- Incorporation of trialkylsilyl and trialkylstannyl groups into ruthenium carbonyl clusters. Carbonyl substitution versus trialkylsilane or trialkylstannane elimination in these clusters
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The clusters [Ru3(μ-H)(μ3,η2-ampy)(PPh 3)n(CO)9-n] (n = 0 (1), 1 (2), 2 (3); Hampy = 2-amino-6-methylpyridine) react with HSiEt3 to give the oxidative substitution products [Ru3(μ-H)2(μ3,η 2-ampy)-(SiEt3)(PPh3)n(CO) 8-n] (n = 0 (4a), 1 (5a), 2 (6a)). Similar reactions of 1-3 with HSnBu3 afford [Ru3(μ-H)2(μ3,η 2-ampy)(SnBu3)(PPh3)n(CO) 8-n] (n = 0 (4b), 1 (5b), 2 (6b)). In all cases, (a) the added hydride spans a metal-metal edge adjacent to that supported by the bridging amido group, (b) the SiEt3 or SnBu3 ligands occupy an equatorial site on the Ru atom bound to the two hydrides, being trans to the hydride which spans the same edge as the amido group, and (c) in the compounds containing PPh3 ligands, these ligands occupy equatorial positions, cis to hydrides, on the Ru atoms bound to only one hydride. The reactions of 4a and 5a with PPh3 produce the elimination of HSiEt3, rendering the complexes 2 and 3, respectively; however, similar reactions of the tin-containing compounds 4b and 5b afford the substitution products 5b and 6b, respectively. The compounds have been characterized by infrared and 1H, 13C, and 31P NMR spectroscopies and, in the case of 4a by X-ray diffraction. Crystal data for 4a: monoclinic, space group P21/n, a = 10.849 (8) A?, b = 20.809 (4) A?, c = 12.049 (8) A?, β = 98.21 (5)°, V = 2692 (2) A?3, Z = 4, μ(Mo Kα) = 17.17 cm-1, R = 0.048, Rw = 0.053 for 2036 reflections and 287 variables.
- Cabeza, Javier A.,Llamazares, Angela,Riera, Víctor,Triki, Smail,Ouahab, Lahcène
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Read Online
- First observation of stable primary radical cations tBu3SiH cation radical formed by directed radiolysis of a pure compound: tBu3SiH
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Following γ-irradiation of neat t-Bu3SiH at 77 K, the ESR spectrum of the primary radical cation was observed; in contrast Et3SiH yields only radicals arising from secondary processes.
- Rhodes, Christopher J.
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Read Online
- ArF laser photolysis of tetraethyl- and tetravinyl silane
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The ArF laser-induced photolysis of tetraethyl- and tetravinyl-silane (C2Hn)4Si, (n=3 and 5), affords C2Hn-1 unsaturates and a silicon-containing deposit.The reactions are suitable for use in low-temperature chemical vapour deposition of Si/C materials.Keywords: Silicon; Silicon carbide; Laser photolysis; Tetraethylsilane; Tetravinylsilane
- Pola, Josef,Parsons, Jonathan P.,Taylor, Roger
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Read Online
- Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases
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The efficient synthesis of hydrosilanes by catalytic hydrogenolysis of chlorosilanes is described using an iridium (III) pincer catalyst. A careful selection of a nitrogen base (including sterically hindered guanidines and phosphazenes) can unlock the preparation of Me3SiH, Et3SiH, and Me2SiHCl in high yield (up to 98%) directly from their corresponding chlorosilanes.
- Durin, Gabriel,Berthet, Jean-Claude,Nicolas, Emmanuel,Cantat, Thibault
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p. 10855 - 10861
(2021/09/08)
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- Regioselective Hydrosilylation of Olefins Catalyzed by a Molecular Calcium Hydride Cation
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Chemo- and regioselectivity are often difficult to control during olefin hydrosilylation catalyzed by d- and f-block metal complexes. The cationic hydride of calcium [CaH]+ stabilized by an NNNN macrocycle was found to catalyze the regioselective hydrosilylation of aliphatic olefins to give anti-Markovnikov products, while aryl-substituted olefins were hydrosilyated with Markovnikov regioselectivity. Ethylene was efficiently hydrosilylated by primary and secondary hydrosilanes to give di- and monoethylated silanes. Aliphatic hydrosilanes were preferred over other commonly employed hydrosilanes: Arylsilanes such as PhSiH3 underwent scrambling reactions promoted by the nucleophilic hydride, while alkoxy- and siloxy-substituted hydrosilanes gave isolable alkoxy and siloxy calcium derivatives.
