N,N′‐Diarylurea and Amines from Aroylhydroxamic Acids and β‐Propiolactone. Mechanism of a Double Lossen Reaction

Abstract

It has been shown that N,N′‐diphenylurea formation in the reaction of benzohydroxamic acid and β‐propiolactone constitutes a sequence of two rearrangements of the Lossen type. The intermediates, O‐(β‐hydroxypropionyl)benzohydroxamate and O‐(N‐phenylcarbamoyl)benzo‐hydroxamate, have been isolated as products of consecutive steps. Their transformations have been shown independently and along the process leading to N,N′‐diphenylurea. Heating of sodium benzohydroxamate, p‐nitro‐ and p‐methoxy‐benzohydroxamate with β‐propiolactone afforded N, N′‐diphenylurea, p‐nitroaniline and N,N′‐di‐p‐methoxyphenylurea, respectively. Improved procedures for preparation of aroylhydroxamic acids are described.