Asymmetric intermolecular Diels-Alder reactions of enantiopure sulfinyl-homo- and -hetero-dienes : preliminary results

Abstract Reaction of (E)-(+)-(R)-2- p -tolylsulfinyl-1,3-pentadiene 1 with maleimide afforded 3 as a single, enantiomerically pure adduct under very mild conditions. 3 resulted from exclusive endo approach by a completely diastereofacialselective route. On the other hand, heterodiene (+)-(S)-3- p -tolylsulfinyl-3-buten-2-one 2 smoothly reacted with sensitive 2-methylenetetrahydrofuran yielding 1:1 diastereomeric dioxaspiroadducts 4a and 4b , readily separated by liquid chromatography.