Intramolecular Diels-Alder Reaction of a Silyl-Substituted Vinylimidazole en Route to the Fully Substituted Cyclopentane Core of Oroidin Dimers.

An intramolecular Diels-Alder reaction of a silyl-substituted vinylimidazole delivers a diastereomeric mixture of C4-silyl functionalized dihydrobenzimidazoles. Subsequent diastereoselective reduction and elaboration of the lactone gives rise to a polysubstituted tetrahydrobenzimidazole, which, upon oxidative rearrangement, affords a single spirofused imidazolone containing all of the relevant functionality for an approach to the oroidin dimers axinellamine, massadine, and palau'amine.