Baeyer-Villiger Oxidation
The Baeyer-Villiger Oxidation is
the oxidative cleavage of a carbon-carbon bond adjacent to a carbonyl, which
converts ketones to esters and cyclic ketones to lactones. The Baeyer-Villiger
can be carried out with peracids, such as MCBPA, or with hydrogen
peroxide and a Lewis acid.
The regiospecificity of the reaction depends on the relative
migratory ability of the substituents attached to the carbonyl. Substituents
which are able to stabilize a positive charge migrate more readily, so that the
order of preference is: tert. alkyl > cyclohexyl > sec. alkyl
> phenyl > prim. alkyl > CH3. In some cases,
stereoelectronic or ring strain factors also affect the regiochemical outcome.
Mechanism of the
Baeyer-Villiger Oxidation
Baeyer-Villiger oxidation is
the oxidation of a ketone to a carboxylic acid ester using a peroxyacid as the
oxidizing agent. eg. 1:
eg. 2:
Mechanism
When the two ligands on the
carbonyl carbon in the ketone are different, Baeyer-Villiger oxidation is
regioselective. Of the two alpha carbons in the ketone, the one that can
stabilize a positive charge more effectively, which is the more highly
substituted one, migrates from carbon to oxygen preferentially.
eg. 1:
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