- Organocalcium Complex-Catalyzed Selective Redistribution of ArSiH3or Ar(alkyl)SiH2to Ar3SiH or Ar2(alkyl)SiH
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Calcium is an abundant, biocompatible, and environmentally friendly element. The use of organocalcium complexes as catalysts in organic synthesis has had some breakthroughs recently, but the reported reaction types remain limited. On the other hand, hydrosilanes are highly important reagents in organic and polymer syntheses, and redistribution of hydrosilanes through C-Si and Si-H bond cleavage and reformation provides a straightforward strategy to diversify the scope of such compounds. Herein, we report the synthesis and structural characterization of two calcium alkyl complexes supported by β-diketiminato-based tetradentate ligands. These two calcium alkyl complexes react with PhSiH3 to generate calcium hydrido complexes, and the stability of the hydrido complexes depends on the supporting ligands. One calcium alkyl complex efficiently catalyzes the selective redistribution of ArSiH3 or Ar(alkyl)SiH2 to Ar3SiH and SiH4 or Ar2(alkyl)SiH and alkylSiH3, respectively. More significantly, this calcium alkyl complex also catalyzes the cross-coupling between the electron-withdrawing substituted Ar(R)SiH2 and the electron-donating substituted Ar′(R)SiH2, producing ArAr′(alkyl)SiH in good yields. The synthesized ArAr′(alkyl)SiH can be readily transferred to other organosilicon compounds such as ArAr′(alkyl)SiX (where X = OH, OEt, NEt2, and CH2SiMe3). DFT investigations are carried out to shed light on the mechanistic aspects of the redistribution of Ph(Me)SiH2 to Ph2(Me)SiH and reveal the low activation barriers (17-19 kcal/mol) in the catalytic reaction.
- Li, Tao,McCabe, Karl N.,Maron, Laurent,Leng, Xuebing,Chen, Yaofeng
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p. 6348 - 6356
(2021/05/29)
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- Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
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We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
- Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
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p. 6388 - 6394
(2021/05/31)
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- METHOD FOR PRODUCING SILYL SODIUM COMPOUND AND METHOD FOR DEOXIDIZING EPOXY COMPOUND
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PROBLEM TO BE SOLVED: To construct a technique which can simply, efficiently and inexpensively synthesize a silyl sodium compound in a small number of processes and in a short time, especially to construct a technique which synthesizes a silyl sodium compound by using easily available reagents from a viewpoint of sustainability without using reagents which are difficult to handle and are toxic. SOLUTION: There is provided a method for synthesizing a silyl sodium compound comprising a step of reacting a dispersion obtained by dispersing a silyl halide compound or a disilane compound with sodium into a dispersion solvent, the silyl halide compound or the disilane compound as a starting compound, in a reaction solvent to obtain the silyl sodium compound. There is also provided a method for deoxidizing an epoxy compound comprising a step of reacting the silyl sodium compound obtained by synthesizing method of the silyl sodium compound with an epoxy compound to deoxidize the epoxy compound to stereoselectively produce an alkene compound. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0081-0083
(2020/05/06)
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- Synthesis of hydrosilanes: Via Lewis-base-catalysed reduction of alkoxy silanes with NaBH4
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Hydrosilanes were synthesized by reduction of alkoxy silanes with BH3 in the presence of hexamethylphosphoric triamide (HMPA) as a Lewis-base catalyst. The reaction was also achieved using an inexpensive and easily handled hydride source NaBH4, which reacted with EtBr as a sacrificial reagent to form BH3in situ.
- Aoyagi, Keiya,Ohmori, Yu,Inomata, Koya,Matsumoto, Kazuhiro,Shimada, Shigeru,Sato, Kazuhiko,Nakajima, Yumiko
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supporting information
p. 5859 - 5862
(2019/05/27)
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- A silicon hydrogenation for the preparation of compounds
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The invention relates to a method for preparing silicon hydrides. Under the protection of Ar gas, THF and/or HMPA are/is used as a solvent, chlorosilane or derivatives of chlorosilane reacts with magnesium metal to prepare the silicon hydrides. The method has the characteristics of being cheap in raw materials, easy to get the raw materials, easy to operate, mild in reaction conditions and low in cost.
