Chiral 1-methylpropargyl alcohol: A simple and powerful helical source for substituted polyacetylenes

(S)- and (R)-1-methylpropargyl alcohols [(S)-1 and (R)-1] and their ester derivatives (S)- and (R)-1-methylpropargyl hexanoates [(S)-2 and (R)-2] were polymerized using (nbd)Rh+[eta(6)-C6H5B-(C6H5)(3)] as catalyst to afford the corresponding substituted polyacetylenes with moderate molecular weights in good yields. The polymers possessed cis-stereoregular structures according to H-1 NMR. Large optical rotations and clear CD signals demonstrated that these polymers took a helical structure with predominantly one-handed screw sense, stabilized by steric repulsion between the side chains containing chiral groups adjacent to the main chain.