Cyclohexyl Bromide and Iodide: Direct Reduction at Vitreous Carbon Cathodes together with Nickel(I) Salen‐ and Cobalt(I) Salen‐Catalyzed Reductions in Dimethylformamide

Cyclic voltammetry and controlled‐potential (bulk) electrolysis have been used to study the direct electrochemical reduction of cyclohexyl bromide ( 1 ) and cyclohexyl iodide ( 2 ) at glassy carbon cathodes in dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate (TMABF 4 ). Direct reduction of 1 is a one‐step process that affords a carbanion intermediate, whereas 2 undergoes stepwise reduction to a radical and then a carbanion intermediate. Mixtures of cyclohexane, cyclohexene, and bicyclohexyl arise from bulk electrolyses of both 1 and 2 . Catalytic reduction of 1 and 2 by nickel(I) salen and cobalt(I) salen electrogenerated at glassy carbon cathodes in DMF‐TMABF 4 has been investigated with the aid of both cyclic voltammetry and bulk electrolysis. Products arising from these catalytic reductions are cyclohexane, cyclohexene, and bicyclohexyl, although significant amounts of unreduced 1 are found when cobalt(I) salen is utilized as the catalyst. Mechanistic aspects of the direct and catalyzed reductions of 1 and 2 are discussed.