- -
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Paragraph 0030; 0031; 0032; 0033
(2018/03/09)
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- Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional iridium catalyst
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Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded, resulting in the formation of chlorohydrosilanes (R2SiHCl or RSiHCl2) as synthetically important building blocks for various organosilicon compounds. A mechanistic study supported the in-situ formation of an iridium hydride species as a key intermediate, which could transfer the hydride to the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from Me3SiCl.
- Beppu, Teruo,Sakamoto, Kei,Nakajima, Yumiko,Matsumoto, Kazuhiro,Sato, Kazuhiko,Shimada, Shigeru
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- Hydrogenation of chlorosilanes by NaBH4
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Hydrogenation of chlorosilane was achieved in acetonitrile using NaBH4, a safe and easy-to-handle reagent. This reaction converted Si-Cl portion(s) in organosilanes into Si-H portion(s) without hydrogenation of cyano, chloro, and aldehyde groups on an alkyl substituent of the Si reagents. In addition, the Si-Cl/Si-H exchange reaction was applicable to dichlorodisilane without Si-Si bond cleavage.
- Ito, Masaki,Itazaki, Masumi,Abe, Takashi,Nakazawa, Hiroshi
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p. 1434 - 1436
(2016/12/03)
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- Iridium Pincer Catalysts for Silane Dehydrocoupling: Ligand Effects on Selectivity and Activity
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Catalytic reactions of bisphosphinite pincer-ligated iridium compounds p-XR(POCOP)IrHCl (POCOP) [2,6-(R2PO)2C6H3, R = iPr, X = H (1); R = tBu, X = COOMe (2); = H (3); = NMe2 (4)] with primary and secondary silanes have been performed. Complex 1 is primarily a silane redistribution precatalyst, but dehydrocoupling catalysis is observed for sterically demanding silane substrates or with aggressive removal of H2. The bulkier compounds (2-4) are silane dehydrocoupling precatalysts that also undergo competitive redistribution with less hindered substrates. Products generated from reactions utilizing 2-4 include low molecular weight oligosilanes with varying degrees of redistribution present or disilanes when employing more sterically demanding silane substrates. Selectivity for redistribution versus dehydrocoupling depends on the steric and electronic environment of the metal but can also be affected by reaction conditions. (Chemical Equation Presented).
- Mucha, Neil T.,Waterman, Rory
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supporting information
p. 3865 - 3872
(2015/08/19)
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- Si-H bond activation at {(NHC)2Ni0} leading to hydrido silyl and bis(silyl) complexes: A versatile tool for catalytic Si-H/D exchange, acceptorless dehydrogenative coupling of hydrosilanes, and hydrogenation of disilanes to hydrosilanes
