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 C 2 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.