Asymmetric Counteranion-Directed Halogen Bonding Catalysis

Halogen bonding has been established as a promising tool in organocatalysis. Asymmetric processes are nevertheless scarce, and their applications are limited to a few studies applying chiral halogen bond donors. Herein, we combine halogen bonding with asymmetric counteranion-directed catalysis, providing the first highly enantioselective example of such an approach. A strong bidentate iodine(III)-based catalyst with chiral disulfonimides as counteranions is applied in the first asymmetric organocatalysis of the Diels–Alder reaction between cyclopentadiene and trans-β-nitrostyrene, the key step in the synthesis of the drug fencamfamine, which was prepared with high enantioselectivity.