Electrochemistry facilitates the chemoselectivity of benzylic alcohol oxidations mediated by flavin-based photoredox catalysis

The use of oxygen for catalyst regeneration in photoredox catalysis causes selectivity problems, due to the generation of reactive oxygen species causing over- and side-oxidations. Herein, we present a system using electrochemical regeneration of a flavin catalyst working under inert conditions, which allows the chemoselective oxidation of primary and secondary benzylic alcohols to carbonyl compounds without unwanted overoxidation to carboxylic acids. The method also tolerates other oxidation-sensitive groups such as methyl, methylsulfanyl, or pinacolboryl groups.光氧化还原催化中采用氧气进行催化剂再生会引发选择性问题，原因是活性氧物种（reactive oxygen species）的生成会导致过度氧化与副氧化反应。本文报道了一套在惰性条件下运行的黄素催化剂（flavin catalyst）电化学再生体系，该体系可实现伯、仲苄醇的化学选择性氧化，将其转化为羰基化合物，且不会发生非预期的过度氧化生成羧酸。该方法对甲基、甲硫基、频哪醇硼基等其他氧化敏感官能团同样具有良好的耐受性。