Activation Of Molecular Oxygen By Small Molecules For Aerobic Oxidative Deoximation

The oxidative deoximation, using oxygen as the terminal oxidant, isregarded as an important transformation in organic synthesis for bothenvironmental and economic advantages. In this paper, two novel andefficient aerobic deoximation systems, employing small moleculars as thecatalysts, have been developed.A mild and effective NaNO₂/Amberlyst-15/O₂deoximation systemhas been developed for a wide range of ketoximes and aldoximes. Underthe optimized conditions:1mmol substrate,10mol%NaNO₂as thecatalyst,0.1000g Amberlyst-15as the initiator, in CH₂Cl₂/H₂O （5:1,6.0mL） at25℃under1atm O₂, the product can be isolated in a yield up to96%. Notably, after the reaction, the Amberlyst-15can be reused withoutregeneration. Based on the investigation, a plausible mechanism is alsoproposed.A simple and easy-handled FeCl₃/TEMPO/O₂deoximation systemhas been developed for various types of aldoximes. Under the optimizedconditions:1mmol substrate,10mol%TEMPO and10mol%FeCl₃as the catalysts, in PhCH₃/H₂O （3:1,4.0mL） at60℃under1atm O₂, thethe desired product is obtained with an isolated yield up to98%. Notably,nitric oxide （NO）, generally regarded as an active species for aerobicoxidation reactions, is assumed to generate in-situ from the cleavage ofoximes, which is further confirmed by the existence of a large quantity ofNO₃^-with Ion Chromatography （IC） and by capturing the active gas ingram-scale experiment. Base on the results, a plausible mechanism for thecatalytic oxidative cycle is also proposed, which may provide an insightinto the novel FeCl₃/TEMPO-catalyzed deoximative system.The newly developed systems, due to its simple experimentalprocedures, mild reaction conditions and desirable oxidative activity, canprovide valuable synthetic methods for practical applications.