Purified mCPBA, a Useful Reagent for the Oxidation of Aldehydes

Purified mCPBA is a useful reagent for the oxidation of several classes of aldehyde. Although linear unbranched aliphatic aldehydes are oxidized to the corresponding carboxylic acids, -branched ones undergo Baeyer-Villiger oxidation to formates. -Branched ,-unsaturated aldehydes provide enolformates and/or epoxides, which can be saponified to -hydroxy ketones with shortening of the carbon chain by 1 carbon. Unbranched ,-unsaturated aldehydes undergo an interesting Baeyer-Villiger oxidation/epoxidation/formate migration/BV oxidation cascade, which results in formyl-protected hydrates with an overall loss of two carbon atoms.