CO₂/Water-Regulating Transamidation of Urea and Amines

The process of urea transamidation with amine to urea derivative has been developed in the presence of both carbon dioxide and water. Through the present reaction route, not only can the urea derivatives be obtained in high yield, but also inorganic salt ammonium bicarbonate (ABic) can be successfully isolated simultaneously from the reaction mixture. The phase behavior observed in situ by high pressure visual autoclave illustrated that the reaction occurred in biphasic conditions during the reaction. A number of verifying tests were conducted to investigate the role of carbon dioxide and water in the system. It was found that reaction temperature, total pressure, reaction time, and water played a crucial role in producing urea derivatives. The further investigation showed that the transamidation reaction between various amines and urea occurred successfully without the addition of any other catalysts in the presence of CO₂ and water. The acidity resulting from reaction of CO₂ with water facilitated the transamidation reaction.