- Schuhknecht, Danny,Spaniol, Thomas P.,Maron, Laurent,Okuda, Jun
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supporting information
p. 310 - 314
(2019/11/26)
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- Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
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Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)CNtBu, Ph2CCH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
- Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
(2019/04/17)
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- Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
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Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)C=NtBu, Ph2C=CH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
- Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
p. 6082 - 6091
(2019/04/17)
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- Interconversion and reactivity of manganese silyl, silylene, and silene complexes
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Manganese disilyl hydride complexes [(dmpe)2MnH(SiH2R)2] (4Ph: R = Ph, 4Bu: R = nBu) reacted with ethylene to form silene hydride complexes [(dmpe)2MnH(RHSiCHMe)] (6Ph,H: R = Ph, 6Bu,H: R = nBu). Compounds 6R,H reacted with a second equivalent of ethylene to generate [(dmpe)2MnH(REtSiCHMe)] (6Ph,Et: R = Ph, 6Bu,Et: R = nBu), resulting from apparent ethylene insertion into the silene Si-H bond. Furthermore, in the absence of ethylene, silene complex 6Bu,H slowly isomerized to the silylene hydride complex [(dmpe)2MnH(SiEtnBu)] (3Bu,Et). Reactions of 4R with ethylene likely proceed via low-coordinate silyl {[(dmpe)2Mn(SiH2R)] (2Ph: R = Ph, 2Bu: R = nBu)} or silylene hydride {[(dmpe)2MnH(SiHR)] (3Ph,H: R = Ph, 3Bu,H: R = nBu)} intermediates accessed from 4R by H3SiR elimination. DFT calculations and high temperature NMR spectra support the accessibility of these intermediates, and reactions of 4R with isonitriles or N-heterocyclic carbenes yielded the silyl isonitrile complexes [(dmpe)2Mn(SiH2R)(CNR′)] (7a-d: R = Ph or nBu; R′ = o-xylyl or tBu), and NHC-stabilized silylene hydride complexes [(dmpe)2MnH{SiHR(NHC)}] (8a-d: R = Ph or nBu; NHC = 1,3-diisopropylimidazolin-2-ylidene or 1,3,4,5-Tetramethyl-4-imidazolin-2-ylidene), respectively, all of which were crystallographically characterized. Silyl, silylene and silene complexes in this work were accessed via reactions of [(dmpe)2MnH(C2H4)] (1) with hydrosilanes, in some cases followed by ethylene. Therefore, ethylene (C2H4 and C2D4) hydrosilylation was investigated using [(dmpe)2MnH(C2H4)] (1) as a pre-catalyst, resulting in stepwise conversion of primary to secondary to tertiary hydrosilanes. Various catalytically active manganese-containing species were observed during catalysis, including silylene and silene complexes, and a catalytic cycle is proposed.
- Price, Jeffrey S.,Emslie, David J. H.
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p. 10853 - 10869
(2019/12/23)
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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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- Catalytic Reduction of Alkoxysilanes with Borane Using a Metallocene-Type Yttrium Complex
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The catalytic reduction of alkoxysilanes with the borane HBpin (pin = pinacolato) was achieved using a metallocene-type yttrium complex as a catalyst precursor. Mechanistic study supported the pivotal role of the rigid metallocene structure of the catalyst, which bears two bulky n5-C5Me4SiMe3 ligands, in suppressing the coordination of the side product MeOBpin that is generated during the reaction.
- Aoyagi, Keiya,Matsumoto, Kazuhiro,Shimada, Shigeru,Sato, Kazuhiko,Nakajima, Yumiko
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supporting information
p. 210 - 212
(2019/02/01)
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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 0038; 0039; 0040; 0041
(2018/03/09)
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- Method for preparing hydrogen silane by using calcium hydride to conduct reduction on chlorosilane
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The invention discloses a method for preparing hydrogen silane by using calcium hydride to conduct reduction on chlorosilane and belongs to the technical field of chlorosilane reduction. The problemsof harsh reaction conditions, low reaction speed and the like of chlorosilane reduction through CaH2 in the prior art are solved. In an organic solvent, under catalysis of a catalyst, calcium hydrideis used as a reducing agent, and chlorosilane is reduced into hydrogen silane; the catalyst is borane or borohydride or lithium aluminum hydride, and the organic solvent is tetrahydrofuran or diethylene glycol dimethyl ether or other ether solvents. The method can be applied to hydrogen silane preparation through chlorosilane reduction.
