Carbonylation of amines by carbon dioxide in the presence of an organoantimony catalyst

Abstract

1,3-Dialkylureas (RNHCONHR; where R=Bu, i-Bu, s-Bu, t-Bu, allyl, Ph) and tetramethylurea were successfully prepared at 80 o C under an initial CO 2 pressure of 4.9 MPa, from the corresponding amines and carbon dioxide with catalysis by triphenylstibine oxide and assistance from tetraphosphorus decasulfide (Ph 3 SbO/P 4 S 10 ). Monitoring of the reaction by 13 C NMR revealed that the successive thiolation of carbamic acid to an intermediate antimony carbamate species and aminolysis of tha carbamothioic acid thus formed constitute the reaction course. Cyclic ureas can also be synthesized by similar carbonylations of diamines (RNHCH 2 CH 2 NHR': where R,R' = H, H; Me, H; Ph, H; HOCH 2 CH 2 , H; HOCHMeCH 2 , H; Me, Me). Furthermore, the Ph 3 SbO/P 4 S 1 0 catalyst system enabled the preparation of trisubstituted ureas such as 1-butyl-3,3-diethylurea by a selective cocarbonylation of butylamine and diethylamine