Further studies on the [1,2]-Wittig rearrangement of 2-(2-benzyloxy)aryloxazolines

Abstract

The behaviour of 14 ortho-functionalised 2-aryloxazolines, 11 of them prepared and characterised for the first time, with butyllithium has been examined. Significant limitations to the Wittig rearrangement of such systems are revealed. In terms of asymmetric Wittig rearrangement, good diastereoselectivity is obtained with a valine-derived 4-isopropyl oxazoline but this is compromised by racemisation upon hydrolysis. More encouraging selectivity is achieved in the Wittig rearrangement of an acyclic phenylalanine-derived ortho-benzyloxy benzamide.