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 organocatalysis 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.