Electrochemical reduction allylic compounds

The electrochemical reduction of a,p-unsaturated ketones and related compounds in aprotic media in the absence of metal cations can, in some cases, lead to relatively stable anion radicals.However, in the presence of proton donors the latter are protonated to form hydroxyallyl radicals, which tend to dimerize more rapidly than they diffuse back to the electrode to undergo further reduction (Scheme 17). Although these allyl radicals prefer to dimerize by coupling at the -position, if this position is sterically hindered, as in the case of cholest-4-en-3-one, coupling at the carbonyl carbon may be observed, yielding pinacols. ... 

Formation of organomercury compounds has been observed in the electrochemical reduction of benzyl iodide [29, 30] and allyl bromide [31]. 

Reductive cleavage of a C-0 bond requires activation of the bond such activation can be obtained in different ways. Conjugated carbinols, like allylic and benzylic alcohols, tt-electron-deficient heterocyclic carbinols, and a-hydroxyketones and the ethers of these compounds, may be reductively cleaved. Reductive elimination of two vicinal hydroxyl groups or derivatives thereof may also be possible. These reactions have been exploited in the electrochemical removal of protecting groups [40,41]. 

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