ma020320y_si_001.pdf (15 kB)
Conformational Study of Poly(N-propargylamides) Having Bulky Pendant Groups
journal contribution
posted on 2002-06-04, 00:00 authored by Junichi Tabei, Ryoji Nomura, Toshio MasudaN-Propargylamides having chiral centers at the α-carbon of the amide groups, 1−3, were
polymerized with (nbd)Rh+[η6-C6H5B-(C6H5)3] to afford polymers with moderate molecular weights (Mn
= 6000−32 000) in good yield. The 1H NMR spectra demonstrated that the polymers have stereoregular
structures (cis = 100%). The polymers were proven to take a helical conformation with an excess of one-handed screw sense in CHCl3, which was supported by their intense CD effects and large optical rotations.
It was confirmed that the helical structure was stabilized not only by the steric repulsion but also by the
intramolecular hydrogen bonds between the pendant groups. CD spectroscopic study showed that the
helical structure is more stable than that of the polymers without a branch at the α-position, which
allowed the polymers to exist in the helical state in various solvents. The electronic absorption, CD effects,
and optical rotations of the polymers closely correlated to the extent of the hydrogen bonding between
the pendant amide groups.