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The unique reactivity of the nickel(0) complex [Ni2(iPr 2Im)4(COD)] (1) (iPr2Im = 1,3-di-isopropyl- imidazolin-2-ylidene) towards hydrosilanes in stoichiometric and catalytic reactions is reported. A series of nickel hydrido silyl complexes cis-[Ni(iPr2Im)2(H)(SiHn-1R4-n)] (n = 1, 2) and nickel bis(silyl) complexes cis-[Ni(iPr2Im) 2(SiHn-1R4-n)2] (n = 1, 2, 3) were synthesized by stoichiometric reactions of 1 with hydrosilanes H nSiR4-n, and fully characterized by X-ray diffraction and spectroscopic methods. These hydrido silyl complexes are examples where the full oxidative addition step is hindered. They have, as a result of the remaining Si-H interactions, remarkably short Si-H distances and feature a unique dynamic behavior in solution. Cis-[Ni(iPr2Im)2(H)(SiMePh 2)] (cis-5) shows in solution at room temperature a dynamic site exchange of the NHC ligands, H-D exchange with C6D6 to give the deuteride complex cis-[Ni(iPr2Im)2(D)(SiMePh 2)] (cis-5-D), and at elevated temperatures an irreversible isomerization to trans-[Ni(iPr2Im)2(D)(SiMePh 2)] (trans-5-D). Reactions with sterically less demanding silanes give cis-configured bis(silyl) complexes accompanied by the release of dihydrogen. These complexes display, similarly to the hydrido silyl complexes, interestingly short Si-Si distances. Complex 1 reacts with 4 eq. HSi(OEt) 3, in contrast to all the other silanes used in this study, to give the trans-configured bis(silyl) complex trans-[Ni(iPr2Im) 2Ni(Si(OEt)3)2] (trans-12). The addition of two equivalents of Ph2SiH2 to 1 results, at elevated temperatures, in the formation of the dinuclear complex [{(iPr 2Im)Ni-μ2-(HSiPh2)}2] (6). This diamagnetic, formal Ni(i) complex exhibits a long Ni-Ni bond in the solid state, as established by X-ray diffraction. The capability of the electron rich {Ni(iPr2Im)2} complex fragment to activate Si-H bonds was applied catalytically in the deuteration of Et3Si-H to Et 3Si-D employing C6D6 as a convenient deuterium source. Furthermore, we show that 1 serves as a catalyst for the acceptorless dehydrogenative coupling of Ph2SiH2 to the corresponding disilane Ph2HSi-SiHPh2 and trisilane Ph 2HSi-Si(Ph)2-SiHPh2, and the coupling of PhSiH3 to give a mixture of cyclic and linear polysilanes with high polydispersity (Mw = 1119; Mn = 924; Mw/M n = 1.2). The capability of 1 to catalyze the formal reverse reaction as well is demonstrated by the hydrogenation of disilanes. The hydrogenation of the disilanes Ph2MeSi-SiMePh2 and PhMe 2Si-SiMe2Ph to the corresponding hydrosilanes Ph 2MeSi-H and PhMe2Si-H, respectively, proceeds effectively in the presence of 1 under very mild conditions (room temperature, 1.8 bar H2 pressure).
- Schmidt, David,Zell, Thomas,Schaub, Thomas,Radius, Udo
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supporting information
p. 10816 - 10827
(2014/07/08)
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- Synthesis of silylium and germylium ions by a substituent exchange reaction
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The reaction of diarylalkylsilanes and -germanes with trityl cation in the presence of a weakly coordinating anion to give the corresponding triarylsilylium or -germylium ions was investigated. This reaction provides a facile access to a larger range of these sterically highly hindered Lewis acids. The factors that promote the substituent exchange were studied, and significant effects of the substituent, of the solvent, and of the group 14 element were revealed. A combined solid-state XRD and NMR investigation of the tris(pentamethylphenyl) silylium borate [(Me5C6) 3Si]2[B12Cl12] disclosed the trigonal planar coordination environment of the silicon atom in this silylium ion. NMR investigations indicate for 2,4,6-triisopropylphenyl-substituted silylium and germylium ions the onset of C-H···E + three-center interactions (E = Si, Ge) between the distant CH bond of the isopropyl group and the positively charged group 14 element atom.
