Studies concerning the double reduction of Diels–Alder derived bicylic sulfonamides

A series of bicyclic sulfonamides, 14–17, was prepared by thermal, intramolecular Diels–Alder cycloaddition. The ratio of exo:endo-diastereoisomers formed following this process was found to be dependent on the substitution pattern of the dienophile. Styryl substituted sulfonamides preferentially formed the corresponding exo-adducts, whereas vinyl substituted sulfonamides preferentially gave the endo-adducts. These adducts were treated under dissolved metal reduction conditions and it was found that compounds possessing an N-benzyl substituent underwent preferential debenzylation and resisted further reduction. The complementary N-isobutyl functionalised materials only underwent the double reduction when a phenyl substituent was present.