Palladium-catalysed N,N'-disubstituted urea synthesis by oxidative carbonylation of amines under CO and O2 at atmospheric pressure

Article abstract of DOI:10.1016/0022-328X(87)87174-7

N,N'-disubstituted ureas have been obtained in good yields by reaction of aromatic and aliphatic primary amines in alcohol solution with CO and O2 under mild conditions (70-90 deg C, 1 atm) and in the presence of catalytic amounts of PdCl2 or a palladium(II) complex.Under more drastic temperature and pressure conditions carbamate esters were obtained instead.In the aniline carbonylation, the catalysis involves the following reactions: .Reaction (1) occurs at room temperature but more drastic conditions (70-90 deg C) are necessary for reaction (2).The influence of onium salts, such as PhNH3⁺X^- (X=Cl, I) or CuCl2, on the catalytic activity has also been studied and the best results obtained with CuCl2.A side reaction involving carbon monoxide oxidation was almost suppressed when the reactions were carried out in alcohol, but enhanced when THF or dimethoxypropane was used as solvent.