- Nouveaux polycarbosilanes modeles. 3-Synthese et caracterisation de car0osilanes lineaires fonctionnels
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A method for synthesizing novel linear polysilmethylenes of general formula Me(HMeSiCH2)xSiMe2H (VIIx) is described.This strategy involves the cocondensation of chloromethylsilanes HMe2Si(CH2SiMeH)mCH2Cl (m=0 or 1) with methyldichlorosilane and 1,3-dichloro-1,3-dimethyl-1,3-disilapropane, respectively, by Grignard reactions.Thus, short chain polycarbosilanes possessing terminal dimethylhydrogensilyl groups were prepared (2x5).They were then converted into the corresponding chlorinated derivatives Me(ClMeSiCH2)xSiMe2Cl (VIIIx) by reaction with CCl4 in the presence of a palladium catalyst.The mass spectra (70 eV) of both series reveal that characteristic fragmentation occur.Moreover, the SiH-containing derivatives VIIx exhibit analogous behavior during their rearrangement under electronic impact and during their pyrolysis.
- Bacque, E.,Pillot, J.-P.,Birot, M.,Dunogues, J.,Bourgeois, G.
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- Asymmetric Synthesis of N-Boc-(R)-Silaproline via Rh-Catalyzed Intramolecular Hydrosilylation of Dehydroalanine and Continuous Flow N-Alkylation
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An asymmetric synthesis of a silicon-containing proline surrogate, N-Boc-(R)-silaproline (1), is described. Starting from N-Boc-dehydroalanine ester, deprotonation, followed by N-alkylation with chloromethyldimethylsilane under flow conditions, afforded the N-alkylated product 8 in 91% yield. An unprecedented enantioselective (NBD)2RhBF4/Josiphos 404-1 catalyzed 5-endo-trig hydrosilylation afforded the silaproline ester in 85-90% yield and >95% ee. Subsequent saponification and salt formation upgraded 1 to >99% ee.
- Chung, John Y. L.,Shevlin, Michael,Klapars, Artis,Journet, Michel
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supporting information
p. 1812 - 1815
(2016/05/19)
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- Cyclic silylated onium ions of group 15 elements
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Five- and six-membered cyclic silylated onium ions of group 15 elements I were synthesized by intramolecular cyclization of transient silylium ions II. Silylium ions II were prepared by the hydride transfer reaction from silanes III using trityl cation as hydride acceptor. It was found that smaller ring systems could not be obtained by this approach. In these cases tritylphosphonium ions IV were isolated instead. Cations I and IV were isolated in the form of their tetrakispentafluorphenyl borates and characterized by multinuclear NMR spectroscopy and, in two cases, by X-ray diffraction analysis. Cyclic onium ions I showed no reactivity similar to that of isoelectronic intramolecular borane/phosphane frustrated Lewis pairs (FLPs). The results of DFT computations at the M05-2X level suggest that the strength of the newly formed Si-E linkage is the major reason for inertness of I[B(C6F5)4] versus molecular hydrogen.
- Reissmann, Matti,Sch?fer, Andr,Panisch, Robin,Schmidtmann, Marc,Bolte, Michael,Müller, Thomas
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p. 2393 - 2402
(2015/03/18)
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- SILICON CARBIDE PRECURSOR
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The compound 2,4,6-trimethyl-2,4,6-trisila heptane, the preparation thereof, and the use thereof as a silicon carbide precursor in chemical vapor deposition and infiltration procedures are disclosed.
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- Synthesis of silicon analogues of acyclonucleotides incorporable in oligonucleotide solid-phase synthesis
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The synthesis of the four silicon analogues of acyclonucleosides was described. In every case, the silicon atom was introduced onto an allyl group on the natural nucleobase following a hydrosilylation reaction. Diols obtained were protected as 4,4'-dimethoxytrityl ethers and subsequently activated as 2-cyanoethyl N,N-diisopropylchlorophosphoramidite in order to be suitable for oligonucleotide solid phase synthesis.
- Thibon, Jacques,Latxague, Laurent,Deleris, Gerard
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p. 4635 - 4642
(2007/10/03)
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- Synthesis of silicon precursors of modified oligonucleotides
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The synthesis of four silicon nucleoside analogues for use as modified antisense oligonucleotide precursors, is described.
- Latxague, Laurent,Thibon, Jacques,Guillot, Christel,Moreau, Serge,Deleris, Gerard
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p. 5869 - 5872
(2007/10/02)
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- (Thioacetoxy-S-methyl)diorganylsilane und (Mercaptomethyl)diorganylsilane: Synthese und Eigenschaften
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The novel synthesis of the (thioacetoxy-S-methyl)diorganylsilanes (CH3)2Si(H)CH2SC(O)CH3 (9) and (C6H5)2Si(H)CH2SC(O)CH3 (10) and the (mercaptomethyl)diorganylsilanes (CH3)2Si(H)CH2SH (11) and (C6H5)2Si(H)CH2SH (12) is described.The silanes 11 and 12 are easy to handle, whereas the structurally analogous (hydroxymethyl)diorganylsilanes (CH3)2Si(H)CH2OH (1) and (C6H5)2Si(H)CH2OH (2) tend to undergo a base-catalyzed decomposition (formation of oligomeric (polymeric) alkoxysilanes and hydrogen).In contrast to the thermally unstable (acetoxymethyl)diorganylsilanes (CH3)2Si(H)CH2OC(O)CH3 (3) and (C6H5)2Si(H)CH2OC(O)CH3 (4) ( -> rearrangement to the corresponding acetoxy(methyl)diorganylsilanes (CH3)3SiOC(O)CH3 (5) and CH3(C6H5)2SiOC(O)CH3 (6)), the thio-analogues 9 and 10 are thermally stable (1 molar solutions in C6D6, 30 h at 180 deg C).
- Tacke, Reinhold,Becker, Beate,Lange, Hartwig
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- Synthetic Pathways to Simple Di- and Trisilylmethanes: Potential Starting Materials for the CVD Deposition of Amorphous Silicon a-SiC:H
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Methods for the preparation of simple silaalkanes with a high content of silicon and hydrogen have been explored.Target molecules, like H3SiCH2SiH3 and HC(SiH3)3, may serve as precursor molecules for the production of photovoltaic elements through thermal or discharge (plasma) CVD processes.Among a variety of synthetic pathways, the reactions between HSiCl3 and HCCl3 in the presence of an amine (Benkeser reaction) and the direct synthesis from silicon and polychloromethanes proved most promising for large scale preparations.The CH2X2/KSiH3 metathesis is most useful on the laboratory scale. - The Grignard synthesis was employed for partly methylated homologues, like H3SiCH2SiH2CH3, H3SiCH2SiH(CH3)2, H3SiCH2Si(CH3)3, and related molecules.The magnesium reduction of CHBr3/SiCl4 and CHBr3/CH3SiCl3 mixtures serves best for the preparation of HC(SiCl3)3, which can be converted into HC(SiH3)3 using LiAlH4.Attempts to synthesize tetrasilylmethane via the same route, C(SiH3)4, led only to the formation of HC(SiH3)3. - Key words: Amorphous Silicon a-SiC:H, Disilylmethane, Trisilylmethane, Direct Synthesis, Polysilylmethanes
- Schmidbaur, Hubert,Ebenhoech, Jan
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p. 1527 - 1534
(2007/10/02)
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