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Paragraph 0090-0091
(2018/07/30)
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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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- PRODUCTION METHOD OF HYDROSILANE
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PROBLEM TO BE SOLVED: To provide a production method of hydrosilane capable of producing hydrosilane efficiently. SOLUTION: Silane having a structure shown by formula (a) is reacted with hydrogen in the presence of iridium complex shown by formula (I) and organic base, to thereby produce hydrosilane efficiently. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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Paragraph 0030-0033; 0040-0043
(2018/10/03)
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- METHOD FOR PRODUCING SILICON HYDRIDE COMPOUND
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PROBLEM TO BE SOLVED: To provide a method for producing a silicon hydride compound by converting a silicon-halogen bond to a silicon-hydrogen bond with a boron hydride, wherein the method allows the reaction to proceed quickly and can be applied to a variety of substrates. SOLUTION: A method for producing a silicon hydride compound includes the step of converting a silicon-halogen bond to a silicon-hydrogen bond with a boron hydride, in the presence of an organic solvent containing nitrogen. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0039; 0041
(2017/11/01)
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- An Isolable Potassium Salt of a Borasilene–Chloride Adduct
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Among the variety of isolable compounds with multiple bonds involving silicon, examples of compounds that contain silicon–boron double bonds (borasilenes) still remain relatively rare. Herein, we report the synthesis of the potassium salt of a chloride adduct of borasilene 1 ([2]?), which was obtained as an orange crystalline solid. Single-crystal X-ray diffraction analysis and reactivity studies on [2]? confirmed the double-bond character of the Si=B bond as well as the reduced Lewis acidity, which is due to the coordination of Cl? to the boron center. A thermal reaction of [2]? afforded a bicyclic product by formal intramolecular C?H insertion across the Si=B bond of 1, which was corroborated by a theoretical study.
- Suzuki, Yuko,Ishida, Shintaro,Sato, Sota,Isobe, Hiroyuki,Iwamoto, Takeaki
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supporting information
p. 4593 - 4597
(2017/04/11)
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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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- A method for preparing inorganic alkoxy silane
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The invention relates to a method for preparing inorganic alkoxy silanes. The method comprises the following steps of: adding different anhydrous alcohols or inorganic chlorosilanes serving as raw materials into the inorganic chlorosilanes or the anhydrous alcohols in a one-time charging mode or a batch charging mode or a continuous charging mode at the normal temperature of -80 DEG C; stirring at the temperature which is more than or equal to the charging temperature for 30 to 180 minutes; introducing ammonia until a system is alkaline; and filtering, washing, and distilling or distilling under reduced pressure to obtain various inorganic alkoxy silanes. According to the method, different inorganic chlorosilanes react with different anhydrous alcohols, so that various inorganic alkoxy silanes can be obtained. The method can be used for preparing various inorganic alkoxy silanes, ammonium chloride can be used as a fertilizer, ethanol can be recycled, and the integral production process is safe, environment-friendly and economic.
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Paragraph 0022; 0023
(2017/04/03)
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- PRODUCTION METHOD OF HYDROSILANE COMPOUND
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PROBLEM TO BE SOLVED: To provide a new production method of a hydrosilane compound. SOLUTION: A hydrosilane compound can be efficiently produced by making an iridium complex having a dialkyl benzimidazole-2-ylidene ligand represented by formula (L1) and a phosphine ligand represented by formula (L2) coexist with a base and gaseous hydrogen so that a nucleophilic substitution reaction (hydride-reduction) of a silane compound, being a raw material compound, with a hydride ion (H-) proceeds (in formulas (L1) and (L2), each of R4 independently represents a 1-6C hydrocarbon group, each of R5 independently represents a 1-6C hydrocarbon group, each of R6 independently represents a 1-10C hydrocarbon group, and n represents an integer of 0-4). SELECTED DRAWING: None COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0020; 0021
(2016/10/07)
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- Regeneration of silyl and boryl compounds
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A method of regenerating a silyl or boryl compound is described. The silyl or boryl compound is contained in an organic phase with conjunct polymer. The silyl or boryl compound is chemically reduced with a hydrogen containing compound in a silane or borane regeneration zone under regeneration conditions to form at least one regenerated silane or borane compound and a metal salt compound. The regenerated silane or borane compound is recovered.
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Page/Page column 15
(2015/09/22)
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- HYDROCARBON CONVERSION PROCESS INCLUDING CATALYST REGENERATION
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A hydrocarbon conversion process is described. The process includes contacting a hydrocarbon feed with an acidic catalyst under hydrocarbon conversion conditions in a hydrocarbon conversion zone. The hydrocarbon feed reacts to form a mixture comprising reaction products, the acidic catalyst, and deactivated acidic catalyst containing conjunct polymer. The mixture is separated into at least two streams, a first stream comprising the reaction products and a second stream comprising the deactivated acidic catalyst. The reaction products are recovered. The deactivated acidic catalyst is contacted with at least one silane or borane compound in a regeneration zone under regeneration conditions, the conjunct polymer reacting with the at least one silane or borane compound resulting in a catalyst phase and an organic phase containing the conjunct polymer and at least one silyl or boryl compound.
