.65 (m, 10H, C8,9,17–19H2), 1.38 and 1.51 (2s, 2×3H, O2CMe2), 1.70 (quintet, 2H, C3H2), 1.96–2.15 (m, 2H, C4,7,16H2), 2.28–2.56 (m, 2H, C13H2), 2.32 (t, 2H, C2H2), 3.58–3.72 (m, 1H, C10H), 3.68 (s, 3H, COOMe), 3.95 (dd, 1H, C11H), 4.18 (dt, 1H, C12H), 5.28–5.60 (m, 4H, C5,6,14,15H); 3J2–3 7.3 Hz, 3J3–4 7.3 Hz, 3J10–11 4.5 Hz, 3J11–12 6.2 Hz, 3J12–13a 6.2 Hz, 3J12–13b 8.9 Hz, 3J19–20 6.5 Hz.For 6: 0.89 (t, 3H, C20H3), 1.23–1.64 (m, 20H, C3–9,17–19H2), 1.38 and 1.51 (2s, 2×3H, O2CMe2), 2.06 (dt, 2H, C16H2), 2.20–2.56 (m, 2H, C13H2), 2.31 (t, 2H, C2H2), 3.58–3.72 (m, 1H, C10H), 3.68 (s, 3H, COOMe), 3.96 (dd, 1H, C11H), 4.18 (dt, 1H, H12), 5.34–5.62 (m, 2H, C14,15H); 3J2–3 7.4 Hz, 3J10–11 4.6 Hz, 3J11–12 5.9 Hz, 3J12–13a 5.9 Hz, 3J12–13b 8.5 Hz, 3J15–16 6.4 Hz, 3J16–17 6.4 Hz, 3J19–20 6.5 Hz.†† High ion MS [Kratos MS 890 instrument, direct inlet at 150 °C, EI, 30 eV, m/z (%)]. For 3: 410 (2.2) [M]+· , 395 (19) [M – Me]+, 392 (2.1) [M – H2O]+· , 377 (1.5) [M –Me – H2O]+, 352 (4.1) [M –Me2CO]+·, 335 (8.8) [M – Me2CO – – OH]+, 321 (8.4) [M – Me2CO – MeO]+, 303 (20) [M – Me2CO – H2O – – MeO]+.For 4: 410 (0.7) [M]+· , 395 (11) [M – Me]+, 392 (0.8) [M – H2O]+· , 377 (0.6) [M –Me – H2O]+, 352 (2.7) [M –Me2CO]+· , 335 (9.2) [M – Me2CO – – OH]+, 321 (7.8) [M – Me2CO – MeO]+, 303 (15) [M – Me2CO – H2O – – MeO]+. For 5: 410 (3.1) [M]+· , 395 (45) [M – Me]+, 352 (12) [M – Me2CO]+· , 335 (15) [M – Me2CO – OH]+, 321 (14) [M – Me2CO – MeO]+, 303 (8.9) [M – Me2CO – H2O – MeO]+.For 6: 412 (1.2) [M]+· , 397 (19) [M – Me]+, 354 (1.3) [M – Me2CO]+· , 337 (2.5) [M – Me2CO – OH]+, 323 (7.7) [M – Me2CO – MeO]+. ‡‡ A solution of acetonide 3 (5.6 mg) in 80% aqueous AcOH (500 ml) was heated at 55 °C for 5 h and then evaporated in a vacuum to dryness producing triol 7 (5.0 mg, 99%) as a clear oil, Rf 0.18 (EtOAc–hexane, 30:70, triple development), [a]D 30 +4.9° (c 0.38, CHCl3). 1H NMR (200.13 MHz, CDCl3) d: 0.90 (t, 3H, C20H3, J 6.7 Hz), 1.15–1.45 (m, 12H, C4–6,17–19H2), 1.64 (quintet, 2H, C3H2, J 7.2 Hz), 1.95–2.15 (m, 3H, C16H2 and C7HaHb), 2.31 (t overlapping m, 2H, C2H2, J 7.4 Hz), 2.22–2.47 (m, 3H, C7HaHb and C13H2), 3.48 (br. s, 1H, C11H), 3.69 (s, 3H, COOMe), 3.76 (br. t, 1H, C12H, J 6.5 Hz), 4.67 (br. s, 1H, C10H), 5.33–5.70 (m, 4H, C8,9,14,15H). §§ Triol 8 was obtained from acetonide 5 analogously to triol 7. For 8: yield 97%, Rf 0.26 (EtOAc–hexane, 30:70, triple development), [a]D 30 –13° (c 0.25, CHCl3). 1H NMR (200.13 MHz, CDCl3) d: 0.90 (t, 3H, C20H3, J 6.1 Hz), 1.20–1.65 (m, 10H, C8,9,17–19H2), 1.68 (quintet, 2H, C3H2, J 7.1 Hz), 1.95–2.38 (m, 10H, C2,4,7,13,16H2), 3.35–4.05 (m, 3H, C10–12H), 3.69 (s over-lapping m, 3H, COOMe), 5.25–5.65 (m, 4H, C4,5,14,15H). Received: 10th March 2000; Com. 00/1623

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Synthesis of GlcNAc-terminated oligosaccharides — fragments of glycoprotein O-chains Galina V. Pazynina and Nicolai V. Bovin* M. M. Shemyakin–Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117871 Moscow, Russian Federation. Fax: +7 095 330 5592; e-mail: bovin@carb.siobc.ras.ru 10.1070/MC2000v010n04ABEH001277 The trisaccharides GlcNAcb1-6(GlcNAcb1-3)GalNAcaOR and GlcNAcb1-6(Galb1-3)GalNAcaOR, and disaccharides GlcNAc b1-3GalNAcaOR and GlcNAcb1-6GalNAcaOR as spacered derivatives (R = CH2CH2CH2NH2) were synthesised using a Troc-protected glucosamine glycosyl donor at the key stage.Eight different cores, i.e., regions connected with Ser or Thr of mammalian glycoprotein O-chains are known; four of them are terminated by a GlcNAcb moiety.1 The above GlcNAcb-terminated oligosaccharides have been identified in mucin-type glycoproteins; at least one of them, core 6 structure, being a substrate for enzyme b-galactosyltransferase, plays a role in oncotransformation.2 Here we describe the synthesis of core 2, 3, 4, and 6 oligosaccharides as spacered compounds 1–4 suitable for further transformation to different glycoprobes, 3 which are indispensable tools for glycobiology.We used 3'-trifluoroacetamidopropyl 2-acetamido-4,6-Obenzylidene- 2-deoxy-a-D-galactopyranoside 5 as a starting building block.4 To synthesise disaccharide 1, compound 5 was glycosylated at the single unprotected 3-OH position (Scheme 1). O O O Ph OH NHAc OCH2CH2CH2NHCOCF3 5 O AcO OAc NHTroc Br AcO 6 O HO HO OAc NHAc OCH2CH2CH2NHCOCF3 9 5 + 6 AgOTf, Me2NCONMe2 O R4O OR4 NHR3 R4O O R2O R2O O NHAc OR1 7 R1 = (CH2)3NHCOCF3, R2R2 = PhCH, R3 = Troc, R4 = Ac, 71% 8 R1 = (CH2)3NHCOCF3, R2 = H, R3 = Troc, R4 = Ac i 8a R1 = (CH2)3NHCOCF3, R2 = R3 = R4 = Ac ii, iii 1 R1 = (CH2)3NH2, R2 = R4 = H, R3 = Ac iv, v 6 + 8 AgOTf, Me2NCONMe2 O R4O OR4 NHR3 R4O O R2O O O NHAc OR1 O R4O OR4 NHR3 R4O 10 R1 = (CH2)3NHCOCF3, R2 = H, R3 = Troc, R4 = Ac, 50% 11 R1 = (CH2)3NHCOCF3, R2 = b-Ac3GlcNTroc, R3 = Troc, R4 = Ac, 21% iii, iv, v 2 R1 = (CH2)3NH2, R2 = R4 = H, R3 = Ac O AcO OAc NHTroc AcO b-Ac3GlcNTroc = O R4O OR4 NHR3 R4O O R5O O OR2 NHAc OR1 6 + 9 AgOTf, Me2NCONMe2 12 R1 = (CH2)3NHCOCF3, R2 = R4 = Ac, R3 = Troc, R5 = H, 46% 13 R1 = (CH2)3NHCOCF3, R2 = R4 = Ac, R3 = Troc, R5 = b-Ac3GlcNTroc, 10% iii, iv, v 3 R1 = (CH2)3NH2, R2 = R4 = R5 = H, R3 = Ac O AcO OAc OAc AcO O HO HO O NHAc OR1 + 6 O R2O OR2 OR2 R2O O HO O O NHAc OR1 O R2O OR2 NHR3 R2O 15 R1 = (CH2)3NHCOCF3, R2 = Ac, R3 = Troc, 65% iii, iv, v 4 R1 = (CH2)3NH2, R2 = H, R3 = Ac 14 Scheme 1 Reagents and conditions: i, AcOH; ii, Ac2O, Py; iii, Zn, AcOH, Ac2O; iv, MeONa, MeOH; v, Et3N, H2O.Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Obtained disaccharide 7 was the starting material in the synthesis of trisaccharide 2; 7 was 4,6-O-debenzylidenated followed by regioselective glycosylation at the position 6-OH of obtained diol 8.In order to synthesise disaccharide 3, the 3-OH group in compound 5 was protected by acetylation followed by removal of the benzylidene group; obtained diol 9 was 6-O-glycosylated as described above.Trisaccharide 4 was synthesised by 6-O-regioselective glycosylation of disaccharide 145 with bromide 6. In all cases, N-Troc-protected glucosyl bromide 6 (Troc is 1,1,1-trichloroethyloxycarbonyl)6 was used for stereocontrolled b-glycosylation, this choice is stipulated by good yields, high b-stereoselectivity of glycosylation,6 and compatibility of this protection with other protecting groups used in the synthesis.Preparative yields of glycosylation with this reagent are shown in Scheme 1, the yields are comparable with published data.6 Because glycosyl donor 6 was taken in some excess, glycosylation of diols 8 and 9 gave rise not only to the aimed monoglycosylation products, but also to corresponding 4,6-di- O-glycosyl derivatives 11 and 13 (Scheme 1). The b-stereochemistry of glycosylation with donor 6 is confirmed by corresponding J1,2 values of 8.0–9.5 Hz, the regioselectivity of the glycosylation reaction in cases of diol aglycons 8, 9 and 14 was confirmed by acetylation of the unprotected hydroxyl group in glycosylation product and an NMR study of the acetylated derivatives, using homonuclear correlation spectroscopy (COSY) and conventional analysis of coupling patterns.Mass spectra (MALDI, Vision-2000, Thermo Bio Corp., England) of deprotected compounds: 1, 505 (M + Na+); 2, 707 (M + Na+); 3, 505 (M + Na+); 4, 666 (M + Na+). Deprotection of sugar moieties and spacer-arm with conventional methods (Scheme 1) gave rise to oligosaccharides 1–4 as 3-aminopropyl glycosides in overall yields of 80–90%.† The synthesis of these oligosaccharides in a convenient spacered form was not described earlier. Compounds 1–4 coupled with polyacrylamide3 were used for characterization of anti-Tk antibodies, the data will be published elsewhere.References 1 E. F.Hounsell, M. J. Davies and D. V. Renouf, Glycoconjugate J., 1996, 13, 19. 