摘要:

O N CO2Z NH3 +Cl– H O O + ZONa CO2Z N H N CO2Me Cl CO2Z N N CO2 Me 1 2 3 O N N CO2Z Me N N N CO2Me CO2Me O [ ] n i ii iii iv v 4 5 CH Z = [CH2] nC a n = 3 b n = 4 + – 40 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 40–41† Intramolecular Nitrile Imide Cycloadditions leading to Benzo[c]pyrazolo[1,5-e][1,5]-oxazonine and -oxazecine Skeletons† Giorgio Molteni Dipartimento di Chimica Organica e Industriale dell’Universit`a, via Golgi 19, 20133 Milano, Italy A synthetic route to the new title compounds 4, which involves an intramolecular nitrile imide cycloaddition to an acetylenic moiety as the key step, is described.Intramolecular 1,3-dipolar cycloadditions represent a valuable tool in the synthesis of a large variety of heterocyclic systems containing a five-membered heterocycle fused or bridged to another hetero- or carbo-cyclic ring.1 However, despite copious literature on this methodology, examples which involve the formation of a medium-sized ring are still rare.2–5 A fruitful approach to the hitherto unreported benzo[ c]pyrazolo[1,5-e][1,5]oxazonine and benzo[c]pyrazolo- [1,5-e][1,5]oxazecine skeletons is here reported, based on the intramolecular cycloaddition of appropriately chosen nitrile imides.The hydrazonoyl chlorides 2, which we have devised as the precursors for the in situ generation of the nitrile imides 3, were obtained starting from isatoic anhydride and the appropriate alkynols (see Scheme 1).Treatment of 2 with silver carbonate in refluxing acetonitrile gave the desired cycloadducts 4 in good yields (see Experimental section). It needs to be added that, under the experimental conditions described above, the nitrile imides 3 underwent, as a side-reaction, a 1,3-dipolar cycloaddition onto the solvent to give the triazole derivatives 5. In order to prevent the formation of such by-products, the hydrazonoyl chloride 2a was treated with silver carbonate in dioxane at 80 °C.The choice of this solvent was determined on the basis of the highly satisfactory results reported in some of our previous works.6 However, in this case, the latter conditions led to a lower yield of the cycloadduct 4a, since large amounts of tarry material were formed. In spite of the well known factors working against the formation of nine- and ten-membered rings,7 the cycloadditive approach to compounds 4 has been proven to be successful and the observed yields of cyclization are valuable on a preparative scale.Experimental Analytical and spectroscopic instruments were as described in a previous paper.8 J Values are given in Hz. Preparation of Alkynyl Anthranilate Hydrochlorides 1. General Procedure.·A solution of the appropriate alkynol (12.0 mmol) in anhydrous toluene (13 ml) was treated with sodium hydride (0.39 g, 16.4 mmol) and then refluxed for 1 h. Isotoic anhydride (1.96 g, 12.0 mmol) in hot pyridine (7 ml) was added and the solution was refluxed for 4 h.The mixture was poured onto crushed ice (50 ml) and extracted with diethyl ether (50 ml). The organic layer was washed with water, dried over sodium sulfate and evaporated. The oily residue was dissolved in anhydrous diethyl ether (70 ml) and a solution of hydrogen chloride in diethyl ether (4 M; 12.0 ml) was added under stirring. The white precipitate was filtered out and dried to give 1. Pent-4-yn-1-yl anthranilate hydrochloride (1a) (1.06 g, 37%) had mp 167 °C; vmax/cmµ1 (Nujol) 3230, 2110, 1730; dH (CDCl3) 1.92–2.08 (3 H, m), 2.38 (2 H, dt, J 6.5, 2.4), 4.46 (2 H, t, J 6.5), 7.43–8.02 (4 H, m), 8.45 (3 H, br s); m/z 239 (M+) (Found: C, 60.02; H, 5.92; Cl, 14.62; N, 5.77.C12H14ClNO2 requires C, 60.13; H, 5.89; Cl, 14.79; N, 5.84%). Hex-5-yn-1-yl anthranilate hydrochloride (1b) (0.91 g, 30%) had mp 137 °C; vmax/cmµ1 (Nujol) 3240, 2110, 1730; dH (CDCl3) 1.58–1.91 (4 H, m), 1.95 (1 H, t, J 2.5), 2.39 (2 H, dt, J 6.5, 2.5), 4.36 (2 H, t, J 6.5), 7.39–8.06 (4 H, m), 8.50 (3 H, br s); m/z 253 (M+) (Found: C, 61.48; H, 6.30; Cl, 14.08; N, 5.60.C13H16ClNO2 requires C, 61.54; H, 6.36; Cl, 13.97; N, 5.52%). Preparation of Hydrazonoyl Chlorides 2. General Procedure.·A solution of 1 (3.5 mmol) in water (12 ml) and methanol (1.5 ml) was treated with hydrochloric acid (12 M; 1.5 ml) and then cooled to 0 °C. Sodium nitrite (0.33 g, 4.7 mmol) in water (2.5 ml) was added dropwise to the reaction mixture whilst it was cooled and stirred. After 30 min, the cold mixture was adjusted to pH 5 with sodium acetate and then methyl 2-chloroacetoacetate (0.53 g, 3.5 mmol) in methanol (3 ml) was added under stirring.The mixture was stirred at room temperature for 15 h and then extracted with diethyl ether (60 ml). The organic layer was washed with sodium hydrogencarbonate, dried (Na2SO4) and evaporated. Recrystallization from diisopropyl ether gave the pure hydrazonoyl chlorides 2. Pent-4-yn-1-yl 2-[2-(1-chloro-2-methoxy-2-oxoethylidene)hydrazino] benzoate (2a) (0.85 g, 75%) had mp 90 °C; vmax/cmµ1 (Nujol) 3280, 3210, 2100, 1730, 1680; dH (CDCl3) 1.93–2.53 (5 H, m), 3.95 (3 H, s), 4.46 (2 H, t, J 6.3), 7.00–7.85 (4 H, m), 11.80 (1 H, br s); m/z 322 (M+) (Found: C, 55.71; H, 4.66; Cl, 11.07; N, 8.75.C15H15ClN2O4 requires C, 55.82; H, 4.68; Cl, 10.98; N, 8.68%). Hex-5-yn-1-yl 2-[2-(1-chloro-2-methoxy-2-oxoethylidene)hydrazino] benzoate (2b) (1.13 g, 96%) had mp 60 °C; vmax/cmµ1 (Nujol) 3280, 3200, 2105, 1730, 1680; dH (CDCl3) 1.50–1.93 (4 H, m), 1.95 (1 H, t, J 2.4), 2.27 (2 H, dt, J 6.2, 2.4), 3.90 (3 H, s), 4.35 (2 H, t, J 6.2), 6.97–7.95 (4 H, m), 11.80 (1 H, br s); m/z 336 (M+) (Found: C, 57.20; H, 5.13; Cl, 10.61; N, 8.44.C16H17ClN2O4 requires C, 57.06; H, 5.09; Cl, 10.53; N, 8.32%). Treatment of Hydrazonoyl Chlorides 2 with Silver Carbonate in Acetonitrile. General Procedure.·A solution of 2 (2.5 mmol) in dry acetonitrile (200 ml) was treated with silver carbonate (2.76 g, 10 †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Scheme 1 Reagents and conditions: i, pyridine, heat; ii, HCl– Et2O; iii, HCl–NaNO2; iv, MeCOCHClCO2Me; v, Ag2CO3–MeCN, refluxJ. CHEM. RESEARCH (S), 1998 41 mmol) and the mixture was refluxed in the dark for 7 h (entry a) or 3 h (entry b).The undissolved material was filtered off, the solvent was evaporated and then the residue was chromatographed on a silica gel column with dichloromethane–ethyl acetate (3:1). The intramolecular cycloadduct 4 was eluted first, followed by the triazole derivative 5. Methyl 8-oxo-5,6-dihydro-4H,8H-benzo[c]pyrazolo[1,5-e][1,5]oxazonine- 2-carboxylate (4a) (0.29 g, 41%) had mp 148 °C (from hexane –benzene); vmax/cmµ1 (Nujol) 1730, 1720; dH (CDCl3) 2.30–2.55 (4 H, m), 3.94 (3 H, s), 4.95 (2 H, br t), 6.69 (1 H, s), 7.38–7.86 (4 H, m); m/z 286 (M+) (Found: C, 63.03; H, 4.98; N, 9.75.C15H14N2O4 requires C, 62.93; H, 4.93; N, 9.79%). Methyl 5-methyl-1-{3-[(pent-4-yn-1-yloxy)carbonyl]phenyl}-1H- 1,2,4-triazole-3-carboxylate (5a) (0.12 g, 15%) had mp 171 °C (from diisopropyl ether); vmax/cmµ1 (Nujol) 1730, 1710; dH (CDCl3) 1.70–1.85 (2 H, m), 1.92 (1 H, t, J 2.4), 2.18 (2 H, dt, J 6.5, 2.4), 2.32 (3 H, s), 3.94 (3 H, s), 4.18 (2 H, t, J 6.5), 7.32–8.21 (4 H, m), 11.80 (1 H, br s); m/z 327 (M+) (Found: C, 62.45; H, 5.20; N, 13.00.C17H17N3O4 requires C, 62.38; H, 5.23; N, 12.84%). Methyl 9-oxo-4,5,6,7-tetrahydro-9H-benzo[c]pyrazolo[1,5-e][1,5]- oxazecine-2-carboxylate (4b) (0.45 g, 60%) had mp 110 °C (from hexane–benzene); vmax/cmµ1 (Nujol) 1740, 1720; dH (CDCl3) 1.70–3.00 (6 H, m), 3.92 (3 H, s), 4.74–4.98 (2 H, m), 6.74 (1 H, s), 7.40–8.30 (4 H, m); m/z 300 (M+) (Found: C, 63.88; H, 5.37; N, 9.35. C16H16N2O4 requires C, 63.99; H, 5.37; N, 9.33%).Methyl 1-{3-[(hex-5-yn-1-yloxy)carbonyl]phenyl}-5-methyl-1H- 1,2,4-triazole-3-carboxylate (5b) (0.13 g, 15%) had mp 146 °C (from diisopropyl ether); vmax/cmµ1 (Nujol) 1730, 1710; dH (CDCl3) 1.55–1.90 (4 H, m), 1.95 (1 H, t, J 2.5), 2.15 (2 H, dt, J 6.2, 2.5), 2.31 (3 H, s), 3.92 (3 H, s), 4.11 (2 H, t, J 6.0), 7.20–8.20 (4 H, m); m/z 341 (M+) (Found: C, 63.26; H, 5.58; N, 12.27. C18H19N2O4 requires C, 63.33; H, 5.61; N, 12.31%). Treatment of Hydrazonoyl Chloride 2a with Silver Carbonate in 1,4-Dioxane.·A solution of 2a (0.64 g, 2 mmol) in dry 1,4-dioxane (160 ml) was treated with silver carbonate (2.76 g, 10 mmol), and the mixture was warmed to 80 °C in the dark for 24 h.The undissolved material was filtered off, the solvent was evaporated, and then the residue was chromatographed on a silica gel column with diethyl ether affording the cycloadduct 4a (86 mg, 15%). Thanks are due to MURST for financial support. Received, 3rd September 1997; Accepted, 6th October 1997 Paper E/7/06455A References 1 (a) A.Padwa, in 1,3-Dipolar Cycloaddition Chemistry, ed. A. Padwa, Wiley, New York, 1984, vol. II, pp. 277–406; (b) A. Padwa, in Advances in Cycloaddition, ed. D. P. Curran, JAI Press, London, 1990, pp. 1–89. 2 J. Brokatzky and W. Eberbach, Tetrahedron Lett., 1980, 4909. 3 M. Engelbach, P. Imming, G. Seitz and R. Tegethoff, Heterocycles, 1995, 40, 69. 4 M. Asaoka, M. Abe, T. Mukuta and H. Takei, Chem. Lett., 1982, 215. 5 (a) G. Broggini, L. Garanti, G. Molteni and G. Zecchi, Org. Prep. Proced. Int., 1996, 28, 699; (b) G. Broggini, L. Garanti, G. Molteni and G. Zecchi, J. Chem. Res., 1995, (S) 385; (M) 2389. 6 (a) G. Broggini, L. Bruch�e, L. Garanti and G. Zecchi, J. Chem. Soc., Perkin Trans. 1, 1994, 433; (b) G. Broggini, L. Garanti, G. Molteni and G. Zecchi, Tetrahedron, 1997, 53, 3005; (c) G. Broggini, L. Garanti, G. Molteni and C. Zecchi, Synthesis, 1995, 1483. 7 (a) M. A. Winnick, Chem. Rev., 1981, 81, 491; (b) G. Illuminati and L. Mandolini, Acc. Chem. Res., 1981, 14, 95. 8 G. Broggini, G. Molteni and G. Zecchi, J. Chem. Res., 1993, (S) 398; (M) 264

