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Synthesis of poly(methylphenylsiloxane) rich in syndiotacticity by Rh‐catalysed stereoselective cross‐dehydrocoupling polymerization of optically active 1,3‐dimethyl‐1,3‐diphenyldisiloxane derivatives
Author(s) -
Oishi Motoi,
Moon JeongYeol,
Janvikul Wanida,
Kawakami Yusuke
Publication year - 2001
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/1097-0126(200101)50:1<135::aid-pi600>3.0.co;2-6
Subject(s) - phenylsilane , disiloxane , chemistry , triethylamine , tacticity , polymer chemistry , triad (sociology) , polymerization , nuclear magnetic resonance spectroscopy , carbon 13 nmr , catalysis , medicinal chemistry , polymer , organic chemistry , psychology , psychoanalysis
Cross‐dehydrocoupling reactions of ( R )‐methyl(1‐naphthyl)phenylsilane (>99%ee) with ( S )‐methyl(1‐naphthyl)phenylsilanol (>99% ee) proceeded with 82–99% retention of configuration of chiral silicon centres in the presence of various Rh‐catalysts. Cross‐dehydrocoupling polymerization of 1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane gave poly(methylphenylsiloxane) of moderate molecular weight in toluene at 60 °C in the presence of [RhCl(cod)] 2 (5.0 mol%) and triethylamine (1.0 equivalent). Assignment of the triad signals of the resulting polymer was made by 1 H NMR spectroscopy of the methyl proton ( I = 0.04, H = 0.09 and S = 0.14 ppm) and 13 C NMR spectroscopy of the ipso carbon of the phenyl group ( S = 136.7, H = 136.9, and I = 137.1 ppm). Although the reaction of optically pure ( S,S )‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane [( S , S ):( S , R ):( R , R )] = 84:16:0] gave a poly(methylphenylsiloxane) of rather low molecular weight, its triad tacticity was found to be rich in syndiotacticity ( S : H : I = 60:32:8) by 13 C NMR spectroscopy. © 2001 Society of Chemical Industry