N,N′-Carbonyldi[2(3H)-benzoxazolethione]: New, Reactive Condensing Agent for the Synthesis of Amides, Esters, Peptides, and Polyamides

A new condensing agent, N,N′-carbonyldi[2(3H)-benzoxazolethione] (3), was readily prepared by the reaction of 2-benzoxazolethiol and trichloromethyl chloroformate in benzene. The condensing agent 3 is shown to be useful for the preparation of amides, esters, and dipeptides under mild conditions. A successful polyamide synthesis by the polycondensation of isophthalic acid with diamines using 3 is also described.