Ru(II)/Chiral Carboxylic Acid-Catalyzed Asymmetric [4 + 3] Annulation of Sulfoximines with α,β-Unsaturated Ketones

Sulfur-stereogenic containing benzo-fused heterocycles
have gained
much attention in drug discovery. However, the asymmetric synthesis
of these chiral molecules with structural diversity is very challenging.
Herein, we report the synthesis of chiral benzothiadiazine-1-oxides
with a seven-membered ring via achiral Ru(II)-catalyzed asymmetric
[4 + 3] annulation of sulfoximines with α,β-unsaturated
ketones assisted by chiral carboxylic acid (CCA). A broad range of
chiral benzothiadiazepine-1-oxides bearing various functional groups
could be prepared in up to 90% yield with up to >99% ee, expanding the chemical space of chiral sulfoximines. Notably, the
oxidative cleavage of the double bonds in the products gave chiral N-benzoyl sulfoximines with a C–S chiral axis.