Chiral Triazole-Substituted\nIodonium Salts in Enantioselective\nHalogen Bond Catalysis

Herein, we present the synthesis of chiral triazole-based\ndiaryliodonium\nsalts and their application as monodentate asymmetric iodine(III)\nderivates in halogen bond (XB) catalyzed reactions. These potential\nLewis acids were successfully benchmarked in the vinylogous Mannich\nreaction of cyanomethyl coumarin with isatin-derived ketimine to obtain\nthe addition product in up to 99% yield and >99:1 e.r. Furthermore,\nthese halogen bond catalysts allowed an efficient functionalization\nof ketimines with various alcohols toward <i>N,O</i>-acetals\nin up to 99% yield and 90:10 e.r. Additionally, we studied the origin\nof the enantioselectivity based on density functional theory (DFT)\nand the catalyst crystal structure. These unveiled an approach of\nasymmetric induction facilitated by using σ-hole stabilized\nchiral moieties in iodine(III)-based catalysts, predominantly predicated\nupon XB activation.