Reactions of Aldehydes and Ketones: Baeyer–Villiger Oxidation

Baeyer–Villiger oxidation uses peracid and an acid catalyst to convert aldehydes to carboxylic acids and ketones to esters via the insertion of an oxygen atom next to the carbonyl carbon.

The substrate's carbonyl oxygen is first protonated, which makes the carbonyl carbon more electrophilic.

A nucleophilic attack by the terminal oxygen of the peracid, followed by the loss of a proton, produces a tetrahedral intermediate.

Protonating the carboxylate facilitates a concerted intramolecular process wherein reformation of the carbonyl bond, migration of a group from carbon to oxygen, and cleavage of the weak O–O bond take place, releasing the final product.

With unsymmetrical ketones, a question that arises is which group undergoes migration? With two possible outcomes, one of the products predominates.

The reaction result depends on the migratory aptitude of different groups; thus, Baeyer–Villiger oxidations are regioselective. Also, note that the reaction retains the stereochemistry at the migrating center.

For aromatic substrates, an electron-donating group accelerates the migration process, while an electron-withdrawing group retards it.