Expedient phosgene-free synthesis of symmetrical diarylureas from carbamates

Abstract

A convenient method for synthesis of symmetrical diarylureas from carbamtes is reported. The diarylureas were obtained in excellent yield when carbamates were boiled at reflux in dry benzene in the presence of sodium hydride as a catalyst and 18-Crown-6 ( 18 C6 ) as a co-catalyst. A plausible mechanism explains the formation of 1,3-diarylureas from carbamates in the presence of basic catalyst is reported. The chemical structure of the diarylureas was confirmed by spectroscopic techniques and compared with an authentic sample prepared using previously reported methods.

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“…The crystal structure with the reference code SIYBUA was submitted to CCDC as CSD Communication (private communication) in 2019. 49 It was crystallized in the monoclinic system with the space group P2 1 /n.…”