Electrochemical Carboxylation of Vinyl Compounds

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Carbon dioxide is well known to be a useful reagent for the trapping of anionic species in solution resulting in the formation of carboxylated products. For example, the electrolytic reduction of activated olefins such as 1-cyanostyrene in the presence of carbon dioxide gives the corresponding saturated compounds with the carboxyl group. With alpha, beta-unsaturated sulfoxides and sulfones, on the other hand, the substitution of sulfinyl or sulfonyl group by carbon dioxide will be expected to occur to yield the corresponding acrylic acid derivatives, in contrast to the above example.The present work deals with the electrochemical carboxylation of alpha, beta-unsaturated sulfoxides and sulfones with carbon dioxide in nonaqueous media. These results are shown below :(1) The electro-carboxylation of beta-methylsulfenyl-beta-methylsulfinylstyrene leads to alpha- (methylsulfenyl) cinnamic acid and beta-methylsulfenylstyrene.This electro-carboxylation is characterized as substitution of the methylsulfinyl group by carbon dioxide.(2) The electro-carboxylation of 1-methylthio-1-p-tolylsulfony1-2-arylethenes gives 3-arylpropenoic acids, indicating that the elimination of both methylthio and p-tolylsulphonyl groups happens.(3) In the electroreductive desulfurization and carboxylation of beta, beta-bis (methylsulfonyl) styrene, the selective cleavage of one carbon-sulfur bond takes place to afford beta-methylsulfonylstyrene in the presence of an efficient proton donor, but the corresponding carboxylated product is not obtained in the presence of carbon dioxide.(4) The electrochemical reduction of alpha, beta-bis (methylsulfonyl) styrene in nonaqueous media leads to beta-methylsulfonylstyrene. This is contrary to experience with above compounds, i. e., this electro-reduction brings about the elimination of the methylsulfonyl group at the alpha-position rather than the beta-position. The electro-carboxylation of this compound gives beta-methylsulfonyl-alpha-phenylacrylic acid.