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Paragraph 0129; 0130
(2015/11/24)
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- A direct method for preparing ethyldichlorosilane and its comparison with known alternative methods
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Various methods, alternative to direct synthesis, for preparing an important commercial organosilicon monomer, ethyldichlorosilane, were studied in detail. The methods, including organomagnesium and organoaluminum procedures, hydrosilylation, and combined methods, were analyzed from the viewpoint of feasibility of laboratory and small-tonnage commercial production, and their advantages and drawbacks were revealed.
- Lebedev,Sheludyakov,Lebedeva,Ovcharuk,Govorov,Kalinina
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p. 629 - 633
(2014/11/08)
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- Catalytic hydrodefluorination of fluoroaromatics with silanes as hydrogen source at a binuclear rhodium complex: Characterization of key intermediates
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Stoichiometric and catalytic hydrodefluorination reactions of fluorinated aromatic substrates on using [Rh(μ-H)(dippp)]2 (1) (dippp = 1,3-bis(diisopropylphosphino)propane) as catalyst and HSiEt3 as a hydrogen source are reported. Treatment of the hydrido complex 1 with the fluoroarenes gave the fluorido complex [Rh(μ-F)(dippp)]2 (2) and organic hydrodefluorination products. An unusual ortho-selectivity was observed in the reaction of 2,3,5,6-tetrafluoropyridine and pentafluorobenzene giving the 1,2-hydrodefluorinated products. The binuclear structure of complex 2 in the solid state was confirmed by X-ray diffraction. The fluorido complex 2 reacted with HSiEt3 and HSiiPr3 by elimination of the corresponding fluorosilanes to afford the η2-silane hydrido complexes [Rh(H)(η2-HSiEt3)(dippp)] (3) and [Rh(H)(η2-HSiiPr3)(dippp)] (4), respectively. The structures of the complexes 3 and 4 were derived from NMR data and DFT calculations. Catalytic reactions of pentafluoropyridine, 2,3,5,6-tetrafluoro- pyridine or 2,3,5,6-tetra-fluoropyridine, hexa- and pentafluorobenzene with HSiEt3 in the presence of 5 mol% of 1 afforded hydrodefluorination products with up to 19 turnovers after 48 h at 50 C. In contrast to the stoichiometric reactions, the catalytic transformations resulted predominantly in hydrodefluorinations at the para-position of the nitrogen atom in the heterocycles giving evidence for two different C-F activation pathways. Compound 3 can be considered to be an intermediate in the catalytic hydrodefluorinations of the fluoroarenes.
- Zámostná, Lada,Ahrens, Mike,Braun, Thomas
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p. 132 - 142
(2013/10/01)
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- Reactions of amine-and phosphane-borane adducts with frustrated Lewis pair combinations of Group 14 triflates and sterically hindered nitrogen bases
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The ability of trialkyl Group 14 triflates in combination with amine and pyridine bases to dehydrogenate amine-and phosphane-borane adducts has been investigated. By using multinuclear NMR spectroscopy, it has been shown that Me2NH ·BH3 (11) is efficiently converted to [Me2N-BH2]2 (12) by the so-called "frustrated Lewis pair" (FLP) of nBu3SnOTf (4, -OTf = -OSO2CF3) and 2,2,6,6-tetramethylpiperidine (6). Within the scope of the study, exchange of the Lewis acid effects the rate of dehydrogenation in the order: 4 gt; Me3Si-OTf (2) gt; Et 3SiOTf (3). Exchange of the Lewis base for 2,6-di-tert-butylpyridine (5) has also been shown to reduce the rate of reaction, whereas 1,3-di-tert-butylimidazol-2-ylidene (7) reacted directly with 2 to afford 1,3-bis-tert-butyl-4-(trimethylsilyl)imidazolium triflate (8[OTf]). For FLP combinations for which dehydrogenation reaction times are longer, detectable quantities of [H2B(μ-H)(μ-NMe2)BH2] (14) are observed. Both the dehydrogenation reaction and competitive formation of this product are proposed to proceed by initial hydride abstraction by the Lewis acid, followed by deprotonation by the Lewis base, or combination with further dimethylamine-borane and elimination of [Me2NH2]OTf (18[OTf]), respectively. In contrast to 11, MeNH2·BH 3 (22) was not found to cleanly dehydrogenate to either [MeNH-BH 2]3 or [MeN-BH]3 under the same conditions. An alternative reaction pathway was observed with either 2 or 4 and 6 with Ph 2PH ·BH3 (23), resulting in P-silylation or P-stannylation of the phosphane-borane, respectively.