ISSN:0308-2342    

DOI:10.1039/a706455a

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

OH 1 2 OH 5 OH N Br Br Br +• 3 (TBPA+•SBCl6 –) 4 OH 1 or 2 (i) 3, dry MeCN, Ar (ii) Na2CO3–MeOH SbCl6 – 42 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 42–43† A Novel Cyclization of Geraniol and Nerol Initiated by Tris(p-bromophenyl)ammoniumyl Radical Cation Wei Wanga and You-Cheng Liu*a,b aNational Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, P.R. China bDepartment of Chemistry, University of Science and Technology of China, Hefei 230026, P.R.China Geraniol (1) and nerol (2) undergo a novel cyclization to cis-p-mentha-2,8-dien-1-ol (4) by reaction with tris(pbromophenyl) ammoniumyl radical cation (3) and the reaction mechanism is discussed. Tris(p-bromophenyl)ammoniumyl hexachloroantimonate (TBPA+.SbCl6 µ, 3) has been used as a one-electron oxidant in a variety of electron transfer reactions. Investigations have shown that 3 can initiate some radical cation cycloadditions, such as the Diels–Alder reaction,1 cyclopropanation2 and Cope rearrangement.3 We have studied the radical cation initiated cyclization of squalene with 3.4 In this article, we wish to report a novel cyclization of the monoterpenol geraniol (1) and nerol (2) to cis-p-mentha-2,8-dien-1-ol (4) by 3, which is reduced to the neutral tris(p-bromophenyl)amine (TBPA) (Scheme 1). 1 or 2 was treated with excess 3 in dry acetonitrile at room temperature under an argon atmosphere for several hours. After quenching of the reaction with sodium carbonate– methanol solution, the main product was isolated and identi- fied as 4.The structure of 4 was determined by mass spectrometry, IR, 1H and 13C NMR spectroscopy and elemental analysis. The results of a 13C-DEPT NMR determination established the structure of 4 and excluded the possibility of structure 5, which was considered as a reasonable alternative. Fig. 1 illustrates the 13C NMR spectra of compound 4. Comparing the three spectra of 4 [(a) ordinary 13C NMR spectrum, (b) DEPT-135 spectrum and (c) DEPT-90 spectrum], it can be seen that 4 has two different CH3, three CH2, three CH and two tert-C groups, which clearly indicate the presence of two differently substituted carbon–carbon double bonds, i.e.CHR‚CHR and CR2‚CH2, and their relative positions. The 13C NMR chemical shifts assignments for 4 are shown in Fig. 1(a). The spectroscopic data are consistent with those reported for 4 obtained from unsensitized photoxidation of limonene.5 Although the cyclization of acyclic monoterpenes has been known for a long time,6 and the acid-catalysed rearrangements of 1 and 2 and solvolyses of their derivatives have been studied as models for terpenoid biosynthesis,7 the title cyclization is of interest because it is initiated by a radical cation.It is also interesting to note that the product 4 obtained from this reaction is rarely observed in most cyclizations of monoterpenes but has been formed by unsensitized photooxidation of limonene.5 Moreover, most of the reactions reported are assumed to involve carbocationic intermediates, and subsequent intramolecular electrophilic cyclizations or rearrangements of these intermediates lead to complicated mixtures that contain products having the p-menthene skeleton without additional unsaturation.8 Recently, the radical cation cyclization of hexa-1,5-diene and its derivatives,9 as well as polyenes10 containing olefinic bonds at 1,5-positions, have been reported. All-trans-geranylgeraniol was converted via radical cation intermediates into fused six-membered ring products by photoinduced cyclization in sodium dodecyl sulfate (SDS) micelle.It was proposed that radical cationic intermediates could potentially play a role in the biogenesis of natural products in addition to the cationic intermediates invoked in classical concepts and especially in the cyclization processes for terpene biosynthesis.10 Accordingly, the title reaction may proceed via a radical cation intermediate as shown in Scheme 2.*To receive any correspondence (E-mail: ycliu@dchp.chp.ustc. edu.cn). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Scheme 1 Fig. 1 13C NMR spectra of product 4. (a) Normal 13C NMR spectrum; (b) DEPT-135 spectrum; (c) DEPT-90 spectrum6 –H+ • • + 1 or 2 3 • + excess of 3 • + 4 + +H+ • + J.CHEM. RESEARCH (S), 1998 43 The radical cation intermediate formed initially undergoes cyclization, deprotonation and dehydrogenation (by excess of 3+.) to give a cyclic triene, which protonates to form the carbocationic intermediate 6. Attack by a water molecule at the cationic centre opposite the isopropenyl group and deprotonation would produce 4. Experimental Melting points were uncorrected.Elemental analyses were carried out on an Italian-1106 elemental analytical apparatus. IR spectra were recorded on a Nicolet FT-170SX spectrometer. 1H and 13C NMR and 13C-DEPT spectra were obtained on a Bruker DMX-500 spectrometer (500.0 MHz for 1H NMR, 125.0 MHz for 13C NMR and 13C-DEPT) using [2H6]DMSO as solvent and tetramethylsilane (TMS) as internal reference. Mass spectra were determined on a VG-ZAB-HS mass spectrometer (EI). 1 and 2 were purchased from TCI Chemical Co. and used without further purification.Compound 3 was synthesized as described;11 mp 143–144 °C (decomp.) (Found: C, 26.58; H, 1.46. C18H12Br3Cl6NSb requires C, 26.50; H, 1.50%). All solvents were purified and dried according to standard procedures.12 cis-p-Mentha-2,8-dien-1-ol (4). To a solution of 1 or 2 (2.0 mmol) in anhydrous acetonitrile (35.0 ml) 3 (4.8 mmol) was added. The mixture was stirred at room temperature for 2 h under argon and checked by TLC. It was then poured into saturated sodium carbonate –methanol solution (15.0 ml), and extracted with trichloromethane (total 75 ml).The organic layer was washed with water and dried with anhydrous magnesium sulfate and the solvent was removed. The oily residue was separated by column chromatography on silica gel (eluent: light petroleum–ethyl acetate, from 40:1 to 15:1 v/v) to give 4 as a yellow oil in yields of 61 to 72% (Found: C, 78.81; H, 10.32. C10H16O requires C, 78.94; H, 10.53%).vmax/cmµ1 (film): 3340 (O•H), 1440 (C‚C), 1220 (C‚CH2). dH ([2H6]DMSO) 1.24 (3 H, s), 1.52 (1 H, m), 1.73 (2 H, m), 1.81 (3 H, s), 2.13 (2 H, m), 3.45 (1 H, br s, OH), 4.68 (2 H, m), 5.20 (1 H, m), 5.72 (1 H, d, J 10.7 Hz). dC ([2H6]DMSO) 149.9, 134.3, 128.2, 114.2, 75.4, 46.1, 31.7, 29.0, 26.2, 21.7; m/z 152 (M+), 134, 119, 91, 79, 43, 41. The 1H NMR spectroscopic data are consistent with those reported for 4.5 We are grateful to the National Natural Science Foundation of China for financial support.Received, 23rd July 1997; Accepted, 22nd September 1997 Paper E/7/05326F References 1 N. L. Bauld, Acc. Chem. Res., 1987, 20, 371 and references cited therein. 2 G. Stufflebeme, K. T. Lorenz and N. L. Bauld, J. Am. Chem. Soc., 1986, 108, 4234. 3 (a) J. P. Dinnocenzo and M. Schmitlel, J. Am. Chem. Soc., 1987, 109, 1567; (b) J. P. Dinnocenzo and D. A. Conlon, J. Am. Chem. Soc., 1988, 110, 2324. 4 Q. X. Guo, W. Wang, W. Yu, Y. C. Liu and Y. D. Wu, in preparation. 5 T. Sato and E. Murayama, Bull. Chem. Soc. Jpn., 1974, 47, 715. 6 (a) K. Stephan, J. Prakt. Chem., 1898, 58, 109; (b) O. Zertschel, Ber. Dtsch. Chem. Ges., 1906, 39, 1780. 7 (a) R. Croteau, Chem. Rev., 1987, 87, 929; (b) D. E. Cane, Acc. Chem. Res., 1985, 18, 220; (c) D. E. Cane, Tetrahedron, 1980, 36, 1109. 8 (a) W. Rittersdorf and F. Cramer, Tetrahedron, 1967, 23, 3015; 1968, 24, 43; (b) O. Cori, L. Chayet, L. M. Perez, C. A. Bunton and D. Hachey, J. Org. Chem., 1986, 51, 1310. 9 (a) Q. X. Guo, X. Z. Qin, J. T. Wang and F. Williams, J. Am. Chem. Soc., 1988, 110, 1974; (b) W. Adam, S. Grabowski, M. A. Miranda and M. Rubenacker, J. Chem. Soc., Chem. Commun., 1988, 142; (c) T. Miyashi, A. Konno and Y. Takahashi, J. Am. Chem. Soc., 1988, 110, 3676. 10 U. Hoffmann, Y. Gao, B. Pandey, S. Klinge, K. D. Warzecha, C. Kruger, H. D. Roth and M. Demuth, J. Am. Chem. Soc., 1993, 115, 10358. 11 F. A. Bell, A. Ledwith and D. C. Sherrington, J. Chem. Soc. C, 1969, 2719. 12 D. D. Perrin and W. L. F. Armarego, Purification of Laboratory Chemicals, Pergamon Press, New York, 3rd edn, 1988. Scheme 2

