Development of a New Strategy and Methodology for Baeyer-Villiger Oxidation

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A conceptually distinct, new strategy for Baeyer-Villiger oxidation (BVO) was developed by utilizing hypernucleofugality of arylbromane(III). Our method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent arylbromane on bromane(III), yielding a new type of Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via reductive elimination of arylbromanyl(III) group, because of the hypernucleofugality. The novel strategy makes it possible to selectively induce the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO. Our BVO takes place with extensive retention of stereochemistry at the migrating center. The carbon chain migration seems to depend primarily upon the electron-donor ability of migrating alkyl groups. Based on the substituent effects for aromatic aldehydes and quantum chemical calculations, the reaction mechanism was discussed.