Stereoselective Baeyer–Villiger oxidation of some bridged bicyclic diketones

Abstract

The regioselectivity of the Baeyer–Villiger oxidation of bicyclo[3.3.1]nonane and bicyclo[2.2.2]octane ketones 1–7 with carbonyl groups located at different positions and bearing other substituents in the bicyclic ring is studied. The impact of the formation of the tetrahedral intermediate and the ring-bond migratory aptitude are considered as major factors governing the reaction's regioselectivity. The distortion from sp²-hybridization of the valence angle of the C-9 carbonyl group is found to be considerably greater than that at the C-2 carbonyl in bicyclo[3.3.1]nonane-2,9-dione structures according to semiempirical calculations. Highly regioselective oxygen insertion leading to the functionalized oxabicyclic keto lactones is accounted for by kinetic and stereoelectronic factors.