ISSN:0308-2342    

DOI:10.1039/a705326f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

NH2 P N P PhCOR R = H, Me, Ph C(R)Ph N P C Pd R OAc/2 OAc/2 Pd(OAc)2 AcOH N P C Pd H DMF 2 1 H2, DMF, 80 °C H R 44 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 44–45† A Reusable Polymer-anchored Palladium Catalyst for Reduction of Nitroorganics, Alkenes, Alkynes and Schiff Bases† Monirul Islam, Asish Bose, Dipakranjan Mal and Chitta R. Saha* Department of Chemistry, Indian Institute of Technology, Kharagpur - 721 302, India The preparation and utility of a new polymer-anchored PdII catalyst for the hydrogenation of a wide range of organic substrates is described.Catalytic reduction1 of organic compounds is an important process both in the laboratory and in industry, and continues to be the subject of active research. Methods based2 on catalytic hydrogenation in homogeneous and heterogeneous media are commonly adopted for the hydrogenation of organic compounds. However, the reproducibility and selectivity of these methods, particularly of noble-metal-catalysed hydrogenation, has restricted their popularity.To improve upon the selectivity of a catalyst, we considered immobilization of a catalytic system. Immobilization of catalysts or reagents to polymer supports often offers many advantages for carrying out organic transformations.3 Ease of work-up, higher yields, product selectivity and re-usability of the catalysts make them more attractive than their homogeneous counterparts. In the area of hydrogenation of organic substrates, extensive work has been performed on the development of Rh-based polymer supported catalysts.4,5 Sometime ago we and others reported the use of a PdII homogeneous catalyst6–9 for the reduction of a host of nitro-aromatics and -aliphatics.To develop its polymer-bound version, we have now prepared a synthetically useful PdII catalyst for reduction of functional groups like •NO2, \ /C‚C / \ , \ /C‚N•, •C‚C•, etc. in excellent yields. Catalyst 1 was readily accessible in two steps from aminopolystyrene10 (sP-NH2).Treatment of the polymer with PhCOR (R=H, Me, Ph) provided the corresponding Schiff bases, which were then treated with PdII acetate in acetic acid to yield catalysts 1 as dark brown solids (Scheme 1). Characterization of 1 was performed by IR and ESCA. The ESCA peaks11 at 338.25 eV (Pd 3d5/2) and 343.75 eV (Pd 3d3/2) and IR signals6,12,13 at 1585, 1420 and 722 cmµ1 indicate the presence of acetato-bridged orthometallated palladium( II) in catalyst 1.Catalysts 1 are activated by stirring them under H2 (1 atm) at 80 °C for 1 h to produce the active species 2. Chemical analysis indicates the presence of 112.25% of Pd in catalyst 2. Characteristic ESCA signals, and IR signals at 722, 1985 (vPd-H)14,6 and 1655 cmµ1 (vco, DMF), confirm the structure 2. Comparable ESCA and IR signals were also observed for the used catalyst. Moreover, the Pd-content of the catalyst, as measured by gravimetric analysis, remained unchanged even after several cycles.Exposure of an organic substrate in DMF–ethyl acetate medium containing catalyst 2 to hydrogen (1 atm) at room temperature resulted in rapid reduction of the substrate. As shown in Table 1, the reduction of nitroaromatics to aminoaromatics proceeds in excellent yields. In contrast, the reduction of nitroaliphatics (Table 3) requires higher temperatures (170 °C) and pressures (110.5Å103 kN mµ2). However, the yields of the products were consistently excellent.Hydrogenation of double bonds of alkenes, alkynes and Schiff bases to their corresponding saturated products under normal conditions is more facile, w-nitrostyrene being reducible to w-nitroethylbenzene in excellent yield. Catalyst 2 when R=H is the most active. The results described in Tables 1–3 involve the use of this catalyst. It offers a high degree of chemoselectivity. Hydrogenation of halonitroaromatics to the corresponding haloanilines is often accompanied by dehalogenation, and entails extensive optimization experiments.1 This problem could be greatly obviated by the use of catalyst 1.For example, a chloro substituent ortho or para to a nitro group remains intact. Similarly, a lactone (Tables 1 and 3, entry 7) group is not affected under the conditions employed. The superiority of catalyst 2 is clearly discernible from entry 8 of Table 1, in which a methoxy substituted nitroester is shown to be reducible to its amine in high yield.It may be noted that *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Atmospheric pressure reduction of nitroaromatics Initial turnover Entry Substrate Time t/h no. minµ1 Product % Yield 12345678 Nitrobenzene o-Nitrotoluene o-Chloronitrobenzene p-Chloronitrobenzene m-Dinitrobenzene 1-Nitronaphthalene 6-Nitrophthalide Methyl 4,5-dimethoxy-2-nitrobenzoate 3.5 6.25 5.37 4.9 7.0 8.0 8.5 8.5 2.30 1.22 1.40 1.70 1.00 0.86 0.80 0.79 Aniline o-Toluidine o-Chloroaniline p-Chloroaniline m-Phenylenediamine 1-Aminonaphthalene 6-Aminophthalide Methyl 4,5-dimethoxy-2-aminobenzoate 97 90 92 94 92 93 94b 92b a[sub] =0.50 mol dmµ3, total vol.=10 ml, medium=DMF; yields refer to GC analysis. bIsolated yield, [cat] =Pd content=1.50Å10µ3 mol.Scheme 1J.CHEM. RESEARCH (S), 1998 45 conventional hydrogenation of nitroesters over Pd or Pd/C provides variable yields of the corresponding amine.15 Although the described use of the catalyst 2 in the reduction of various organic substrates is quite general, it involves a restricted choice of reaction media. It appears that DMF is the best solvent for such reactions though hydrogenation occurs in ethyl acetate at a slower rate. The remarkable advantages with the use of the catalyst 2 are the ready accessibility of the catalysts, their reusability and storage. Even after recycling 7 or 8 times, the catalyst retains its original activity. Furthermore, the used catalysts are free from fire hazards or explosions. They can be used for selective reduction of an aromatic nitro group in the presence of an aliphalic nitro group, under atmospheric pressure, as evident from Tables 1 and 3.Further studies on product selectivity are under way. Experimental In a typical procedure, a solution of a substrate (5.0 mmol) in DMF (10 ml) containing the catalyst 2 (14.0 mg) was subjected to hydrogenation under hydrogen (1.0 atm) in a magnetically stirred glass reactor.The rate of hydrogen consumption was measured using a glass manometric apparatus. The detailed experimental setup and hydrogenation procedure have been described earlier.8 After the completion of the reaction, the catalyst was filtered off and the filtrate analysed by GC. In certain cases the products were isolated by usual work-up followed by preparative tlc.Received, 19th May 1997; Accepted, 4th September 1997 Paper E/7/03426A References 1 A. M. Tafesh and J. Weiguny, Chem. Rev., 1996, 96, 2035. 2 R. A. W. Johnstone, A. H. Wilby and I. D. Entwistle, Chem. Rev., 1985, 85, 129. 3 M. E. Wright and S. R. Pulley, J. Org. Chem., 1987, 52, 5036. 4 Z. Jaworska, S. Gobas, W. Mistra and J. Wrzysz, J. Mol. Catal., 1994, 88, 13. 5 D. T. Gokak and R. N. Ram, J.Mol. Catal., 1989, 49, 285. 6 A. Bose and C. R. Saha, J. Mol. Catal., 1989, 49, 281. 7 P. K. Santra and C. R. Saha, J. Mol. Catal., 1987, 39, 279. 8 D. K. Mukherjee, B. K. Palit and C. R. Saha, Indian J. Chem., 1992, 31A, 243. 9 A. M. Tafesh and M. Beller, Tetrahedron Lett., 1995, 36, 9305. 10 R. B. King and M. E. M. Sweet, J. Org. Chem., 1979, 44, 385. 11 B. M. Choudary, K. Ravikumar and M. Lakshmi Kantam, J. Catal., 1991, 41, 130. 12 T. A. Stephenson and G. Wilkinson, J. Inorg.Nucl. Chem., 1967, 29, 2122. 13 H. Onoue and I. Moritani, J. Organomet. Chem., 1972, 43, 431. 14 (a) J. V. Kingston and G. R. Scollary, Chem. Commun., 1969, 455; (b) E. H. Brooks and F. Glocking, J. Chem. Soc. A, 1966, 1241. 15 C. A. Fetscher and M. T. Bogert, J. Org. Chem., 1939, 4, 71. Table 2 Atmospheric pressure reduction of miscellaneous substratesa Initial turnover Entry Substrate Time/h no. minµ1 Product % Yield 12345678 Hex-1-ene Styrene w-Nitrostyrene Fumaric acid Isoprene Phenylacetylene Benzylideneaniline N-Methylbenzaldimine 1.2 0.70 1.4 2.8 0.72 0.81 1.96 1.5 7.0 14.70 5.80 3.00 14.70 13.10 4.30 5.60 Hexane, hex-2-ene Ethylbenzene w-Nitroethylbenzene Succinic acid 2-Methylbutane Ethylbenzene N-Phenylbenzylamine N-Methylbenzylamine 86, 12 98 95 92 97 97 100 100 a[sub] =0.50 mol dmµ3, reaction mixture vol.=10 ml, medium=DMF. Table 3 High pressure reduction of nitroaliphaticsa Initial turnover Entry Substrate Time (t/h) no. minµ1 Products % Yield 1234567 Nitroethane 1-Nitropropane 2-Nitropropane 1-Nitroheptane w-Nitroethylbenzene Acetonitrile Phthalic anhydride 6.2 6.5 7.2 6.8 7.0 8.6 8.5 3.56 3.33 2.93 3.11 2.99 2.12 1.58 Ethylamine 1-Aminopropane 2-Aminopropane 1-Aminoheptane w-Aminoethylbenzene Diethylamine Phthalide 98 97 96 94 95 93 86b aMedium=DMF, [sub] =1.50 mol dmµ3, total vol.=10 ml; bisolated yield, [cat] =1.70Å10µ3 g.atom dmµ3, pH2=10.5Å10µ3 kN mµ2, T=70 °C.

