Catalytic Magnesium-Oppenauer Oxidation of Alcohols

A catalytic magnesium-Oppenauer oxidation reaction was developed. When a solution of alcohols in toluene was successively treated with 15–30 mol % of EtMgBr and 1.0 equiv. of trifluoromethyl ketone (oxidant), a hydride transfer-type oxidation reaction (Oppenauer oxidation) occurred to give corresponding ketones in good chemical yields (up to 85%). It was noteworthy that even a weakly basic alkoxide derived from trifluoromethyl ketone worked as an efficient Brønsted base to deprotonate the starting material (alcohols) at ambient temperature (25 °C). The efficiency of the present method was highlighted by applying the method to substrates having a nitrogen atom, which were sensitive to various oxidation conditions. A catalytic Oppenauer oxidation reaction was developed. When a solution of alcohols in toluene was successively treated with 15–30 mol % of EtMgBr and 1.0 equiv. of trifluoromethyl ketone (oxidant), a hydride transfer-type oxidation reaction (Oppenauer oxidation) occurred to give corresponding ketones in good chemical yields.