Oxidation of carbonyl compounds

Abstract In 1899, Baeyer and Villiger investigated reactions of ketones with Caro’s reagent, peroxomonosulfuric acid, and they observed a previously unknown transformation: an oxygen atom was inserted into the C—C bond αto the carbonyl group, affording esters and lactones. Later, for this new type of oxidation the term ‘Baeyer–Villiger reaction’ was coined. Various peroxy compounds such as peracids, hydrogen peroxide, and alkyl peroxides can be used as oxidants yielding esters and lactones from acyclic and cyclic ketones, respectively. Acids, bases, enzymes (see Chapter 5, Section 5.3 for biological Baeyer–Villiger reaction), and metal-containing reagents catalyse Baeyer–Villiger reactions. As to the mechanism of the Baeyer–Villiger reaction of ketones with organic peracids, a two-step process originally proposed by Criegee is generally accepted: the first step is a reversible proton-catalysed addition of the peroxy compound to the ketone carbonyl affording an intermediate tetrahedral peroxyhemiketal. The following, in most cases, rate-determining step involves the migration of one of the two substituents to the next oxygen atom, simultaneous 0—0 bond cleavage and release of the acid moiety.