Baeyer-Villiger Oxidation of Aldehydes and Ketones

When treated with a peroxy acid, ketones can be converted into esters via the insertion of an oxygen atom  

This reaction, discovered by Adolf von Baeyer and Victor ViUiger in 1899, is called the Baeyer-Villiger oxidation. This process is beUeved to proceed via Mechanism 20.13. 

This step can occur intramolecularly, because it would involve a five-membered transition state 

The carbonyl group is reformed, with simultaneous migration of an alkyl group 

The peroxy acid attacks the carbonyl group of the ketone, giving a tetrahedral intermediate that then undergoes an intramolecular proton transfer (or two successive intermolecular proton transfers). Finally, the C=0 double bond is re-formed by migration of an R group. This rearrangement produces the ester. 

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Hassall, C. W., The Baeyer-Villiger oxidation of aldehydes and ketones. Organic Reactions. 9, 73-106, 1957. 

C. H. Hassall, The Baeyer-Villiger Oxidation of Aldehydes and Ketones, Organic Reactions 9, 73 (1957). 

Iodine-catalysed hydroperoxidation of cyclic and acyclic ketones with aqueous hydrogen peroxide in acetonitrile is an efficient and eco-friendly method for the synthesis of gem -dihydroperoxides and the reaction is conducted in a neutral medium with a readily available low-cost oxidant and catalyst.218 Aryl benzyl selenoxides, particularly benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide, are excellent catalysts for the epoxidation of alkenes and Baeyer-Villiger oxidation of aldehydes and ketones with hydrogen peroxide.219 Efficient, eco-friendly, and selective oxidation of secondary alcohols is achieved with hydrogen peroxide using aqueous hydrogen bromide as a catalyst. Other peroxides such as i-butyl hydroperoxide (TBHP), sodium... 

Preparing Aldehydes and Ketones A Review Introduction to Nucleophilic Addition Reactions Oxygen Nucleophiles Nitrogen Nucleophiles Mechanism Strategies Sulfur Nucleophiles Hydrogen Nucleophiles Carbon Nucleophiles Baeyer-Villiger Oxidation of Aldehydes and Ketones Synthesis Strategies... 

Supercritical CO2 is a non-polar, aprotic solvent and promotes radical mechanisms in oxidation reactions, similar to liquid-phase oxidation. Thus, wall effects might occur as known, e.g. from olefin epoxidation with 02 or H202 which may decrease epoxide selectivities. The literature covers the synthesis of fine chemicals by oxidation either without catalysts (alkene epoxidation, cycloalkane oxidation, " Baeyer-Villiger oxidation of aldehydes and ketones to esters ), or with homogeneous metal complex catalysts (epoxidation with porphyrins, salenes or carbonyls ). Also, the homogeneously catalysed oxidation of typical bulk chemicals like cyclohexane (with acetaldehyde as the sacrificial agent ), toluene (with O2, Co +/NaBr ) or the Wacker oxidation of 1-octene or styrene has been demonstrated. 

Detty et al. reported the use of selenoxide 416 as catalyst in the Baeyer-Villiger oxidation of aldehydes and ketones with [295], An example and the putative two catalytic cycles proposed are shown in Scheme 7.90. 

Mechanism of Baeyer-Villiger Oxidation Both aldehydes and ketones are oxidized by peroxy acids. This reaction, called the Baeyer- Villiger oxidation, is especially useful with ketones. 

Baeyer-Villiger oxidation of alkyl- and aryl-substituted C -C, cycloalkanones, steroid ketones and branched chain aliphatic ketones is catalysed by arsonated polystyrene resins [53], Larger size cycloalkanones and linear ketones react much slower. Water miscible and immiscible solvents can be used. With the latter, the resin behaves as an effective catalyst and a phase-transfer agent (triphase catalysis). The same compounds are also epoxidation catalysts. More recently, a method for the preparation of phenols by the oxidation of aromatic aldehydes and ketones has been reported. The most convenient catalysts are nitro-substituted arylseleninic acids and corresponding diselenides [54]. 

Acidic products result from further oxidation of aldehydes (or ketones), again by a radical process. Oxidation of an aldehyde to a carboxylic acid in the presence of air involves a peroxy acid (compare peroxyacetic acid. Section 8.1.2). Finally, a reaction between the peroxy acid and a molecule of aldehyde yields two carboxylic acid molecules this is not a radical reaction, but is an example of a Baeyer-Villiger oxidation. Baeyer-Villiger... 

TABLE 33. Results of the Baeyer-Villiger oxidation of various ketones and aldehydes using different methods... 

Krow GR (1993) The Baeyer-Villiger oxidation of ketones and aldehydes. Org React (New York) 43 251-798... 

NaH, dimethylformamide (DMF), CH3I], undergoes electrophilic nitration (89), Friedel-Crafts acylation (90), and alkylation (91) at the C-9 position. Although attempts to effeet a Baeyer-Villiger oxidation of ketone 90 were successful, the route was laborious since oxidation to amine oxide 92 preceded oxidation of the methyl ketone 90. However, a Dakin reaction of aldehyde 91 gave 9-hydroxy-6-methylellipticine (93) in excellent yield. It remains to be seen if this methodology can be extended to an N-unsubstituted ellipticine. 

Syper, L. The Baeyer-Villiger oxidation of aromatic aldehydes and ketones with hydrogen peroxide catalyzed by selenium compounds. A convenient method for the preparation of phenols. Synthesis 1989, 167-172. 

M. Renz, T. Blasco, A. Corma, V. Fornes, R. Jensen, L. Nemeth, Selective and shape-selective Baeyer-Villiger oxidations of aromatic aldehydes and cyclic ketones with Sn-beta zeolites and H2O2, Chem. Eur. J. 8 (2002) 4708. 

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