2 Y. Yamashita, Y. S. Chung, R. Horie, R. Kannagi and M. Sowa, J. Natl. Cancer. Inst., 1995, 87, 441. 3 N. V. Bovin, Glycoconjugate J., 1998, 15, 431. 4 N. V. Bovin, T. V. Zemlyanukhina and A. Ya. Khorlin, Bioorg. Khim., 1986, 12, 533 [Sov. J. Bioorg. Chem. (Engl. Transl.), 1986, 12, 282]. 5 N. V. Bovin, T.V. Zemlyanukhina and A. Ya. Khorlin, Bioorg. Khim., 1985, 11, 1256 (in Russian). 6 V. Ellervik and G. Magnusson, Carbohydr. Res., 1996, 280, 251. GlcNAcb1-3GalNAcaO-Ser/Thr (core 3) GlcNAcb1-6 GalNAcaO-Ser/Thr (core 4) GlcNAcb1-3 GlcNAcb1-6GalNAcaO-Ser/Thr (core 6) GlcNAcb1-6 GalNAcaO-Ser/Thr (core 2) Galb1-3 GlcNAcb1-3GalNAcaO-CH2CH2CH2NH2 GlcNAcb1-6 GalNAcaO-CH2CH2CH2NH2 GlcNAcb1-3 GlcNAcb1-6GalNAcaO-CH2CH2CH2NH2 GlcNAcb1-6 GalNAcaO-CH2CH2CH2NH2 Galb1-3 1 2 3 4 † 1H NMR data (D2O, 500 MHz, d/ppm); solutions contained 5% of trifluoroacetic acid. Signals of the OCH2CH2CH2N group: 3.6–3.7, 3.0– 3.1, 1.8–2.0.For 1, GlcNAcb1-3 unit: 4.516 (d, H-1, J1,2 8.5 Hz), 3.631 (dd, H-2, J2,3 9.9 Hz), 3.481 (dd, H-3, J3,4 9.3 Hz), 3.397 (dd, H-4, J4,5 9.3 Hz), 3.494 (m, H-5), 3.833 (dd, H-6a, J5,6a 1.5 Hz, J6a,6b 12.8 Hz), 3.351 (unresolved m, H-6b), 1.955 (s, Ac); GalNAca1-Osp unit: 4.790 (d, H-1, J1,2 3.8 Hz), 4.197 (dd, H-2, J2,3 11.8 Hz), 3.898 (dd, H-3, J3,4 3.0 Hz), 4.150 (d, H-4, J4,5 < 1.0 Hz), 3.658–3.778 (m, H-6a and H-6b), 1.983 (s, Ac).For 2, GlcNAcb1-3 unit: 4.487 (d, H-1, J1,2 8.7 Hz), 3.620 (dd, H-2, J2,3 10.2 Hz), 3.385–3.490 (m, H-3), 3.370 (dd, H-4, J4,5 10.2 Hz), 3.855 (dd, H-6a, J5,6a 1.5 Hz, J6a,6b 12.8 Hz), 1.937 (s, Ac); GalNAcb1-6 unit: 4.424 (d, H-1, J1,2 8.8 Hz), 3.601 (dd, H-2, J2,3 10.2 Hz), 3.353 (dd, H-4, J4,5 10.2 Hz), 3.809 (dd, H-6a, J5,6a 1.5 Hz, J6a,6b 12.8 Hz), 1.961 (s, Ac); GalNAca1-Osp unit: 4.732 (d, H-1, J1,2 3.8 Hz), 4.164 (dd, H-2, J2,3 11.5 Hz), 3.869 (dd, H-3, J3,4 3.0 Hz), 4.114 (d, H-4, J4,5 1 Hz), 3.942 (m, H-5), 4.008 (dd, H-6a, J5,6a 3.0 Hz, J6a,6b 11.5 Hz), 1.937 (s, Ac). For 3, GlcNAcb1-6 unit: 4.449 (d, H-1, J1,2 9.0 Hz), 3.640 (dd, H-2, J2,3 10.2 Hz), 3.468 (dd, H-3, J3,4 8.3 Hz), 3.367 (dd, H-4, J4,5 9.6 Hz), 3.868 (dd, H-6a, J5,6a 1.5 Hz, J6a,6b 12.5 Hz), 1.958 (s, Ac); GalNAca- Osp unit: 4.814 (d, H-1, J1,2 3.8 Hz), 4.088 (dd, H-2, J2,3 11.5 Hz), 3.836 (dd, H-3, J3,4 3.2 Hz), 3.905 (d, H-4, J4,5 1 Hz), 3.935 (m, H-5), 4.018 (dd, H-6a, J5,6a 3.5 Hz, J6a,6b 11.5 Hz), 1.972 (s, Ac).For 4, GlcNAcb1-6 unit: 4.489 (d, H-1, J1,2 8.5 Hz), 3.682 (dd, H-2, J2,3 10.2 Hz), 3.513 (dd, H-3, J3,4 8.2 Hz), 3.426 (dd, H-4, J4,5 8.2 Hz), 3.906 (dd, H-6a, J5,6a 1.5 Hz, J6a,6b 11 Hz), 1.995 (s, Ac); Galb1-3 unit: 4.432 (d, H-1, J1,2 7.7 Hz), 3.499 (dd, H-2, J2,3 11.1 Hz), 3.588 (dd, H-3, J3,4 3.5 Hz), 3.884 (dd, H-4, J4,5 1 Hz); GalNAca-Osp unit: 4.852 (d, H-1, J1,2 3.8 Hz), 4.301 (dd, H-2, J2,3 11.1 Hz), 3.982 (dd, H-3, J3,4 3.0 Hz), 4.193 (d, H-4, J4,5 1 Hz), 4.003 (m, H-5), 4.058 (dd, H-6a, J5,6a 2.5 Hz, J6a,6b 10.8 Hz), 1.995 (s, Ac). < < < < Received: 8th February 2000; Com. 00/1603

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Reaction of [(PPh3)3RuCl2] with white phosphorus: synthesis of the first RuII complex featuring a tetrahedro-tetraphosphorus ligand Maurizio Peruzzini,*a Sonia Mañas,b Antonio Romerosa*b and Alberto Vaccac a ISSECC-CNR, 50132 Florence, Italy. Fax: +39 055 247 8366; e-mail: peruz@fi.cnr.it b Área de Química Inorgánica, Facultad de Ciencias, Universidad de Almería, 04071 Almería, Spain.E-mail: romerosa@ualm.es c Dipartimento di Chimica, Università di Firenze, 50144 Florence, Italy 10.1070/MC2000v010n04ABEH001271 The title reaction affords slightly air- and light-sensitive [(PPh3)2ClRu(m-Cl)3Ru(PPh3)2(h1-P4)], which belongs to a very rare family of soluble tetrahedro-tetraphosphorus complexes and represents the first ruthenium species of this type.White phosphorus, which exhibits an unique structure formed by tetrahedral P4 molecules, is the principal material used for the industrial preparation of organophosphorus compounds. These compounds are of commercial interest and are produced in megaton amounts as fertilizers, pesticides, detergents, additives for lubricants in polymers, metal extractants in nuclear industry, flame retardants for plastic materials etc.1 Presently, the industrial use of white phosphorus is based on the preliminary transformation of P4 to PCl3 by a reaction with chlorine.The chlorination step causes serious environmental problems due to the emission of large amounts of HCl into the atmosphere. For this reason, it is environmentally important to develop a cleaner process for the preparation of organophosphorus derivatives with comparable or reduced costs.An interesting alternative to the current technology may be catalytic activation and functionalisation of P4 by transition metal complexes. 2 To successfully accomplish this goal, a deeper knowledge of the co-ordination chemistry of the P4 molecule with transition metals is required.One of the most largely employed homogeneous catalyst is [(PPh3)3RuCl2] 1.3 Therefore, we believed that this ruthenium derivative and related complexes can also be useful materials to study the catalytic functionalisation of white phosphorus. Despite the vast literature concerning P4 as a source of Px ligands in transition metal complexes,4 the reaction of P4 with 1 was not yet studied, and the number of ruthenium complexes featuring polyphosphorus units is also very limited.5 Here, we report on our preliminary studies in the reaction of white phosphorus with 1, which, to the best of our knowledge, leads to the synthesis of the first ruthenium complex supporting an intact P4 ligand.6 When a solution of white phosphorus in dry and deoxygenated toluene is added to one equivalent of 1 dissolved in the same solvent, a dark brown solution forms within 15 min on standing at room temperature.† From this solution, reddish-brown microcrystals of binuclear ruthenium species [(PPh3)2ClRu- (m-Cl)3Ru(PPh3)2(h1-P4)] 2 are obtained after layering with n-hexane.Release of two equivalents of PPh3 into the solution (31P NMR detected) accompanies the formation of the binuclear complex.Changing the ratio between 1 and P4 does not modify the course of the reaction, and even when a tenfold excess of white phosphorus is used only 2 forms. Solutions of 2 in organic solvents are unstable (air- and lightsensitive). A slow decomposition takes place, even under nitrogen, at room temperature to afford a brown precipitate, which is almost insoluble in all common organic solvents and cannot be further characterised.However, once generated from 1 and P4, the stability of 2 in toluene at room temperature is enough to allow the characterization of 2 by variable-temperature 31P{1H} NMR spectroscopy and then to propose a reliable structure for this unusual complex in solution.The 31P{1H} NMR spectrum of 2 (Figure 1) displays a temperature- dependent ABMNQX3 spin system with a strong coupling between the nuclei Q and X (1JQX = 230.7 Hz, T = –30 °C) and less intense couplings between the other P nuclei. An analysis of both coupling constants and chemical shifts suggests that the P4 molecule is h1-coordinated to one ruthenium atom, with cis-disposed PPh3 ligands.The signals due to the naked phosphorus atoms, PQ and PX, are practically temperature invariant in the temperature range examined (from –80 to 40 °C), indicating that the P4 molecule coordinated to Ru is freely rotating in solution. The two P resonances originating from the P4 ligand appear at very high fields (dQ –320.61, dX –472.43) and exhibit a large ‘coordination-chemical shift’, [D = dPcoord – – dP4 free], in comparison with the free P4 molecule by approximately 53 (PX) and 205 ppm (PQ), respectively.The D value experienced by PQ atom indicates that the Ru-bonded P atom is electronically perturbed upon coordination. Noticeably, the low-field shift of the PQ atom in 2 is larger than that observed for the corresponding metal-coordinated P atoms in the other two known complexes featuring a tetrahedro-P4 ligand.Thus, [(triphos)Re(CO)2(h1-P4)]+ shows a coordinated P atom at –390.5 ppm (D = 136.4 ppm) [triphos = MeC(CH2PPh2)3],6(c) while in the tungsten complex [(CO)3(PPh3)W(h1-P4)], the metal-coordinated P atom resonates at –422.0 ppm (D = 104.9 ppm).6(b) The high D value for PQ in 2 suggests that the coordinated P4 ligand should exhibit an enhanced reactivity towards nucleophiles with respect to the free molecule and then makes such a species amenable to testing as a promoter of alcohol phosphorylation reactions.The theoretical modelling of the catalytic oxidative phosphorylation of methanol with white phosphorus indicates that the formation of an h1-P4 complex is a necessary prerequisite to accomplish the P–O bond-forming step.7 The binuclear structure of 2 was confirmed by computer simulation of the eight-nuclei spin system.‡ The proposed struc- † Synthesis of 2: an excess of white phosphorus (0.13 g, 1.09 mmol) was added to a stirred solution of 1 (0.96 g, 1.0 mmol) in dry toluene (10 ml) under nitrogen.After 20 min, the dark brown solution was layered with n-hexane (10 ml) and cooled at 0 °C.The reddish-brown microcrystals of 2 were separated by filtration under nitrogen, washed with n-hexane and dried in a brisk stream of nitrogen. Yield 40%. 31P{1H} NMR (–30 °C, [2H8]toluene, 81.01 MHz, reference 85% H3PO4), ABMNQX3 spin system: dA 51.83, dB 47.54, dM 40.15, dN 39.69, dQ –320.61, dX –472.43, (1JQX = 230.7 Hz, 2JMQ = 41.2 Hz, 2JAB = 37.8 Hz, 2JNQ = 29.0 Hz, 2JMN = 27.5 Hz, 4JBQ = 5.6 Hz).The assignment of the phosphorus network has been confirmed by the 31P,31P-COSY 2D-NMR spectrum. Found (%): C, 56.43; H, 4.16; Cl, 9.02; P, 16.84. Calc. for C72H60Cl4P8Ru2 (%): C, 57.01; H, 3.99; Cl, 9.35; P, 16.33. ‡ The computer simulation of the 31P{1H} NMR spectrum was carried out with the SCANDAL program, developed by A. Vacca (University of Florence, Italy) and J.A. Ramirez (University of Valencia, Spain). The initial choices of shifts and coupling constants were refined by iterative least-squares calculations using the experimental digitised spectrum. The final parameters gave a satisfactory fit between experimental and calculated spectra, the agreement factor being less than 1% in all cases. P P P P Ph3P Ru PPh3 PPh3 Cl Cl 1 Ru Cl Ru Cl Cl PPh3 Cl PPh3 Ph3P Ph3P P P toluene – 2PPh3 P P 2 A B M N Q X X X 2Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) ture entails a binuclear system with two ruthenium atoms experiencing different coordination environments imposed by the presence of the unique P4 ligand. The ruthenium atom bearing the tetrahedro-P4 ligand is at the centre of an octahedron with the coordination polyhedron completed by three bridging chlorides and two cis PPh3 ligands forming the strongly perturbed secondorder MN part of the experimental splitting pattern.The remaining metal atom, more far away from the P4 molecule, is also hexacoordinate by two cis phosphines, which form a slightly perturbed AB spin system at relatively lower fields, and by four chloride ligands, three of which are in bridging positions.The long-range coupling between PB and PQ (4JQB = 5.6Hz) agrees with the proposed binuclear structure. Binuclear complexes are ubiquitous among RuII-phosphine complexes,8 and among them a number of asymmetric face-sharing bioctahedral complexes with three bridging halides have also been reported.9 Although variable-temperature 31P{1H} NMR spectroscopy and 2D-exchange spectroscopy (at 20 °C) do not indicate any intermetallic exchange between the two pairs of PPh3, a dynamic process scrambling the two phosphines coordinated to each metallic site (intrametallic exchange) takes place slightly over –15 °C.However, the fast-exchange limit of the spectrum could not be reached as extensive decomposition of 2 occurs just over room temperature to form an intractable brown precipitate.Studies are in progress in our laboratories aimed at either extending the number of tetrahedro-P4 complexes to other ruthenium precursors or investigating the reactivity of the Ru-coordinated P4 ligand. Studies on the latter topic are important because ruthenium complexes can cause the catalytic conversion of white phosphorus and organic substrates to organophosphorus derivatives.10 This work was supported by EC (INCO Copernicus project ERB IC15CT960746), the bilateral program ‘Azione Integrata’ between the Universities of Florence (Italy) and Almeria (Spain) and by the CNR (Italy)–RAS (Russian Federation) agreement.References 1 D. E. C. Corbridge, Phosphorus, an Outline of its Chemistry, Biochemistry and Technology, 5th edn., Elsevier, Amsterdam, 1995. 2 (a) Ya. A. Dorfman, M. M. Aleshkova, G. S. Polimbetova, L. V. Levina, T. V. Petrova, R. R. Abdreimova and D. M. Doroshkevich, Usp. Khim., 1993, 62, 928 (Russ. Chem. Rev., 1993, 62, 877); (b) R. R. Abdreimova, D. Akbaeva, F. Faisova and M. Peruzzini, in preparation. 3 (a) Ch.Elschenbroich and A. Salzer, Organometallics, a Concise Introduction, 2nd edn., VCH, Weinheim, 1992; (b) B. R. James, in Comprehensive Organometallic Chemistry, eds. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon Press, Oxford, 1982, vol. 8, ch. 51; (c) D. Hesse, in Applied Homogeneous Catalysis with Organometallic Compounds, 1st edn., VCH, Weinheim, 1996. 4 (a) M. Peruzzini, M.Di Vaira and P. Stoppioni, Polyhedron, 1987, 6, 351; (b) O. J. Scherer, Angew. Chem., Int. Ed. Engl., 1990, 29, 1104; (c) M. Scheer and E. Herrmann, Z. Chem., 1990, 29, 41; (d) M. Scheer, Coord. Chem. Rev., 1997, 163, 271; (e) K. H. Whitmire, Adv. Organomet. Chem., 1998, 42, 2; (f ) O. J. Scherer, Acc. Chem. Res., 1999, 32, 751. 5 (a) E. Charalambous, L. Heuer, B. F.G. Johnson, J. Lewis, W.-S. Li, M. McPartlin and A. D. Massey, J. Organomet. Chem., 1994, 468, C9; (b) B. Rink, O. J. Scherer and G. Wolmershäuser, Chem. Ber., 1995, 128, 71. 6 (a) P. Dapporto, S. Midollini and L. Sacconi, Angew. Chem., Int. Ed. Engl., 1979, 12, 469; (b) T. Gröer, G. Baum and M. G. Scheer, Organometallics, 1998, 17, 5916; (c) M. Peruzzini, L. Marvelli, A. Romerosa, R.Rossi, F. Vizza and F. Zanobini, Eur. J. Inorg. Chem., 1999, 931; (d) M. Di Vaira, M. Ehses, P. Stoppioni and M. Peruzzini, Eur. J. Inorg. Chem., in press. 7 A. Tamulis, R. R. Abdreimova, J. Tamuliene, M. Peruzzini and M. L. Balevicius, Inorg. Chim. Acta, in press. 8 E. A. Seddon and K. R. Seddon, The Chemistry of Ruthenium, Elsevier, Amsterdam, 1984, ch. 10. 9 (a) P. W. Armit and T. A. Stephenson, J. Organomet. Chem., 1974, 73, C33; (b) A. J. F. Fraser and R. O. Gould, J. Chem. Soc., Dalton Trans., 1974, 1139; (c) R. Contreras, C. G. Elliot, R. O. Gould, G. A. Heath, A. J. Lindsay and T. A. Stephenson, J. Organomet. Chem., 1981, 215, C6; (d) F. A. Cotton and R. C. Torralba, Inorg. Chem., 1991, 30, 2196. 10 C. Bianchini, M. Peruzzini, R. R. Abdreimova, D. N. Akbayeva and G. S. Polimbetova, Italian patent FI2000A000021. 50 45 40 –315 –320 –325 –471 –476 d/ppm * * (a) (b) (c) 1 2 3 Figure 1 (a) Computed and (b), (c) experimental 31P{1H} NMR spectra of 2 in [2H8]toluene at –30 °C. ABMNQX3 system; 1 refers to the PPh3 resonances (AB and MN components), 2 and 3 denote the resonances due to the ruthenium-coordinated P atom (Q) and the three equivalent basal (X3) P nuclei of the P4 ligand, respectively. Signals of a secondary product, likely an isomer of 2, are indicated by asterisks. Received: 31st January 2000; Com. 00/1597

