Organocatalytic\nEnantioselective Synthesis of [5.7]-Fused\nε‑Sultam <i>N</i>,<i>O</i>‑Heterocycles\nvia (3 + 2)-Annulation of Seven-Membered Cyclic <i>N</i>‑Sulfonylimines with γ‑Hydroxy-α,β-Unsaturated\nKetones

A highly stereoselective protocol for the (3 + 2)-annulation\nof\nbiphenyl-bridged seven-membered cyclic <i>N</i>-sulfonylimines\nwith γ-hydroxy-α,β-unsaturated ketones was developed.\nThe reactions afforded a wide range of chiral [5.7]-fused ε-sultams\nbearing N-adjacent 1,3-stereocenters in excellent yields (93–98%\nyields) and high enantio/diastereoselectivities (up to >99% ee,\n>20:1\nd.r.) and two other examples with alkoxyl groups were obtained in\n52–61% yields, 95% ee, and >20:1 d.r. by utilizing organocatalysis\nwith quinine-derived squaramides.