Catalytic reduction of cyclohexanecarbonyl chloride with electrogenerated nickel(I) salen in acetonitrile

In the presence of electrogenerated nickel(I) salen in acetonitrile containing tetramethylammonium tetrafluoroborate, cyclohexanecarbonyl chloride is catalytically reduced to form ultimately a tetrameric species, 1,2-dicyclohexylethene-1,2-diol dicyclohexanoate. Initially, the acyl chloride accepts an electron from nickel(I) salen to form an acyl radical, and two acyl radicals couple to afford 1,2-dicyclohexylethane-1,2-dione. As soon as it is formed, the latter α-diketone undergoes either direct (noncatalytic) or nickel(I) salen-catalyzed reduction to its radical-anion, which can attack unreduced cyclohexanecarbonyl chloride; the resulting intermediate is further reduced and acylated to produce the tetramer.