Substituent and Solvent Effects in the Reactions of Diaryldiazomethanes with 2,3-Dichloro-5,6-dicyanobenzoquinone

Article abstract of DOI:10.1246/bcsj.54.2039

Kinetic studies have been made of the reactions of fifteen meta- and para-substituted diphenyldiazomethanes(DDMs) with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in benzene.The second order rate constants, k, increased with the electron-donability of the substituents, and the value could be correlated with the Yukawa-Tsuno equation: log k/k₀ = -2.33(?⁰ + 0.47Δ<*>⁺) + 0.017, (r = 0.996, 30 deg C).The ρ value, -2.33, indicates the development of a positive charge at the diazo carbon in the transition state, while the R value, 0.47, confirms the moderate stabilization of the positive charge by the ?-electronic contribution of the para substituents.The rate constants have also been determined for the reaction of diphenyldiazomethane(DDM) with DDQ in 28 aprotic solvents.The effects of solvents can be interpreted in terms of the basicity and the steric nature of the solvents.The products of these reactions were poly(2,3-dichloro-5,6-dicyanohydroquinone benzhydryl ether)s, which were easily convertible into benzophenones and α,α-dimethoxydiphenylmethane, together with 2,3-dichloro,5,6-dicyanohydroquinone, under the influence of water and methanol.These solvolysis products were also obtained in excellent yields in the initial presence of these additives.