Helix-Sense-Controlled Polymerization of Optically Active Phenyl Isocyanides

Abstract

A series of optically active phenyl isocyanides bearing various chiral functional groups, such as l-alanine, l-alaninol, l-phenylalanine, and l-lactic acid residues, with a long n-decyl chain as the pendants were prepared, and these were polymerized with an achiral nickel catalyst (NiCl2) in various organic solvents at different temperatures. The chiroptical properties and structures of the resulting helical polyisocyanides investigated by circular dichroism (CD) and IR spectroscopy revealed that the Cotton effect signs and intensities of the polyisocyanides, which correspond to their helical senses (right- or left-handed helix) and the excess of one helical sense, respectively, were significantly dependent on the pendant structures of the polymers and the polymerization conditions, such as the solvent polarity and temperature. The effect of the alkyl chain length of l-alanine-bound phenyl isocyanides on the helix-sense-controlled polymerization was also investigated.