One-Pot Synthesis of Disubstituted Urea from Carbon Dioxide, Propylene Oxide, and Amines Catalyzed by Imidazolium-Tetraiodoindate

摘要

In this article, synthesis of 1,3-disubstituted urea (DSU) from three component reagent systems comprising amine, carbon dioxide, and propylene oxide is described. DSU is synthesized in the presence of a variety of ionic liquids (ILs) with/without promoters. Among used ILs, 1-butyl-3-methylimidazolium tetraiodoindate~(III) (represented as [Bmim][InI4]) is found to give the highest DSU product. A serious experiment clearly indicates that the tetraiodoindate anion plays an important role for the selective production of the DSU. Based on the in situ infrared spectroscopic studies, a plausible reaction mechanism for pro-ducing dicyclohexylurea from cyclohexylamine is proposed. The synthesis and characterization of [Bmim][InI4] are given in details. Moreover, the effect of reaction variables such as time, temperature, pressure, and the molar ratio of substrate to catalyst is also studied.