Correlation of Oxidation and Reduction Potentials of Reactants with Product Distribution in the Reactions of Various Organomagnesium Reagents with Aromatic Carbonyl and Nitro Compounds

Abstract

Abstract In the electron transfer initiated fifteen reactions of five organomagnesium reagents, a semiquantitative relationship between the product distribution and the electron-donating and -accepting abilities (EDA and EAA) of reactants was obtained. The EDA was estimated by cyclic voltammetry of oxidation peak potentials of reagents and/or by the product distribution in their reactions, the decreasing order of EDA being: ArMgBr>ArSMgBr>ArNHMgBr>ArN(MgBr)2>ArOMgBr. The EAA of six quinones, eight nitroarenes, eleven aromatic ketones and an imine, and five azoxyarenes were similarly estimated by their reduction potentials (redox) in THF. The values of differences between the oxidation peak and reduction potentials were taken as an estimate of the relative efficiency of electron transfer, and were correlated to the distribution of normal (addition, condensation, replacement, and azoxy-deoxygenation) and abnormal (radical) products. Some exceptional cases were explained by modifying EDA and/or EAA based on the effect of coordination of substrate’s oxygen to reagent’s Mg atom.