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Self-propagating high-temperature synthesis of strontium-doped lanthanum chromites Maxim V. Kuznetsov,*a Sergei G. Bakhtamov,a Yuri G. Morozov,a Ivan P. Parkin,b Quentin A. Pankhurst,c Louise Affleckc and Amanda M. E. Hardyb a Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax: +7 095 962 8025; e-mail: kuznets@ism.ac.ru b Department of Chemistry, University College London, London, WC1H OAJ, UK. Fax: +44 0171 380 7463 c Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK 10.1070/MC2000v010n04ABEH001290 Strontium-substituted lanthanum chromites (La1 – xSrxCrO3) were prepared by self-propagating high-temperature synthesis (SHS) using solid oxidisers. Strontium-doped lanthanum chromites are widely used as electrode materials in magneto-hydrodynamic generators and as an interconnect material in solid oxide fuel cells.1,2 The material has been synthesised from a stoichiometric mixture of La2O3, Cr2O3 and SrCO3 by conventional ceramic processes involving extensive heating, milling3 and reheating.It has also been formed by glycino–nitrate4 and citrate precipitation5 processes. Unsubstituted lanthanum chromites have been prepared by self-propagating high-temperature synthesis (SHS) in an oxygen atmosphere and using solid oxidising agents such as sodium perchlorate. 6,7 These reactions proceed by means of a synthesis wave that moves through the reactant powders.The process is sufficiently exothermic to allow the ignition of successive layers of reactants. These syntheses include rapid reactions and minimal processing of the solids. In many cases, pure lanthanide chromite was formed directly in the reaction. Here, we report a synthesis of the strontium-substituted lanthanum chromites La1 – xSrxCrO3 (0 < x < 0.25).In particular, we explored the effect of an internal oxidising agent on the reaction mixture. We investigated the reaction pathway using quenching techniques and thermogravimetry and differential thermal analysis (TGA/ DTA). Combustion processes were carried out in air with mechanically ground mixtures of La2O3, SrO2, SrCO3, Cr, CrO3 and NaClO4. All reagents were combined in stoichiometric quantities according to the reactions: This starting material (~10 g) was placed on a ceramic boat to form a line of powder of dimensions 1×5 cm.An electric filament on the upper surface of the sample was used to ignite the reactions. This promoted an orange propagation wave, which travelled at 2–5 mm s–1. The reaction products were triturated with water to remove sodium chloride and analysed by X-ray powder diffraction, Raman spectroscopy, vibrating sample magnetometry and scanning electron microscopy/energy dispersive analysis by X-rays (SEM/EDAX).The reactions were studied by TGA/DTA on a SETARAM TAG24S24 instrument. The SHS reaction is driven by the exothermic oxidation of chromium metal. Sodium perchlorate and strontium peroxide are internal oxidising agents in the reaction.Lanthanum oxide acts as a heat sink. In the strontium carbonate reaction, carbon dioxide is released. The maximum reaction temperature was 2170 K for the strontium carbonate reaction (2) and 2270 K for the strontium peroxide reaction (1). Chloride chemical analysis of the SHS product proves that more than 70% co-produced sodium chloride (formed by decomposition of the internal oxidising agent sodium perchlorate) is sublimed away from the product.The remaining sodium chloride is removed from the product to below detection limits simply by washing the product with water. The particle size of the washed products was in all cases around 50 mm. The specific surface areas of all the powders were in the range 3400–4000 m2 kg–1.The EDAX spot analysis of the washed products showed the expected Sr:La:Cr ratios and notably no sodium or chlorine. Raman spectroscopy analysis (1 mm resolution) showed that the samples were homogeneous; an unsubstituted sample gave bands at 152, 177, 257, 439, 591 and 679 cm–1. The introduction of strontium into lanthanum chromite causes additional bands to appear around 840 cm–1.The X-ray powder diffraction data for the SHS-prepared powders are consistent with that for materials prepared by conventional ceramic synthesis. The replacement of lanthanum by strontium in La1 – xSrxCrO3 causes a reduction in the unit-cell 5 0 –5 –10 –15 –20 –25 –30 –35 Dm (%) 250 200 150 100 50 0 –50 U/mV 900 K 200 400 600 800 1000 1200 1400 1600 T/K Figure 1 TGA and DTA curves for the SHS reaction La2O3 + SrO2 + Cr + + NaClO4 under conditions of linear heating.(1 – x)/2La2O3 + xSrO2 + Cr + yNaClO4 ® (1 – x)/2La2O3 + xSrCO3 + Cr + zNaClO4 ® La1 – xSrxCrO3 + zNaCl + xCO2 (x = 0, 0.16 or 0.25; y and z were adjusted to the oxygen stoichiometry) La1 – xSrxCrO3 + yNaCl (1) (2) 0 –5 –10 –15 –20 Dm (%) 750 K 300 250 200 150 100 50 0 –50 U/mV T/K 200 400 600 800 1000 1200 1400 1600 Figure 2 TGA and DTA curves for the SHS reaction La2O3 + SrCO3 + + Cr + NaClO4 under conditions of linear heating.Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) volume (Table 1). The unsubstituted lanthanum chromite has an orthorhombic unit cell. The samples of La0.84Sr0.16CrO3 and La0.75Sr0.25CrO3 indexed with rhombohedral unit cells.The calculated pseudo-cubic parameter a0 decreases with strontium substitution. This is related to a partial non-isovalent substitution of La3+ (ionic radius of 0.106 nm) from rare-earth sites of the perovskite-type structure by Sr2+ (ionic radius of 0.127 nm). The substitution of strontium in the structure partially oxidises the chromium to Cr4+ to maintain a charge balance.This oxidation of chromium causes a decrease in both the chromium– oxygen bond length and the unit-cell volume. As can be seen in Table 1, increasing strontium substitution leads to a reduction in the density and specific magnetisation. The reduction in magnetisation is caused by a change in the chromium-to-chromium interaction and can be correlated to the changes in the unit-cell structure.3 The reactions to form strontium-substituted lanthanum orthochromites were also studied using a 50:50 mix of CrO3 and chromium metal. In this case, a drop in the synthesis temperature of 200 K was observed for both the strontium carbonate and strontium peroxide reactions.Chromium(VI) oxide acts both as a heat sink, reducing the exothermic effect of the reaction, and as an oxygen source to promote the fusion reaction: The reaction mechanism was probed using liquid nitrogen to extinguish the reaction front and a large conical metal construction that inhibits the propagation wave as the neck of the cone decreases.8 The level-by-level analysis of the frozen reaction zone by powder X-ray diffraction indicates that in both of the systems LaCrO3, LaCrO4 and SrO were formed as intermediates.The reaction mechanism was also probed by extensive TGA/ DTA measurements of all of the individual components over the temperature range 300–1800 K. Analysis of the chromium metal fuel source shows that it starts to oxidise under a flow of oxygen at 980 K and shows a maximum heat evolution at 1120 K. This oxidation corresponds to a weight increase by 13.3% and is incomplete.In the presence of La2O3 the oxidation of chromium metal occurs in a stepwise manner; the oxidation begins at 1150 K, and a maximum heat evolution is observed at 