Asymmetric [3 + 2]/[4 + 2] annulations for the synthesis of ε-sultams promoted by bifunctional base catalysts

Abstract

Herein, we report a bifunctional hydrogen-bonding organocatalyst that enables the synthesis of chiral ε-sultams through two distinct annulation pathways: a [3 + 2] cycloaddition between seven-membered cyclic N-sulfonylimines and γ-hydroxy-α,β-unsaturated ketones (C–O bond formation) and a [4 + 2] cycloaddition employing 2-aminophenyl enones (C–N bond formation). This method proceeds under mild conditions with broad substrate compatibility, affording the corresponding products in good yields with excellent stereoselectivities.