- Schaefer, Andre,Reissmann, Matti,Jung, Sebastian,Schaefer, Annemarie,Saak, Wolfgang,Brendler, Erica,Mueller, Thomas
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p. 4713 - 4722
(2013/09/24)
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- Integrated palladium-catalyzed arylation of heavier groupa 14 hydrides
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A convenient procedure has been developed for the preparation of Groupa 14 compounds by integrated palladium-catalyzed cross-coupling of aromatic iodides with the corresponding Groupa 14 hydrides in the presence of a base. The reaction conditions can be applied to the cross-coupling of tertiary, secondary, and primary Groupa 14 compounds. In most cases, the desired arylated products were obtained in synthetically useful yields. Even in the case of aryl iodides containing OH, NH2, CN, or CO2R groups, the reactions proceeded with good to high yields with tolerance of these reactive functional groups. A possible application of this method is the unique synthesis of a fungicidal diarylmethyl(1H-1,2,4-triazol-1-ylmethyl)silane derivative. A convenient procedure has been developed for the preparation of Groupa 14 compounds by integrated palladium-catalyzed cross-coupling of aromatic iodides with the corresponding Groupa 14 hydrides in the presence of a base (see picture). Application of this method in the synthesis of a fungicidal diarylmethyl(1H-1,2,4-triazol-1-yl-methyl)silane derivative is demonstrated. Copyright
- Lesbani, Aldes,Kondo, Hitoshi,Yabusaki, Yusuke,Nakai, Misaki,Yamanoi, Yoshinori,Nishihara, Hiroshi
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supporting information; experimental part
p. 13519 - 13527
(2011/02/24)
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- Acceleration of the substitution of silanes with Grignard reagents by using either LiCl or YCl3/MeLi
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Getting up to speed: Both LiCl and the YCl3/MeLi catalyst system have an acceleration effect upon the substitution of silanes using Grignard reagents (see scheme). The method provides access to benzyl-, allyl-, and arylsilanes in good yields from the starting silanes.
- Hirone, Naoki,Sanjiki, Hiroaki,Tanaka, Ryoichi,Hata, Takeshi,Urabe, Hirokazu
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supporting information; experimental part
p. 7762 - 7764
(2010/12/25)
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- Silyl-directed, iridium-catalyzed ortho-borylation of arenes. A one-pot ortho-borylation of phenols, arylamines, and alkylarenes
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The regioselectivity of the borylation of arenes catalyzed by the combination of 4,4′-di-tert-butylbipyridine (dtbpy) and [Ir(cod)Cl]2 has typically been governed by steric effects. We describe a strategy that makes use of a new substituent for ortho-functionalization to overcome this bias. We show that arenes containing hydrosilyl substituents on an atom attached to the arene ring undergo borylation at the position ortho to the hydrosilyl group. Using iridium-catalyzed formation of silyl ethers and silylamines from silanes and either phenols or arylamines, we have developed the ortho-borylation into a one-pot conversion of free phenols and monoprotected anilines into hydroxy- and amino-substituted organoboron derivatives. Copyright
- Boebel, Timothy A.,Hartwig, John F.
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p. 7534 - 7535
(2008/12/22)
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- Analysis of an unprecedented mechanism for the catalytic hydrosilylation of carbonyl compounds
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This work details an in-depth evaluation of an unprecedented mechanism for the hydrosilylation of carbonyl compounds catalyzed by (PPh3) 2Re(O)2I. The proposed mechanism involves addition of a silane Si-H bond across one of the rhenium-oxo bonds to form siloxyrhenium hydride intermediate 2 that reacts with a carbonyl substrate to generate siloxyrhenium alkoxide 4, which, in turn, affords the silyl ether product. Compelling evidence for the operation of this pathway includes the following: (a) isolation and structural characterization by X-ray diffraction of siloxyrhenium hydride intermediate 2, (b) demonstration of the catalytic competence of intermediate 2 in the hydrosilylation reaction, (c) 1H and 31P{1H} NMR and ESI-MS evidence for single-turnover conversion of 2 into 1, (d) observation of intermediate 2 in the working catalyst system, and (e) kinetic analysis of the catalytic hydrosilylation of carbonyl compounds by 1.
- Nolin, Kristine A.,Krumper, Jennifer R.,Pluth, Michael D.,Bergman, Robert G.,Toste, F. Dean
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p. 14684 - 14696
(2008/09/20)
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- METHOD OF MAKING PHENYL-CONTAINING CHLOROSILANES WITH ALIPHATIC OR CYCLOPARAFFINIC HYDROCARBON SOLVENTS
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Phenylmethyldichlorosilanes and diphenylmethylchlorosilanes are prepared by a Grignard process involving the step of contacting a phenyl Grignard reagent, an ether solvent, a trichlorosilane, and an aliphatic or cycloparaffinic hydrocarbon coupling solvent; in a mole ratio of the ether solvent to the phenyl Grignard reagent is 2 to 5, the mole ratio of the trichlorosilane to the phenyl Grignard reagent is 0.1 to 10, and the mole ratio of the aliphatic or cycloparaffinic hydrocarbon coupling solvent to the phenyl Grignard reagent is 3 to 7. Preferred reactants include phenylmagnesium chloride as the phenyl Grignard reagent; diethyl ether as solvent; n-heptane as the aliphatic hydrocarbon coupling solvent, or cyclohexane as the cycloparaffinic hydrocarbon coupling solvent; and methyltrichlorosilane.