1270 K. The addition of an internal oxidant such as sodium perchlorate or strontium peroxide considerably modifies the chromium combustion process. As it is shown in Figure 1, in the reaction of chromium, lanthanum oxide, strontium peroxide and sodium perchlorate at temperatures higher than 393 K oxygen is partially released from SrO2.In the range 393–668 K, a weight loss of 4.55% is observed, which was assigned to the partial decomposition of strontium peroxide The partial oxidation of chromium metal powder starts in the same time and temperature ranges.Further, with an increase in the temperature to 700–890 K, all strontium peroxide decomposes to form SrO. The decomposition of sodium perchlorate starts at 880 K As a result of the considerable release of oxygen accompanying the decomposition of sodium perchlorate and strontium peroxide, there is considerable oxidation of chromium, which together with the formation of SrO, promotes the formation of SrCrO4.The heat evolved in the reaction was maximum at 900 K (primarily from the oxidation of chromium metal); this promotes the reactions of chromium and lanthanum oxides The mutual dissolution of the intermediate reaction products happens in the temperature range 880–1120 K and is completed by the formation of the final product La1 – xSrxCrO3 from the melt at 1260–1270 K.The TGA/DTA curves for the reaction with SrCO3 instead of SrO2 are shown in Figure 2. The oxidation source in this reaction comes only from the decomposition of sodium perchlorate. The decomposition of sodium perchlorate is incremented with some oxygen released at 600–620 K, but the majority was released at 720–750 K. This second pulse of oxygen release corresponds to the maximium exotherm in the DTA.Note that in this system the intermediate SrCrO4 is not formed. The temperature of CO2 desorption from SrCO3 with formation of SrO occurs at 990–1170 K. With a further increase in the temperature, SrO dissolved in the LaCrO3–LaCrO4 melt according to reactions (10) and (11) with subsequent crystallization of the final product from the melt.SHS reactions offer a fast single-step route to the high-purity single-phase La1 – xSrxCrO3. The reaction is promoted by the oxidation of chromium metal. The heat evolved in the reaction is sufficient to form a good solid solution without recourse to annealing of the product. The products from the SHS process show physical properties equivalent to those of conventionally prepared materials.3–5 A number of important intermediates such as SrO, SrCrO4, LaCrO3, LaCrO4 and Cr2O3 were isolated on the route to La1 – xSrxCrO3.References 1 N. Q. Minh, J. Am. Ceram. Soc., 1993, 76, 563. 2 M. Mori, T. Yamamoto, H. Itoh and T. Watanabe, J. Mater. Sci., 1997, 32, 2423. 3 D. D. Sarma, K. Maiti, E. Vescovo, C. Carbone, W. Eberhardt, O. Rader and W. Gudat, Phys.Rev. B, 1996, 53, 13369. 4 S. W. Paulik, S. Baskaran and T. R. Armstrong, J. Mater. Sci., 1998, 33, 2397. 5 L. W. Tai and P. A. Lessing, J. Mater. Res., 1992, 7, 502. 6 M. V. Kuznetsov, Neorg. Mater., 1998, 34, 1264 [Inorg Mater., 1998, 34, 1065]. 7 M. V. Kuznetsov and I. P. Parkin, Polyhedron, 1998, 17, 4443. 8 A. S. Rogachev, A. S. Mukasyan and A. G. Merzhanov, Dokl. Akad.Nauk SSSR, 1987, 297, 1425 [Dokl. Phys. Chem. (Engl. Transl.), 1987, 297, 1120]. CrO3 + Cr®Cr2O3. (3) Table 1 Structural and magnetic properties of La1 – xSrxCrO3 compounds prepared by SHS (d is the picnometric density; s is the specific saturation magnetization; V is the volume of a formula unit; a0 is the pseudo-cubic parameter; EDAX compositions were determined to within 0.02). x Crystal lattice Unit-cell parameters/nm V/10–2 nm3 a0 (V1/3/nm) s/10–3 A m2 kg–1 EDAX composition d/103 kg m–3 0 Orthorhombic a = 0.5502 b = 0.5481 c = 0.7761 5.581 0.3882 0.106 La1.01Cr1.00O3 6.50 0.16 Rhombohedral a = 0.5462 (a = 60.260°) 5.794 0.3870 0.055 La0.84Sr0.15CrO3 5.24 0.25 Rhombohedral a = 0.5450 (a = 60.520°) 5.790 0.3869 0.031 La0.75Sr0.25CrO3 5.04 2Cr + 1.5O2 ® Cr2O3. (4) SrO2 ® SrO1.28 + 0.36O2. (5) NaClO4 ® NaClO2.5 + 0.75O2. (6) 2SrO + Cr2O3 + 1.5O2 ® 2SrCrO4. (7) La2O3 + Cr2O3 ® 2LaCrO3; (8) La2O3 + Cr2O3 +O2 ® 2LaCrO4. (9) (1 – x)LaCrO3 + xSrO + 0.5xCr2O3 ® (1 – x)LaCrO4 + xSrO + 0.5xCr2O3 ® La1 – xSrxCrO3 + 0.75xO2 La1 – xSrxCrO3 + 0.25xO2 (10) (11) Received: 29th February 2000; Com. 00/1616

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) New quintet carbenonitrene system formed in the photolysis of 2,6-bis(4,5-dimethoxycarbonyl-1H-1,2,3-triazolo)-4-azido-3,5-dichloropyridine Sergei V. Chapyshev,*a Richard Waltonb and Paul M. Lahtib a Institute for Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax: +7 096 515 3588; e-mail: chap@icp.ac.ru b Department of Chemistry, University of Massachusetts, Amherst, MA 01003–4510, USA. Fax: +1 413 545 4490; e-mail: lahti@grond.chem.umass.edu 10.1070/MC2000v010n04ABEH001309 New triplet pyridyl-4-nitrene, triplet pyridyl-2-imidoylcarbene and quintet 4-nitrenopyridyl-2-imidoylcarbene have been detected by EPR spectroscopy after photolysis of 2,6-bis(4,5-dimethoxycarbonyl-1H-1,2,3-triazolo)-4-azido-3,5-dichloropyridine at 77 K.Recently,1 azide 1 was synthesised, which is a very interesting compound for photochemical studies. Upon irradiation, this compound can undergo decomposition of the azido group and triazole rings to form nitrene 2, carbenonitrene 3 and dicarbenonitrene 4. In the case of a coplanar arrangement of spin carriers in 3 and 4, these species may have quintet and septet ground spin states, respectively.Thus, only quintet (3-nitrenophenyl)- methylene was isolated in cryogenic matrices.2 Here, we report on a quintet EPR spectrum formed in the photolysis of compound 1, which is consistent with expectations for a carbenonitrene system. Azide 1 was irradiated in degassed frozen solutions of 2-methyltetrahydrofuran (MTHF) with light at l > 300 nm for 5 min at 77 K.Upon irradiation, the sample became blue and displayed four signals at 3233, 5197, 6541 and 6765 G in the X-band EPR spectrum (Figure 1). The high-field signals at 5197 and 6765 G lie in regions typical of triplet carbenes3 and nitrenes4 and hence can be assigned to isolated triplet imidoyl carbene (|D/hc| = = 0.420 cm–1) and triplet pyridylnitrene (|D/hc| = 0.934 cm–1) units.† In comparison with earlier studied cyclic imidoyl carbenes (|D/hc| = 0.12–0.17 cm–1),5 a new acyclic imidoyl carbene has rather large zero-field splitting (zfs) D-parameter, which is obviously explained by the effect of a carbomethoxy substituent at this unit.Thus, many carbalkoxy carbenes have zfs values of |D/hc| = 0.61 cm–1.6 The lower intensity of the carbene signal relative to the nitrene peak is apparently associated with the shorter lifetime of this species. Contrary to nitrenes, many carbenes are unstable even at 77 K and can only be detected by EPR spectroscopy at temperatures below 20 K.3 The signal at 3233 G is of considerable interest.Recently,7 it was found that quintet pyridyl-2,4-dinitrenes display a characteristic EPR signal at about 3000 G (|D/hc|quintet = 0.23 cm–1), and quintet pyridyl-2,6-dinitrene 8 gives a signal at 3345 G (|D/hc|quintet = 0.280 cm–1).According to these data, a signal observed at 3233 G lies at a too high magnetic field to be assigned to quintet 2,4-dinitrene 7, at least by analogy to the previous work.The peak at 3233 G is also at a significantly lower field than that expected for quintet dinitrene 8.7 A reasonable assumption for the carrier of 3233 G is quintet carbenonitrene 3. Taking into account that many quintet species give, as a rule,8,9 one or two weak EPR peaks in high