手性铜(Ⅱ)-席夫碱配合物催化苯乙烯不对称环丙烷化反应

Twelve chiral copper(Ⅱ) Schiff base complexes, derived from (R) (+) 2 amino 1,1 diaryl 1 propanol with substituted salicylaldehydes, were examined as a catalyst for asymmetric cyclopropanation of styrene with ethyl diazoacetate. It was found that the substituents at 3 and 5 positions of salicylaldehyde in the ligands had great effects on catalytic activity and enantioselectivity of the catalyst. The complex with strong electron withdrawing group (NO 2) at 5 position and the smallest stereo hinder (H) at 3 position of salicylaldehyde showed highly catalytic activity and enantioselectivity, up to ee =87 4% for trans and ee =82 8% for cis isomers respectively, and the ratio 39/61 of cis to trans isomers was obtained at 40 ℃ with 1,2 dichloroethane as solvent.

Chiral Copper(Ⅱ)-Schiff Base Complexes as Catalysts for Asymmetric Cyclopropanation of Styrene

Twelve chiral copper(Ⅱ)-Schiff base complexes, derived from (R)-(+)-2-amin o-1,1-diaryl-1-propanol with substituted salicylaldehydes, were examined as a catalyst for asymmetric cyclopropanation of styrene with ethyl diazoacetate. I t was found that the substituents at 3- and 5- positions of salicylaldehyde in the ligands had great effects on catalytic activity and enantioselectivity of t he catalyst. The complex with strong electron-withdrawing group (NO2) at 5-p osition and the smallest stereo-hinder (H) at 3-position of salicylaldehyde sh owed highly catalytic activity and enantioselectivity, up to ee=87.4% for trans and ee=82.8% for cis isomers respectively, and the ratio 39/6 1 of cis to trans isomers was obtained at 40 ℃ with 1,2-dichloroethane as solvent.