Metal salt catalyzed carbenoides—XIV: The mechanisms of carbene dimer formation from diazoacetic ester and dimethyl diazomalonate in the presence of some soluble copper catalysts

An examination of partial rate data for the decomposition of diazo acetic ester and dimethyl diazomalonate, in the presence of soluble copper salts and cyclohexene, revealed the existence of two paths to carbene dimer formation, one with a unimolecular dependence upon catalyst, the other with a bimolecular dependence. Assuming carbenoid formation, this is taken as indicative of dimer formation occurring by carbenoid + diazo compound and carbenoid + carbenoid paths. Conformational analyses indicate a preference for diethyl maleate formation by the carbenoid-diazo ester path for the case of diazoacetic ester and a preference for diethyl furmate formation by the carbenoid + carbenoid path.