Studies on reactions of the N-phosphonium salts of pyridines—XV : Direct carbonylation of amines with carbon dioxide by a hydrolysis-dehydration reaction with phosphorus compounds

Carbon dioxide reacts with amines in the presence of phosphorus compounds and tertiary amines to give the corresponding ureas in high yield, and carbon disulfide gave thioureas. The presence of tertiary amines such as pyridine or imidazole facilitated the reactions. Aryl esters of phosphorous, phosphonous, phosphinous and phosphonic acids were effective, whereas their corresponding alkyl esters were ineffective. Various molar ratios of phosphite:tartiary amine:amine (aniline), produced variations in yield showing that the reaction proceeds via a carbamoyloxy and a thiocarbamoylthioxy N-phosphonium salt of the tertiary amine.