Kinetics of the BpCu-Catalyzed Carbene Transfer Reaction (Bp = Dihydridobis(1-pyrazolyl)borate). Is a 14-Electron Species the Real Catalyst for the General Copper-Mediated Olefin Cyclopropanation?

Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu ( 1 ) and in the presence or absence of olefin have led to the determination of several kinetic and thermodynamic parameters, and a consistent mechanism has been proposed for the olefin cyclopropanation reaction. Related studies with the complexes [Cu(bipy) 2 ]I (bipy = bipyridine) and [Cu(bis(oxazoline)) 2 ]OTf have shown strong similarities with the results obtained with 1 . A general mechanism covering the copper-based systems reported in the literature has been proposed, the real catalyst (i.e., the species to be reacted with EDA) in all cases being a neutral, 14-electron fragment of composition (L−L)Cu (L−L = Bp- and Tp-like ligands, semicorrins, salicylaldehyde derivatives) or, alternatively, the isoelectronic, cationic [(L−L)Cu] + (for L−L = bis(oxazoline), bipyridine).