ISSN:0308-2342    

DOI:10.1039/a703426a

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

R NO2 R NO2 Zn E.T. – • Ac2O –AcO– R N(O)OAc • (i) E.T. (ii) –AcO– R NO R NO – • Ac2O –AcO– R NOAc • E.T. R NOAc – Ac2O –AcO– R N(Ac)OAc E.T. 4 46 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 46–47† Synthesis of N,O-Diacetylated N-Arylhydroxylamines by Reduction of Nitroaromatics with Zinc and Acetic Anhydride† Byeong Hyo Kim,*a Young Moo Jun,a Seung Won Suh,a Woonphil Baikb and Byung Min Leec aDepartment of Chemistry, Kwangwoon University, Seoul, 139-701, Korea bDepartment of Chemistry, Myong Ji University, Kyung Ki Do, Korea cKRICT, Taejon, Korea Reduction of nitroaromatic compounds with zinc and acetic anhydride in dichloromethane gave N,O-diacetylated N-arylhydroxylamines in good yields under mild conditions.Esters of N-hydroxy-N-arylacetamides, such as ArN(OR)- COMe (1a; R=COMe, 1b; R=SO3 µ), are considered to be the reactive metabolites of mutagenic and carcinogenic aromatic amides.1 In spite of their biological interest, useful preparative methods for 1 were not well-established. While the direct chemical reductive diacetylation of nitroarene was not successful,2,3 the electrochemical reduction of both aliphatic and aromatic nitro or nitroso compounds in aprotic media with Ac2O produced N,O-diacetylated hydroxylamines in yields from 40 to 80%.4 We now wish to report on the study of an efficient chemical method for the one-pot N,O-diacetylation of nitroaromatics by using zinc dust and Ac2O in an aprotic solvent under mild conditions.Nitrobenzene (1 mmol), when treated with acetic anhydride (4 mmol) and Zn (5 mmol) in CH2Cl2 at room temperature for 50 min, gave N,O-diacetylated N-phenylhydroxylamine, PhN(OAc)Ac, in 87% yield along with 5% of acetanilide (Table 1, entry 1). Surprisingly, reduction to aniline was barely observed on GLC. In protic solvents such as methanol, the acetylation reaction was completed within 25 min at 0 °C to give PhN(OAc)Ac in 71% yield and acetanilide in 7%.For the desired N,O-diacetylated N-phenylhydroxylamine, the aprotic solvent dichloromethane showed better yield than the protic methanol medium in all cases even though it proceeded more slowly at relatively higher reaction temperatures. The formation of nitrosobenzene was observed by GC-MS analysis during the reductive acetylation of nitrobenzene. To verify the intermediate step of the reaction, we carried out the same reaction with nitrosobenzene in place of nitrobenzene, and diacetylated product 2a was obtained in 95% yield and a trace amount of monoacetylated product 3a was detected on GLC (Table 1, entry 2).Therefore acetylations of nitroaromatics to 2 and 3 seem to proceed through nitrosoaromatic intermediates. We have extended the acetylation reaction to a variety of nitroaromatics and the results are summarized in Table 1. In most cases, diacetylations of nitroaromatics were successful with fair to excellent yields. It is worth mentioning that in the case of halo-substituted nitroarene the corresponding diacetylated product was obtained in high yield without giving any dehalogenated products (Table 1, entries 6, 8), which are frqeuently encountered problems in electrochemical methods.Not only for nitroarene derivatives but also for nitropyridine, the diacetylation product was obtained in high yield (Table 1, entry 8). Upon reductive acetylation of 4-nitrophenol in the presence of Ac2O (4 equiv.)/Zn (5 equiv.) in dichloromethane at room temperature (45 min), additional acetylation on the hydroxy group occurred to produce p-AcOC6H4N-(Ac)OAc (56%) and p-AcOC6H4NHOAc (43%).To manifest the direction of electron transfer from zinc to nitro functionality, the cyclic voltammetric behaviour of nitrobenzene and acetic anhydride was examined. In case of nitrobenzene the reductive wave was observed at µ0.92 V (Pt cathode, 0.1 M TBAP/CH2Cl2, Ag/AgCl, 20 mV sµ1), which indicated that nitrobenzene could be a good electron acceptor. However, under the same cyclic voltammetric conditions acetic anhydride did not exhibit any observable reduction wave.Thus, the reaction would be initialized as nitrobenzene accepts an electron. The possible reaction path is shown in Scheme 1. The radical anion of nitrobenzene gener- *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J.Chem. Research (M). Table 1 Reductive acetylation of nitroarenes or nitrosoarene in the presence of Ac2O (4 equiv.)/Zn (5 equiv.) in CH2Cl2 at room temperature R–NOx+Ac2OhR–N(Ac)OAc+R–NHAc 2 3 Entry Substrate Time (t/min) Product (% yield)a 12345678 Nitrobenzene Nitrosobenzene 2-Nitrotoluene 3-Nitrotoluene 4-Nitrotoluene 1-Bromo-3-nitrobenzene 2-Nitrofluorene 2-Chloro-5-nitropyridine 50 50 120 50 50 50 50 50 2a (87) 2a (95) 2b (73) 2c (78) 2d (85)b 2e (91) 2f (83)b 2g (93) 3a (5) 3a (tr) 3b (27) 3c (20) 3d (13)b 3e (7) 3f (5)b — aGLC yield with an internal standard; bisolated yield.Scheme 1J. CHEM. RESEARCH (S), 1998 47 ated by the electron transfer from zinc to nitrobenzene may react rapidly as a nucleophile toward the acetic anhydride electrophile to form an intermediate, 4. Following electron transfer, loss of the acetate anion could produce the nitroso intermediate. Through similar continuous electron transfer and acetylation, the nitroso intermediate may be transformed to an N,O-diacetylated N-arylhydroxylamine.In conclusion, we have now established a mild and novel reaction route for N,O-diacetylated hydroxylamines by using Ac2O/Zn/CH2Cl2, which would be a useful chemical method for the reductive diacetylation of nitroaromatics. As far as dehalogenation is concerned, our chemical method is superior to the electrochemical one. Experimental Most of the chemical reagents were purchased from Aldrich and used without further purification in most cases.Acetic anhydride was purchased from Duksan P. and purified by a standard method. Zinc powder was purchased from Junsei Chemical Co. and was used without further purification. Solvents were purchased and dried by the usual laboratory techniques. Solvents were deoxygenated before use by bubbling argon through them. Analytical GC was performed on a Donam 6200 gas chromatograph equipped with a DB-1 column and Hitachi D-2500 integrator. 1H NMR spectra were recorded on a 300 MHz Bruker instrument and 13C NMR spectra were recorded on a 125 MHz Bruker instrument. Chemical shifts are in ppm from tetramethylsilane (TMS). High-resolution mass spectra (EI) were recorded on a Jeol JMS-DX 303 mass spectrometer. Infrared spectra (IR) were recorded on a Nicolet 205 FT-IR. Most products were isolated by flash column chromatography on silica gel (70–230 mesh ATSM, Merck) with eluents of mixed solvents (hexane and ethyl acetate).GC yields were determined by using an internal standard (toluene) and were corrected with predetermined response factors. General Procedure for the Diacetylation of Nitro- or Nitroso-aromatics. ·Zinc powder (327 mg, 5 mmol) and CH2Cl2 (3 ml) were placed in a 20 ml vial equipped with a rubber septum. Acetic anhydride (0.38 ml, 4 mmol) was added to the reaction mixture followed by nitrobenzene (0.10 ml, 1 mmol). The mixture was stirred under nitrogen or argon at room temperature.It was then quenched with 10% NH4Cl and extracted with CH2Cl2 (3Å20 ml). The combined CH2Cl2 extract was dried over MgSO4 and the solvent evaporated. The GC yield was determined with an internal standard and, if necessary, the products were isolated by flash column chromatography with ethyl acetate–hexane co-solvent. In general, dC (125 MHz, CDCl3) for OCOCH3 and NCOCH3 of the following compounds were 167–168 and 165–166, respectively. N-(Acetyloxy)-N-phenylacetamide (2a).·The compound was obtained as a liquid. The yield was 87% when nitrobenzene was starting substrate, and 95% with nitrosobenzene.TLC (30% ethyl acetate–hexane) Rf 0.37; dH (300 MHz, CDCl3) 7.48–7.40 (5 H, m), 2.20 (3 H, s), 2.07 (3 H, s); vmax/cmµ1 (Nujol) 3059, 2993, 1803, 1694, 1600, 1496 (Found: m/z, 193.0754. C10H11NO3 requires Mr, 193.0739). N-(Acetyloxy)-N-(2-methylphenyl)acetamide (2b). Yield: 73% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.38; dH (300 MHz, CDCl3) 7.51–7.27 (4 H, m), 2.38 (3 H, s), 2.17 (3 H, s), 1.92 (3 H, s); vmax/cmµ1 (Nujol) 3057, 2993, 1799, 1694, 1430, 1185 (Found: m/z, 207.0895.C11H13NO3 requires Mr, 207.0895). N-(Acetyloxy)-N-(3-methylphenyl)acetamide (2c). Yield: 78% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.39; dH (300 MHz, CDCl3) 7.35–7.21 (4 H, m), 2.38 (3 H, s), 2.19 (3 H, s), 2.06 (3 H, s); vmax/cmµ1 (Nujol) 3057, 2993, 1799, 1688, 1378 (Found: m/z, 207.0899.C11H13NO3 requires Mr, 207.0895). N-(Acetyloxy)-N-(4-methylphenyl)acetamide (2d). Yield: 85% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.39; dH (300 MHz, CDCl3) 7.35 (2 H, d, J 8.4 Hz), 7.25 (2 H, d, J 8.4 Hz), 2.38 (3 H, s), 2.18 (3 H, s), 2.03 (3 H, s); vmax/cmµ1 (Nujol) 3064, 2992, 1799, 1688, 1428, 1284 (Found: m/z, 207.0888. C11H13NO3 requires Mr, 207.0895). N-(Acetyloxy)-N-(3-bromophenyl)acetamide (2e). Yield: 91% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.39; dH (300 MHz, CDCl3) 7.65 (1 H, t, J 1.9 Hz), 7.44–7.41 (2 H, m), 7.31–7.29 (1 H, m), 2.23 (3 H, s), 2.10 (3 H, s); vmax/cmµ1 (Nujol) 3057, 2989, 1805, 1703, 1589, 1425, 1272 (Found: m/z, 270.9856.C10H10BrNO3 requires Mr, 270.9844). N-(Acetyloxy)-N-(9H-fluoren-2-yl)acetamide (2f). Yield: 83% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.34; dH (300 MHz, CDCl3) 7.74–7.72 (2 H, m), 7.61 (1 H, s), 7.50–7.42 (2 H, m), 7.37–7.26 (2 H, m), 3.82 (2 H, s), 2.17 (3 H, s), 2.07 (3 H, s); vmax/ cmµ1 (Nujol) 3057, 2988, 1799, 1691, 1425, 1272, 1187 (Found: m/z, 281.1046.C17H15NO3 requires Mr, 281.1052). N-(Acetyloxy)-N-(2-chloropyridin-5-yl)acetamide (2g). Yield: 93% (liquid); TLC (30% ethyl acetate–hexane) Rf 0.32; dH (300 MHz, CDCl3) 8.49 (1 H, d, J 2.6 Hz), 7.85 (1 H, dd, J 2.6 and 8.5 Hz), 7.39 (1 H, d, J 8.5 Hz), 2.26 (3 H, s), 2.16 (3 H, s); vmax/cmµ1 (Nujol) 3063, 2983, 1810, 1703, 1612, 1425, 1266 (Found: m/z, 228.0286. C9H9ClN2O3 requires Mr, 228.0301). This work was supported by the Korea Science and Engineering Foundation (951-0301-011-2) and partly by Kwangwoon University. Received, 4th August 1997; Accepted, 4th September 1997 Paper E/7/05670B References 1 Recent reviews include (a) J. A. Miller, Cancer Res., 1970, 30, 559; (b) J. A. Miller and E. C. Miller, EHP, Environ. Health Perspect., 1983, 49, 3; (c) E. Kriek and J. G. Westra, in Chemical Carcinogens and DNA, ed. P. L. Grover, CRC Press, Boca Raton, FL, 1979,, vol. 2, pp. 1–28; (d) D. Dalejka-Giganti, in Chemistry and Biology of Hydroxamic Acids, ed. H. Kehl, Karger, Basel, 1982, pp. 150–159; (e) D. E. Hathaway and G. F. Kolar, Chem. Soc. Rev., 1980, 9, 241. 2 A. K. Koul, J. M. Bachhawat, N. S. Remegowda, B. Prashad and N. K. Mathur, Indian J. Chem. Educ., 1972, 3, 22. 3 J. A. Miller, C. S. Wyatt, E. C. Miller and H. A. Hartman, Cancer Res., 1961, 21, 1465. 4 (a) L. H. Klemm, P. E. Iversion and H. Lund, Acta Chem. Scand., Sect. B, 1974, 28, 593; (b) L. Christensen and P. E. Iversion, Acta Chem. Scand., Sect. B, 1979, 33, 352; (c) J. H. Wagenknecht and G. V. Johnson, J. Electrochem. Soc., 1987, 134, 2754.

