Oxidation is a core technology for converting petroleum-based materials to useful chemicals of a higher oxidation state. Hydrogen peroxide (H₂O₂) is an ideal oxidant, because the atom efficiency is excellent and water is theoretically the sole co-product. However, H₂O₂ can be a clean oxidant only if it is used in a controlled manner without organic solvents and other toxic compounds. Thus, the discovery of an efficient catalyst and the choice of reaction conditions are the keys to realizing an ideal oxidation procedure. In this context, we developed various oxidation reactions with aqueous H₂O₂ under organic solvent- and halide-free conditions.