Hydrodimerization of activated alkenes

The formation of dimers by reduction of a,p-unsaturated ketones in aqueous media is well documented in the early literature of electrochemistry. Reductants include sodium or aluminium amalgams [58], dissolving zinc and a lead cathode in both acid and alkaline conditions [59,60]. Mixtures of dimers and dihydro derivatives were isolated. As the concept of the hydrodimerization of activated alkenes... 

Hydrodimerization of activated alkenes is a well-established process. 7r-Electron-deficient heteroaromatic compounds activate a double bond similarly to a cyano or car-bethoxy group, and in accordance with that analogy vinylpyridines can be hydrodimer-ized. 4-Vinylpyridine [380] forms l,4-bis-(4-pyridyl)butane in 82% yield on electrolysis in a mildly alkaline solution containing methyltriethylammonium / -toluenesulfonate and some DMF. The mechanism is discussed in Chapter 21. 

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