The Baeyer-Villiger oxidation is an organic reaction in which a ketone is oxidized to an ester by treatment with peroxy acids or hydrogen peroxide. ^{[1] [2]} Key features of the Baeyer-Villiger oxidation are its stereospecificity and predictable regiochemistry.^[3] It is named after the German chemist Johann Friedrich Wilhelm Adolf von Baeyer (1835-1917) and the Swiss chemist Victor Villiger (1868-1934).

Reagents typically used to carry out this rearrangement are meta-chloroperoxybenzoic acid (mCPBA), peroxyacetic acid, or peroxytrifluoroacetic acid ^[4]. The original reagent in the 1899 publication is Caro's acid discovered just a year earlier. ^[5] Disodium hydrogen phosphate is added as a buffering agent to prevent transesterification.

The reaction mechanism of this oxidative cleavage involves first addition of the peroxy acid to the carbonyl forming a tetrahedral intermediate also called the Criegee intermediate for its similarity with rearrangement of that name. The transition state for this step is envisioned as a hydrogen relay involving three peroxy acid molecules with linear O-H-O interactions ^[6]. Next is a concerted migration of one of the adjacent carbons to oxygen with loss of a carboxylic acid. For unsymmetrical ketones, the migrating group is the one that gives the most stable cation. If the migrating carbon is chiral, the stereochemistry is retained.

In the transition state for this migration step the R-C-O-O dihedral angle should be 180° in order to maximise the interaction between the filled R-C sigma bond and the antibonding O-O sigma bond. This step is also (at least in silico) assisted by two or three peroxyacid units enabling the hydroxyl proton to shuttle to its new position^[6].

Thus, cyclic ketones produce lactones and aldehydes produce first a formate and then a carboxylic acids although sometimes a alcohol is formed when the formate is hydrolytically unstable.

source: 100 Years of Baeyer-Villiger Oxidations Michael Renz, Bernard Meunier European Journal of Organic Chemistry Volume 1999, Issue 4 , Pages 737 - 750


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