Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

Anodic fluorination of dithioacetals bearing electron-withdrawing ester, acetyl, amide, and nitrile groups at their alpha-positions was comparatively studied using various supporting poly(HF) salts like Et3N center dot nHF (n = 3-5) and Et4NF center dot nHF (n = 3-5). In the former two cases, the corresponding alpha-fluorination products or fluorodesulfurization products were obtained selectively depending on supporting poly(HF) salts used. In sharp contrast, in the latter two cases, fluorination product selectivity was strongly affected by the electron-withdrawing ability of alpha-substituents: A dithioacetal bearing a relatively weak electron-withdrawing amide group provided a fluorodesulfurization product selectively while a dithioacetal having a strongly electron-withdrawing nitrile group gave the alpha-fluorination product predominantly regardless of the poly(HF) salts used.