Effect of Lithium Compounds on the SN2 Reaction of Anionic Living Polyisoprene with 4-Bromobutoxy-tert-butyldimethylsilane in Heptane
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The additive effect of lithium tetrahydrofurfuryloxide (<b>LiTHF</b>) and alkyl lithium on the nucleophilic substitution reaction of anionic living polyisoprene with 4-bromobutoxy-<i>tert</i>-butyldimethylsilane (<b>BBS</b>) in heptane was investigated.<br>When <b>BBS</b> was allowed to react with polyisoprenyllithium in heptane in the absence of any additives, considerable amount of dimeric polymers as well as aimed end-functionalized polymer were formed via lithium-halogen exchange followed by the homo coupling of the polymers. Degree of the dimer formation was dramatically suppressed when the reaction was carried out in the presence of <b>LiTHF</b>. Quantitative introduction of silyl-protected hydroxy group was achieved when the reaction was carried out in heptane at 0°C in the presence of <b>LiTHF</b> (5 eq to active chain end). Similar additive effect was observed for <i>n</i>-butyllithium whereas no such an effect was observed for <i>sec</i>-butyllithium.<br>The cross-association of these lithium compounds with the active chain end of anionic living polyisoprene might have prevented the homo coupling of the polymers.
- e-Journal of Soft Materials
e-Journal of Soft Materials (6), 1-8, 2010
THE SOCIETY OF RUBBER SCIENCE AND TECHNOLOGY, JAPAN