Cathodic Dimerization

The technical, electrochemical, and preparative aspects of cathodic dimerization, which leads to bifunctional compounds, are reviewed. With the hydrodimerization of acrylonitrile as an example, the effects of the reaction parameters and the mechanism are discussed in detail. In addition to the hydrodimerization of activated compounds, the coupling can also proceed via elimination of halide or via the discharge of cations. Processes of special preparative interest are those in which two different molecules are coupled, which can yield e.g. esters, alcohols, or ketones with cyano groups, as well as asymmetric diols. The reductive dimerizations of acrylonitrile, β‐chloropropionitrile, acetone, acetylpyridine, nitrobenzene (→ benzidine), and pyridinium salts have already found industrial use.