Asymmetric Mannich-Type Reaction in Aqueous Media

Significance

An asymmetric Mannich-type reaction of an α-hydrazono ester with silyl enol ethers in aqueous media afforded α-hydrazino esters in excellent enantioselectivity in the presence of a catalytic amount of ZnF₂ and a chiral diamine ligand. The reaction proceeded through a dual activation of the electrophile and nucleophile by the Lewis acid Zn(II) and the Lewis base F^-, respectively. The reaction is stereospecific since the Z-enol ether produces the syn product, while the E-enol ether produces the anti product.