Substituted bicyclic and tricyclic oxazolo[4,5-d]-1,2,3-triazole systems: ring expansions to 1,3,4,5-oxatriazines and ring contractions to 1,2,3-triazaspiroalkane derivatives

Abstract

Synthesis of a range of new bicyclic and tricyclic fused oxazolo[4,5-d]-1,2,3-triazole systems is described. Treatment of these with acid caused transformations to substituted 1,3,4,5-oxatriazine and new 1,2,3-triazaspiroalkane systems which were isolated in high yields. Kinetic studies of the ring transformations indicated the presence of a delocalised carbocation intermediate and the mechanism of the ring expansion and contraction is discussed.