Stereoselectivity in the 1,3-dipolar cycloaddition of nitrones to 1-substituted 3,3-methylene-5,5-dimethyl-2-pyrrolidinones

摘要

The stereoselectivity of the nitrone cycloaddition with 1-substituted 3,3-methylene-5,5-dimethyl-2-pyrrolidinones1is discussed. C,N-Diarylnitrones give mixtures of diastereomeric spirocycloadducts3and4, in which3always dominates. In contrast, N-methylnitrones react under the formation of4as major products. Cycloaddition of C-benzoyl nitrones7with1affords exclusively single isoxazolidines8. Semi-empirical quantum mechanical methods (AM1) were used to rationalize the regio- and stereoselectivity of the reactions.