Green and Efficient: Oxidation of Aldehydes to Carboxylic Acids and Acid Anhydrides with Air

An economic, safe, practical, and environmentally benign protocol for the oxidation of aldehydes to carboxylic acids and acid anhydrides with ambient air as the sole oxidant was developed. This oxidation is operationally simple and external catalyst-, initiator-, and base-free, with outstanding functional group tolerance (moisture-, acid-, base-, and oxidant-sensitive groups). It also provides a practical protocol for large scale synthesis (>100 g), late-stage modification of polyfunctional compounds, and one-pot sequential transformation starting from aldehydes.