- Whittell, George R.,Balmond, Edward I.,Robertson, Alasdair P. M.,Patra, Sanjib K.,Haddow, Mairi F.,Manners, Ian
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experimental part
p. 3967 - 3975
(2011/01/11)
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- Novel catalytic hydrogenolysis of silyl enol ethers by the use of acidic ruthenium dihydrogen complexes
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Treatment of 1-trimethylsilyloxy-1-cyclohexene (1a) in the presence of a catalytic amount of the acidic dihydrogen complex [RuCl(η2-H2)(dppe)2]OTf (4a) [dppe=1,2-bis(diphenylphosphino)ethane, OTf=OSO2CF3] (10 mol.%) under 1 atm of H2 in anhydrous ClCD2CD2Cl at 50 °C for 8 h afforded cyclohexanone (3a) and Me3SiH in quantitative NMR yields. Silyl enol ethers such as 1-triethylsilyloxy-1-cyclohexene (1b), 1-t-butyldimethylsilyloxy-1-cyclohexene (1c), and other trimethylsilylethers (1d, 1e, and 1f) reacted similarly with H2 to afford the corresponding ketones and trialkylsilanes. The direct proton transfer from H2 to the trimethylsilyl enol ethers (1a and 1d-1f) was confirmed by the experiments employing D2 gas, where α-monodeuterated ketones (3a′ and 3d′-3f′) were obtained in high yields. The enantioselective protonation of prochiral silyl enol ethers with 1 atm of H2 by employing [RuCl(η2-H2) ((S)-BINAP)2]OTf (4e) [BINAP=2,2′-bis (diphenylphosphino)-1,1′-binaphthyl] and [RuCl(η2-H2)((R, R)-CHIRAPHOS)2]OTf (4f) [CHIRAPHOS=2,3-bis(diphenylphosphino)butane] showed that no enantioselectivity was observed in either catalytic or stoichiometric protonation reactions under various reaction conditions. The reaction of [RuHCl(dppe)2] (5a) with one equivalent of Me3SiOTf under 1 atm of H2 produced rapidly 4a, concurrent with the formation of Me3SiH. Based on these studies, the mechanism for this novel hydrogenolysis of silyl enol ethers is proposed which involves heterolytic cleavage of the coordinated H2 on the ruthenium atom caused by the nucleophilic attack of the oxygen atom of enol ethers to give ketones and Me3SiOTf, and the subsequent reaction of the resultant complex 5a with Me3SiOTf under 1 atm of H2 to regenerate the original dihydrogen complex 4a. On the other hand, the stoichiometric reaction of a lithium enolate 6e with one equivalent of 4e at -78 °C in CH2Cl2 under 1 atm of H2 afforded 2-methyl-1-tetralone (3e) with 75% ee (S) in >95% yield, together with the formation of [RuHCl((S)-BINAP)2] (5e).
- Takei, Izuru,Nishibayashi, Yoshiaki,Ishii, Youichi,Mizobe, Yasushi,Uemura, Sakae,Hidai, Masanobu
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- Radiochemical study of the gas phase reaction of nucleogenic diethylsilylium ions with methanol and butanol
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The gas phase ion-molecule reactions between alcohols (methanol and n-butanol) and nucleogenic diethylsilylium ions generated by the β-decay of the tritiated diethylsilane were studied by the radiochromatographic method. Among the labelled neutral product
- Kochina,Vrazhnov,Ignatyev
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p. 258 - 261
(2007/10/03)
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- The mechanism of polarity-reversal catalysis as involved in the radical-chain reduction of alkyl halides using the silane-thiol couple
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The mechanism by which thiols promote the radical-chain reduction of alkyl halides by a variety of simple silanes, such as Et3SiH and Ph3SiH, has been investigated in detail. Kinetic studies of the thiol-catalysed reduction of 1-bromooctane and of 1-chlorooctane by Et3SiH in cyclohexane at 60°C are consistent with a mechanism that involves reversible abstraction of hydrogen by the thiyl radical from the silane, followed by abstraction of halogen from the octyl halide by the resulting triethylsilyl radical and quenching of the derived octyl radical by the thiol to give octane. On the basis of this mechanism, rate constants for abstraction of hydrogen from Et3SiH by the adamantane-1-thiyl radical (kXSH) and for transfer of hydrogen in the reverse direction (KSiH) were determined as 3.2 × 104 M-1 s-1 and 5.2 × 107 M-1 s-1, respectively, at 60°C. The equilibrium constant kXSH/kSiH is thus 6.2 × 10-4 at 60°C and corresponds to ΔrH ≈ ΔrG = +20.4 kJ mol-1 for abstraction of hydrogen from Et3SiH by 1-AdS, implying that the Si-H bond in the silane is stronger by ca. 20 kJ mol-1 than the S-H bond in the alkanethiol. The silanethiol (ButO)3SiSH was found to be a more effective catalyst than 1-AdSH, because kXSH is greater (1.3 × 105 M-1 s-1) while kSiH is very similar (5.1 × 107 M-1 s-1). The value of kXSH/kSiH is now 2.6 × 10-3 at 60°C and thus the S-H bond in this silanethiol is stronger by ca. 4 kJ mol-1 than that in 1-AdSH. The proposed mechanism for alkyl halide reduction is strongly supported by kinetic studies of the thiol-catalysed H/D-exchange between R3SiH/D and XSH/D and the thiol-catalysed racemisation of (S)-ButMePhSiH, radical-chain processes that provide independent confirmation of the values of kXSH derived from octyl bromide reduction. The value of ΔrH determined in this work indicates that abstraction of hydrogen from Et3SiH by an alkanethiyl radical in cyclohexane solvent is ca. 11 kJ mol-1 less endothermic than implied by the difference in the currently-favoured experimental gas-phase dissociation enthalpies for the Et3Si-H and MeS-H bonds.
