Studies toward the Total Synthesis of Axinellamine and Massadine

Intramolecular Diels−Alder reactions of several N−O linked 4-vinylimidazole dimers provide the expected adduct in moderate to good yield as
a single, all trans stereoisomer, along with smaller amounts of the inverse electron demand adduct. Oxidative rearrangement of the cycloadducts
occurs on treatment with Davis' reagent, providing a single spiro imidazolone in good yield and with excellent levels of stereocontrol albeit
epimeric at the spiro center found in axinellamine and massadine.