Hypervalent Iodine(III)-Mediated Regioselective N-Acylation of 1,3-Disubstituted Thioureas

Reaction of asymmetrical 1,3-disubstituted thioureas with
diacetoxyiodobenzene (DIB) produces regioselectively N-acetylurea in shorter time. Regioselectivity is dependent on
the pKa's of the amine attached to the thiourea moiety with
acylation taking place toward the amine having a lower pKa.
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.