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摘要
Aldehydes may be directly converted to O-silyl-alpha-hydroxyamides by reaction with N-methoxymethyl-N-methylcarbamoyl(trimethyl)silane. In an attempt to extend this chemistry, we found that N-methoxymethyl-N-methylcarbamoyl(trimethyl)silane did not react with alpha-ketoamides. So we started testing activity within the variety of carbonyl compounds towards N,N-dimethylcarbamoylsilane and found that the addition reaction of N,N-dimethylcarbamoyl(trimethyl)silane with a series of N-methyl-N-methoxymethyl-alpha-ketoamides could afford good yields (71%similar to 86%) of unsymmetrical alpha-organyl-alpha-hydroxymalonamide derivatives or unsymmetrical alpha-organyl-alpha-siloxymalonamide compounds. When 1.2 equiv. of a carbamoylsilane 1 was allowed to react with alpha-ketoamides 2 in anhydrous toluene solution under anhydrous conditions at ambient conditions or below, good yields of alpha-siloxyamides 3 were obtained, generally within long time. Their structures were characterized by elemental analysis, H-1 NMR, C-13 NMR and IR spectra. A novel method for synthesis of unsymmetrical alpha-organyl-alpha-hydroxymalonamide derivatives was provided. The experiments indicated that the steric environment was an important factor in the addition reaction since longer reaction time was needed both in case of 2b and 2c than in case of 2a, and the electronic effect influenced on the rate of the reaction since the yields were obtained about the same from a variety of aryl-alpha-ketoamides, the stronger donor ability of substituted group on the benzene ring of the aryl-alpha-ketoamides, the longer reaction time was needed. A reaction mechanism involving two intermediates is proposed, in which carbamoylsilane 1 can rearrange to its nucleophilic carbene form A, which attacked the carbonyl group of alpha-ketoamides to produce an unstable intermediate B, the subsequent silyl group transfer leads to corresponding the O-silylated adducts 3. The latter can be hydrolyzed to form the alpha-organyl-alpha-hydroxymalonamide derivatives 4.
- 出版日期2013-8-15
- 单位山西师范大学
