Synthesis and Polymerization of Optically Active N ‐Propargylphosphonamidates: A Novel Helical Polymer Carrying a P‐Chiral Center

Summary: A diastereomeric pair of novel N ‐propargylphosphonamidates, HCCCH 2 NHP(O)(CH 3 )O‐ L ‐menthyl was synthesized by the successive condensations of methylphosphonic dichloride with L ‐menthol and propargylamine. The ( R )‐P‐isomer ( 1a ) was isolated, and the absolute configuration was determined by XRD. Polymerization of 1a , and a mixture of 1a and ( S )‐P‐isomer ( 1b ) was carried out with a zwitterionic Rh complex as a catalyst. cis ‐Stereoregular polymers with number‐average molecular weights of 5 600–9 800 were obtained in good yields. Poly( 1a ) and poly( 1a 29 ‐ co ‐ 1b 71 ) exhibited large specific rotations (+408 and −146°), and intense Cotton effects ([ θ ] = +2.25 and −0.9 × 10 4 deg · cm 2  · dmol −1 ) based on the conjugated polyacetylene backbone around 325 nm in CHCl 3 , indicating that these polymers have helical structures, whose predominant helical senses are opposite.Polymerization of N ‐propargylphosphonamidate.