Cyclocondensation of o-aminophenols with α-ketothioesters in acidic media: A facile synthesis of 2-acylbenzoxazoles

Abstract

We herein report the cyclocondensation of o-aminophenols with α-ketothioesters in acidic media for the highly regioselective synthesis of 2-acylbenzoxazoles in DMF at 80 °C. The generality of the reaction was demonstrated by using various o-aminophenols and α-ketothioesters bearing electron donating and electron withdrawing groups. In the absence and catalytic amount of acid, isomeric mixture of products: benzoxazoles and benzo[b][1,4]oxazin-2-ones were observed. Notably, in the presence of equivalent amount of acid, exclusively and regioselectively benzoxazoles are formed. The probable mechanism of formation of benzoxazoles is also presented.