One‐Handed Helical Polyacetylenes Bearing Axially‐Chiral 2‐Arylpyridyl‐<i>N</i>‐Oxide Units for Efficient Chromatographic Enantioseparation of Chiral Aromatic and Aliphatic Alcohols
Tomoyuki Ikai, Masaki Ito, Kosuke Oki, Nozomu Suzuki, Eiji Yashima
Abstract
A series of poly(biarylylacetylene)s (PBAs) bearing axially-chiral (S)-and (R)-pyridyl-N-oxide residues with a methoxy, propoxy, or acetyloxy substituent at the 3-position of the biaryl units was synthesized. All the PBAs formed a preferred-handed helix, while the helical sense preference was varied depending on the substituents despite the same twist-sense of the biaryl units. Among them, the propoxy-bound helical PBA showed an exceptionally high chiral recognition ability as a chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) and efficiently resolved not only various chiral aromatic alcohols, but also a variety of chiral aliphatic alcohols; the latter still remains difficult to resolve by commercially-available CSPs in HPLC. Such practically-useful both handed helical PBA-based CSPs can be produced from the racemic PBA composed of fully racemic monomer units through deracemization of the biaryl units with a chiral alcohol.