Hypervalent iodine(III)-mediated regioselective N-acylation of 1,3-disubstituted thioureas

Abstract

Reaction of asymmetrical 1,3-disubstituted thioureas with Diacetoxyiodobenzene (DIB) produces regioselectively N-acetylurea in shorter time. Regioselectivity is dependent on the pK_a's of the amine attached to the thiourea moiety with acylation taking place toward the amine having a lower pK_a. This is the first example of DIB being employed as an N-acetylating agent. A mechanism for this novel transformation is also proposed. Mild reaction conditions, shorter reaction times, high efficiencies, environmentally benign methods and facile isolation of the desired product make the present methodology a most suitable alternative.