Green, selective and swift oxidation of cyclic alcohols to corresponding ketones

Cyclohexanol oxidation to cyclohexanone is an important reaction in both organic chemistry and industry. We propose here an efficient, eco-friendly, and general method for oxidizing five- to eight-membered cyclanols used as model substrates, with aqueous hydrogen peroxide (H2O2) in the presence of tungstic acid (H2WO4) as a catalyst and an ammonium-based ionic liquid (IL) as a co-catalyst under organic solvent-free conditions. Cyclohexanol was found to be the most reactive of the four tested cyclanols. In addition, the role of the IL as a phase transfer catalyst was confirmed by the use of Aliquat 336 and the kinetic of the reaction was significantly improved under microwave or ultrasonic activation, leading to excellent yields in only a few minutes. (C) 2014 Elsevier B.V. All rights reserved.