K3PO4-catalyzed carboxylation of amines to 1,3-disubstituted ureas: A mechanistic consideration

Abstract K 3 PO 4 was found to effectively catalyze the carboxylation of amines by CO 2 , producing corresponding 1,3-disubstituted ureas in high yields and selectivities. X-ray diffraction and FT-IR spectroscopic analysis of the solid mixture, recovered from the carboxylation of n -butylamine, revealed that K 3 PO 4 was completely transformed into KH 2 PO 4 and KHCO 3 . Mechanistic and computational studies suggested that the high activity of K 3 PO 4 could be attributed to the synergy effect exerted by the co-presence of KHCO 3 and KH 2 PO 4 , generated from the interaction of K 3 PO 4 with CO 2 and water.