Merging the ring opening of benzoxazoles with secondary amines and an iron-catalyzed oxidative cyclization towards the environmentally friendly synthesis of 2-aminobenzoxazoles

Abstract

A facile and environmentally friendly method was developed through merging the ring opening of benzoxazoles with secondary amines and an iron-catalyzed oxidative cyclization towards the synthesis of 2-aminobenzoxazoles. In the oxidative cyclization step, with catalytic amounts of FeCl and aqueous H₂O₂ as a green oxidant, highly desirable 2-aminobenzoxazoles were isolated in excellent yields of up to 97%. A plausible radical process is proposed for the oxidative cyclization on the basis of mechanistic studies.