Chirality induction in cyclocopolymerization. 14. Template effect of 1,2-cycloalkanediol in the cyclocopolymerization of bis(4-vinylbenzoate)s with styrene

A series of chiral 1,2-cycloalkanediols including (1S, 2S)-1,2-cyclopentane diol, (1S,2S)-1,2-cyclohexanediol, (1S,2S)-1,2-cycloheptanediol, and (1S,2S )-1,2-cyclooctanediol (a, b, c, and d) were used as chiral templates in the cyclocopolymerization of bis(4-vinylbenzoate)s (1a-d) with styrene. The co polymerizations of la with styrene produced an insoluble gel at a high mole fraction of la in the feed. On the other hand, the copolymerization of 1b- d with styrene proceeded homogeneously to yield polymers 2b-d, which were s oluble in chloroform and tetrahydrofuran. After the removal of the chiral t emplate from the resulting polymers 2a-d, polymers 3b-d exhibited optical r otations ([alpha](435), c 1.0, CHCl3) of -2.2 to -17.9 degrees whose signs were opposite to those of polymers 2b-d, while polymer 3a showed little or no optical activity. Hence, the efficiency of templates on the chirality in duction improved by expansion of the ring size of the chiral template; i.e. , 1a much less than 1b < 1c < 1d. The A values of the CD spectra of monomer s 1a-d related to the dihedral angle between two 4-vinylbenzoyl groups of t he monomers which decreased with increasing ring size. Therefore, the resul ts indicated that the dihedral angle affected the chiral inductivity of the template.