K sub(3)PO sub(4)-catalyzed carboxylation of amines to 1,3-disubstituted ureas: A mechanistic consideration

K sub(3)PO sub(4) was found to effectively catalyze the carboxylation of amines by CO sub(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 sub(3)PO sub(4) was completely transformed into KH sub(2)PO sub(4) and KHCO sub(3). Mechanistic and computational studies suggested that the high activity of K sub(3)PO sub(4) could be attributed to the synergy effect exerted by the co-presence of KHCO sub(3) and KH sub(2)PO sub(4), generated from the interaction of K sub(3)PO sub(4) with CO sub(2) and water.