Chiral Phosphoric Acid-Catalyzed Addition of Thiols to <i>N</i>-Acyl Imines: Access to Chiral <i>N</i>,<i>S</i>-Acetals

The first catalytic asymmetric method to prepare enantioenriched N,S-acetals using chiral BINOL phosphoric acids is reported. The reaction combines N-acyl imines with thiols to generate products in excellent yield and enantioselectivity. The addition reaction could also be achieved with an exceptional substrate to catalyst (S/C) molar ratio. Electron-rich and electron-deficient aromatic N-acyl imines, as well as a broad range of aliphatic and aromatic thiols, showed excellent reactivity.