Steric Effect of Protonated Tertiary Amine in Primary-Tertiary Diamine Catalysis: A Double-Layered Sterimol Model.

Steric shielding effects are seldom adopted in the stereocontrol with chiral primary amine catalysts. An unexpected steric shielding effect of protonated tertiary amine, a typical hydrogen-bonding moiety, was disclosed. A linear free energy relationship between structure and enantioselectivity was established in three reactions when a double-layered Sterimol model was introduced.