A Metallomicellar Catalyst for Controlled Oxidation of Alcohols and Lignin Mimics in Water using Open Air as Oxidant

Abstract

AbstractAlcohol groups and β‐O‐4 (C−C) linkages are widespread in biomass feedstock that are abundant renewable resource for value‐added chemicals. The development of sustainable protocols for direct oxidation or oxidative cleavage of feedstock materials in a controlled fashion, using open air as an oxidant is an intellectually stimulating task to produce industrially important value‐added carbonyls. Further, the oxidative depolymerization of lignin into fine chemicals has evoked interest in recent times. Herein, we report the first example of a catalyst system that could activate molecular oxygen from atmospheric air for controlled oxidation and oxidative cleavage/depolymerization of feedstock materials such as alcohols, β‐O‐4 (C−C) linkages and real lignin in water under open air conditions. The selectivity of carbonyl products is controlled by altering the pH between ~7.0 and ~12.0. The current strategy highlights the non‐involvement of any external co‐catalyst, oxidant, radical additives, and/or destructive organic solvents. The catalyst shows a wide substrate scope and eminent functional group tolerance. The upscaled multigram synthesis using an inexpensive catalyst and easily available oxidant evidences the practical utility of the developed protocol. A plausible mechanism has been proposed with the help of a few controlled experiments, and kinetic and computational studies.