Diastereofacial selectivity in azomethine ylide cycloaddition reactions derived from chiral α-cyanoaminosilanes

Abstract

A series of α-cyanoaminosilanes has been found to act as azomethine ylide equivalents. Treatment of these compounds with silver fluoride in the presence of electron deficient olefins gives substituted pyrrolidines in high yield. The extent ofdiastereoselectivity associated with the 1,3-dipolar cycloaddition of chiral azomethine ylides with several dipolarophiles has been studied. Reasonable levels of such diastereoselectivity have been found when optically active α-cyanoaminosilanes are employed as azomethine ylide equivalents. These compounds can be prepared in multigram quantities by treating the appropriate chiral amine with chlorotrimethylsilane followed by reaction of the resulting secondary amine with formaldehyde in the presence of potassium cyanide. It was found that N-benzyl-N-cyanomethyl-N-trimethylsilylmethylamine undergoes stereospecific cycloaddition with dimethyl fumarate and maleate. The stereospecificity of the reaction is consistent with a concerted cycloaddition reaction.