Chirality induction in cyclopolymerization. VI. Enantioselective cationic cyclopolymerization of divinyl ethers with chiral 10-camphorsulfonic acid/zinc chloride initiating system
✍ Scribed by Osamu Haba; Makoto Obata; Kazuaki Yokota; Toyoji Kakuchi
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 708 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
SYNOPSIS
Cyclopolymerization of benzaldehyde divinyl acetal ( 1) and 1,2-divinyloxybenzene (4) was carried out using (+)-or (-)-camphorsulfonic acid [(+)-or (-)-2]/ZnCIZ initiating system. Polymer 3 obtained from monomer 1 consisted essentially of cyclic repeating units, whereas polymer 5 from 4 possessed a small amount of residual vinyloxy groups. Both polymers 3 and 5 using (+)-2 /ZnC12 showed optical activity with a negative sign of optical rotation. The molar optical rotation values of polymer 3 using ZnC12. OEt, were larger than those using ZnClz. The CD spectra of the polymer with [@]~!s = -30.10 (( -)-3) and (4S,6S)-4,6dimethyl-2-phenyl-1,3-dioxane showed a negative Cotton effect at 210 nm, whereas the polymer with [@]~~5= +24,10 ((+) -3)and (4R,6R)-4,6-dimethy l-2-phenyl-l,3-dioxane had mirror image CD curves with a positive Cotton effect at 210 nm. The absolute configurations of the major chiral cyclic units in (-)-and (+)-3 were the SS -and RR-forms, respectively.