Gram scale, metal-free and selective aerobic oxidation of alcohol and alkyl benzenes using homogeneous recyclable TAIm[MnO4] oxidative ionic liquid under mild conditions: Microwave/ ultrasonic-assisted to carboxylic acid

Abstract

A homogeneous catalyst-free system has been developed for the selective oxidation of alcohols and alkyl benzenes to the corresponding carbonyl compounds using a recyclable TAIm[MnO4] oxidative ionic liquid. The reactions were performed in the presence of previously reported TAIm[MnO4]/ TAIm[OH] ionic liquids and KMnO4 at ambient temperature under solvent-free conditions. Benzyl alcohols were selectively transferred to benzaldehydes, while under ultrasonic or microwave irradiation, they oxidized to benzoic acid selectively and directly. Scalability of the process also studied at high scale. Also, the ionic liquid could be readily recycled from the aqueous mixture and reused for several consecutive times without any pre-treatment and loss of catalytic activity. In this work, the highly active and toxic KMnO4 salt has been transformed into a mild recyclable oxidant reagent with high selectivity towards alcohol oxidation.