The reaction of 2-arenoylaziridines with aldehydes to form oxazolidines

Abstract

2-Arenoylaziridines undergo thermal 1,3-dipolar addition to aromatic aldehydes and chloral via azomethine ylides to give exclusively 4-arenoyloxazolidines. Proof of the orientation of the addition was obtained and the formation of an alternative ring-expansion product was excluded by specific deuterium-labelling experiments. The lack of dependence of the course of the reaction on the stereochemistry of the aziridine, and the observed lack of base-catalysed epimerisation of the oxazolidines, suggested exclusive formation of the oxazolidines via the more stable trans-azomethine ylide and allowed an assignment of the full stereochemistry of the products.