ISSN:0308-2342    

DOI:10.1039/a705670b

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

48 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 48–49† Reductive Cleavage of the S–Si Bond in Arylsulfanyltrimethylsilanes: a Novel Method for the Synthesis of Unsymmetrical Sulfides† Songlin Zhang and Yongmin M. Zhang* Department of Chemistry, Hangzhou University, Hangzhou, 310028, P. R. China Arylsulfanyltrimethylsilanes are reduced by samarium diiodide to yield samarium arylthiolates which react with alkyl halides to give unsymmetrical sulfides. The application of samarium diiodide in organic synthesis has received increasing attention in the last decade.1–3 It is a powerful one-electron transfer reductant. We have reported the reductive cleavage of S–S bonds with SmI2.4 Recently, we have considered that the S–Si bond might be also reduced with samarium diiodide.Since organic sulfur compounds have become increasingly useful and important in organic synthesis,5,6 convenient preparations of appropriate sulfides have been developed continuously7–11 For example, sulfoxides are reduced to sul- fides with the Cp2TiCl2/Sm or TiCl4/Sm7,8 system, while the reaction between benzyl chloride and thiols in the presence of a modified montmorillonite clay containing 3-aminopropyltriethoxysilane has also been reported.10 Here we report that SmI2 reduces arylsulfanyltrimethylsilanes to samarium arylthiolates under a nitrogen atmosphere.This new thiolate anion species reacts with akyl halides to give unsymmetrical sulfides in good yield under neutral conditions (Scheme 1).Experimental General Procedure.·A solution of arylsulfanyltrimethylsilane (1 mmol) in THF (1 ml) was added by syringe to a deep blue solution of SmI2 (2.2 mmol) in THF (10 ml) at reflux temperature under an inert atmosphere of nitrogen. The deep blue colour of the solution gradually became brown within 5 h, which showed that the S–Si bond had been reductively cleaved by SmI2 and that the samarium arylthiolate (ArSmI2) had been generated.An alkyl halide (1 mmol) in THF (1 ml) was then added by syringe to the mixture and stirred under reflux for 4 h; a dilute solution of HCl and diethyl ether were added. The organic layer was washed with water (20 mlÅ2) and dried over anhydrous Na2SO4. The solvent was removed in vacuo. The crude product was purified by preparative TLC on silica gel (light petroleum:ethyl acetate=100:1 as eluent). Some results are summarized in Table 1. Data of Products.·1: mp 38–39 °C; dH (CCl4) 3.97 (2 H, s), 7.00–7.28 (10 H, m); vmax/cmµ1 3080, 3040, 2940, 1595, 1500, 1488, 1460, 1445, 1250, 1090, 1070, 1025, 735, 690. 2: oil; dH 0.83 (3 H, t), 1.0–1.67 (16 H, m), 2.80 (2 H, t), 7.03–7.23 (5 H, m); vmax/cmµ1 3090, 3080, 2960–2920, 2860, 1595, 1495, 1470, 1445, 1022, 730, 682. 3: oil; dH 0.87 (3 H, t), 1.02–1.70 (8 H, m), 2.80 (2 H, t), 7.03–7.22 (5 H, m); vmax/cmµ1 3090, 3080, 2970–2940, 2860, 1600, 1496, 1470, 1446, 1022, 728, 680. 4: mp 45–46 °C; dH 0.86 (3 H, t), 1.03–1.72 (28 H, m), 2.83 (2 H, t), 7.03–7.24 (5 H, m); vmax/cmµ1 3092, 3080, 2960–2920, 2860, 1600, 1469, 1470, 1447, 1021, 729, 678. 5: mp 47–49 °C; dH 3.46 (4 H, s), 7.17 (10 H, s); vmax/cmµ1 3080, 3060, 3019, 1585, 1480, 1450, 1240, 1185, 900, 760, 682. 6: oil; dH 0.84 (3 H, t), 1.07–1.43 (16 H, m), 2.23 (2 H, t), 3.54 (2 H, s), 7.20 (5 H, s); vmax/cmµ1 3100, 3080, 3040, 2970–2930, 2860, 1610, 1500, 1470, 1460, 1380, 1070, 1030, 760, 690. 7: oil; dH 0.84 (3 H, t), 1.07–1.43 (20 H, m), 2.23 (2 H, t), 3.54 (2 H, s), 7.20 (5 H, s); vmax/ cmµ1 3100, 2080, 3040, 2980–2940, 2864, 1610, 1500, 1472, 1465, 1460, 1380, 1070, 1029, 760, 690. 8: oil; dH 0.86 (3 H, t), 1.02–1.70 (8 H, m), 2.23 (2 H, t), 3.53 (2 H, s), 7.17 (5 H, s); vmax/cmµ1 3100, 3080, 3040, 2982–2940, 2860, 1610, 1500, 1470, 1460, 1380, 1070, 1030, 760, 690. 9: oil; dH 0.87 (3 H, t), 1.10–1.60 (8 H, m), 2.77 (2 H, t), 7.13–7.23 (4 H, m); vmax/cmµ1 3090, 3085, 2900–2800, 1585, 1490–1480, 1400, 1100–1090, 1010, 810, 740, 720. 10: oil; dH 0.87 (3 H, t), 1.13–1.40 (20 H, m), 2.76 (2 H, t), 7.14-7.23 (4 H, m); vmax/ cmµ1 3090, 3085, 2920–2800, 1585, 1490–1480, 1395, 1100–1090, 1010, 810, 740, 720. 11: oil; dH 0.87 (3 H, t), 1.15–1.42 (16 H, m), 2.76 (2 H, t), 7.14–7.23 (4 H, m); vmax/cmµ1 3090, 3085, 2920–2800, 1585, 1490–1480, 1395, 1100–1095, 1010, 810, 740, 720. 1H NMR spectra were recorded on a PMX-60 MHz instrument, and IR spectra were determined on a PE-683 spectrometer.We are grateful to the National Natural Science Foundation of China and Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, for financial support. Received, 21st July 1997; Accepted, 12th September 1997 Paper E/7/05190E *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J.Chem. Research (M). Table 1 Sulfide products from arylsulfanyltrimethylsilanes (ArSSiMe3) and alkyl halides (RX) Entry Ar R–X Product Yieldc(%) 123456789 10 11 12 Ph Ph Ph Ph Ph PhCH2 PhCH2 PhCH2 PhCH2 4-ClC6H4 4-ClC6H4 4-ClC6H4 PhCH2Cla PhCH2Clb Me[CH2]9Br Me[CH2]5Br Me[CH2]15Br PhCH2Cla Me[CH2[9Br Me[CH2]11Br Me[CH2]5Br Me[CH2]5Br Me[CH2]11Br Me[CH2]9Br PhSCH2Ph (1) PhSCH2Ph (1) PhS[CH2]9Me (2) PhS[CH2]5Me (3) PhS[CH2]15Me (4) PhCH2SCH2Ph (5) PhCH2S[CH2]9Me (6) PhCH2S[CH2]11Me (7) PhCH2S[CH2]5Me (8) 4-ClC6H4[CH2]5Me (9) 4-ClC6H4[CH2]11Me (10) 4-ClC6H4[CH2]9Me (11) 85 80 89 83 78 84 78 77 77 78 80 82 aAlkylation at room temp.for 4 h; breduction at room temp. for 10 h, alkylation at room temp. for 4 h; cyields of isolated products. SmI2/THF R–X ArS–SiMe3hArSSmI2hArS–R reflux 5 h reflux 4 h Scheme 1J. CHEM. RESEARCH (S), 1998 49 References 1 P. Girard, J. L. Namy and H. B. Kagan, J. Am. Chem. Soc., 1980, 102, 2693. 2 G. A. Molander, Chem. Rev., 1992, 92, 29. 3 G. A. Molander and C. R. Harris, Chem. Rev., 1996, 96, 307. 4 X. S. Jia and Y. M. Zhang, Synth. Commun., 1994, 24, 787. 5 G. Solladie, in Comprehensive Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon Press, Oxford, 1991, vol. 6, pp. 133–170. 6 K. Ogura, in Comprehensive Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon Press, Oxford, 1991, vol. 1, pp. 505–539. 7 Y. M. Zhang, Y. P. Yu and W. L. Bao, Synth. Commun., 1995, 25, 1825. 8 J. Q. Wang and Y. M. Zhang, Synth. Commun., 1995, 25, 3545. 9 N. M. Yoon, J. Chei and J. H. Ahn, J. Org. Chem., 1994, 59, 3490. 10 P. Kannan, K. Pitchumani, S. Rajagopal and C. Srinivasan, Chem. Commun., 1996, 369. 11 G. H. Lee, E. B. Choi and C. S. Dak, Tetrahedron Lett., 1994, 35, 2195.

