Conversion of chiral oxiranes into chiral aziridines with retention of configuration by way of chiral episulfonium ions and reactions of the aziridines with Grignard reagents

Abstract

Chiral oxiranes are converted into chiral aziridines with overall retention of configuration by means of sulfur chemistry. The key step of this procedure is the transformation of the organosulfur intermediates, i.e., the replacement of a hydroxy group bound to a chiral carbon by a tosylamino group with retention of configuration through the anchimeric assistance of an arylsulfanyl group. The resulting tosylamines bearing the arylsulfanyl group on the β-carbon atom are cyclized to chiral aziridines through derivation to the sulfonium salt followed by intramolecular substitution of the sulfur moiety by the nitrogen atom. Ring opening of the chiral aziridines by Grignard reagents provides a useful procedure for the preparation of chiral amine derivatives.