Hauser–Kraus Annulation of Phthalides with Nitroalkenes for the Synthesis of Fused and Spiro Heterocycles

Abstract

Hauser–Kraus annulation of sulfonylphthalides with simple conjugated nitroalkenes follows the expected pathway to furnish naphthoquinones in moderate yields. However, a strategic variation of this reaction by employing nitroalkenes bearing an additional nucleophilic site results in [4+4] annulation leading to complex fused and spiro heterocycles in high yields with high selectivity through a cascade process involving Michael addition, Dieckmann cyclization, and a series of eliminations and rearrangements.