- Selective synthesis of halosilanes from hydrosilanes and utilization for organic synthesis
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Selective synthesis of halosilanes has been examined. Various types of halosilanes and halohydrosilanes, such as R3SiX, R2SiHX, R2SiX2, RSiH2X, RSiHX2 (X=Cl, Br, F), were obtained by the reactions of the corresponding hydrosilanes with Cu(II)-based reagents selectively in high yields. This method could be also applied to the synthesis of chlorofluorosilanes and chlorohydrogermanes. On the other hand, iodo- and bromosilanes and germanes were obtained by Pd- or Ni-catalyzed hydride-halogen exchange reactions of hydrosilanes with alkyl or allyl halides. Their synthetic applications have been demonstrated by using iodo- and bromosilanes and chlorofluorosilanes.
- Kunai, Atsutaka,Ohshita, Joji
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- Nucleophilic fluorination of alkoxysilane with alkali metal salts of perfluorinated complex anions. Part 2
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Alkali metal salts of perfluorinated complex anions have been used to effect nucleophilic fluorination of alkyl-, arylalkyl- and arylalkoxy-silanes both in the presence and absence of solvent. Near-quantitative yields of fluorinated silanes are obtained using equimolar quantities of fluoride ion equivalents and alkoxysilanes. In certain cases, intermediate organoboron and organophosphorus compounds derived from the corresponding complex anions and alkoxysilanes are identified in the reaction mixtures, and based on these intermediates a mechanism of reaction has been proposed.
- Farooq, Omar
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p. 661 - 665
(2007/10/03)
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- Nucleophilic fluorination of alkoxysilane with alkali metal hexafluorophosphate 1 - part 1
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Alkali metal hexafluorophosphates were used to effect nucleophilic fluorination of a few selected alkoxysilanes both in the presence and absence of polar solvents. Near-quantitative yields of fluorinated silanes were obtained using both alkoxy-equivalent of the complex salt and fluoride equivalents of alkoxysilanes. Some of the intermediate fluorosilanes and fluorophosphorus compounds were identified and the mechanism of fluorination is proposed.
- Farooq, Omar
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p. 189 - 197
(2007/10/03)
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- Anion complexation by bidentate Lewis acidic hosts, ortho-bis(fluorosilyl) benzenes
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Ortho-bis(fluorosilyl)benzenes, precursors for bis-siliconates, o-C6H4(SiPhF2)2 (1), o-C6H4(SiF3)(SiPh2F) (2) and o-C6H4(SiPhF2)(SiPh2F) (3), possess anion binding properties as bidentate Lewis acidic hosts in organic solvents. Compound 1 quantitatively binds a fluoride ion from KF suspended in acetone or tetrahydrofuran without support of 18-crown-6 to form the corresponding soluble bis-siliconate [o-C6H4(SiPhF2)2F]K (4). The binding constants of a series of fluorosilanes for a fluoride ion are measured by 1H and 19F NMR spectroscopies. The affinity of fluorosilanes towards a fluoride ion increases in the order PhMeSiF2 (7) 2SiF2 (9) 1.1 × 109 M-1 at 193 K. These bidentate Lewis acids 1-3 are among the strongest organic hosts for a fluoride ion in organic solvents ever reported.
- Tamao, Kohei,Hayashi, Takashi,Ito, Yoshihiko
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- Reactions of Lithio-aminofluorosilanes with Covalent Element Halides
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Halides of boron, germanium, phosphorus, and arsenic react with lithio-aminofluorosilanes (1a-e) with elimination of lithium halide and substitution (to 2a, b, 3c, 4b, 5b, 5d, 6b).Depending on the bulkiness of the substituents and the reaction conditions, halosilanes are also cleaved off and four-membered rings (8d, 10b, 11b, 13b, 14b) are formed.The reaction of 1e with (Me3Si)2NPF2 leads to the formation of the aminoiminophosphane 9e.A 1,3-migration of a silyl group from the alkyl- to the arylamino-nitrogen is observed in this reaction. 5d reacts with lithiated (2,4,6-trimethylphenyl)(trimethylsilyl)amine to give 15d and LiF.The aminoiminophosphane 16d is obtained by thermal difluorosilane elimination from 15d.An aminoiminodifluorophosphane (12b) is formed in the reaction of 1b with PF5, isobutene, tert-butyldifluorophenylsilane, and LiF being claved off.
- Neemann, Jutta,Klingebiel, Uwe
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p. 527 - 535
(2007/10/02)
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- USE OF SbF5 INTERCALATED IN GRAPHITE AS FLUORINATING REAGENT IN ORGANO-SILICON AND -GERMANIUM CHEMISTRY
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The use of SbF5 intercalated in graphite as fluorinating reagent of organo-silicon and -germanium derivatives is described.While Si-O and Si-Cl bonds are readily cleaved, Si-H and Si-S bonds are only reactive in bifunctional silanes.Ge-X bonds (X=Br, Cl, OR, H) are unreactive.Allyl-silicon and allyl-germanium bonds are broken under mild conditions and in high yields, leading to the corresponding fluorosilane or fluorogermane.With bifunctional silanes, it is always possible to obtain the difluorinated derivatives.
- Corriu, R.J.P.,Fernandez, J.M.,Guerin, C.
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p. 347 - 352
(2007/10/02)
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