ISSN:0308-2342    

DOI:10.1039/a705190e

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

O O AcO AcO 1 2 50 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 50–51† The Stereochemistry of Epoxidation of D5-Steroids with Sodium Perborate and Potassium Permanganate† James R. Hanson,* Nicolas Terry and Cavit Uyanik School of Molecular Sciences, University of Sussex, Brighton, Sussex, UK, BN1 9QJ Sodium perborate, with potassium permanganate as a catalyst, has been shown to be a novel reagent for the epoxidation of steroidal 5-enes with the attack occurring predominantly on the b-face.The epoxidation of steroidal 5-enes with peracids takes place predominantly from the a-face of the molecule to afford the 5a,6a-epoxides.1 Recently there has been an effort to prepare2,3 the biologically interesting but relatively inaccessible 5b,6b-epoxides. A number of groups4–9 have shown that these epoxides can be obtained from the 5-enes using the biphasic systems involving potassium permanganate and transition metal nitrates or sulfates. Many years ago, it was shown–10 that potassium permanganate in acetic acid would epoxidize 3b-acetoxyandrost-5-en-17-one (1) although at the time the stereochemistry of the epoxides was unknown.We have now repeated this work and shown that the major product was the 5b,6b-epoxide (2:1; b-epoxide:a-epoxide). The epoxides may be clearly distinguished by the position of the 6-H resonance in the 1H NMR spectrum (dH 2.87, a-epoxide; dH 3.07 b-epoxide). 11 In this paper we report the catalytic use of potassium permanganate in forming the b-epoxides.Sodium perborate in glacial acetic acid provides an epoxidizing agent for alkenes.12 With 1 it slowly gave a mixture of the 5a,6a- and 5b,6b-epoxides, containing predominantly the 5a,6a-epoxides (ca. 4:1; a:b-epoxides) paralleling the stereochemical results obtained with other peracids.1 However, in the presence of catalytic amounts of potassium permanganate, the reaction was much faster and the stereoselectivity was reversed with the b-epoxide now predominating.A number of steroidal 5-enes were examined, including some with b-substituents at C-4. The ratios of the epoxides that were formed are given in Table 1. In the case of 1 some cleavage of the epoxide and allylic oxidation also took place. A similar oxidation has been reported with the permanganate –periodate reagent in pyridine.13 Interestingly, the 5a,6a-epoxide, identical to the product of peracid oxidation, was obtained from the B-nor steroid, 3b-acetoxy-7-norandrost- 5-en-17-one (2).These results confirm the earlier observations10 that the epoxidation on the b-face of a steroidal 5-ene occurs with potassium permanganate and show that the b-epoxidation does not have an absolute requirement for a metal sulfate. We have suggested previously that the stereochemical-determining feature of the potassium permanganate–metal sulfate epoxidation is the kinetically preferred pseudo-axial attack of the electron-deficient manganese, in a Markownikov sense, on the alkene to form a manganate, the collapse of which to form an epoxide in the second step was facilitated by the metal sulfate.5,7 In the six-membered ring B of the steroids, the axial position at C-6 is b-oriented whilst in the five-membered 7-nor series the pseudo-axial position is a-oriented.This interpretation has been challenged8 and the alternative view has been proposed that prior complexation by the metal sulfate on the less hindered face of the alkene occurs, directly the permanganate to the more hindered face of the molecule.Although we also considered this7 it has difficulty in explaining why the 7-nor steroid affords the same epoxide with both peracid and permanganate. In the case of the perborate system the role of the perborate/acetic acid (peracetic acid) is to re-oxidize the manganese. This reaction is faster than the peracetic acid epoxidation. In conclusion the potassium permanganate/sodium perborate/ glacial acetic acid reagent is a novel, cheap epoxidizing system that in this instance has afforded epoxides, albeit in moderate yield, that differ in their stereochemistry from those formed by conventional peracids.Experimental Experimental details have been described previously.5 General Experimental Procedure.•Sodium perborate (1.1 g) was dissolved in glacial acetic acid (15 cm3) with gentle warming s50 °C. Potassium permanganate (80 mg) in water (1 cm3) was added to a solution of the steroid (900 mg) in glacial acetic acid (10 cm3).The sodium perborate solution was then added in portions (2.5 cm3) over a period of 1 h. The mixture was left to stand at room temperature overnight. It was poured into aqueous sodium hydrogen carbonate and the products were recovered in ethyl acetate. The extract was washed with aqueous sodium sulfite, aqueous sodium hydrogen carbonate and water, and dried over sodium sulfate. The solvent was evaporated to give a gum, which was assayed by 1H NMR for its epoxide content [ratio of signals at dH 2.87 (a) to 3.07 ppm (b)] and separated by chromatography on silica by elution with increasing concentrations of ethyl acetate in light petroleum (bp 60–80°C).The epoxides were identified by their mps and 1H NMR spectra. 3b-Acetoxycholest-5-ene (900 mg) gave the starting material (85 mg), 3b-acetoxy-5b,6b-epoxycholestane (295 mg)14 and 3b-acetoxy- 5a,6a-epoxycholestane (62 mg).14 3b-Acetoxyandrost-5-en-17-one (1) (900 mg) gave the starting material (79 mg), 3b-acetoxy-5b,6b-epoxyandrostan-17-one (292 mg),15 3b-acetoxy-5a,6a-epoxyandrostan-17-one (67 mg),15 3b-acetoxyandrost- 5-ene-7,17-dione (30 mg)16 and 3b,6b-diacetoxy- 5a-hydroxyandrostan-17-one (73 mg).10 3b-Acetoxyandrost-5-ene (900 mg) gave the starting material (105 mg) and 3b-acetoxy-5b,6b-epoxyandrostane (345 mg). 3b,17b-Diacetoxyandrost-5-ene (500 mg) gave the starting material (53 mg) and 3b,17b-diacetoxy-5b,6b-epoxyandrostane (104 mg).17 *To receive any correspondence.†This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Epoxidation of steoridal D5-alkenes Compound Ratio a:b-epoxide Cholesteryl acetate 3b-Acetoxyandrost-5-en-17-one (1) 3b-Acetoxyandrost-5-ene 3b,17b-Diacetoxyandrost-5-ene 3b-Acetoxy-4b-hydroxyandrost-5-en-17-one 4b-Acetoxy-3b-hydroxyandrost-5-en-17-one 3b-Acetoxy-7-norandrost-5-en-17-one (2) 1:5 1:4 b-Epoxide only b-Epoxide only 1:4 1:6.5 a-Epoxide onlyJ.CHEM. RESEARCH (S), 1998 51 3b-Acetoxy-4b-hydroxyandrost-5-en-17-one (500 mg) gave the starting mterial (45 mg) and 3b-acetoxy-5b,6b-epoxy-4b-hydroxyandrostan- 17-one (98 mg). 4b-Acetoxy-3b-hydroxyandrost-5-en-17-one (500 mg) gave the starting material (32 mg) and 4b-acetoxy-5b,6b-epoxy-3b-hydroxyandrostan- 17-one (99 mg). 3b-Acetoxy-7-norandrost-5-en-17-one (2) (500 mg) gave the starting material 913 mg) and 3b-acetoxy-5a-6a-epoxy-7-norandrostan- 17-one (223 mg).18 3b-Acetoxy-5b,6b-epoxyandrostane: mp 98–100 °C; dH (CDCl3) 0.68 (3 H, s, 18-H), 1.01 (3 H, s, 19-H), 2.03 (3 H, s, OAc), 3.08 (1 H, s, 6a-H), 4.76 (1 H, tt, J 11.3 and 5.5 Hz, 3a-H) (Found: C, 76.1; H, 9.9. C21H32O3 requires C, 75.9; H, 9.7%). 3b-Acetoxy-5b,6b-epoxy-4b-hydroxyandrostan-17-one had mp 182–185 °C; dH (CDCl3) 0.81 (3 H, s, 18-H), 1.17 (3 H, s, 19-H), 2.08 (3 H, s, OAc), 3.25 (1 H, d, J 2 Hz, 6a-H), 3.44 (1 H, dd, J 3.5 and 1 Hz, 4a-H), 4.79 (1 H, ddd, J 3.5, 4.5 and 11.5 Hz, 3a-H) (Found: C, 69.3; H, 8.4.C21H30O5 requires C, 69.6; H, 8.3%). 4b-Acetoxy-5b,6b-epoxy-3b-hydroxyandrostan-17-one had mp 181–184 °C; dH (CDCl3) 0.74 (3 H, s, 18-H), 1.09 (3 H, s, 19-H), 2.07 (3 H, s, OAc), 3.20 (1 H, d, J 4 Hz, 6a-H), 3.89 (1 H, ddd, J 3.5, 5 and 11.5 Hz, 3a-H), 4.32 (1 H, dd, J 3.5 and 1.1 Hz, 4a-H) (Found: C, 65.7; H, 8.0.C21H30O5.H2O requires C, 66.3; H, 8.5%). C. U. wishes to thank Kocaeli University, Izmit, Turkey, for study leave and financial assistance. Received, 26th August 1997; Accepted, 17th September 1997 Paper E/7/06111K References 1 K. D. Bingham, T. M. Blaiklock, R. C. B. Coleman and G. D. Meakins, J. Chem. Soc. C, 1970, 2330. 2 J. R. Hanson and A. Truneh, J. Chem. Soc., Perkin Trans. 1, 1988, 2001. 3 L. R. Galagovsky and E. G. Gras, J. Chem. Res.(S), 1993, 137. 4 M. S. Syamala, J. Das, S. Baskaran and S. Chandrasekaran, J. Org. Chem., 1992, 57, 1928. 5 J. R. Hanson, P. B. Hitchcock, M. D. Liman, S. Nagaratnam and R. Manickavasagar, J. Chem. Res., 1995, (S) 200; (M) 1335. 6 E. J. Parish, H. Li and S. Li, Synth. Commun., 1995, 25, 927. 7 J. R. Hanson, S. Nagaratnam and J. Stevens, J. Chem. Res. (S), 1996, 102. 8 E. J. Parish and S. Li, J. Chem. Res. (S), 1996, 288. 9 J. A. R. Salvador, M. L. Sae Melo and A. S. Campos Neves, Tetrahedron Lett., 1996, 37, 687. 10 M. Ehrenstein and M. T. Decker, J. Org. Chem., 1940, 5, 544. 11 A. D. Cross, J. Am. Chem. Soc., 1962, 84, 3206. 12 For a review see: A. McKillop and W. R. Sanderson, Tetrahedron, 1995, 51, 6145. 13 H. R. Nace and A. L. Rieger, J. Org. Chem., 1970, 35, 3846. 14 P. N. Chakravarty and R. Levin, J. Am. Chem. Soc., 1942, 64, 2317. 15 L. Ruzicka and A. C. Muhr, Helv. Chim. Acta, 1944, 27, 503. 16 A. M. Bell, A. D. Boul, E. Jones, G. D. Meakins and A. L. Wilkins, J. Chem. Soc., Perkin Trans. 1, 1975, 1364. 17 M. Akhtar and D. H. R. Barton, J. Am. Chem. Soc., 1964, 86, 1528. 18 J. Joska, J. Fajkos and F. Sorm, Coll. Czech. Chem. Commun., 1963, 28, 82.

ISSN:0308-2342    

DOI:10.1039/a706111k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

O O Hg HgCl R R O O + a R = H b R = 4-Me c R = 4-Cl d R = 4-Br e R = 4-OMe 2a–e heat or microwave 1 52 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 52–53† Microwave-induced Selective Mercuration of 1,4-Naphthoquinone† Mazaahir Kidwai,* Seema Kohli and Parven Kumar Department of Chemistry, University of Delhi, Delhi-110007, India An efficient mercuration of 1,4-naphthoquinone at the C-2 position is reported using arylmercury(II) chloride under microwave irradiation. Recently there has been much interest in the use of microwave irradiation in synthesis1 owing to substantial reductions in reaction times.In continuation of our earlier work2–6 on microwave-assisted synthesis it was thought worthwhile to synthesize the mercury-containing 1,4-naphthoquinone under microwave activation. The microwave procedure for the mercuration owes its importance to the fact that the reaction is completed in 2–4 min with improved yields when compared to conventional heating which requires 12–13 h.A comparative study in terms of yield and reaction time is also reported (Table 2) using conventional heating. Experimental Mps (uncorrected) were recorded on an Electrothermal apparatus. The purities of the compounds were checked on silica-coated Al plates (Merck). General Procedure for the Synthesis of Arylmercury (II) Chloride 1a–e.•Mercury(II) acetate (0.01 mol) was added to a mixture of DMF (10 ml) and benzene/toluene/chlorobenzene/bromobenzene/ anisole (0.1 mol) in a 100 ml beaker and the mixture was irradiated in a microwave oven for 1.0–1.5 min at 2450 MHz.The contents were concentrated in vacuo to remove most of the unreacted benzene/toluene/chlorobenzene/bromobenzene/anisole and DMF. To this, EtOH (15 ml) was added. A boiling aqueous solution of NaCl (0.01 mol) was added slowly with stirring when a white precipitate separated out. The solid obtained was filtered off, washed with water, dried and recrystallized from acetone. The melting points were comparable to the reported mps7–11 and are given in (Table 1).General Procedure for the Synthesis of 2-[arylmercury (II)]- 1,4-naphthoquinone 2a–e.•Method A (thermal ). To a solution of 2 (0.01 mol in 15 ml acetone) anhydrous K2CO3 (2 g) and arylmercury( II) chloride (0.01 mol) were added (Scheme 1). The reaction mixture was stirred under reflux for a specified time (Table 2). It was then cooled and filtered to remove the inorganic salt; excess of solvent from the clear filtrate was evaporated under reduced pressure. The solid obtained was filtered off, dried and recrystallized from acetone–light petroleum (bp 40–60°C).Method B (microwave irradiation). To a solution of 2 (0.01 mol) in N,N-dimethylacetamide anhydrous K2CO3 (2 g) and arylmercury (II) chloride (0.01 mol) were added in a 100 ml beaker. The beaker was irradiated in a microwave oven for 2.0–3.0 min at 2450 MHz. The reaction mixture was cooled and filtered to remove the inorganic salt.Excess of solvent was evaporated under pressure. *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Arylmercury(II) chlorides produced Reaction time Mp (T/°C) % Yield Compound R Lit./h M.W.I.a/min Found Lit. Lit. M.W.I.a 1a 1b 1c 1d 1e H 4-Me 4-Cl 4-Br 4-OMe 3.0b 4.0c 4.5d 5.0e 5.0f 1.0 1.0 1.5 1.5 1.5 256–258 237 208–210 248–249 247–248 258b 238–239c 210d 250e 250f 80b 75c 70d 60e 55f 90 80 80 75 65 aM.W.I.=microwave induced.bRef. 7. cRef. 8. dRef. 9. eRef. 10. fRef. 11. Table 2 Comparison of reaction times and yields obtained using microwave-induced (M.W.I.) and classical method % Yield (time/min) % Yield (time/h) Compound R Mol. formula M.W.I. Classical method Mp(T/°C) 2a 2b 2c 2d 2e H 4-Me 4-Cl 4-Br 4-OMe C16H10HgO2 C17H12HgO2 C16H9ClHgO2 C16H9BrHgO2 C17H12HgO3 85 (2) 78 (2.3) 70 (2.3) 65 (2.5) 64 (3) 80 (12) 69 (13) 68 (12) 60 (12) 60 (13) 210 200–202 212–213 195 188–190J.CHEM. RESEARCH (S), 1998 53 The solid obtained was filtered off, dried and recrystallized from acetone–light petroleum (bp 40–60°C). Received, 28th July 1997; Accepted, 22nd September 1997 Paper E/7/05428I References 1 S. Caddick, Tetrahedron, 1995, 51, 10403. 2 M. Kidwai, R. Kumar and Y. Goel, Main Group Metal Chem., 1997, 6, 367. 3 M. Kidwai, P. Kumar and S. Kohli, J. Chem. Res. (S), 1997, 24. 4 M. Kidwai and P. Kumar, J. Chem. Res. (S), 1996, 254. 5 M. Kidwai and P. Kumar, J. Chem. Res. (S), 1997, 178. 6 M. Kidwai, P. Kumar, Y. Goel and K. Kumar, Indian J. Chem., 1997, 36B, 175. 7 E. Michael, J. Perie and A. Lattes, J. Organomet. Chem., 1981, 1, 204. 8 A. N. Nesemeyanov, Ber. Dtsch. Chem. Ges., 1929, 62, 1010. 9 M. E. Hanke, J. Am. Chem. Soc., 1923, 45, 1321. 10 A. N. Nesmeyanov, L. G. Makarova and I. V. Polovyanyuk, J. Gen. Chem. USSR, 1965, 35, 682. 11 P. J. Banney and P. R. Wells, Aust. J. Chem., 1971, 24, 317.

