- Reactions of [Cu(X)(BPEP-Ph)] (X = PF6, SbF6) with silyl compounds. Cooperative bond activation involving non-coordinating anions
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Bond activation of silyl compounds, assisted by the cooperative action of non-coordinating anions, is achieved using Cu(i) complexes coordinated with a PNP-pincer type phosphaalkene ligand, [Cu(X)(BPEP-Ph)] (X = PF6 (1a), SbF6 (1b); BPEP-Ph = 2,6-bis[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine). Complexes 1a and 1b react with Me3SiCN to form Me3SiF and Cu(i) cyanide complexes of the formula [Cu(CN-EF5)(BPEP-Ph)] (E = P (2a), Sb (2b)), in which the CN ligand is associated with the EF5 group arising from EF6-. Formation of the intermediary isonitrile complex [Cu(CNSiMe3)(BPEP-Ph)]+SbF6- (3b) is confirmed by its isolation. Thus, a two-step reaction process involving coordination of Me3SiCN, followed by nucleophilic attack of SbF6- on the silicon atom of 3b is established for the conversion of 1b to 2b. Complex 1b cleaves the H-Si bond of PhMe2SiH as well. The isolation and structural identification of [Cu(BPEP-Ph)]+BArF4- (1c) (BArF4 = B{3,5-(CF3)2C6H3}4) as a rare example of a T-shaped, three-coordinated Cu(i) complex is reported.
- Nakajima, Yumiko,Tsuchimoto, Takahiro,Chang, Yung-Hung,Takeuchi, Katsuhiko,Ozawa, Fumiyuki
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Read Online
- Facile synthesis of cyclic fluorosiloxanes
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Novel 1,3,5,7-tetrafluorocyclotetrasiloxanes were synthesized from cyclotetrasiloxanetetraol by a facile synthetic method. By adjusting the amount of the fluorinating reagent, synthesis of a single isomer of 1,3,5,7-tetrafluorocyclotetrasiloxanes as well as the preparation of all four isomers were accomplished. The products are expected to serve as potential precursors to not only well-defined silsesquioxanes but also asymmetric cyclic siloxanes.
- Oguri, Naoki,Takeda, Nobuhiro,Unno, Masafumi
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supporting information
p. 1506 - 1508
(2015/11/24)
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- Enhanced nucleophilic fluorination and radiofluorination of organosilanes appended with potassium-chelating leaving groups
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Here we aimed to explore the feasibility of enhancing the fluorination of organosilanes by appending potassium-chelating groups to the substrates. For this purpose, eight organosilanes were prepared in which a linear or cyclic leaving group, with putative
- Al-Huniti, Mohammed H.,Lu, Shuiyu,Pike, Victor W.,Lepore, Salvatore D.
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- Zinc-catalyzed nucleophilic substitution reaction of chlorosilanes with organomagnesium reagents
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Zinc-catalyzed nucleophilic substitution reactions of chlo-rosilanes with organomagnesium reagents afford various tetraorganosilanes under mild reaction conditions. The reactions can be performed on large scale and allow efficient preparation of functionalized tetraorganosilanes.
- Murakami, Kei,Yorimitsu, Hideki,Oshima, Koichiro
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body text
p. 1415 - 1417
(2009/06/28)
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- 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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- Tetrabutylammonium butyldifluorodimethylsilicate and difluorodimethylphenylsilicate, new nucleophilic fluorinating reagents
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Tetrabutylammonium butyldifluorodimethylsilicate (TAMBS, 1a) and tetrabutylammonium difluorodimethylphenylsilicate (TAMPS, 1b) were conveniently prepared from the corresponding substituted fluorodimethylsilanes and tetrabutylammonium fluoride. Both fluorosilicates 1a, 1b are powerful nucleophilic fluorinating reagents which transform primary or secondary halides, tosylates, or mesylates to the corresponding fluorides in moderate to good yields.
- Kví?ala,Mysík,Paleta
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p. 547 - 549
(2007/10/03)
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- A convenient one-pot synthesis of stannylsilanes
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Stannylsilanes were synthesized in high yields by reaction of organotinchlorides with organofluorosilanes and magnesium. The fluorosilanes were prepared in good yields and under mild conditions by reaction of the corresponding chlorosilanes with [n-Bu4N][Ph3SnF2]. All products were characterized by 29Si, 119Sn NMR spectroscopy and elemental analysis.