magnetic fields, the signal at 6541 G may also have a contribution from putative quintet carbenonitrene 3.If we assume that this is the highest field transition of quintet 3 and that its second highest field transition is coincident with the carbene peak at 5197 G,‡ we find zfs parameters of |D/hc| = 0.099 cm–1 and |E/hc| = 0.0052 cm–1. The D-value for 3 thus calculated falls between the relevant values for quintet m-phenylenedicarbenes (|D/hc| = 0.070–0.084 cm–1)8(a),(b) and quintet m-phenylenedinitrene (|D/hc| = 0.156 cm–1),8(a) and it is close to the D-value reported for (3-nitrenophenyl)methylene (|D/hc| = 0.124 cm–1).2 The latter displayed a low-field signal at about 3200 G and the highest field transition at 7295 G.A difference in the EPR characteristics of two quintet carbenonitrenes obviously results from different chemical bonding and spatial arrangements of spin carrier units in these species.The low intensity of EPR signals of 3 can tentatively be explained either by a short lifetime of this species at 77 K or by a low concentration of conformational isomers of 3 with a nearly coplanar arrangement of the carbene and nitrene units. Accord- † According to our observations, the azido group in 1 is more photolabile and decomposes first.On this basis, we excluded imidoyl carbene 5 from further consideration. Q R C N 0 2000 4000 6000 8000 10000 Magnetic field/G Figure 1 EPR spectrum after the photolysis of azide 1 (n0 = 9.560 GHz) with light at l > 300 nm for 5 min in MTHF at 77 K. The peaks N, C, Q and R correspond to an isolated triplet nitrene unit, an isolated triplet carbene unit, a quintet carbenonitrene system and a radical from MTHF, respectively.‡ The zfs parameters were estimated using the Wasserman procedure.8(a) This allowed us to compare the zfs parameters of 3 with those for quintet dicarbenes8 and quintet dinitrenes.8(a),9(a)–(c) The more advanced eigenfield simulation gives higher zfs D-values for meta-dinitrenes.7,9(d),(e) For details of the eigenfield method, see ref. 10. Assuming that |E/hc| = = 0.035 cm–1, in accordance with findings,7 the approximate zfs for the quintet peak at 3233 G is |D/hc| ~ 0.27 cm–1 (this is an approximate value because other quintet features are insufficiently pronounced to be adequately identified). Figure 2 Orbital density distribution in the SOMO of quintet 3.Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) ing to PM3 computations,§ only such conformers (Figure 2) have the SOMO symmetry and high p-orbital densities at both triplet units that are favourable12 to the high ground spin multiplicity of 3. Note that the absence of EPR signals for 4 does not exclude the possibility of formation of 4 as low-spin conformers. An EPR study of derivatives of 4 with less bulky triazole substituents at a pyridine ring may be helpful to clarify this uncertainty.The quintet carbenonitrene system described represents an unusual quintet heterospin molecule, the high-spin state of which results from the ferromagnetic exchange interaction between remote imidoyl carbene and aryl nitrene units. Despite the lack of a rigid structure, this system has a reasonably long lifetime in an organic glass at 77 K to be observable by EPR spectroscopy. This work was supported by the National Science Foundation (grant nos. CHE-951595 and CHE-9740401).References 1 S. V. Chapyshev, Mendeleev Commun., 1999, 164. 2 H. Tukuda, K. Mutai and H. Iwamura, J. Chem. Soc., Chem. Commun., 1987, 1159. 3 W. Sander, G. Bucher and S. Wierlacher, Chem.Rev., 1993, 93, 1583. 4 (a) E. Wasserman, Prog. Phys. Org. Chem., 1971, 8, 319; (b) S. V. Chapyshev, A. Kuhn, M. Wong and C. Wentrup, J. Am. Chem. Soc., 2000, 122, 1572; (c) S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 7. 5 H. Murai, M. Torres and O. P. Strausz, J. Am. Chem. Soc., 1980, 102, 1421. 6 H. D. Roth and R. S. Hutton, Tetrahedron, 1985, 41, 1567. 7 S. V. Chapyshev, R. Walton, J. A. Sanborn and P. M. Lahti, J. Am. Chem. Soc., 2000, 122, 1580. 8 (a) E. Wasserman, R. W. Murray, W. A. Yager, A. M. Trozzolo and G. Smolinsky, J. Am. Chem. Soc., 1967, 89, 5076; (b) K. Itoh, Chem. Phys. Lett., 1967, 1, 235; (c) K. Itoh, Pure Appl. Chem., 1978, 50, 1251. 9 (a) S. Murata and H. Iwamura, J. Am. Chem. Soc., 1991, 113, 5547; (b) C. Ling, M.Minato, P. M. Lahti and H. van Willigen, J. Am. Chem. Soc., 1992, 114, 9959; (c) C. Ling and P. M. Lahti, J. Am. Chem. Soc., 1994, 116, 8784; (d) R. S. Kalgutkar and P. M. Lahti, J. Am. Chem. Soc., 1997, 119, 4771; (e) S. V. Chapyshev, R. Walton and P. M. Lahti, Mendeleev Commun., 2000, 114. 10 (a) G. G. Belford, R. L. Belford and J. F. Burkhalter, J. Magn. Reson., 1973, 11, 251; (b) Y.Teki, T. Takui and K. Itoh, J. Chem. Phys., 1988, 88, 6134; (c) Y. Teki, I. Fujita, T. Takui, T. Kinoshita and K. Itoh, J. Am. Chem. Soc., 1994, 116, 11499; (d) Y. Teki, Ph.D. Thesis, Osaka City University, 1985; (e) K. Sato, Ph.D. Thesis, Osaka City University, 1994. 11 (a) J. J. P. Stewart, J. Comput. Chem., 1989, 10, 221; (b) Spartan version 4.0, Wavefunction, Inc., USA, 1995. 12 W. T. Borden and E. R. Davidson, J. Am. Chem. Soc., 1977, 99, 4587. § The structure of quintet carbenonitrene 3 was calculated with the full optimization of geometry parameters using the PM3 method (UHF, SCF level).11 Quintet 3 is in the most stable s-Z conformation for a carbene moiety, if we consider the mutual arrangement of a carbene unit and a carbomethoxy group. Usually, s-Z conformers of carbalkoxy carbenes are the major products of photolysis of diazo precursors.3 N Cl N3 Cl N N N N NN MeO2C CO2Me CO2Me CO2Me hn N Cl N Cl N N N N NN MeO2C CO2Me CO2Me CO2Me N Cl N Cl N N N N MeO2C CO2Me CO2Me CO2Me N Cl N Cl N N CO2Me CO2Me MeO2C CO2Me 1 2 3 4 N Cl N3 Cl N N N N CO2Me CO2Me CO2Me CO2Me 5 N Cl N3 Cl N N N N CO2Me CO2Me 6 N Cl N Cl N N N N CO2Me CO2Me 7 N Cl N3 Cl N N 8 Received: 28th March 2000; Com. 00/1635

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) Synthesis and transformations of picrylacetaldehyde Vasilii M. Vinogradov, Igor L. Dalinger, Aleksei M. Starosotnikov and Svyatoslav A. Shevelev* N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: shevelev@cacr.ioc.ac.ru 10.1070/MC2000v010n04ABEH001322 A method for the synthesis of picrylacetaldehyde was developed, and its reactivity was examined.In the context of chemical utilisation of 2,4,6-trinitrotoluene (TNT),1 we developed a procedure for preparing picrylacetaldehyde starting from TNT. This previously unknown aldehyde is of interest as a new building block because of the presence of a highly reactive formyl group, an active methylene unit, nitro groups, and an aromatic ring of the picryl moiety (nucleophilic substitution for nitro groups, vicarious and oxidative nucleophilic substitution for hydrogen, etc.).Picrylacetaldehyde 2 was prepared by acidic hydrolysis of b-dimethylamino-2,4,6-trinitrostyrene 1, which in turn was readily formed by TNT condensation with dimethylformamide dimethyl acetal.Enamine 1 can be used as a masked form of picrylacetaldehyde because it easily undergoes hydrolysis in acidic media. For example, bromination and nitrosation of 1 results in picrylacetaldehyde modified at the methylene group The same products (3 and 4) were also obtained using picrylacetaldehyde as the starting compound. A tendency to deformylation under the action of even weak bases such as pyridine with the regeneration of TNT is a characteristic property of picrylacetaldehyde.In particular, for this reason picrylacetaldehyde does not form arylhydrazones and oximes with arylhydrazines and hydroxylamine. Hydrazone 5 was formed only by the