Reduction of Organic Compounds at Lead Cathodes and Mediation by Dimethylpyrrolidinium Ion

Article abstract of DOI:10.1021/jo00264a004

Reduction of several organic compounds at Pb cathodes was studied and the use of dimethylpyrrolidinium (DMP⁺) as a mediator for such reactions was evaluated.Following previous reports that have shown that the reduction product of DMP⁺ at Pb deposits as a monolayer and bulk DMP(Pb₅), the catalytic properties of both phases for organic electroreduction were investigated.Of the organic compounds investigated, the monolayer catalyzes the reduction of alkyl chlorides only.Bulk DMP(Pb₅) mediates electron transfer also to several ketones, allylbenzene, and difluorobenzene.Of particular interest is the fact that the reduction of 6-hepten-2-one (5), 6-heptyn-2-one, and 5-phenylpentan-2-one can be catalyzed whereas other ketones are unaffected.Preparative electrolyses at Pb were performed with 6-chloro-1-hexene (4) and 6-hepten-2-one (5).The main product of 4 was 1-hexene, whereas 5 yielded 1,2-dimethylcyclopentanol exclusively.The reduction of 4 and 5 in the presence of catalytic amounts of DMP⁺ can be achieved at potentials 400 - 500 mV positive of the reduction potentials when DMP⁺ is absent.The mechanism of the reductive cyclization of 5 is discussed.