Chirality induction in cyclopolymerization, 5. Template effect of chiral acyclic 1,2‐glycols on the cyclo‐copolymerizations of (S)‐1,2‐propanediyl and (2S,3S)‐2,3‐butanediyl bis(4‐vinylbenzoate)s with styrene

Abstract

AbstractThe copolymerizations of (S)‐1,2‐propanediyl and (2S,3S)‐2,3‐butanediyl bis(4‐vinyl‐benzoate)s (2a and 2b) (M1) with styrene (M2) were carried out using 2,2′‐azoisobutyronitrile in toluene at 60 °C. For the cyclocopolymer 3, the extent of cyclization of 3b is higher than that of 3a. The monomer reactivity ratios are r1 = 8.34 and r2 = 0.27 for 2a and r1 = 6.82 and r2 = 0.19 for 2b. The specific rotation ([α] in deg · dm−1 · g−1 · cm3 c = 1.0 g · dL−1; CHCl3) changes from +230 to +176 for 3a and from +319 to +150 for 3b. After removing the chiral templates, the resulting poly[(methyl 4‐vinylbenzoate)‐co‐styrene]s showed a specific rotation ([α] in deg · dm−1 · g−1 · cm3 c = 1.0 g · dL−1; CHCl3) of −2 for 4a and of −8 for 4b, indicating that the (2S,3S)‐2,3‐butanediyl template shows a higher ability to cause asymmetric induction by comparison with the (S)‐1,2‐propanediyl one. A split Cotton effect due to the positive chirality was observed in the CD spectrum of 2 and the reversed one for 4. According to the CD exciton chirality method, the clockwise‐twist of two 4‐vinylbenzoate for 2 transmitted its chirality to 4 in which two 4‐vinylbenzoyl groups are twisted counterclockwise, i. e., an (R,R)‐configuration of vicinal (methyl 4‐vinylbenzoate) units in the main chain.