INTRAMOLECULAR DIELS-ALDER REACTIONS VIA SULFONE-SUBSTITUTED 3-SULFOLENES

Regiospecific alkylation of the dianion of sulfone-substituted 3-sulfolenes 1-4 attached an unsaturated alkyl chain at the C2 position to form convenient precursors for IMDA reactions. The substituents on the diene moiety have a significant effect on the reactivity of the IMDA reactions (H) Me(3)Si > PhS). The stereochemistry of the cyclization reaction depends on the chain length connecting the diene and dienophile. The hydronaphthalene products 12a and 12b are obtained only in the trans form, and the hydroindene products 10 and 11 have predominantly the trans ring structure. All the products have the useful vinylic sulfone structure.