Substituent Effects on the Regioselectivity of the Baeyer-Villiger Oxidation of 7-Oxabicyclo[2.2.1]Heptan-2-Ones

New 3-oxy substituted and 3,6-dioxydisubstituted 7-oxabicyclo[2.2.1]heptan-2-ones have been prepared. The regioselectivity of their Baeyer-Villiger oxidation has been determined and compared with that of other 7-oxabicyclo[2.2.1[heptan-2-one derivatives. If the substituent at C(3-exo) is an O-acyl or another group less electron-releasing, the bridgehead C(1) migration is favoured, leading to 2,8-dioxa-bicyclo[3.2.1]octan-3-ones. When the substituent at C(3) is a MeO or (tBu)Me2SiO group, the Baeyer-Villiger oxidation leads to 3,8-dioxabicyclo[3.2.1]octan-2-ones due to preferred C(3) migration. The latter regioselectivity is higher for 3-endo-MeO than for 3-exo-MeO substituted ketones and it can be enhanced by remote oxy substituents at the C(6-endo) position.