ISSN:0308-2342    

DOI:10.1039/a705428i

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

54 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 54–55† Photocatalytic Oxidative C–C Bond Cleavage of the Pyrrole Ring in 3-Methylindole induced by Colloidal CdS Particles† Anil Kumar,* Sanjay Kumar and D. P. S. Negi Department of Chemisry, University of Roorkee, Roorkee - 247 667, U.P., India Binding of 3-methylindole (3-MI) to the surface of colloidal CdS particles modifies their luminescence behaviour so that the trapped electron and hole generated upon photoirradiation are scavenged by adsorbed O2 and 3-MI to yield 2-acetylformanilide and 2-aminoacetophenone.Recently, intense interest has been aroused in the investigation of the photochemical and photophysical behaviour of colloidal semiconductors in regard to understanding their photocatalytic properties.1 Many of these investigations have focused on colloidal CdS particles because of their stability in various homogeneous and heterogeneous media and their absorption which extends to the visible region.1 The high specific surface of these particles has been exploited in order to modify their photophysics by binding different additives2–6 and to enhance the reactivity of the photogenerated charge carriers for performing useful synthetic transformations.6–12 Moreover, unlike bulk semiconductors, nanosized particles can be utilized to carry out simultaneous oxidation and reduction.In the present investigation, colloidal CdS-sensitized oxidation of 3-MI was examined in the presence of air.Interestingly, the reaction occurred through cleavage of the pyrrole ring C–C bond. The electronic spectrum of the reaction mixture containing colloidal CdS and 3-MI neither depicted any new peak in the entire recorded wavelength region (200–600 nm) nor caused any change in the absorption of CdS in the visible region. This suggested the absence of any chemical interaction between CdS and 3-MI. 3-MI is, however, adsorbed onto the surface of the CdS clusters.The amount of adsorbed 3-MI was computed by subtracting the absorbance of the reaction mixture from the sum of the absorbances due to blank CdS and 3-MI at various wavelengths at which 3-MI depicted absorption. The observed adsorption isotherm is shown in Fig. 1. At low [3-MI], the adsorption data followed the Langmuir isotherm (inset Fig. 1) from which the intensity of its adsorption was calculated to be 2.1Å103 dm3 molµ1. Photolysis of the aerated reaction mixture containing 0.4 mM CdS and 4 mM 3-MI by visible light in the wavelength range 410–440 nm resulted in growth of its absorption in the blue-green region.A chloroform extract of the product showed lmax at 325 nm. In TLC and GC experiments this extract was found to contain three components, the retention times of which in the GC chromatogram were 4.29, 5.37 and 6.78 min, respectively. In GC-MS experiments, the fragmentation pattern of component I [m/z 135 (64%, M+), 120 (100), 92 (69), 65 (60) and 44 (27)] was identical with that of an authentic sample of 2-aminoacetophenone 6, while that of component III [m/z 163 (22%, M+), 148 (9), 135 (55), 120 (100), 92 (50), 65 (53) and 43 (53)] matched the earlier reported fragmentation pattern of 2-acetylformanilide 5.13 Component II was identified as being the unreacted 3-MI.The amount of 6 was quantified by GC (using an authentic sample for calibration purposes) and was found to form with a quantum efficiency of 0.07 after 5 min of irradiation.Thus CdS-induced oxidation of 3-MI results in the formation of products due to cleavage of its pyrrole ring. At low [3-MI] (s2 mM), the amount of product formed was much less and anodic dissolution of the particles occurred efficiently. No product formation was detected in the absence of photocatalyst. To illustrate the mechanism of this reaction, the luminescence behaviour of colloidal CdS in the absence and presence of 3-MI was monitored (Fig. 2). In the presence of 3-MI, the luminescence spectrum of CdS showed a new band in the green region at 540 nm along with a simultaneous small quenching of red emission. The band at 540 nm is different to the fluorescence maxima of 3-MI.14 Any contribution to this emission due to 3-MI can also be excluded because of the excitation wavelength used (400 nm) since 3-MI does not absorb in the visible region. It may be noted that the 540 nm band is red-shifted from the band-gap emission due to CdS itself, and that the luminescence intensity increases with an increase in [3-MI] together with a further small red shift in emission maxima at higher [3-MI].These emission changes did not exhibit any isoemissive point. An increase in emission intensity and a shift in the emission maxima with increasing [3-MI] without depicting any isoemissive point indicate the formation of luminescing exciplexes of varying stoichiometry between the excited-state CdS and 3-MI.The low extent of quenching of red emission (Fig. 2) is understood by the fact that the colloidal CdS and its complex in the excited state with 3-MI might have similar emission characteristics in this wavelength region. Colloidal CdS emission is known to consist of a range of lifetimes.9,15 The emission decay curve recorded with the used CdS colloids at 600 nm could be fitted into three exponential decay programmes having t1=0.054 ns (B1=0.5341), t2=1.03 ns (B2=1.2193Å10µ3) and t3=19.82 ns (B3=1.2496Å10µ3) with < t > of about 8 ns.In the presence of 2.25 mM 3-MI, this emission decayed within the lamp pulse which suggests that the quenching of the red emission which occurs is due to interception of the photogenerated hole by the adsorbed 3-MI. This eventually results in the formation of 5 and 6 as products. The mechanism of this reaction may be depicted as in Scheme 1. In basic medium, the indolyl cation 2, having pKa=5,16 is converted into the indolyl radical 3.This may couple with O2 µ to yield the corresponding hydroperoxide17 4 which decomposes to produce 2-acetylformanilide 5 [eqn. (4)]. The relative amounts of 5 and 6 as a function of irradiation time were also followed by GC. The yield of 5 increased proportionately whereas the amount of 6 attained a limiting value after 10 min of irradiation. This suggests that 6 is not To receive any correspondence (e-mail: chemt@rurkiu.ernet.in). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Fig. 1 Adsorption isotherm of 3-MI on 0.32 mM colloidal CdS. Inset: Plot of Langmuir adsorption isotherm of 3-MINH Me CdS + 1 CdS(e–h+----3-MIads)* hn (lirr 400 nm) e– + O2 O2 – NH Me 2 ads + h+ NH Me + + CdS (1) (2) (3) • N Me N OOH N Me 3 4 5 C O Me C H H O + O2 – (4) • N 5 C O Me C H H O NH2 C O Me Hydrolysis 6 (5) J.CHEM. RESEARCH (S), 1998 55 produced photochemically but possibly by hydrolysis of 5 [eqn. (5)].18 Thus 3-MI at its low concentration binds to the shallow traps on the surface of the colloidal CdS, modifying its luminescence behaviour by forming green luminescing exciplexes of varying stoichiometry between the excited CdS and 3-MI. The quenching of the red emission which occurs is due to transfer of the deep trapped holes1,10,12 from the irradiated semiconductor to the secondary layers of adsorbed 3-MI which eventually results in the formation of 5 and 6.This work elucidates the mechanism of an interesting system in which products are formed via C·C bond cleavage of the pyrrole ring. Photophysical and photochemical studies of 3-MI are also important since this molecule is considered as a model for tryptophan in proteins. The photocorrosion of CdS particles could be prevented under the experimental conditions used. Investigations on related heterocycles are under way to arrive at a general mechanism.Efforts are being made to bring about increased charge separation in these systems upon photoirradiation. Experimental Absorption data were recorded on a Shimadzu UV-2100/s spectrophotometer. Emission measurements were made on a Shimadzu RF-5000 spectrofluorophotometer. Fluorescence lifetimes were determined on an IBH-5000 single photon counting fluorimeter using a nanosecond discharge lamp for excitation. Decay curves were analysed by using a multiexponential fitting program from IBH.Steady-state photolysis experiments were designed on an Oriel photolysis assembly equipped with 200 W Hg(Xe) lamp and cut filters. Colloidal CdS was prepared by injecting a stoichiometric amount of SHµ to the deaerated Cd(ClO4)2 solution containing sodium hexametaphosphate as stabilizer following an earlier reported method6,10 and was characterized by its electronic and emission spectra.The particles had an average size of 4 nm (determined by a Philips EM-400 transmission electron microscope). GC separation of products was achieved on an HP-1 capillary column under non-isothermal conditions. The column was temperature- programmed from 50 to 230 °C at a heating rate of 10 °C minµ1. GC-MS data were obtained on a Shimadzu QP-2000 instrument at 70 eV after elution of the solvent. The financial assistance of DST and UGC, New Delhi, is gratefully acknowledged. S.K. thanks CSIR, New Delhi, for the award of RA. Thanks are also due to Dr A. Samanta, University of Hyderabad, for providing facilities for emission lifetime measurements. Received, 5th March 1997; Accepted, 22nd September 1997 Paper E/7/01555K References 1 A. Henglein, Top. Curr. Chem., 1988, 143, 113; P. V. Kamat, Chem. Rev., 1993, 93, 267; H. Weller, Angew. Chem., Int. Ed. Engl., 1993, 32, 41; A. Hagfeldt and M. Gr�atzel, Chem. Rev., 1995, 95, 49; M. R. Hoffmann, S. T. Martin, W.Choi and D. W. Bahnemann, Chem. Rev., 1995, 95, 69. 2 L. Spanhel, M. Haase, H. Weller and A. Henglein, J. Am. Chem. Soc., 1987, 109, 5649. 3 T. Dannhauser, M. O’Neil, K. Johansson, D. Whitten and G. McLendon, J. Phys. Chem., 1986, 90, 6074. 4 Y. Wang, A. Suna, J. McHugh, E. Helinski, P. A. Lucas, R. D. Johnson, J. Chem. Phys., 1990, 92, 6927. 5 J. Kuczynski and J. K. Thomas, J. Phys. Chem., 1983, 87, 5498. 6 A. Kumar and S. Kumar, J. Photochem. Photobiol. A: Chem., 1994, 83, 251. 7 A. Fojtik, H. Weller, U. Koch and A. Henglein, Ber. Bunsenges. Phys. Chem., 1984, 88, 969. 8 T. Shiragami, H. Ankyu, S. Fukami, C. Pac, S. Yanagida, H. Mori and H. Fujita, J. Chem. Soc., Faraday Trans., 1992, 88, 1055. 9 P. V. Kamat and N. M. Dimitrijevic, J. Phys. Chem., 1989, 93, 4259. 10 A. Kumar and S. Kumar, J. Photochem. Photobiol. A: Chem., 1992, 69, 91. 11 P.V. Kamat, N. M. Dimitrijevic and R. W. Fessenden, J. Phys. Chem., 1987, 91, 396. 12 J. J. Ramsden and M. Gr�atzel, J. Chem. Soc., Faraday Trans. 1, 1984, 80, 919. 13 K. C. Picel, V. Stamoudis and M. S. Simmons, Photolytic and Partitioning Behaviour of Polynuclear Aromatic Compounds, Aromatic Amines and Phenols in Aqueous Coal Oil, DOE/ MC/49533-1837, June 1985, p. 80. 14 M. V. Hershberger, R. Lumry and R. Verrall, Photochem. Photobiol., 1981, 33, 609 and references cited therein. 15 N. Chestnoy, T. D. Harris, R. Hull and L. E. Brus, J. Phys. Chem., 1986, 90, 3393. 16 X. Shen, J. Lind and G. Merenyi, J. Phys. Chem., 1987, 91, 4403. 17 X. Shen, J. Lind, T. E. Eriksen and G. Merenyi, J. Chem. Soc., Perkin Trans. 2, 1990, 597. 18 N. A. Evans, Aust. J. Chem., 1971, 24, 1971. Fig. 2 Luminescence spectra of 0.24 mM colloidal CdS in the absence (———) and presence of varying concentrations of 3-MI (mM): 0.5 (---); 1.0 (- . -); 2.0 (- . . -); 2.5 (– . . . –); excitation wavelength 400 nm Sche

