Vitamin B12 model complex catalyzed methyl transfer reaction to alkylthiol under electrochemical conditions with sacrificial electrode

Abstract

Catalytic methyl transfer reactions from methyl tosylate to 1-octanethiol catalyzed by heptamethyl cobyrinate perchlorate, [Cob(II)7C₁ester]ClO₄, were investigated under electrochemical conditions. As a model study for the cobalamin-dependent methyl transfer reaction from methyltetrahydrofolate to homocysteine, controlled-potential electrolyses were carried out at −1.0 V vs. Ag/AgCl using a zinc plate as the sacrificial anode at 50 °C in the dark. A turnover behaviour for the methyl transfer reaction was observed for the first time under non-enzymatic reaction conditions. Co(I) species, which is generated from the continuous electrolysis of [Cob(II)7C₁ester]ClO₄, and its methylated CH₃-Co complex were found to be important intermediates. The mechanism for such a methyl transfer reaction was investigated by product analysis, electronic spectroscopy and ESR spin-trapping experiments. A simple vitamin B₁₂ model complex was also utilized as the catalyst for the methyl transfer reaction.