Umpolung using Electroorganic Reaction - Carbon-Carbon Bond Forming Reaction by the use of Sulfonates as a Nucleophile.

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Electrochemical reduction (ER) of 3-phenylpropyl tosylate gave 3-phenyl-1-propanol predominantly. On the other hand, a similar ER of 3-phenylpropyl mesylate in the presence of ketones, such as cyclohexanone, resulted in C-C bond forming reaction between mesylate and ketone to obtain the corresponding 1-(3-phenylpropyl)cycloalkanol in up to 30% yields. However, the yields of C-C bond forming reaction products could not be improved even though the reaction was carried out under various reaction conditions.We next tried ER of alkyl mesylates to the corresponding alkanes. A constant current electrolysis of 1-dodecyl mesylate with a platinum cathode and a magnesium anode in DMF in the presence of polycyclic aromatic compounds such as naphthalene, biphenyl and phenanthrene exclusively gave desired n-dodecane in moderate yields. After optimization of reaction conditions, it was found that n-dodecane could be obtained in 74% yield when ER of 1-dodecyl mesylate was carried out in the presence of biphenyl (4 equiv.) and t-BuOH (10 equiv.). This reaction system was applicable to various alkyl mesylates having epoxide, olefin, ester, acetal, and cyano groups to obtain the corresponding alkanes in good yields without change of these functional groups.In connection with the present research, ER of aliphatic ketones in the presence of carbon dioxide was also carried out, and it was found that an efficient fixation of CO_2 at a-position of carbonyl group in saturated aliphatic ketones could be achieved by a constant current electrolysis of the ketones in a CH_3CN or DMF solution with a platinum cathode and a magnesium anode under an atmospheric pressure of CO_2 to obtain the corresponding β-keto carboxylic acids in moderate to good yields.