Intramolecular Diels–Alder Reactions of Tethered Enoate Substituted Furans Induced by Dialkylaluminum Chloride

Gold­(I)-catalyzed cycloisomerization of enynols 11 and 17, obtained by Sonogashira coupling, led to the tethered enoate-substituted furans 14 and 19. While attempts at thermal and several Lewis acid induced intramolecular Diels–Alder reactions remained fruitless, dialkylaluminum chloride led to the formation of hexahydroindene and octahydronaphthalene derivatives 20–23. Their formation can be explained by Lewis acid induced opening of the epoxy bridge with transfer of one alkyl group to the intermediate cycloadduct.