Reactions of o-Quinone Methides with Halogenated 1H-Azoles: Access to Benzo[e]azolo[1,3]oxazines

Abstract

A simple route to the series of azolo-condensed benzo[e][1,3]oxazines such as 9H-benzo[e][1,2,4]triazolo[5,1-b][1,3]oxazines, 9H-benzo[e]pyrazolo[5,1-b][1,3]oxazines, and 5H-benzo[e]imidazo[2,1-b][1,3]oxazines has been developed. The reaction proceeds through formation of an ortho-quinone methide intermediate followed by aza-Michael addition of the halogenoazoles to the o-quinone methide and intramolecular nucleophilic substitution.