interaction of picrylacetaldehyde with an extremely weak base, benzoic acid hydrazide. We also detected a trace impurity of tautomer 6.At the same time, under neutral and acidic conditions, picrylacetaldehyde behaves as a typical aliphatic aldehyde. Picrylglyoxal monooxime 4, which is a picrylacetaldehyde derivative without an a-methylene group, exhibit similar properties. Oxime 4 gives with nitrogen nucleophiles usual derivatives at the formyl group. Apart from benzoic acid hydrazide, phenylhydrazine and O-methylhydroxylamine also react with oxime 4.The acylation of picrylacetaldehyde with acetic anhydride afforded enol acetate 10 The acylation of picrylacetaldehyde derivative 4 having no methylene group resulted in acylal 11. Picrylacetaldehyde with ethylene glycol forms cyclic acetal 12. Oxime 4 also forms analogous acetal 13 under more severe conditions.Pic Me i Pic NMe2 ii Pic O 1 2 Reagents and conditions: i, 1 equiv. H2NCH(OMe)2, toluene, 20 °C, 24 h, 70% yield; ii, 2 M HCl in H2O/CHCl3, 61 °C, 5 h, 78% yield. TNT Pic NMe2 1 Pic O Br Br 3 Pic O 4 NOH i ii Reagents and conditions: i, 1 equiv. Br2, CHCl3, 20 °C, 5 h, 52% yield; ii, 2 equiv. NaNO2, HCl (conc.), 20 °C, 3 h, 66% yield. Pic O 2 i Pic N NH Ph O Pic NH NH Ph O 5 6 Reagents and conditions: i, 1 equiv. PhCONHNH2, EtOH, 78 °C, 1 h, 80% yield of 5.Pic O 4 NOH Pic N NOH NH Ph 8 Pic N NOH 7 NH Ph O Pic N NOH 9 OMe i ii iii Reagents and conditions: i, 1 equiv. PhCONHNH2, EtOH, 78 °C, 3 h, 61% yield; ii, 1 equiv. PhNHNH2·HCl, EtOH, 78 °C, 3 h, 91% yield; iii, 1 equiv. MeONH2, EtOH, 78 °C, 3 h, 76% yield. Pic O Pic 2 10 OAc i Reagents and conditions: i, Ac2O, 80–90 °C, 78% yield, E/Z ª 1:2. Pic O 4 NOH i Pic OAc 11 NOH OAc Reagents and conditions: i, Ac2O, 80–90 °C, 5 h, 89% yield.Pic O 2 Pic 12 O O i Reagents and conditions: i, 2 equiv. HO(CH2)2OH, 0.1 equiv. TsOH, benzene, 81 °C, 2 h, 95% yield. Pic O 4 Pic 13 O O i NOH NOH Reagents and conditions: i, 2 equiv. HO(CH2)2OH, 0.1 equiv. TsOH, toluene, 110 °C, 5 h, 87% yield.Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) As a protected aldehyde, dioxolane 12 is stable to alkaline media. Using the reaction with thiophenol in N-methylpyrrolidone in the presence of K2CO3 as an example, we found the nucleophilic substitution for a nitro group in 12. The reaction is regioselective: only the ortho-nitro group was replaced, and sulfide 14 was formed.In contrast to picrylacetaldehyde, under the action of bases, oxime 4 forms 2-cyano-3,5-dinitrophenol 16. 3-Carbonyl-4,6- dinitro-1,2-benzisoxasole 15 is a probable intermediate. Such benzisoxasoles are unstable in alkaline media and are transformed into salicylic acid nitriles.2 All of the compounds prepared were characterised by physicochemical methods.† This work was supported by the International Science and Technology Center (ISTC), project no. 419. References 1 V. A. Tartakovsky, S. A. Shevelev, M. D. Dutov, A. Kh. Shakhnes, A. L. Rusanov, L. G. Komarova and A. M. Andrievsky, in Conversion Concepts for Commercial Applications and Disposal Technologies of Energetic Systems, ed. H. Krause, Kluwer Academic Publishers, Dordrecht, 1997, p. 137. 2 K.-H. Wunsch and A. J. Boulton, Adv. Heterocycl. Chem., 1967, 8, 277. 3 S. R. Eturi, A. Bashir-Hashemi and S. Iyer, U.S. Patent, 5969155, A 19991019, 1999. 4 N. E. Burlinson, M. E. Sitzman, L. A. Kaplan and E. Kayser, J. Org. Chem., 1979, 44, 3695. † 1H NMR spectra were measured on a Bruker AM 300 spectrometer in [2H6]DMSO with TMS as a standard. 1: mp 155–157 °C (toluene) (lit.,3 155–157 °C). 2: mp 90–91 °C (CHCl3). 1H NMR, d: 4.5 (s, 2H, CH2), 9.0 (s, 2H, Harom), 9.8 (s, 1H, O=CH). 3: mp 149–151 °C (CHCl3). 1H NMR, d: 8.9 (s, 2H, Harom), 9.2 (s, 1H, O=CH). 4: mp 108–110 °C (CHCl3). 1H NMR, d: 9.1 (br. s, 1H, OH), 9.2 (s, 2H, Harom), 9.8 (s, 1H, O=CH). 5: mp 198–200 °C (decomp.) (EtOH). 1H NMR, d: 4.1 (s, 2H, CH2), 7.2–7.6 (m, 4H, Ph, HC=N), 7.8 (m, 2H, Ph), 9.0 (2H, Pic), 11.4 (1H, NH). 7: mp 142–145 °C (EtOH). 1H NMR, d: 7.4–7.6 (m, 3H, Ph), 7.7–7.9 (m, 2H, Ph), 8.5 (s, 1H, N=CH), 9.1 (s, 2H, Pic), 11.9 (s, 1H, NH), 12.7 (s, 1H, OH). 8: mp 126–127 °C (CHCl3). 1H NMR (major stereoisomer) d: 6.7–6.8 (m, 3H, Ph), 7.0–7.2 (m, 2H, Ph), 7.8 (s, 1H, N=CH), 9.1 (s, 2H, Pic), 10.6 (s, 1H, NH), 12.0 (s, 1H, OH). NO2 O2N NO2 O O SPh O2N NO2 O O i 12 14 Reagents and conditions: i, 1 equiv.PhSH, 1 equiv. K2CO3, N-methylpyrrolidone, 20 °C, 24 h, 32% yield. NO2 O2N NO2 O 4 NOH i NO2 O2N 15 O N O NO2 O2N OH CN 16 Reagents and conditions: i, 1 equiv. K2CO3, EtOH, 20 °C, 24 h, 75% yield. Received: 16th May 2000; Com. 00/1648 9: mp 154–156 °C (CHCl3). 1H NMR, d: 3.8 (s, 3H, OMe), 8.0 (s, 1H, N=CH), 9.1 (s, 2H, Harom), 12.8 (s, 1H, OH). 10: mp 71–75 °C (E/Z mixture). 1H NMR d: (Z)-isomer, 2.0 (s, 3H, Me), 6.3 (d, 1H, a-H, 3J 6.9 Hz), 7.5 (d, 1H, b-H, 3J 6.9 Hz), 9.0 (s, 2H, Pic); (E)-isomer, 2.0 (s, 3H, Me), 6.7 (d, 1H, a-H, 3J 12.7 Hz), 7.4 (d, 1H, b-H, 3J 12.7 Hz), 9.1 (s, 2H, Pic). 11: mp 178–180 °C (EtOH). 1H NMR, d: 2.0 (s, 6H, 2Me), 2.05 (s, 3H, Me), 7.7 [s, 1H, CH(OAc)2], 9.3 (s, 2H, Pic). 12: mp 102–104 °C (EtOH). 1H NMR, d: 3.6 (d, 2H, CH2, 3J 4.2 Hz), 3.6–3.8 [dm, 4H, O(CH2)2O], 5.15 (t, 1H, OCHO, 3J 4.2 Hz), 8.95 (s, 2H, Pic). 13: mp 85–87 °C (EtOH). 1H NMR, d: 3.6–3.9 [dm, 4H, O(CH2)2O], 5.6 (s, 1H, OCHO), 9.1 (s, 2H, Pic), 12.2 (s, 1H, OH). 14: mp 103–106 °C (EtOH). 1H NMR, d: 3.6 (d, 2H, CH2, 3J 5.3 Hz), 3.7 [m, 4H, O(CH2)2O], 5.2 (t, 1H, OCHO, 3J 5.3 Hz), 7.5–7.6 (m, 5H, Ph), 7.9 (s, 1H, arom.), 8.5 (s, 1H, arom.). 16: mp 187–188 °C (CHCl3). 1HNMR, d: 8.0 (d, 1H, arom., 4J 2.0 Hz), 8.3 (d, 1H, arom., 4J 2.0 Hz); this compound was described in ref. 4; however, the melting point was not given.

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年代:2000

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Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) N,C-Cross-coupling of trimethylsilyl derivatives of azoles with N,N-bis(silyloxy)enamines Igor V. Bliznets,a Alexey V. Lesiv,b Lyudmila M. Makarenkova,c Yuri A. Strelenko,c Sema L. Ioffe*c and Vladimir A. Tartakovskiic a Higher Chemical College, Russian Academy of Sciences, 125047 Moscow, Russian Federation. Fax: +7 095 135 8860 b Moscow Chemical Lyceum, 109033 Moscow, Russian Federation.Fax: +7 095 362 3440 c N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328 10.1070/MC2000v010n04ABEH001293 N-Trimethylsilyl derivatives of di- and triazoles smoothly undergo N,C-cross-coupling reactions with terminal and internal N,N-bis(silyloxy)enamines to give a-azolyl-substituted oximes.Bis(trialkylsilyloxy)enamines1 (BSENA) are convenient reagents for organic synthesis.2 BSENA, as formal b-carbon electrophiles, smoothly undergo C,C-cross-coupling reactions with a-nitro carbanions3 or trimethylsilyl derivatives of aliphatic nitro compounds.4 They also enter into N,C-cross-coupling with trimethylsilyl derivatives of N-nitramines5 and primary6 or secondary1 amines.The main products of these processes are a-substituted oximes, and the main side reaction is the rearrangement of BSENA into trimethylsilyl derivatives of 2-trimethylsilyloxy-substituted oximes, which is catalysed by Lewis or Brönsted acids1,7 and amines.6 It was found3 that at least some of the above reactions can proceed via a-nitroso alkenes as key intermediates.It is interesting that N,C-cross-coupling reactions of BSENA with alkyl-Nnitroamines, which are N–H acids, can be performed using trimethylsilyl derivatives of N-nitramines; however, N-trimethylsilyl derivatives of amines do not react with BSENA. Therefore, it is very interesting to examine the N,C-cross-coupling