Self-Neutralizing in Situ Acidic CO2/H2O System for Aerobic Oxidation of Alcohols Catalyzed by TEMPO Functionalized Imidazolium Salt/NaNO2

A reversible in situ acidic catalytic system comprising recyclable TEMPO functionalized imidazolium salt ([Imim-TEMPO][Cl])/NaNO2/CO2/H2O was developed for selective transformation of a series of aliphatic, allylic, heterocyclic, and benzylic alcohols to the respective carbonyl compounds. Notably, the system avoids any conventional acid and can eliminate unwanted byproducts, facilitate reaction, ease separation of the catalyst and product, and also provide a safe environment for oxidation involving oxygen gas.