- Cai, Yudong,Roberts, Brian P.
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p. 1858 - 1868
(2007/10/03)
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- Reaction of carbonyl compounds with trialkylsilyl phenylselenide and tributylstannyl hydride under radical conditions
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A novel method for the hydrosilylation of carbonyl compounds has been developed. When carbonyl compounds were allowed to react with trimethylsilyl phenylselenide and tributylstannyl hydride in the presence of a catalytic amount of AIBN as the radical initiator, hydrosilylation of the carbonyl compounds efficiently proceeded to give the corresponding silyl ethers in moderate to good yields. In the absence of carbonyl compounds, the triethylsilyl hydride was obtained by the reaction of PhSeSiEt3 with Bu3SnH. Although the tributylgermyl phenylselenide instead of PhSeSiMe3 was treated with tributylstannyl hydride in the presence of a benzaldehyde under radical conditions, hydrogermylated product was not obtained and tributylgermyl hydride was mainly formed.
- Nishiyama, Yutaka,Kajimoto, Hiroyuki,Kotani, Kazuya,Nishida, Takuma,Sonoda, Noboru
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p. 5696 - 5700
(2007/10/03)
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- Biphenylsulfonamides and derivatives thereof that modulate the activity of endothelin
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Biphenylsulfonamides and methods for modulating or altering the activity of the endothelin family of peptides are provided. In particular, bicyclic or tricyclic carbon or heterocyclic ring biphenylsulfonamides and methods using these sulfonamides for inhibiting the binding of an endothelin peptide to an endothelin receptor by contacting the receptor with the sulfonamide are provided. Methods for treating endothelin-mediated disorders by administering effective amounts of one or more of these sulfonamides or prodrugs thereof that inhibit or increase the activity of endothelin are also provided.
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- Unsaturated Ru(0) species with a constrained bis-phosphine ligand: [Ru(CO)2((t)Bu2PCH2CH2P(t)Bu2)]2. Comparison to [Ru(CO)2(P(t)Bu2Me)2]
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The synthesis of Ru(C2H4)(CO)2(d(t)bpe) (d(t)bpe = (t)Bu2PC2H4P(t)Bu2), then green [Ru(CO)2(d(t)bpe)](n) is described. In solution, n = 1, while in the solid state, n = 2; the dimer has two carbonyl bridges. DFTPW91, MP2, and CCSD(T) calculations show that the potential energy surface for bending one carbonyl out of the RuP2C(O) plane is essentially flat. Ru(CO)2(d(t)bpe) reacts rapidly in benzene solution to oxidatively add the H-E bond of H2, HCl, HCCR (R = H, Ph), [HOEt2]BF4, and HSiEt3. The H-C bond of C6HF5 oxidatively adds at 80 °C. CO adds, as does the C=C bond of H2C=CHX (X = H, F, Me). The following do not add: N2, THF, acetone, H3COH, and H2O.
- Gottschalk-Gaudig, Torsten,Huffman, John C.,Gerard, Helene,Eisenstein, Odile,Caulton, Kenneth G.
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p. 3957 - 3962
(2008/10/08)
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- Ion-molecule reactions of free diethylsilicenium ions with benzene in the gas and liquid phases
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Diethylsilicenium ions were generated by the nuclear-chemical method, and their reactions with benzene in the gas and liquid phases were studied. The potential energy surface of the C4H11Si+ cation was examined quantum-chemically, and the most stable isomeric forms of this cation were determined. In the course of reaction diethylsilicenium ion (C2H5)2HSi+ can decompose into ethylsilicenium ion (C2H5)SiH+2 and ethylene. In turn, (C2H5)SiH+2 isomerizes into the more stable dimethylsilicenium ion (CH3)2SiH+. A possible reaction mechanism, based on the experimental and theoretical results obtained, was proposed; the mechanism involves isomerization of diethylsilicenium ion.
- Kochina,Vrazhnov,Ignat'ev,Nefedov,Sinotova
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p. 905 - 909
(2007/10/03)
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- Symetrical hydroxyphenyl-s-triazine compositions
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The invention is concerned with compounds of formula I: STR1 which are useful as sun screening agents.
