Spontaneous and Direct Transformation of <i>N</i>,<i>O</i>-Diaryl Carbamates into <i>N</i>,<i>N</i>′-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 (EtN) 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.

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

“…Yamasaki et al 243 developed a method to transform N , O -diaryl carbamates directly and spontaneously into N , N ′-diarylureas ( Table 16 ). The Et 3 N catalyzes the reaction by abstraction of the carbamate proton, forming the aniline derivative, which can then react with more of substrate 187 to form diarylurea 188 .…”

Expedient phosgene-free synthesis of symmetrical diarylureas from carbamates

“…Recently, triethylamine and dimethylformamide (DMF) were used with some limitations for synthesis of particular 1,3-disubstituted phenyl ureas. 36 Other miscellaneous synthesis methods for 1,3-diaryl ureas can also be found in literature. [37][38][39] For example, diarylureas were unexpectedly synthesized from the reaction of nicotinic acids and ethylchloroformate with a moderate yield (60-65%).…”