A New Application of the Pictet-Spengler Reaction to the Preparation of 4-Substituted 1H-2,3-Benzoxazines

Abstract

Intramolecular coupling reaction of benzylic O-hydroxamates and aldehydes was investigated to afford a variety of 4-substituted 1H-2,3-benzoxazine ring systems in good to excellent yields. The reaction involved an intramolecular C-C bond formation between an N-acyl-or N-sulfonyl-oxoiminium ion with the aryl ring. Under the studied conditions, electron-donating groups in the aryl ring are essential for the desired coupling reactions.