Cross-Linkable Carbosilane Polymers with Imbedded Disilacyclobutane Rings Derived by Acyclic Diene Metathesis Polymerization
摘要:
Cyclolinear carbosilane polymers with disilacyclobutane (DSCB) rings in the main-chain structure were prepared by means of acyclic diene metathesis (ADMET) polymerization of the corresponding 1,3-dibutenyl-1,3-disilacyclobutanes. The copolymerization of a monomer of this type with a noncyclic organosilane diene allowed for the incorporation of a varying number of DSCB rings into the polymer backbone. Subsequent hydrogenation of the double bonds with p-toluenesulfonhydrazide resulted in a saturated hydrocarbon structure in the main chain without affecting the DSCB ring. All of the resultant polymers are well-defined materials with DSCB rings incorporated into the backbone structure, as evidenced by NMR spectroscopy and GPC analyses. The thermal behavior of these polymers was characterized by DSC and TGA. DSC indicated low T(g)s, and TGA evidenced high thermal stability in an inert atmosphere. In addition, large exothermic peaks were observed in the DSC, which indicated, along with the IR and solid-state Si-29 NMR spectra, that cross-linking occurs during heating to ca. 250 degreesC via opening of the imbedded DSCB rings. The swelling properties of the resultant, thermally stable, carbosilane network materials on exposure to various solvents were also examined.
Pentacoordinate hydrochlorosilanes with lactamomethyl ligand
作者:Vadim A. Pestunovich、Svetlana V. Kirpichenko、Natal’ya F. Lazareva、Aleksander I. Albanov、Mikhail G. Voronkov
DOI:10.1016/j.jorganchem.2007.01.035
日期:2007.5
The synthesis and reaction behavior of pentacoordinate hydrochlorosilanes LCH2SiRHCl (L- 2-piperidonyl ligand, R = Me, Ph, Bn) are described. The intramolecular O–Si and N–Si coordination is discussed on the basis of the NMR data. The strength of the O–Si coordinate bond is nearly the same for chelates 5, 6, 8 irrespective of the equatorial substituent R at the silicon atom. However, the nature of
The enantioselective construction of silicon-stereocenter by asymmetric enamine catalysis is reported. The reaction proceeds via an unprecedented desymmetric intramolecular aldolization of prochiral siladials for the diverse synthesis of multifunctional silicon-stereogenic silacycles.