Sulfated-Tungstate-Catalyzed Synthesis of Ureas/Thioureas via Transamidation and Synthesis of Forchlorofenuron

N, N'-Disubstituted ureas and thioureas have been efficiently and expeditiously synthesized by transamidation reaction between unsubstituted or monosubstituted ureas/thioureas and amines under solvent-free condition using sulfated tungstate as a heterogeneous mild solid acid catalyst. This protocol offers several advantages such as wide substrate scope, providing both symmetrical and unsymmetrical ureas and thioureas, solvent-free reaction, recyclability of the catalyst and a simple work-up procedure. Application of the methodology is demonstrated through simple and one step synthesis of forchlorofenuron [1-(2-chloropyridine-4-yl)-3-phenylurea] (CPPU), an approved plant growth regulator.