Spontaneous and direct transformation of N,O-diaryl carbamates into N,N′-diarylureas

Abstract

We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N′-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (Et3N) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates. Substrates bearing an electron-donating methoxy group on either of the aryl groups reacted slowly under these conditions.