Chiral Brønsted Acid Catalyzed Asymmetric Baeyer–Villiger Reaction of 3‐Substituted Cyclobutanones by Using Aqueous H₂O₂

A catalytic amount of a chiral Brønsted acid with aqueous H2O2 as the oxidant is sufficient for the enantioselective Baeyer–Villiger oxidation of 3-substituted cyclobutanones to give the corresponding γ-lactones in excellent yields and up to 93 % ee. The method employs benign aqueous H2O2 instead of stoichiometric amounts of a dangerous peracid.