一篇化学文献的翻译 - 图文

1 Ph 4-ClC6H4 A 63:37 81 2 Ph 4-ClC6H4 B 62:38 80 3 Ph Ph A 63:37 84 4 4-ClC6H4 Ph B 64:35 80 5 4-ClC6H4 4-ClC6H4 A 64:36 84 6 4-ClC6H4 4-ClC6H4 B 65:35 83 7 3-NO2C6H4 4-ClC6H4 B 47:53 95 8 3-NO2C6H4 4-ClC6H4 A 46:54 95 9 3-NO2C6H4 Ph B 58:42 90 10 3-NO2C6H4 Ph A 55:45 94

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11 4-NO2C6H4 4-ClC6H4 B 56:44 90 12 4-NO2C6H4 4-ClC6H4 A 57:43 88 13 2,4-Cl2C6H3 3,4-Cl2C6H3 B 41:59 80 14 2,4-Cl2C6H3 3,4-?Cl2C6H3 A 39:61 93 15 2,4-Cl2C6H3 4-ClC6H4 B 66:34 80 16 2,4-Cl2C6H3 Ph B 68:32 83 17 2-MeOC6H4 Ph B 65:33 60 18 4-MeOC6H4 4-ClC6H4 B 54:46 70 19 4-OMeC6H4 4-ClC6H4 B 50:50 72 20 4-MeO2CC6H4 Ph B 72:28 88

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21 4-ClC6H4 4-(i-Pr)C6H4 B 62:38 80 22 (CH3)2CH Ph B - 25 23 2-naphthyl 4-ClC6H4 B 43:57 85 24 2-thienyl 4-ClC6H4 B 62:38 87 a?Reaction conditions:? aldehyde (3 mmol), amine (3.1 mmol), and cyclohexanone (5 mmol) were successively added to a solution of catalyst (10 mg) in water (5 mL) placed in a test tube, and the reaction mixture was vigorous stirred at room temperature for 3?16 h.b?Yields of isolated products.c?Diastereomeric ratio mearsured by 1H NMR spectroscopy analysis of the crude reaction mixture. The regioselectivity was determined by 1H and 13C NMR spectroscopy and by comparison with known compounds reported in the literature.8 In general, anti selectivity was observed in the reaction of cyclohexanone and 2-butanone. Despite of the low solubility of aldehydes, ketones, and amines in water, the heteropoly acid-catalyzed Mannich reactions still proceed efficiently at ambient temperature. The reaction might take place at the interface of organic materials with water in the heterogeneous system. It was found that vigorous stirring was required for the success of these reactions. The possibility of recycling the catalyst was examined. For this reason, the reaction of 4-chlorobenzaldehyde, aniline and cyclohexanone in water at room temperature in the presence of H3PW12O40 was studied. When the reaction was complete, ethyl acetate was added and organic materials were extracted and the aqueous solution was saved for the next reaction. When the same reaction was carried out in this solution, containing the used catalyst, low yields (ca. 60%) of the product were obtained. Another characteristic feature of the present protocol is the high chemoselectivity of cyclohexanone toward aldimines, prepared in situ from the reaction of aldehydes and amines, in preference to aldehydes as shown in Scheme 2. Although conventional Lewis acids activate aldehydes preferentially, in this media, aldehydes do not undergo aldol reaction by

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means of HPAs in water. The high chemoselectivity is rationalized by considering the higher basicity of nitrogen over oxygen. A related phenomenon was recently reported in the reactivity between aldimines and aldehydes by the use of proline, HBF4, and dibutyltin dimethoxide.11 Scheme 2.?Aldole and Mannich Reaction in Water In conclusion, this procedure offers several advantages including low loading of catalyst, improved yields, clean reaction, use of unmodified ketones, which make it a useful and attractive strategy for the multicomponent reactions of combinational chemistry. In addition, a very easy workup has been realized that does not require organic solvents. When the products are solid and insoluble in water, the pure products can be obtained directly by filtration and washing the filtrate with water and by crystallization from ethanol or diethyl ether. No extraction or separation by column chromatography is necessary in some cases. Current efforts in our research group are attempting to expand the application of heteropoly acids in water for other reactions. Acknowledgment We are grateful to the Research Council of Sharif University of Technology for financial support. We thank “Volkswagen-Stiftung, Federal Republic of Germany” for financial support toward the purchase of chemicals. We also thank Professor J. Ipaktschi (University of Giessen) for his valuable advice and suggestions.

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