reaction of azoles with BSENA since the N–H acidity of azoles and N-nitroamines is almost the same,8 whereas the basicity of azoles is close to that of amines.9 We found that trimethylsilyl derivatives of azoles 1 containing at least two nitrogen atoms react smoothly with model terminal and internal BSENA 2† without a solvent at room temperature to give derivatives of oximes 3,‡ which could be transformed into free a-azolyl-substituted oximes 4§ after alcoholysis (Scheme 1).The target products can be purified by fractionation in vacuo (for 3) and by crystallization (for 4). The reactions between 1 and 2 afforded derivatives 3 in good yields only when BSENA were dried by azeotropic evaporation of water with benzene followed by distillation before the N,C-cross-coupling reaction.The structure of compounds 3 and 4 was confirmed by 1H and 13C NMR data and additionally by elemental analysis for oximes 4 (the error was no higher than 0.19% for carbon or 0.35% for hydrogen). The (E)-configuration of an oximino fragment for oximes 4a,c,e and their derivatives 3a,c,e was found using the published rules.3,5,6 Oximes 4b,d,f and their derivatives 3b,d,f represent mixtures of (Z)- and (E)-isomers.¶ The reactions of 1,2,4-triazole 1c with BSENA 2 are not regioselective (Scheme 2). However, only pure 1-substituted triazoles 3e,f and 4e,f were isolated from the reaction mixture by distillation in vacuo or by crystallization. † A solution of BSENA 2 (1 mmol) in dry hexane (3 ml) was added dropwise to the TMS derivative of azole 1 (1 mmol) at 20 °C in an inert atmosphere.The mixture was stirred at 20 °C for 30 min, evaporated at 20 °C (10 Torr), then stirred for 24 h. Finally, the residue was dried in vacuo at 20 °C (0.1 Torr) to constant weight. Target derivative 3 was isolated by distillation of the residue in vacuo. ‡ NMR spectra were recorded on a Bruker AM 300 spectrometer at 300.31 MHz and 75.47 MHz for 1H and 13C, respectively; TMS as an internal standard. 3a: yield 95%, bp 53 °C (0.06 Torr). 1H NMR (CDCl3) d: 0.19 (s, 9H, SiMe3), 1.57 (s, 3H, Me), 4.80 (s, 2H, CH2), 6.25 (t, 1H, 4-H, 3JH,H 2 Hz), 7.33 and 7.47 (d, 2H, 3-H and 5-H, 3JH,H 2 Hz). 13C NMR (CDCl3) d: –0.75 (SiMe3), 11.91 (Me), 55.89 (CH2), 106.38 (4-C), 128.99 and 139.44 (3-C and 5-C), 157.44 (C=N). 3b: yield 78%, bp 44 °C (0.08 Torr). 3c: yield 88%, bp 65 °C (0.08 Torr). 3d: yield 97%, bp 73 °C (0.09 Torr). E/Z ª 6:1. 1H NMR (CDCl3) d: (E)-isomer: 0.20 (s, 9H, SiMe3), 1.65 (d, 3H, Me, 3JH,H 7 Hz), 4.90 (m, 1H, CH, 3JH,H 7 Hz), 6.90 and 7.05 (br. s, 2H, 4-H and 5-H), 7.51 (d, 1H, CH=N, 3JH,H 7 Hz), 7.67 (s, 1H, 2-H); (Z)-isomer: 0.19 (s, 9H, SiMe3), 1.63 (d, 3H, Me, 3JH,H 7 Hz), 5.50 (m, 1H, CH, 3JH,H 7 Hz), 6.90 and 7.05 (br.s, 2H, 4-H and 5-H), 7.43 (d, 1H, CH=N, 3JH,H 7 Hz), 7.67 (s, 1H, 2-H). 13C NMR (CDCl3) d: (E)-isomer: –0.90 (SiMe3), 19.00 (Me), 52.31 (CH), 117.14 and 129.76 (4-C and 5-C), 135.55 (2-C), 153.18 (C=N); (Z)-isomer: –0.90 (SiMe3), 18.00 (Me), 47.63 (CH), 117.30 and 129.76 (4-C and 5-C), 135.55 (2-C), 153.91 (C=N). 3e: yield ~100%, bp 60 °C (0.08 Torr). 3d: yield 95%, bp 64 °C (0.08 Torr).§ 4a: yield 91%, mp 94–95 °C (from H2O). 4b: yield ~100%, oil. E/Z ª 5:2. 1H NMR (CDCl3) d: (E)-isomer: 1.65 (d, 3H, Me, 3JH,H 6.6 Hz), 5.10 (m, 1H, CH, 3JH,H 6.6 Hz), 6.24 (d, 1H, 4-H, 3JH,H 2 Hz), 7.42 and 7.53 (d, 2H, 3-H and 5-H, 3JH,H 2 Hz), 7.58 (d, 1H, CH=N, 3JH,H 6.6 Hz), 9.36 (br. s, 1H, OH); (Z)-isomer: 1.66 (d, 3H, Me, 3JH,H 6.6 Hz), 5.72 (m, 1H, CH, 3JH,H 6.6 Hz), 6.24 (d, 1H, 4-H, 3JH,H 2 Hz), 6.95 (d, 1H, CH=N, 3JH,H 6.6 Hz), 7.45 and 7.55 (d, 2H, 3-H, 5-H, 3JH,H 2 Hz), 9.36 (br.s, 1H, OH). 13C NMR (CDCl3) d: (E)-isomer: 18.54 (Me), 56.71 (CH), 105.95 (4-C), 128.00 and 139.59 (3-C and 5-C), 149.58 (C=N); (Z)-isomer: 17.69 (Me); 52.15 (CH); 105.59 (4-C), 128.57 and 139.83 (3-C and 5-C), 150.30 (C=N). 4c: yield ~100%, mp 162–167 °C (from H2O). 1HNMR ([2H6]DMSO) d: 1.63 (s, 3H, Me), 4.66 (s, 2H, CH2), 6.88 and 7.08 (br. s, 2H, 4-H and 5-H), 7.61 (s, 1H, 2-H), 10.92 (s, 1H, OH). 13C NMR ([2H6]DMSO) d: 11.37 (Me), 49.87 (CH2), 119.56 and 128.55 (4-C and 5-C), 137.64 (2-C), 151.58 (C=N). 4d: yield 95%, mp 109–112 °C (from H2O). 4e: yield ~100%, mp 149–151 °C (from EtOH). 4f: yield ~100%, mp 109–113 °C (from H2O).¶ A mixture of two regio isomers (see Scheme 2). Y N X SiMe 3 R' R N(OSiMe 3)2 Y N X R' R NOSiMe 3 i Y N X R' R NOH ii 1a–c 2a,b 3a–f 4a–f 1: a X = N, Y = CH b X = CH, Y = N c X = Y = N 2: a R = H, R' = Me b R = Me, R' = H 3,4: a X = N, Y = CH, R = H, R' = Me b X = N, Y = CH, R = Me, R' = H c X = CH, Y = N, R = H, R' = Me d X = CH, Y = N, R = Me, R' = H e¶ X = Y = N, R = H, R' = Me f¶ X = Y = N, R = Me, R' = H Scheme 1 Reagents and conditions: i, molar ratio 1:2 = 1:1, without a solvent, room temperature, 24 h; ii, an excess of EtOH, room temperature, 20 h.Mendeleev Communications Electronic Version, Issue 4, 2000 (pp. 125–166) The interaction of BSENA with free azoles was studied using a model reaction of enamine 2a with pyrazole. This process is not chemoselective and includes a rearrangement of 2a into 5†† catalysed by pyrazole (Scheme 3).We can conclude that the reactivity of azoles in the N,C-crosscoupling reactions with BSENA is similar to the reactivity of N-nitramines in analogous reactions.5 Thus, a convenient preparative method for synthesis of 2-azolylsubstituted oximes from available aliphatic nitro compounds and azoles was developed. Oximes 4 are promising synthetic building blocks for drug and plant protection research.10,11 This work was performed at the Scientific Educational Centre for Young Scientists and supported by the Russian Foundation for Basic Research (grant nos. 99-03-32015 and 00-15-97455) and by the Federal Programme ‘Integration’ (grant no. A0082). References 1 H. Feger and G.Simchen, Liebigs Ann. Chem., 1986, 1456. 2 A. D. Dilman, A. A. Tishkov, I. M. Lyapkalo, S. L. Ioffe, Yu. A. Strelenko and V. A. Tartakovsky, Synthesis, 1998, 181. 3 A. D. Dilman, I. M. Lyapkalo, S. L. Ioffe, Yu. A. Strelenko and V. A. Tartakovsky, Synthesis, 1999, 1767. 4 A. D. Dilman, I. M. Lyapkalo, Yu. A. Strelenko, S. L. Ioffe and V. A. Tartakovskii, Mendeleev Commun., 1997, 133. 5 S. L. Ioffe, L. M. Makarenkova, Yu. A. Strelenko, I. V. Bliznets and V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 1998, 2045 (Russ. Chem. Bull., 1998, 47, 1989). 6 L. M.Makarenkova, I. V. Bliznets, S. L. Ioffe, Yu. A. Strelenko and V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2000, 1265 (in Russian). 7 H. Feger and G. Simchen, Liebigs Ann. Chem., 1986, 428. 8 H.Feuer, The Chemistry of the Nitro and Nitroso Groups, New York, 1969, vol. 1, p. 470. 9 T. L. Gilchrist and W. Stretch, J. Chem. Soc., Perkin Trans. 1, 1987, 2235. 10 J. G. Keay, E. F. V. Scriven and N. Shobana, Heterocycles, 1994, 37, 1951. 11 T. L. Gilchrist, D. A. Lingham and T. G. Roberts, J. Chem. Soc., Chem. Commun., 1979, 1089. †† 5: E/Z ª 4:1 (ref. 7). 13C NMR (CDCl3) d: (E)-isomer: –0.68 and –0.45 (2SiMe3), 11.54 (Me), 64.86 (CH2), 160.82 (C=N); (Z)-isomer: –0.45 and –0.17 (2SiMe3), 16.50 (Me), 58.72 (CH2), 163.4 (C=N). N N N SiMe 3 R' R N(OSiMe 3)2 N N N R' R NOSiMe 3 1c 2a,b 3e,f i N N N R' R NOSiMe 3 3e',f' Molar ratio 3e:3e' ~ 6:1; 3f:3f' ~ 2:1 Scheme 2 Reagents and conditions: i, molar ratio 1:2 = 1:1, without a solvent, room temperature, 20 h. NH N N(OSiMe 3)2 N N NOSiMe 3 i 2a Me3SiO NOSiMe 3 3a (30%) 5 (60%) Scheme 3 Reagents and conditions: i, molar ratio pyrazole:2a = 1:1, without a solvent, room temperature, 20 h. Received: 1st March 2000; Com. 00/1619

ISSN:0959-9436     

出版商:RSC    

年代:2000

数据来源: RSC