Novel generation and cycloaddition of N-silylated azomethine ylides from alpha-silylimidates and trifluorosilane

The Generation of N-silylated azomethine ylides was achieved by the reactio n of alpha-silylimidates and trifluorophenylsilane. The generated azomethin e ylides can be regarded as synthetic equivalents of nitrile ylides since t hey have an alkoxy group which may serve as a leaving group. Cycloaddition with acetylenic or olefinic dipolarophiles proceeded smoothly to give pyrro le or pyrroline derivatives in good to excellent yields. For example, alpha -silylimidate 1 was treated with 1.2 equiv of trifluorophenylsilane in the presence of 1 equiv of dimethyl acetylenedicarboxylate to give pyrrole 2 in 97% yield. Furthermore, when starting with a secondary alpha-silylamide, t he one-pot synthesis of N-unsubstituted azomethine ylides could be achieved by the successive treatment with alkylation and desilylation agents. (C) 1 999 Elsevier Science Ltd. All rights reserved.