alpha-oxosulfines, IV - Intramolecular hetero Diels-Alder reactions of alpha,alpha '-dioxosulfines - A new access to the [3.3.1]-bicyclic skeleton

Simple transformations of tert-butylthio-substituted 1,4-oxathiin permitted the preparation of oxathiin S-oxides. These in turn were suitable precurso rs of corresponding alpha,alpha'-dioxosulfine dienes with tethered internal electron-rich double bonds. Examining the synthetic utility of these sulfi nes, we observed either hydrolysis or intramolecular cycloaddition, dependi ng on the distance between the reactive centres and the substitution on the double bond. Bicyclic derivatives with a [3.3.1] skeleton and an sp(2) bri dgehead carbon were obtained from the cycloadditions.