- Hummeltenberg, Reinhard,Jurkschat, Klaus,Uhlig, Frank
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p. 255 - 261
(2007/10/03)
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- The Phenyldimethylsilyl Group as a Masked Hydroxy Group
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A phenyldimethylsilyl group attached to carbon can be converted into hydroxy group 1->5, with retention of configuration at the migrating carbon, by any of three main methods.The first involves protodesilylation, to remove the phenyl ring from the silicon atom, followed by oxidation of the resulting functionalized silicon atom using peracid or hydrogen peroxide.The second uses mercuric acetate for the same purpose, and can be combined in one pot with the oxidative step using peracetic acid.This method has a variant in which the mercuric ion is combined with palladium(II) acetate, both in less than stoichiometric amounts.The third uses bromine, which can also be used in one pot in conjuction with peracetic acid.In this method, but not in the method based on mercuric acetate, the peracetic acid may be buffered with sodium acetate.The method using bromine as the electrophile for removing the benzene ring has a more agreeable variant in which it is administered in the form of potassium bromide, which is oxidised to bromine by the peracetic acid.The scope and limitations of each of these methods are reported with a range of examples possessing between them many of the common functional groups.Simple benzene rings, alcohols, ethers, esters, amides and nitriles are compatible with all three methods, and ketones do not undergo Baeyer-Villiger reaction under any of the conditions.Amines, however, are oxidised to amine oxides.Ketones may be brominated in the third of the three main species.The absence of acid in the third method makes it especially valuable when the phenyldimethylsilyl group has a neighbouring nucleofugal group such as hydroxy or acetoxy.Carbon-carbon double bonds are incompatible with the methods, except for terminal monosubstituted double bonds, which can survive the conditions used in the first of the three methods.
- Fleming, Ian,Henning, Rolf,Parker, David C.,Plaut, Howard E.,Sanderson, Philip E. J.
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p. 317 - 338
(2007/10/02)
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- Preparation of the iodides (Me3Si)2C(SiMe2C6H4Y)(SiMe2I) and some related compounds
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The preparations of: (a) the iodides (Me3Si)2C(SiMe2C6H4Y)(SiMe2I) (Y=H, p-OMe, p-Me, p-Cl, m-CF3), via the corresponding hydrides; (b) the compounds (Me3Si)2C(SiMe2Ph)(SiMe2X) with X=F, O2CCF3, OMe, N3, NCS and Cl: and (c) the iodide (p-MeC6H4)3CSiMe2I are described. Key words: Silicon; Iodide; Fluoride; Hydride; Trimethylsilyl
- Eaborn, Colin,Jones, Karen L.,Lickiss, Paul D.
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- Electrochemical Oxidation of Hydrosilanes. A Synthetic Approach to Halosilanes and Disilanes
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Electrolytic oxidation of dimethylphenylsilane (1) in the presence of CuCl2 or CuCl afforded chlorodimethylphenylsilane in high yields (>90percent), while similar electrolysis of 1 in the presence of BF4- ions afforded fluorodimethylphenylsilane in 90percent yield. 1,2-Diphenyltetramethyldisilane was obtained from 1 in 48percent yield by the electrolysis with a Pt-Cu electrode system.A "paired" electrolysis of methyldiphenylsilane on the anode and chloromethyldiphenylsilane on the cathode afforded 1,2-dimethyltetraphenyldisilane in 64percent yield.
