Ligand-Promoted Palladium-Catalyzed [4 + 4] Cycloaddition Affording Benzo[ d ]isothiazole 1,1-Dioxide-Fused Chiral Eight-Membered N -Heterocycles

Synthesis of chiral eight-membered rings with high regioselectivity and stereoselectivity has been a great challenge in asymmetric catalysis. There is no report on the synthesis of benzo[d]isothiazole 1,1-dioxide-fused chiral eight-membered N-heterocycles thus far. Herein, we report a palladium-catalyzed asymmetric [4 + 4] cycloaddition of 3-styryl-1,2-benzoisothiazole 1,1-dioxides with γ-methylidene-δ-valerolactones at room temperature providing highly functionalized benzo[d]isothiazole 1,1-dioxide-fused chiral eight-membered N-heterocycles in high yields with excellent diastereoselectivity and enantioselectivity (76-89% yields, >20:1 dr, and 84-99% ee), in which the optimization of adjustable axially chiral cyclic phosphoramidite ligands developed by us is crucial for reactivity of the substrates and stereoselectivity of the products. Further modification of the synthesized products afforded other chiral eight-membered N-heterocycles containing a benzo[d]isothiazole 1,1-dioxide unit.