Abstract
The oxidation procedure must be high-yielding and with high selectivity without any by-products through a simple, safe operation using a clean, well-behaving, and cheap oxidant. Aqueous hydrogen peroxide is an ideal oxidant, because the atom efficiency is excellent and water is a sole theoretical side product. We here report the no-solvent oxidation using aqueous hydrogen peroxide under entirely halide-free conditions. A catalytic system consisting of sodium tungstate and methyltrioctylammonium hydrogensulfate effects oxidation of secondary alcohols to ketones and primary alcohols to carboxylic acids using 3-30% hydrogen peroxide without any organic solvents. The turnover number is two orders of magnitude higher than any previously reported hydrogen peroxide oxidation. Substituted benzyl alcohols are oxidized selectively to benzaldehydes and/or benzoic acids, depending on the property of the substituents. Addition of (aminomethyl) phosphonic acid accelerates epoxidation of olefins. These oxidation methods are high-yielding, clean, safe, operationally simple, and cost-effective and therefore meet with the requirements of contemporary organic synthesis. Cyclohexene is converted directly to analytically pure, crystalline adipic acid in an excellent yield. Sulfides are oxidized to sulfoxides or sulfones in high yield. Aldehydes are oxidized to carboxylic acids without affecting olefinic or alcoholic functions.
