Electrochemical Reduction of Cyclohex‐2‐enones

The electrochemical reduction of the cyclohex‐2‐enones 1a–1e (mercury cathode, CH 3 CN, Bu 4 NBF 4 ) was studied by means of cyclic voltammetry, d.c. polarography, coulometry and chemical product analysis. Compounds 1a–1c give a mixture of the hydrodimers 4 and 5 via formation of the radical anion 2 by an irreversible one electron transfer, followed by protonation and dimerization of the allylic radical 3 . The 6‐halocyclohex‐2‐enones 1d and 1e exhibit two distinct reduction waves. The first corresponds to an irreversible two electron transfer with formation of the halide anion and the enolate anion 6 which gives 1b by protonation. The second wave corresponds to a quasi ‐reversible one electron transfer to 6 to afford the radical dianion 7 ( Scheme 2 ).