Reactivity of mixed organozinc and mixed organocopper reagents: 10 Comparison of the transferability of the same group in acylation of mixed and homo halozinc diorganocuprates with benzoyl chloride. A kinetic study

A detailed kinetic study has been carried out for the acylation of iodozinc n-butyl (substituted phenyl) cuprates, n-Bu(FG-C6H4) CuZnI and iodozinc din-butylcuprate, n-Bu2CuZnI with benzoyl chloride in THF at 15-(-15)degrees C. Third order reaction was found which is first order in benzoyl chloride and second order in cuprate. We offered a reaction mechanism for the acylation of halozinc diorganocuprates depending on the kinetic data and activation parameters. Lower reaction rate of transferable group, n-Bu in mixed cuprate, n-Bu(PhCuZnI than that of homocuprate, n-Bu2CuZnI and Hammett correlation of the reaction rate of transferable group, n-Bu in n-Bu(FG-C6H4)CuZnI reagents with the substituent constants of residual group, FG-C6H4 with a positive reaction constant (relative reactivity of FG: 4-Br > 3-MeO > H > 3-Me > 4-Me > 4-MeO) are in accordance with the proposed mechanism. These findings support our hypothesis that the reaction rate of transferable group, R-T changes depending on the residual group, R-R in mixed cuprates. RRRTCuM (M = Li, MgX, ZnX) and also provide a kinetic explanation for the commonly accepted hypothesis regarding the dependence of the R-T group transfer ability on the strength of the R-R-Cu bond in mixed cuprates, RRRTCuLi. (c) 2013 Elsevier B.V. All rights reserved.