Optically-active polyurethanes containing coumarin dimer component: Synthesis,characterization, and chiral recognition ability

Optically-active polyurethanes ( 2a-2c ) were prepared by polyaddition reaction of diamide ( 1a, 1b ) and diester ( 1c ) derivatives of chiral coumarin dimer with 4,4′-diphenylmethane diisocyanate (MDI) in chloroform and methyl ethyl ketone, respectively. The inherent viscosity of the polyurethanes are between 0.13 and 0.21 dL/g in N,N-dimethylacetamide (DMAc) at 30°C. Treated silica gels were absorbed with ca. 25 wt % of the polyurethanes, and packed as chiral stationary phases for direct optical resolution of 16 racemates with aromatic groups by high-performance liquid chromatography (HPLC). Polyurethanes 2a and 2b , obtained from diamide derivatives, show efficient resolution ability to some of the racemates (α = 1.06-1.79), especially the atropic ( R5 ) and trans ( R6-R9 ) isomers. The recognition ability of the polyurethanes can be attributed to the simultaneous aromatic stacking and hydrogen-bonding interactions with racemates. © 1992 John Wiley & Sons, Inc.