Regio- and Stereospecific 1,4-Polymerization of 2-(Triethylsilyl)-1,3-butadiene

摘要

There is considerable interest in stereoregular polymerization of 1,3-diene monomers. Anionic polymerization of isoprene initiated by alkyllithium reagents in hydrocarbon solvents such as cyclohexane yields polyisoprene of narrow molecular weight distribution whose microstructure has been shown by IR, 1H NMR, and 13C NMR to be predominantly cis-1,4 (approx. 80%). However, appreciable amounts of trans-1,4 (approx. 15%) and 3,4 (approx. 5%) units are also present. Anionic polymerization of isoprene in the presence of donor solvents such as ether and THF leads to a polymer whose microstructure is predominantly 3,4 (approx. 60%). Thus, the anionic polymerization of isoprene is regio- and stereoselective but neither regio- nor stereospecific.