Synthesis and Polymerization of an Optically Active Bifunctional Disiloxane. 2. Preparation of Optically Active (S)-2-(1-Naphthyl)-2-phenyl-5,5-dimethyl-1-oxa-2,5-disilacyclopentane and Its Ring-Opening Polymerization

An optically active (>98.2% ee) five-membered cyclic silicon compound, ( S )-2-(1-naphthyl)-2-phenyl-5,5-dimethyl-1-oxa-2,5-disilacyclopentane, was synthesized by intramolecular hydrosilylation of (1 S )-1-(1-naphthyl)-1-phenyl-1-vinyl-3,3-dimethyl-3-hydro-1,3-disiloxane in good yield (as high as 74.3%). This cyclic compound could be easily polymerized by common nucleophilic initiators, such as PhLi, MeONa, and t -BuOK. The polymerization using the lithium initiator showed a very high regioselectivity in ring opening (head-to-tail content 98.7% at 0 °C) and consequently afforded an optically active and highly isotactic poly[{(1 S )-1-(1-naphthyl)-1-phenyl-3,3-dimethyldisiloxane-1,3-diyl}ethylene] ([α] 25 D = − 8.5°, M n = 20 800 (calculated from 29 Si NMR), M w / M n = 1.12 (by SEC)).