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Page/Page column 7-9
(2008/06/13)
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- Sodium bis(trimethylsilyl)amide in the oxidative conversion of aldehydes to nitriles
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The feasibility of the Me3Si species acting as a nucleofuge was investigated in compounds containing the NSiMe3 moiety. Treatment of various aromatic aldehydes with 2.2 equiv. of NaN(SiMe3)2 at 185°C in a sealed tube produced the corresponding nitriles in high yields (81-98%). In these reactions, NaN(SiMe3)2 acted as an oxidizing agent. Results from control experiments indicate that the Me 3Si unit can depart efficiently from the NSiMe3 moiety of N-silylimine intermediates. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Jih, Ru Hwu,Fung, Fuh Wong
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p. 2513 - 2516
(2007/10/03)
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- Catalytic functionalization of hydrocarbons by σ-bond-metathesis chemistry: Dehydrosilylation of methane with a scandium catalyst
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C-H activation with scandium: Reaction of [Cp2*ScCH3] (1, Cp* = C5Me5) with MesSiH3 (Mes=2,4,6-C6H2Me3) yielded a new scandium silyl complex [Cp2*ScSiH2Mes] (2) by an unusual σ-bond metathesis pathway. Complex 2 activates the C-H bonds of benzene and methane. In the presence of excess Ph2SiH2, the catalytic dehydrosilation of saturated and unsaturated hydrocarbons, including methane, was accomplished, with [Cp2*ScH] (see scheme; R=CH3, C3H5, CH=CMe2) which can be formed from 1 or 2. This appears to be the first example of catalytic methane functionalization by σbond metathesis.
- Sadow, Aaron D.,Tilley, T. Don
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p. 803 - 805
(2007/10/03)
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- Reactions of diaryliodonium trifluoromethanesulfonates with low-valent ytterbium and samarium reagents
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The reduction of diaryliodonium trifluoromethanesulfonates with low-valent ytterbium and samarium reagents has been studied. In the reaction of diphenyliodonium trifluoromethanesulfonate with two equimolar amounts of metallic ytterbium, benzene is formed
- Makioka, Yoshikazu,Fujiwara, Yuzo,Kitamura, Tsugio
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p. 509 - 513
(2007/10/03)
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- Catalytic and stoichiometric reactions of tertiary silanes with [Ir(Me)2Cp*L] (Cp=η5-C5Me5; L=PMe3, PMe2Ph, PMePh2, PPh3) in the presence of one-electron oxidants. A unique case of Si-H, Si-C, Ir-C and P-F bonds one-step activation: Crystal structure of [Ir(Ph)(SiPh2F)Cp*(PMe3)]
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The iridium(III) dimethyl derivatives [Ir(Me)2Cp*L] (Cp=η5-C5Me5; L=PMe3 1a, PPh3 1d) catalyze the dehydrogenative coupling of dimethylphenylsilane in the presence of one-electron oxidants to yield Me2PhSiSiPhMe2. Compounds 1a-d react with triphenylsilane in the presence of [FeCp2]PF6 to give methane and [Ir(Ph)(SiFPh2)Cp*L] (L=PMe3 (2a), PMe2Ph (2b), PMePh2 (2c), PPh3 (2d)). 2a was structurally characterized by single-crystal X-ray diffraction experiments. The `three-legged piano stool' coordination polyhedron is slightly deformed.
