Copper Complexes of Chiral Tetradentate Binaphthyl Schiff-Base Ligands: Syntheses, X-ray Crystal Structures and Activity in Catalytic Asymmetric Cyclopropanation of Alkenes

摘要

A number of new chiral monomeric binaphthyl Schiff-base ligands H_2L [where H_2L = 2,2'-bis(3-R~1-5-R~2-2-hydroxyben-zylideneamino)-1,1'-binaphthyl] and a series of chiral copper(II) complexes [CuL] were prepared in good or nearly quantitative yields. Some of the free ligands and the [CuL] complexes were structurally characterized by X-ray crystallography. Almost all the [CuL] complexes were found to be active ctatlysts for the asymmetric cyclopropanation of al-kenes with ethyl or tert-butyl diazoacetate. Enantioselectivities of up to 77% ee were observed.