電極還元反応による特異な活性種の創造とその有機合成への応用

Abstract

Several carbon-carbon bond forming reactions useful for organic synthesis are achieved by electrochemical reduction. (1) Electroreduction of ketones in isopropyl alcohol containing a tetraalkylammonium salt generates anion radical species which reacts with aromatic rings, nitriles, and O-alkyl oximes intra- and intermolecularly. Some ring-fused sesquiterpenes and α, β-disubstituted cyclopentanones such as dihydrojasmone are synthesized by electroreduction of γ-cyano ketones. (2) Electroreduction of a system comprising CX3Y, CHX2Y, and an aldehyde leads to an anionic chain reaction and gives the corresponding coupling products, RCH(OH)CX2Y, in high current efficiencies and yields. The addition of -CCl2CO2Me to α-branching aldehydes shows high diastereoselectivity. (3) Electroreduction of aromatic imines in the presence of chlorotrimethylsilane generates anionic species which reacts with electrophiles to give the corresponding inter- and intramolecular cross-coupling products. (4) Electroreduction of aromatic diimines under acidic conditions gives intramolecular coupling products stereoselectively. This reaction is useful for the synthesis of substituted piperazines and 1, 4-diaza-crown ethers.