Pd/C-Catalyzed Domino Synthesis of Urea Derivatives Using Chloroform as the Carbon Monoxide Source in Water

A Pd/C-catalyzed domino synthesis of symmetrical and unsymmetrical ureas from aryl iodides, sodium azide, amines and CHCl3 in water has been developed. This reaction proceeds with sequential carbonylation, Curtius rearrangement and nucleophilic addition. CHCl3 serves as a convenient and safe alternation of CO gas in the presence of KOH. A series of urea derivatives were obtained in moderate to good yields with good functional group tolerance. Furthermore, the Pd/C catalyst could be readily recovered with slight decrease in the catalytic activity after six consecutive runs.