Facile synthesis of 2-benzimidazolones via carbonylation of o-phenylenediamines with CO2

An efficient synthesis for the benzimidazolones and various 1,3-disubstituted urea derivatives prepared from several nucleophiles like o-phenylenediamines and o-aminophenols with CO2 (1 MPa) under transition-metal-free or acetate complex free conditions has been developed. A variety of chemicals were synthesized in moderate to good yields promoted by tributylamine (TBA) using the nucleophiles and CO2 as a green and renewable C1 source. The cyclization of CO2 and o-phenylenediamine offered a general and straightforward synthesis of benzimidazolones and cyclic ureas promoted by the inexpensive and environmentally-friendly TBA as the carbonylation catalyst. Thus, various valuable cyclic ureas and their carbonyl homologs were synthesized in good yields through this green carbonylation process.