Oxazol-5(4H)-ones. Part 7. New synthesis of oxazolo[5,4-b]pyridines

Abstract

Oxazolo[5,4-b]pyridines 4 are synthesized by heating the iminophosphoranes 1 and alkylideneoxazol-5(4H)-ones 2. At room temperature the reaction of 4-ethoxymethyleneoxazol-5(4H)-one 2f with iminophosphorane 1a yields the enamino lactone 6, which is, in turn, transformed by heating in acetic acid into the 2(1H)-pyridone 7.