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- THIENYL-, FURYL- AND PYRROLYL SULFONAMIDES AND DERIVATIVES THEREOF THAT MODULATE THE ACTIVITY OF ENDOTHELIN
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Thienyl-, furyl-and pyrrolyl-sulfonamides and methods for modulating or altering the activity of the endothelin family of peptides are provided. In particular, N-(isoxazolyl)thienylsulfonamides, N-(isoxazolyl) furylsulfonamides and N-(isoxazolyl)pyrrolylsulfonamides and methods using these sulfonamides for inhibiting the binding of an endothelin peptide to an endothelin receptor by contacting the receptor with the sulfonamide are provided. Methods for treating endothelin-mediated disorders by administering effective amounts of one or more of these sulfonamides or prodrugs thereof that inhibit or increase the activity of endothelin are also provided.
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- Yb/TMS-Br promoted homocoupling reactions of aliphatic ketones and α,β-unsaturated ketones
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Ytterbium metal reacts with trimethylsilyl bromide (TMS-Br) to give divalent YbBr2. YbBr2 thus formed in situ, causes coupling reactions of aliphatic ketones and α,β-unsaturated ketones to give bissilylated 1,2-diols and 1,6-ketones, respectively, in good yields.
- Taniguchi, Yuki,Nakahashi, Manabu,Kuno, Tatsuhiro,Tsuno, Masumi,Makioka, Yoshikazu,Takaki, Ken,Fujiwara, Yuzo
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p. 4111 - 4114
(2007/10/02)
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- Catalytic Disproportionation of Alkylsilanes over Sulfated ZrO2
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Gas phase heterogeneous catalytic conversions of diethylsilane(E2), triethylsilane(E3) and diethyldimethylsilane(E2M2) were examined at 373 - 573 K in a closed recirculation reactor by using a sulfated ZrO2(SO3/ZrO2) catalyst. The catalyst exhibited high disproportionation activity even at 373 K.
- Fujisawa, Hideo,Yamaguchi, Tsutomu
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p. 593 - 596
(2007/10/02)
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- Vitamin D3 analogs
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Compounds of the formula STR1 wherein R is hydrogen or hydroxy, R5 is hydrogen, and A is --C C--, STR2 or --CH2 --CH2 --, with the proviso that when A is --C C--, R5 may also be deuterium, are described. The compounds of formula I are useful as agents for the treatment of hyperproliferative disorders of the skin such as psoriasis, as agents for the treatment of neoplastic diseases such as leukemia, and as agents for the treatment of sebaceous gland diseases such as acne or seborrheic dermatitis.
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- Process for reducing silicon, germanium and tin halides
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A process for reducing halogen-containing compounds of silicon, germanium or tin with lithium hydride in the presence of tetrahydrofuran wherein the lithium hydride is first heated in the tetrahydrofuran and then the halogen-containing compound is added.
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- New hexacoordinate silicon complexes, the process for their preparation and their application
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The present invention relates to new hexacoordinate silicon complexes, the process for their preparation and their application. These new complexes correspond to the general formula I: STR1 in which: A represents an alkali metal or alkaline earth metal except for magnesium, and n=0 or 1.
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- REDUCTION OF ALKOXYSILANES, HALO-SILANES AND -GERMANES WITH LITHIUM ALUMINIUM HYDRIDE UNDER PHASE-TRANSFER CONDITIONS
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In the presence of phase-transfer catalysts, silicon and germanium organohydrides were obtained in high yield by reduction of the corresponding halo and alkoxy derivatives with lithium aluminium hydride in the solid LiAlH4/hydrocarbon two-phase system.
- Gevorgyan, V. N.,Ignatovich, L. M.,Lukevics, E.
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p. C31 - C32
(2007/10/02)
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- INSERTION REACTIONS OF CALCIUM ATOM INTO Si-Cl AND Ge-Cl BONDS
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Calcium atom is inserted into Si-Cl and Ge-Cl bonds of organosilylchlorides and organogermylchlorides to give the corresponding organosilylcalcium chlorides and organogermylcalcium chlorides, respectively.