- Kunai, Atsutaka,Kawakami, Toshihiro,Toyoda, Eiji,Sakurai, Tomohiro,Ishikawa, Mitsuo
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p. 1945 - 1948
(2007/10/02)
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- Fluoride Ion Catalyzed Reduction of Aldehydes and Ketones with Hydrosilanes. Synthetic and Mechanistic Aspects and an Application to the Threo-Directed Reduction of α-Substituted Alkanones
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Reduction of aldehydes and ketones with hydrosilanes proceeded in the presence of a catalytic amount of tetrabutylammonium fluoride or tris(diethylamino)sulfonium difluorotrimethylsilicate in aprotic polar solvents under mild conditions.A significant isotope effect (kH/kD = 1.50) was observed in competitive reduction of acetophenone with HSiMe2Ph and DSiMe2Ph.The reaction was of first order in the concentration of an aprotic polar solvent HMPA.Reduction of 2-methylcyclohexanone gave cis-2-methylcyclohexanol with selectivities up to 95percent.The kinetic and stereochemical results suggest that a hexavalent fluorosilicate - is involved. α-Alkoxy (acyloxy or dimethylamino) ketones were transformed to threo alcohols in high diastereoselectivities.The reduction was also applied to α-methyl-β-keto amides, RCOCH(MeCONR)2, to afford the corresponding threo alcohols in >98percent selectivity.The threo selectivity is explained in terms of the Felkin-Anh model in which interaction of carbonyl oxygen with a countercation is ideally suppressed.The threo-directed reduction was applied to (R)-1-phenyl-4-(2-tetrahydropyranyloxy)-1-penten-3-one and N-(2-benzoylpropanoyl)piperidine.The resulting threo alcohols were respectively converted into (2R,3S)-2,3-(cyclohexylidenedioxy)butanal, a key intermediate of daunosamine synthesis, and into a pharmacologically useful compound threo-N-(3-hydroxy-2-methyl-3-phenylpropyl)piperidine.
- Fujita, Makoto,Hiyama, Tamejiro
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p. 5405 - 5415
(2007/10/02)
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- Zur Synthese von Siloxanen XI. Spaltung von Siloxanen durch Bortrifluorid
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The cleavage of siloxane bonds by BF3 was investigated kinetically by 1H NMR spectroscopy.The reactions could be evaluated by use ofa pseudo-first order rate law, when a sufficiently large excess of BF3 was used.The order with respect to BF3 was found to be 4.7.The rate constants obtained could be correlated to ?*- values with a ρ*-value of -1.0.The ?*-value found previously by 29Si NMR spectroscopy for the Me3SiO group of 0.35 was confirmed.
- Scheim, U.,Porzel, A.,Ruehlmann, K.
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- REACTIONS IN THE CHLOROSILANE-SILANOL-SILOXANE SYSTEM
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We obtained the first ?*-values and ES-values for siloxy groups by spectroscopic and kinetic methods.Detailed mechanistic investigations are performed on the hydrolysis of chlorosilanes, the cleavage of Si-O-Si bonds by HCl, and the substituent exchange reaction between silanols and chlorosilanes.
- Ruehlmann, K.
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p. 139 - 152
(2007/10/02)
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- REACTION OF (BROMODIFLUOROMETHYL)PHENYLDIMETHYLSILANE WITH ORGANOMETALLIC REAGENTS
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A new fluorine-containing organosilicon compound, (bromodifluoromethyl)phenyldimethylsilane (II), was synthesized by the N-bromosuccinimide (NBS) bromination of (difluoromethyl)phenyldimethylsilane (I), which was prepared from phenyldimethylsilyllithium and chlorodifluoromethane.Compound II reacted with dimethyl sulfoxide to give dimethyl sulfide and phenyldimethylfluorosilane in quantitative yield.The reaction of II with nucleophiles, such as sodium ethoxide, Grignard or lithium reagents, afforded products arising from cleavage of the carbon-silicon bond.In contrast, the reaction of II with Grignard reagents in the presence of appropriate catalysts (Group VIII transition metal salts or complexes) afforded the homo-coupling product of II, 1,2-bis(phenyldimethylsilyl)-1,1,2,2-tetrafluoroethane (IV), in excellent yield.The silver(I) salt-catalyzed reaction of II with ethylmagnesium bromide gave the cross-coupling product, (1,1-difluoropropyl)phenyldimethylsilane (V) as well as III and IV.When cuprous bromide was employed as catalyst, the reaction of II with ethylmagnesium bromide afforded 1-phenyldimethylsilyl-1-propene (VI) and 3-phenyldimethylsilyl-2-pentene (VII) as main products.
- Fuchikami, Takamasa,Ojima, Iwao
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p. 145 - 153
(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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