Complete Control of the Chemoselectivity in Catalytic Carbene Transfer Reactions from Ethyl Diazoacetate:  An <i>N</i>-Heterocyclic Carbene−Cu System That Suppresses Diazo Coupling

The complex IPrCuCl (1) catalyzes the transfer of the :CHCO2Et group from ethyl diazoacetate (EDA) to unsaturated and saturated substrates (olefins, amine, alcohols) with very high yields. In the absence of substrate, the complex 1 does not react with EDA to give the diazo coupling products (fumarate and maleate), a rare example in the field of metal-catalyzed diazocompounds decomposition.