An efficient and practical system for the catalytic oxidation of alcohols, aldehydes, and α,β-unsaturated carboxylic acids

Upon exposure to commercial bleach (similar to 5% aqueous sodium hypochlorite), nickel(II) chloride or nickel( II) acetate is transformed quantitatively into an insoluble nickel species, nickel oxide hydroxide. This material consists of high surface area nanoparticles (ca. 4 nm) and is a useful heterogeneous catalyst for the oxidation of many organic compounds. The oxidation of primary alcohols to carboxylic acids, secondary alcohols to ketones, aldehydes to carboxylic acids, and alpha,beta-unsaturated carboxylic acids to epoxy acids is demonstrated using 2.5 mol % of nickel catalyst and commercial bleach as the terminal oxidant. We demonstrate the controlled and selective oxidation of several organic substrates using this system affording 70-95% isolated yields and 90-100% purity. In most cases, the oxidations can be performed without an organic solvent, making this approach attractive as a "greener" alternative to conventional oxidations.