Diethylzinc addition to imines

Dahmen and Erase demonstrated the first highly enantioselective diethylzinc addition to imines in the absence of other metal catalysts such as Ti, Zr, and Cu complexes (Scheme 4.46) [40]. A simple method that uses only a catalytic amount of chiral N,0-ligand (132) based on [2,2] paracyclophane without an additional central metal is notable. Although they used a specific N-protected a-(p-Ts)benzylamine (130) as the highly reactive N-protected imine precursor (133) via an in situ preparation, the reaction was catalyzed by only 2 mol% of (132) for various functionalized aromatic imines. While the corresponding Et adducts (131) were obtained in almost quantitative yields and excellent enantiomeric excesses, 3 equiv of diethylzinc was used. 

Zhang HL, Liu H, Cui X, Mi AQ, Jiang YZ, Gong LZ. Development of chiral catalysts by asymmetric activation for highly enantioselective diethylzinc addition to imines. Synlett 2005 (4) 615-618. 

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