Synthesis and Secondary Structure of Poly(1-methylpropargyl-N-alkylcarbamate)s

Abstract

3 (5) were synthesized and polymerized using (nbd)Rh þ [η 6 -C 6 H 5 B -(C 6 H 5 ) 3 ] (nbd = 2,5-norbornadiene) as a catalyst. Substituted cis-stereoregular polyacetylenes with moderate molecular weights were obtained in good yields. Poly[(R)-1], poly[(S)-1], poly[(S),(R) 0 -2], and poly[(S),(R) 0 -3] exhibited large optical rotations (|[R] D | = 344°-508°), clear CD signals (Δε = 4.8-7.0 M -1 cm -1) in CHCl 3 , and high viscosity indices (0.82-0.87), demonstrating the formation of helical structures with predominantly one-handed screw sense, which were stable up to 55 °C in the solvent. The solution state IR measurement confirmed the presence of intramolecular hydrogen bonding between the pendent carbamate groups of the polymers. Chiral amplification was observed in chiral/achiral [(S)-1/5] and R/S [(R)-1/(S)-1] copolymerizations. Conformational analysis revealed that the polymers adopt a tightly twisted helical conformation with a dihedral angle of 70°at the single bond on the main chain. The molecular mechanics calculation and X-ray diffraction measurement suggested that the diameter of the helix is 25 and 17 A ˚, respectively.

Helical poly(phenylacetylene)s containing schiff-base and amino groups: Synthesis, secondary structures, and responsiveness to benzoic acid

“…The magnitude of the CD signal reversibly recovered the original one by lowering the temperature. Similar results were observed with 2b and other helical polyacetylene derivatives including poly(1‐methylpropargyl‐ N ‐alkylcarbamate)s, poly(ethynylcarbazole), and poly(phenylacetylene)s . This is a characteristic of the dynamic helical conformation in polyacetylene derivatives …”

“…The magnitude of the CD signal reversibly recovered the original one by lowering the temperature. Similar results were observed with 2b and other helical polyacetylene derivatives including poly(1-methylpropargyl-N-alkylcarbamate)s, 40 poly(ethynylcarbazole), 41 and ARTICLE poly(phenylacetylene)s. 42 This is a characteristic of the dynamic helical conformation in polyacetylene derivatives. 1 Chiroptical Properties of the Polymers Containing Secondary Amino Groups As aforementioned, polymers containing free secondary amino groups, 2d and 2e, were successfully synthesized by the polymerization of the corresponding monomers.…”

Synthesis of End‐Functionalized Polyacetylenes that Contain Polar Groups by Employing Well‐Defined Palladium Catalysts

“…Synthesis of propargyl-N-hexylcarbamate (4): Compound 4 was synthesized according to a modified literature procedure. [60] A solution of propargyl alcohol (1.6 g, 29 mmol) and pyridine (2.9 g, 37 mmol) in CH 2 Cl 2 (40 mL) was added dropwise to a solution of p-nitrophenyl chloroformate (10.0 g, 50 mmol) in CH 2 Cl 2 (60 mL) at À50 8C and the resulting mixture was stirred at À50 8C for 14 h. Then, the mixture was washed successively with aqueous solutions of NaHCO 3 and NaCl. The organic phase was separated, dried over anhydrous MgSO 4 , filtered, and concentrated on a rotary evaporator.…”

Polymerization of substituted acetylenes and features of the formed polymers

“…113,114 Poly(1-methylpropargyl-N-alkylcarbamate)s (39, Chart 16) utilize intramolecular N-H/O]C hydrogen bonding in addition to the steric repulsion between the methyl groups adjacent to the main chain. 115 The polymers form a pseudohexagonal columnar structure by self-assembly or self-organization in the solid state. Thus, chiral 1-methylpropargyl alcohol is a simple but extremely powerful and useful helical source for substituted polyacetylenes.…”