AbstractCopper‐catalyzed decarboxylation of peroxides in the presence of O‐methyl‐N‐nitroisourea provides an access to O‐methyl‐N‐alkylnitroisoureas, an underdeveloped class of nitrogenated compounds, which can be regarded as isocyanate surrogates and find useful as AB‐type monomers, for polyurethane synthesis.