Catalytic asymmetric Mannich reactions of imines with weakly acidic simple amides were developed using a chiral potassium hexamethyldisilazide (KHMDS)−bis(oxazoline) potassium salt (K-Box) catalyst system. The desired reactions proceeded to afford the target compounds in high yields with high diastereo-and enantioselectivities. It was suggested that a K enolate interacted with K-Box to form a chiral K enolate that reacted with imines efficiently. In this system, K-Box (potassium salt of Box) worked as a chiral ligand of the active potassium species.