- Diversi, Pietro,Marchetti, Fabio,Ermini, Valentina,Matteoni, Simona
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p. 154 - 160
(2007/10/03)
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- Selective synthesis of monohydrosilanes by the reactions of organoytterbium iodides with dihydrosilanes
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Monohydrosilanes can be prepared selectively in high yields from the reaction of various aryl and alkyl iodides with ytterbium metal followed by the reaction with dihydrosilanes.
- Jin, Wu-Song,Makioka, Yoshikazu,Kitamura, Tsugio,Fujiwara, Yuzo
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p. 955 - 956
(2007/10/03)
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- The differing modes of reaction of 1-(8-dimethylamino-1-naphthyl)-1-hydrodisilane and 1-(1-naphthyl)-1-hydrodisilane in nickel-catalyzed reactions with acetylene: Formation of a pseudo-pentacoordinate silole via Si-Si bond cleavage vs. hydrosilation without Si-Si bond cleavage
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Pseudo-pentacoordinate 1-(8-dimethylamino-1-naphthyl)-1-hydrodisilanes 1 and 2 and the tetracoordinate counterpart 3 have been prepared. In the presence of an Ni(0) complex as catalyst, 1 and 2 undergo degradation to generate a silylene species and a hydrosilane. The complex with Ni of the silylene species from 1 has been trapped with an excess of diphenylacetylene to give a pseudo-pentacoordinate silole 4. The X-ray structure of 4 indicates that this silole occupies two pseudo-equatorial positions. In contrast, the tetracoordinate hydrodisilane 3 undergoes hydrosilation without Si-Si bond cleavage.
- Tamao, Kohei,Asahara, Masahiro,Kawachi, Atsushi
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p. 325 - 334
(2007/10/03)
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- Access to Stabilized Silyl Anions by Electroreduction of Chlorosilanes
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Using the sacrificial anode technique, the electroreduction of arylchlorosilanes into the corresponding arylhydrosilanes occurs via a silylaluminium intermediate characterized for the first time in such reactions.
- Duprat, C.,Biran, C.,Bordeau, M.,Constantieux, T.,Gerval, P.,Dunogues, J.
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p. 2107 - 2108
(2007/10/02)
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- Nickel catalyzed Coupling of Phenylhydrosilanes
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Activated nickel, prepared by lithium reduction of nickel iodide in tetrahydrofuran, catalyses the dehydrogenative coupling of phenylsilanes to form di-, tri-, and tetrasilanes.
- Boudjouk, Philip,Rajkumar, Amirthini B.,Parker, W. L.
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p. 245 - 246
(2007/10/02)
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- Uebergangsmetall-Silyl-Komplexe XXXIII. Einfluss der Substituenten am Silicium auf Stabilitaet und Zerfallsprodukte von Bissilyl-Komplexen des Palladiums, (R'3P)2Pd(SiR3)2
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Bissilyl complexes of PdII, (R'3P)2Pd(SiR3)2, are stable in the presence of electron-withdrawing silyl groups (e.g.SiCl3) or if the elimination of disilane is prevented by use of suitable chelate ligands.Reaction of cis-L2PdMe2 (L=MePh2P) with H2SiMePh or H2SiPh2 gives the complexes cis-L2Pd(SiHR2)2 (2) that are only detected spectroscpically; they decompose rapidly by cleavage of H2Si2R4.Reaction of L2PdMe2 with H2SiPh2 not only yields the bissilyl complex, but also HSiMePh2; with HSiPh3 only SiMe2Ph2, but no corresponding bissilyl complex is formed.In contrast, the distinctly more stable complex Pd(Ph2PCH2CH2SiMe2)2 is obtained by reaction of L2PdMe2 with Ph2PCH2CH2SiMe2H.Silanes containing chloro substituents (HSiCl3,HSiCl2Me, SiCl4) do not react with L2PdMe2 to give silyl complexes but undergo chloro/methyl exchange instead to give L2PdCl2 and methylated silanes.Trans-L2Pd(SiCl3)2 (4) was prepared by a novel route, viz., reaction of L2PdCl2 with HSiCl3 and KH.On thermolysis of 4 L2PdCl2 is formed in place of Si2Cl6.
