Oxidative desulfurization of disubstituted thioureas using Pb(II) salts and investigation of pK _a-dependent regioselective N-acylation

摘要

A highly efficient method for the N-acylation of both symmetrical and unsymmetrical thioureas by the use of lead (II) salts and triethylamine has been achieved. The reaction gives regioselective N-acylated product for unsymmetrical thiourea. For unsymmetrical thiuourea, regioselective N-acylation takes place towards the amine having lower pK _a. A linear correlation between the pK _as of the amines and the regioselective N-acylation is found. Another attractive feature of this transformation is that lead sulfide, which is important to material science, is obtained as a side product (nanocubes of 20Â nm).