Distinctive Chiral Conformations Induced to Poly (naphthalene-1,4-diyl) by Helix-sense-selective Polymerization and Circularly Polarized Light Irradiation.

Optically active poly(naphthalene-1,4-diyl) was prepared through helix-sense-selective polymerization of the corresponding monomers and also through circularly polarized light (CPL) irradiation, resulting in distinctive circular dichroism (CD) spectral patterns. Chirality of the helix-sense-selective polymerization -based polymer is ascribed to preferred-handed helicity while that of the CPL-based polymer to a non-helical, chiral conformation ('biased-dihedral conformation') with preferred-handedness which was stable only in the solid state. The helix of the helix-sense-selective polymerization-based polymer gradually racemized in tetrahydrofuran while it was stabilized by aggregate formation in a hexane-dichloromethane solution. Both helix-sense-selective polymerization- and CPL-based polymers exhibited efficient circularly polarized luminescence.

Application of Polysaccharide-Based Chiral High-Performance Liquid Chromatography Columns for the Separation of Regio-, E/Z-, and Enantio-Isomeric Mixtures of Allylic Compounds.

Daicel Chiralpak IA, IB, and IC, which are the polysaccharide-based chiral stationary phase (CSP) columns for high-performance liquid chromatography (HPLC), were applied in the separation of the non-enantiomeric isomeric mixtures obtained by the various allylation reactions and were highly effective in separating the regio- and (E)/(Z)-isomers in the allylation products. Due to the close structural similarity of the isomeric allylic compounds in the reaction mixtures, separations of the isomers are laborious and could not be accomplished by the conventional methods such as silica gel column chromatography, silica gel HPLC, preparative GPC, distillation, and so forth. This study has shown potential advantages of using the polysaccharide-based CSP columns in the separation of not only enantiomeric but also non-enantiomeric isomeric mixtures.

Diastereo- and Enantioselective Metathesis Dimerization/Kinetic Resolution of Racemic Planar-Chiral Vinylferrocenes.

Diastereo- and enantioselective kinetic resolution of racemic planar-chiral 1-R-2-vinylferrocenes (rac-1) was attained by the molybdenum-catalyzed asymmetric metathesis dimerization (AMD). Two sequential AMD reactions of rac-1a (R = Br) provided (E)-(S,S)-1,2-di(2-bromoferrocenyl)ethylene in >99% ee, which was converted to (S,S)-1,2-bis[(2-diphenylphosphino)ferrocenyl]ethane (S,S)-5. Planar-chiral bisphosphine (S,S)-5 coordinated to a dichloropalladium(II) fragment in a trans-chelating fashion, which was applied as a chiral ligand in the palladium-catalyzed asymmetric allylic alkylation showing enantioselectivity of up to 90% ee.