- Schubert, Ulrich,Mueller, Christine
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p. 165 - 172
(2007/10/02)
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- Siliciumhaltige Carben-Komplexe XII. Synthese kleiner organischer Ringsysteme aus alkoxy- oder alkylthio-substituirten Silylcarben-Komplexen (CO)5MC(XEt)SiR3 (M=Cr, Mo, W; X=O, S) und davon abgeleiteten Ketenen R3Si(EtX)C=C=O
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Ketenes R3Si(EtO)C=C=O (1), prepared in situ from the carbene complexes (CO)5MC(OEt)SiR3 (M=Cr, Mo, W) by reaction with CO, react with ethyl vinyl ether or cyclopentadiene by -cycloaddition.Two stereoisomeric cyclobutanone derivatives, in which the positions of the R3Si and the EtO group are interchanged, are obtained in each case.The reactions proceed with high stereoselectivity.Ethyl vinyl ether also reacts directly with the carbene complexes to yield a single stereoisomer of 1,2-diethoxy-1-silyl-cyclopropane (6).Reaction of the ethyl-thio-substituted ketene Ph3Si(EtS)C=C=O (2) with 2,3-dihydrofuran gives the corresponding cyclobutanone only as a by-product. 3-Oxa-8-silyl-1-thia-bicyclooctan-7-one (8) is formed as the main product by loss of an ethylene unit.Ketene 1 reacts with N-methyl- or N-phenylbenzimine, but not with cyclic imines, to give β-lactames.Each of these reactions also yields two stereoisomers.
- Kron, Johanna,Schubert, Ulrich
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p. 203 - 220
(2007/10/02)
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- Hypervalent silicon hydrides: evidence for their intermediacy in the exchange reactions of di- and tri-hydrogenosilanes catalysed by hydrides (NaH, KH and LiAlH4)
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Di and tri-hydrogenosilanes, RR'SiH2 and RSiH3 (R=aryl, allyl or benzyl; R'=aryl or alkyl), readily undergo exchange reactions, involving silicon-carbon bonds and silicon-hydrogen bonds, in the presence of hydrides (LiAlH4, KH and NaH) as catalysts.These results are discussed in terms of five-coordinate silicon hydrides as intermediates in the reaction.
- Becker, B.,Corriu, R. J. P.,Guerin, C.,Henner, B. J. L.
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p. 147 - 154
(2007/10/02)
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- Chlorotrimethylsilane, Hexamethyldisilane, and 1,2-Dimethyl-1,1,2,2-tetraphenyldisilane as Oxidizing Agents in the Conversion of Hydrazines to 2-Tetrazenes. Trimethylsilyl Anion as a Leaving Group
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The possibility of the Me3Si- species to be a nucleofuge of a compound containing the NSiMe3 group was investigated.Treatment of hydrazines with 1.1 equiv of Me3SiCl, Me3SiSiMe3, or Ph2MeSiSiMePh2 in the presence of 1.0 equiv of potassium hydride gave the corresponding 2-tetrazenes (R1R2NN=NNR1R2) in fair to good yields.The hydrazines included 1-methyl-1-phenylhydrazine (9), 1-aminopiperidine (10), 1-amino-2,6-dimethylpiperidine (11), 4-aminomorpholine (12), and 1-aminohomopiperidine (13).In these reactions, Me3SiCl, Me3SiSiMe3, and Ph2MeSiSiMePh2 acted as oxidizing agents.Results from control experiments supported the proposed mechanism: silylation of hydrazines gave monosilylhydrazines, decomposition of monosilylhydrazines generated aminonitrenes, and dimerization of aminonitrenes afforded 2-tetrazenes.In the decomposition of monosilylhydrazines, Me3Si- behaved as a leaving group from the NSiMe3 moiety.
- Hwu, Jih Ru,Wang, Naelong,Yung, Richard T.
