An easy access to unsymmetrical ureas: a photocatalytic approach to the Lossen rearrangement

Abstract

An efficient and operationally simple method for the synthesis of unsymmetrical ureas from various hydroxamic acids and amines has been developed. Plausibly, the protocol involves visible-light-initiated in situ formation of Vilsmeier–Haack reagent and COBr₂ with CBr₄ and a catalytic amount of DMF in the presence of Ru(bpy)₃Cl₂ as a photocatalyst to bring about the Lossen rearrangement at room temperature.