Design and synthesis of chiral poly(binaphthyl salen zinc complex) and application of the asymmetric field based on its helical conformation to a catalytic asymmetric reaction

According to a rational design of helices (i.e., fusing C2 chiral binaphthyl units and metallosalen complexes inevitably results in the formation of helical polymers), chiral poly(binaphthyl salen zinc complex)es (3-Zn) were synthesized from an (R)-3,3′-diformylbinaphthol derivative, α,ω-diamines, and zinc acetate or diethylzinc. Their helical structures were well supported by their infrared, ultraviolet, and circular dichroism spectra, in addition to MM calculations and a CPK model study. The catalysis of 3-Zn during the asymmetric addition of diethylzinc to aldehydes was investigated. In the presence of 5 unit mol % 3-Zn, diethylzinc reacted with benzaldehyde to yield 1-phenyl-1-propanol in high yields (∼100%) and with high enantioselectivity (∼95%). The asymmetric yield of 1-phenyl-1-propanol increased significantly as the temperature was lowered, whereas both the asymmetric yield and the absolute configuration were drastically changed as the structure of the diamine unit of 3-Zn was varied. Several aromatic aldehydes were converted into their corresponding alcohols with high enantioselectivity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4693–4703, 2004