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p. 1070 - 1073
(2007/10/02)
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- COUNTERATTACK REAGENTS: HEXAMETHYLDISILANE AND 1,2-DIMETHYL-1,1,2,2-TETRAPHENYLDISILANE IN THE SYNTHESIS OF POLYSILYLATED HYDRAZINES
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Polysilylated hydrazines have wide applicability.It is tedious to prepare these compounds by classic means.However, using hexamethyldisilane and 1,2-dimethyl-1,1,2,2-tetraphenyldisilane as counterattack reagents, we synthesized polysilylated hydrazines under alkaline conditions in good to excellent yields.This one-pot method is expedient and more efficient than other procedures.Polysilylated hydrazines were found to react with aldehydes or ketones in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate to give the corresponding hydrazones under anhydrous conditions.
- Hwu, Jih Ru,Wang, Naelong
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p. 4181 - 4196
(2007/10/02)
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- Reactivity of Hypervalent Species: Reactions of Anionic Penta-Coordinated Silicon Complexes towards Nucleophiles
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The reactivity of anionic penta-coordinated silicon complexes 4-O)2>-Na+ 1 with nucleophilic reagents has been studied. 1 can be reduced to organosilanes RSiH3 by metallic hydrides.Reactions with an excess of Grignard or organolithium reagents (R'MgX or R'Li) gave tetraorganosilanes RSiR'3.When only two molar equivalents of Grignard reagents (R'MgX) or lithium reagents (R'Li) are added to complexs 1 functional silanes RR'2SiX can be prepared.
- Boudin, Alain,Cerveau, Genevieve,Chuit, Claude,Corriu, Robert J. P.
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p. 101 - 106
(2007/10/02)
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- Pentacoordinate silicon complexes, the process for their preparation and their application to the preparation of organosilanes
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The present invention relates to new pentacoordinate silicon complexes, the process for their preparation and their application to the preparation of organosilanes. The pentacoordinate silicon complexes according to the invention correspond to the general formula I: STR1 in which: R denotes an alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl, aralkynyl or alkylaryl radical in which the aliphatic fragments are linear, branched or cyclic and contain from 1 to 20 carbon atoms, A represents an alkali metal or alkaline earth metal, with the proviso however that A represents neither sodium nor potassium when R is a phenyl radical, and n=1 or 2.
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- SIMPLIFIED APPROACH TO SILAANTHRONES AND DISILAANTHRACENES
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An improved synthesis of bis(o-chlorophenyl)methylsilane is reported from reaction of a mixture of o-BrC6H4Cl and MeSiHCl2 with Mg shavings in THF.The diarylsilanes, (o-ClC6H4)2SiMeR (R = H, Me) could be converted to diGrignard reagents with Mg prepared by the Rieke method but not from commercial Mg (shavings or mesh).The diorganomatallic reagents generated from (o-XC6H4)2SiMeR (R = H, Me) are used to prepare disilaanthracenes or silaanthrones.A new spiro derivative, bis(dimethyl-o,o'-diphenylsilyl)spirosilane, is obtained on addition of HSiCl3 to the diGrignard reagent generated from (o-ClC6H4)2SiMe2.When gaseous CO2 is added to the dilithio reagent formed from (o-BNrC6H4)2SiMe2, silaanthrone is produced which provides a new route to the silaanthracene framework.Aspects of this new ring closure route are described.
- Corey, J. Y.,McCarthy, W. Z.
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p. 319 - 326
(2007/10/02)
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- Ylide Reactions of Benzyldimethylammonium Halides
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Deprotonation of benzyldimethylammonium halides (10) with sodium amide or n-butyllithium afforded silylated ylide intermediates 11, which were rearranged into N,N-dimethyl-2-benzylamines (13) accompanied by the formation of Sommelet-Hauser and Stevens rearrangement products (12 and 22).The ylide formation by the cleavage of carbon-silicon bonds also is discussed in the reaction of 10 with sodium amide and lithium aluminum hydride.
- Sato, Yoshiro,Yagi, Yoko,Koto, Masami
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p. 613 - 617
(2007/10/02)
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