Syntheses of isoalloxazines, alloxazines, toxoflavins, and fervenulins by oxidative cyclization of the Michael-type adducts from substituted 6-aminouracils and azo-compounds

Abstract

Treatment of the Michael-type adducts from 6-anilinouracil derivatives and diethyl azodiformate (DAD) or 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) with an oxidizing agent caused oxidative rearrangement, followed by thermal or photochemical cyclization, to give the corresponding (iso)alloxazines. Similarly, oxidative cyclization of the Michael-type adducts from 6-benzylidenehydrazinouracil derivatives and DAD gave toxoflavin and fervenulin derivatives.