Cinnamic acid esters radical anions

Electrolyses of substrates of the cinnamic acid ester family (Table 4) in anhydrous MeCN were shown to result in formation of 7-60% of the CHD [Eq. (3)], corresponding exclusively to the ( ) coupling as determined from the stereochemistry of the cyclopenta-none formed by hydrolytic decarboxylation [61]. The stereochemistry was later verified by x-ray crystallography [65]. The stereoselectivity in the coupling step was originally rationalized in terms of orientation of the substrate molecules at the electrode surface [61]. However, later kinetic studies have shown that dimerization of the radical anions is fairly slow (Table 3), and takes place in the diffusion layer at a distance from the electrode. 

Baizer and coworkers established the most brilliant industrial electroorganic synthesis of the hydrodimerization of acrylonitrile to adiponitrile. They extended this hydrodimerization to a variety of activated olefins and in some cases [41 3] paid attention to the stereochemistry of products. However, their stereochemical data were not enough to discuss the stereochemical course of the reaction. Afterward, an attempt was made to provide a working hypothesis in the hydrodimerization of cinnamates by considering an orientated adsorption of radical anion intermediates on a cathode surface, but this was not persuasive because of a lack of experimental data on the stereochemistry of both the starting olefins and products. Recently Utley and coworkers [44-46] have reported stereochemical data of hydrodimers derived from a variety of cinnamic acid esters with chiral alcohol components. 

Cinnamic acid ethyl ester is a carbonyl compound, which like ben/.ophenone has the ability to accept an electron to form a rather stable anion radical. As tin t. /hunsaturated ester it may produce 1.2- and... 

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