Experimental Study on the Reaction Pathway of α-Haloacetophenones with NaOMe: Examination of Bifurcation Mechanism

The reaction of PhCOCH2Br and NaOMe in MeOH gave PhCOCH2OH as the major product and PhCOCH2OMe as the minor product. Substituent effects on the reactivity and product selectivity revealed that an electron-withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was indicated that the alcohol was formed via carbonyl addition-epoxidation, whereas the ether was formed by direct substitution. Substituent effects on the reaction rates, as well as the effects of NaOMe concentration on the rate and product ratio for both reactions of PhCOCH2Br and PhCOCH2Cl are in line with the mechanism that the alcohol and ether products were formed via two independent and concurrent routes, carbonyl addition and α-carbon attack, respectively, and thus the reaction mechanism could be different from the bifurcation mechanism previously predicted for the reaction of PhCOCH2Br by a simulation study in the gas phase.