Asymmetric Catalytic Diverse Ring Opening/Cycloadditions of Cyclobutenones with (E)‑Alkenyloxindoles and (E)‑Dioxopyrrolidines

Highly enantioselective ring-opening/cycloaddition reactions of cyclobutenones were achieved by employing chiral N,N′-dioxide/metal complexes as the catalysts. The Diels–Alder type cycloaddition with (E)-alkenyloxindoles yielded spirocyclohexaneoxindoles with excellent results. Meanwhile, a hetero-Diels–Alder process occurred with (E)-dioxopyrrolidines to afford spiropyrrolidinone-dihydropyranone derivatives.