Synthesis of 7-oxindolylidene-3a,9a-diphenylimidazothiazolo[2,3-c][1,2,4]triazines by skeletal rearrangement of their [3,2-b]-fused isomers

Previously unavailable 7-oxindolylidene-1,3-dimethyl-3a,9adiphenylimidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazines were obtained in 63–90% yields by skeletal amidine rearrangement of the thiazolo-triazine system in the corresponding imidazo[4,5-e]thiazolo[3,2-b][1,2,4]triazines on treatment with sodium methoxide.