ISSN:0308-2342    

DOI:10.1039/a701555k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

C CH O R R¢ Br + PPh2 P PPh2Br] P [ C CH R O– R¢ PPh2O P C CH R R¢ + Br– PPh2 P CH C R¢ R + O Br– or R C O CH2 R¢ + PPh2 + MeBr P O MeOH MeOH + 56 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 56† Debromination of a-Bromo Ketones using Polymersupported Triphenylphosphine† Sameer P. Dhuru, Kamlesh J. Padiya and M. M. Salunkhe* Department of Chemistry, The Institute of Science, 15, Madam Cama Road, Mumbai - 400 032, India An effective method for the debromination of a-bromo ketones using polymer-supported triphenylphosphine is described.The use of polymeric reagents in organic synthesis has been a subject of substantial interest in recent years.1 Among the several advantages offered by these reagents,2 the one most frequently utilized is the ease of work-up, which often consists of a simple filtration. This feature is of more importance especially when the reaction products are toxic or noxious and when they are unstable to lengthy and tedious work-ups.We have developed a mild and high-yielding method for the debromination of a-bromo ketones using a polymer-supported reagent. Polymer-supported triphenylphosphine has been earlier used in a number of reactions such as in the conversion of alcohols into alkyl halides,3 the Wittig reaction4 and the conversion of aromatic disulfides into thiols.5 The polymeric phosphine oxide obtained as a by-product can be recycled after reduction to phosphine.3,4 The debromination of a-bromo ketones has been extensively studied and the mechanism carefully detailed.6–8 However, separation of the ketone from the triphenylphosphine oxide by-product and any excess of phosphine is difficult.Also, the yields obtained in the above reactions are considerably low. We report here the debromination of a-bromo ketones using polymer-supported triphenylphosphine as shown in Scheme 1. To a solution of the bromo ketone in anhydrous benzene is added the insoluble phosphine reagent.This results in the formation of the phosphonium salt which is decomposed by alcohol to yield the corresponding ketone. The yield of product and the rate of reaction, when carried out in toluene, acetonitrile, THF, etc. were found to be very low. Polymeric phosphine oxide is obtained as a by-product, which is separated by filtration. Removal of the solvent under reduced pressure yields the pure ketone. Various a-bromo ketones were investigated, as outlined in Table 1. The yields indicated are for isolated products without additional purification. In all cases the isolated products were found to be homogeneous by TLC and were characterised by IR and NMR spectroscopy.In summary, the use of polystyryldiphenylphosphine represents a very effective procedure for the debromination of a-bromo ketones. The reaction offers improved yields and a convenient isolation procedure. Experimental General Procedure for the Debromination of a-Bromo Ketones.·The a-bromo ketone (0.125 mmol) was dissolved in anydrous benzene (10 ml). Polymer-bound triphenylphosphine (50 mg; 2% crosslinked with DVB, 3 mmol gµ1) was added to form the phosphonium salt after which methanol (1 ml) was added and the reaction mixture was refluxed. When the reaction was complete (TLC), the reaction mixture was cooled, polymeric phosphine oxide was filtered off and the solvent was removed under reduced pressure to give the product ketone in pure form.We are thankful to Dr N. V. Thakkar, Institute of Science, Mumbai, for helpful discussions. Received, 7th July 1997; Accepted, 29th September 1997 Paper E/7/04778I References 1 For recent reviews see: Polymers as Aids in Organic Chemistry, ed. N. K. Mathur, C. K. Narang and R. E. Williams, Academic Press, New York, 1980; Polymer Supported Reactions in Organic Synthesis, ed. P. Hodge and D. C. Sherrington, Wiley, London, 1980; A. Akelah and D. C. Sherrington, Chem. Rev., 1981, 81, 1557; A.Akelah, Synthesis, 1981, 413; Functionalised Polymers and Their Applications, ed. A. Akelah and A. Moet, Chapman and Hall, 1990. 2 J. M. J. Frechet, Tetrahedron, 1981, 37, 663. 3 L. R. Steven and P. L. Dan, J. Org. Chem., 1975, 40, 1669. 4 M. Bernard and W. T. Ford, J. Org. Chem., 1983, 48, 326. 5 R. A. Amos and S. M. Fawcett, J. Org. Chem., 1984, 49, 2637. 6 I. J. Borowitz and L. I. Grossmann, Tetrahedron Lett., 1962, 11, 471. 7 I. J. Borowitz and R. Virkhaus, J. Am. Chem. Soc., 1963, 85, 2183. 8 P. A. Chopard, R. F. Hudson and G. Klopman, J. Chem. Soc., 1965, 1379. *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Debromination of a-bromo ketones Time a-Bromo ketones Product (t/min) % Yielda Phenacyl bromide p-Nitrophenacyl bromide 2-Bromocyclohexanone 3-Bromocamphor Acetophenone p-Nitroacetophenone Cyclohexanone Camphor 45 30 50 40 96 (64) 85 (53) 89 (62) 97 (51) aFigures in parentheses indicate percentage yields in solution-phase reactions. Scheme 1

ISSN:0308-2342    

DOI:10.1039/a704778i

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

+ ArCH NAr¢ ArCHNHAr¢ CH3CN, room temp. 1 2a–e 3a–e 2,3 abcde Ar Ph Ph Ph Ph 2-furyl Ar¢ Ph 4-ClC6H4 4-BrC6H4 4-NO2C6H4 Ph 50% NaOH, TEBA J. CHEM. RESEARCH (S), 1998 57 J. Chem. Research (S), 1998, 57† Addition of Fluorene to Schiff Bases† Kostadinka Popandova-Yambolieva Department of Chemistry, University of Sofia, 1 J.Bourchier Avenue, 1126 Sofia, Bulgaria Addition of fluorene to N-arylmethylideneanilines under conditions of phase-transfer catalysis gives N-aryl-N-[9H-fluoren- 9-yl(aryl)methyl]amines 3a–e.It is known that indene and fluorene have acidic properties, but their application in the Michael addition has been little described. The addition of fluorene to some a,b-unsaturated ketones,1 nitriles and esters2 has been realized under various conditions. Some years ago we reported our preliminary results on the Michael addition of fluorene to some a,b-unsaturated ketones, esters and nitriles under conditions of phase-transfer catalysis (PTC) in acetonitrile.3 Later a similar addition was realized with other a,b-unsaturated ketones and nitriles under PTC conditions in benzene.4 There is no report in the literature on the addition of fluorene to Schiff bases.Having in mind that some fluorenyl derivatives of aminobenzoic acids are anti-inflammatory agents,5 we decided to study the behaviour of fluorene (1) towards N-arylmethylideneanilines (2). We now present the results of our studies on the reaction of 1 with 2 under PTC conditions.The expected compounds 3a–e were obtained (Scheme 1). The reaction was carried out at room temperature with an excess of aqueous sodium hydroxide, a catalytic amount of TEBA (triethylbenzylammonium chloride) and acetonitrile as solvent. For 4-methoxy- and 4-dimethylamino-benzylideneanilines only the starting Schiff bases were recovered. Also, owing to steric hindrance, there was no reaction with either N-phenylbenzophenone imine or with N-benzylidenetert- butylamine.The structures of the new compounds 3a–e were assigned by IR and 1H NMR spectroscopy and by elemental analysis. Experimental Melting points were determined by a Boetius micropoint apparatus and are uncorrected. IR spectra were recorded on a Specord 71 spectrophotometer (Carl Zeiss, Iena). 1H NMR spectra were measured with a TESLA BS 487-C spectrometer (80 MHz) using CDCl3 solutions and Me4Si as internal standard. The starting Narylmethylideneanilines were prepared by reported procedures.Typical Procedure.·Aqueous sodium hydroxide (50% w/v; 3 cm3) was added to a stirred solution of fluorene (1.66 g, 10 mmol), the corresponding Schiff base 2 (10 mmol) and TEBA (0.23 g, 1 mmol) in acetonitrile (10 cm3). The reaction mixture was stirred at room temperature for 1 h. Water (100 cm3) was added and the solid was filtered off, washed until neutral and recrystallized from methanol–ethyl acetate. The following products were obtained: N-[9H-fluoren-9-yl(phenyl)methyl]-N-phenylamine (3a) (1.48 g, 43%), mp 152–153 °C; vmax/cmµ1 (CHCl3) 3430 (NH) (Found: C, 89.78; H, 6.3; N, 3.9.C26H21N requires C, 89.9; H, 6.05; N, 4.0%); dH 3.18 (1 H, br s, NH), 4.48 (1 H, d, J 4.5 Hz), 5.18 (1 H, d, J 4.5 Hz), 6.15–7.80 (18 H, m, aromatic); N-(4-chlorophenyl)-N-[9H-fluoren- 9-yl(phenyl)methyl]amine (3b) (0.8 g, 22%), mp 162–164 °C; vmax/ cmµ1 (CDCl3) 3430 (NH) (Found: C, 81.6; H, 5.3; N, 3.6. C26H20ClN requires C, 81.7; H, 5.2; N, 3.7%); dH 3.44 (1 H, br s, NH), 4.45 (1 H, d, J 4.1 Hz), 5.08 (1 H, d, J 4.1 Hz), 6.08–7.80 (17 H, aromatic); N-(4-bromophenyl)-N-[9H-fluoren-9-yl(phenyl- )methyl]-amine (3c) (0.7 g, 17%), mp 170–172 °C; vmax/cmµ1 (CHCl3) 3420 (NH) (Found: C, 73.1; H, 4.7; N, 3.4.C26H20BrN requires C, 73.2; H, 4.7; N, 3.3%); dH 3.36 (1 H, br s, NMH), 4.40 (1 H, d, J 4.0 Hz), 5.11 (1 H, d, J 4.0 Hz), 6.10–7.80 (17 H, m, aromatic); N-[9H-fluoren-9-yl(phenyl)methyl]-N-(4-nitrophenyl)amine (3d) (0.8 g, 20%, mp 127–128 °C; vmax/cmµ1 (CHCl3) 3370 (NH), 1590 (NO2) (Found: C, 79.3; H, 5.1; N, 6.9.C26H20N2O2 requires C, 79.5; H, 5.1; N, 7.1%); N-[9H-fluoren-9-yl(2-furyl)methyl]- N-phenylamine (3e) (0.95 g, 29%), mp 178–180 °C; vmax/cmµ1 (CDCl3) 3430 (NH) (Found: C, 85.5; H, 5.7; N, 3.9. C24H19NO requires C, 85.4; H, 5.7; N, 4.1%). dH 3.46 (1 H, br s, NH), 4.68 (1 H, d, J 4.1 Hz), 5.26 (1 H, d, J 4.1 Hz), 6.04 and 6.30 (2 H, 2 d, J 6; J 6 Hz), 6.62 (1 H, d, J 14 Hz), 6.90–7.75 (13 H, m, aromatic). Received, 23rd September 1997; Accepted, 2nd October 1997 Paper E/7/06890E References 1 S. Hashimoto, K. Matsumoto, S. Otani and J. Haiami, Syntheis, 1984, 164. 2 G. Bram, J. Sansoulet, H. Galon, Y. Ben Said, G. Gomber- Farnoux and M. Miocque, Tetrahedron Lett., 1985, 26, 4601. 3 K. Popandova-Yambolieva and S. Georgieva, Proceedings of the anniversary session ‘100 years of the Faculty of Chemistry’, Sofia, 1990, pp. 113–117. 4 Ch. Yan. W. Lu and J. Wu, Org. Prep. Proced. Int., 1993, 25, 241 (Chem. Abstr., 1993, 119, 95059p). 5 J. Perumattam, US Pat., 5472 973, 1995 (Chem. Abstr., 1996, 124, p201802r). *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Scheme 1

ISSN:0308-2342    

DOI:10.1039/a706890e

出版商:RSC    

年代:1998

数据来源: RSC