Microwave-assisted preparation of cyclic ureas from diamines in the presence of ZnO

Article abstract of DOI:10.1016/j.tetlet.2004.08.042

A MW-assisted direct synthesis of cyclic ureas has been developed that proceeds expeditiously in the presence of ZnO thus shortening its reaction time; the process also eliminates the formation of byproducts when compared to the traditional methods involving conventional heating. A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120°C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this reaction is attributed to the deployment of ZnO whose absence results in poor yield and the generation of byproducts.