- Mochida, Kunio,Manishi, Masaharu
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p. 1077 - 1080
(2007/10/02)
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- REACTIONS OF BENZENE VAPOR-CALCIUM ATOM WITH ORGANIC HALIDES AND CARBONYL COMPOUNDS
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Reactions of benzene vapor-calcium atom with organic halides and carbonyl compounds were examined.Benzene vapor-calcium atom reacted with organic halides (RX) to give phenyl-substituted products (PhR) and reduced products (RH).The reactions of benzene vapor-calcium atom with ketones (RR'CO) or benzaldehyde gave two kinds of alcohol PhRR'COH and RR'CHOH, or Ph2CHOH and PhCH2OH, respectively
- Mochida, Kunio,Takeuchi, Hidenori,Hiraga, Yoo,Ogawa, Hiroyasu
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p. 1989 - 1992
(2007/10/02)
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- Photochemistry of iron and ruthenium carbonyl complexes: Evidence for light-induced loss of carbon monoxide and reductive elimination of triethylsilane from cis-mer-HM(SiEt3)(CO)3(PPh3)
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The near-UV photochemistry of M(CO)4PPh3 and HM(SiEt3)(CO)3(PPh3) (M = Fe, Ru) has been investigated. The HM(SiEt3)(CO)3(PPh3) complexes have a meridional structure with the H cis to both PPh3 and the SiEt3 and are referred to as the cis-mer isomer. In low-temperature (～100 K) rigid organic glasses the M(CO)4PPh3 undergoes dissociative loss of CO to form the 16-electron M(CO)3PPh3, M-(CO)3(PPh3)(2-MeTHF), M(CO)3(PPh3)(1-C5H10), or cis-mer- and fac-HM(SiEt3)(CO)3(PPh3) complex when the organic glass is an alkane, 2-MeTHF, 1-C5H10, or Et3SiH, respectively. The fac-HM(SiEt3)(CO)3(PPh3) complexes undergo thermal isomerization to the cis-mer isomer upon warmup to 298 K. Near-UV excitation of cis-mer-HM(SiEt3)(CO)3(PPh3) at ～100 K in an organic glass gives evidence for both the loss of CO and reductive elimination of Et3SiH. Photochemistry of the complexes at 298 K in fluid solution accords well with photoreactions observed at ～100 K in rigid media. Irradiation of cis-mer-HM(SiEt3) (CO)3(PPh3) in a hydrocarbon solution of Ph3SiH at 298 K results in the formation of cis-mer-HM(SiPh3) (CO)3(PPh3) and Et3SiH with a 313-nm quantum yield of ～0.6. The process is photochemically reversed if the cis-mer-HM(SiPh3) (CO)3(PPh3) is irradiated in the presence of excess Et3SiH. Irradiation of cis-mer-HM-(SiEt3)(CO)3(PPh3) in a hydrocarbon solution at 298 K in the presence of 13CO yields both 13CO-enriched M(CO)4PPh3 and 13CO-enriched cis-mer-HM(SiEt3)(CO)3(PPh3). Irradiation of cis-mer-HM(SiR3)-(CO)3(PPh3) (R = OMe, OEt) or cis-mer-HRu(SiMeCl2)(CO)3(PPh3) at 298 K in the presence of Et3SiH yields cis-mer-HM(SiEt3)(CO)3(PPh3), establishing the light-induced reductive elimination of R3SiH to occur for a wide range of R groups for these complexes.
- Liu, David K.,Brinkley, Cynthia G.,Wrighton, Mark S.
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p. 1449 - 1457
(2008/10/08)
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- Trinuclear Ruthenium Cluster Anions Containing Triorganylsilyl, -germyl, and -stannyl Ligands
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The reaction of Na with triorganylsilanes, -germanes, and -stannanes R'R2XH (X = Si, Ge, Sn; R, R' = organyl) affords trinuclear cluster anions of the type -, which can be isolated as the bis(triphenylphosphoranyliden)ammonium or the tetraethylammonium salts.The structure of an isosceles Ru3 triangle with one hydride bridge and two XR2R' ligands at the bridgehead ruthenium atoms is proposed for the anions on the basis of NMR evidence.The reaction proceeds under elimination of H2 and CO and is reversible; the formation of - from - and Et3SiH reveals the eliminated hydrogen to be arising from the cluster.
- Suess-Fink, Georg,Ott, Jutta,Schmidkonz, Bertram,Guldner, Karlheinz
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p. 2487 - 2493
(2007/10/02)
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- THERMAL ISOMERIZATION AND DECOMPOSITION OF 3,3-DIETHYL-2,4-DIMETHYL-3-SILATHIETANE
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Pyrolisis of 3,3-diethyl-2,4-dimethyl-3-silathietane (I) has been studied at temperatures from 300 to 530 deg C using the pulse pyolytic GC-MS method.Decomposition of I proceeds with the elimination of ethane, ethylene, propylene, butadiene, cis- and trans-but-2-ene, and also with the loss of atomic sulphur.Isomerization into sulphur-containing unsaturated compounds is the main transformation process of I.The intermediacy of 1,1-diethyl-2-methyl-1-silaethylene and diethylsilathione is also discussed.
- Gusel'nikov, L. E.,Sokolova, V. M.,Vonina, E. A.,Zalikin, V. G.,Nametkin, N. S.,et al.
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p. 145 - 154
(2007/10/02)
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