- Synthesis of trans-mono(silyl)palladium(ii) bromide complexes
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The stoichiometric reaction of cis-[Pd(ITMe)2(SiR3)2], where (SiR3 = SiMe3 and SiMe2Ph and ITMe = 1,3,4,5-tetramethylimidazol-2-ylidene) with allyl bromide affords the corresponding allylsilanes along with complexes of the type trans-[Pd(ITMe)2(SiR3)(Br)]. The structure of trans- [Pd(ITMe)2(SiMe2Ph)Br] 2b has been determined in the solid state and displays a slightly distorted square-planar geometry with the two N-heterocyclic carbene ligands in a trans-configuration.
- Ansell, Melvyn B.,Kostakis, George E.,Navarro, Oscar,Spencer, John
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Read Online
- Isomeric C5H11Si+ ions from the trimethylsilylation of acetylene: An experimental and theoretical study
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The gas phase offers a unique medium to conduct the electrophilic addition reaction of (CH3)3Si+ (trimethylsilylium ion) to acetylene. However, this deceptively simple reaction displays a remarkable dependence on the gas phase pressure, revealing the interplay of competitive pathways. In FT-ICR mass spectrometry at ca 10-8 mbar, the nascent (CH3)3Si+-acetylene complex undergoes a rearrangement process yielding the CH2C(CH3)Si(CH 3)2+ ion. This structure has been assigned on the basis of the ion-molecule reactivity displayed by the sampled C 5H11Si+ adducts, matching the one of the model ion obtained from 2-(trimethylsilyl)propene. Whereas the absolute values of kinetic rate constants could not discriminate between isomeric species, the branching ratios for competitive addition-elimination channels in the reaction with i-C3H7OH and t-C4H9OCH 3 were found to be diagnostic of different structures. The pathways leading from the (CH3)3Si+-acetylene complex primarily formed to the candidate C5H11Si+ isomers have been investigated by ab initio quantum chemical calculations at CCSD(T)/6-311 ++G(2d,2p)//B3LYP/6-311G(2d,p) level. The energy profiles show that the path to the CH2C(CH3)Si(CH3) 2+ isomer is associated to the lowest activation energy barrier, below the reactants energy level. The energy released in the (CH 3)3Si+-acetylene association process, remaining stored in the complex formed at low pressure, thus allows the isomerization to a species holding the positive charge on electropositive silicon. Interestingly, the most stable of the conceivable isomers, (E)-(CH3)CHCHSi(CH 3)2+, is not accessed because of an activation energy barrier protruding above the reactants energy level. The combined information of ion-molecule reactivity and ab initio calculations of potential isomers and rearrangement pathways has thus afforded a comprehensive view of the (CH3)3Si+ addition reaction to acetylene under various pressure regimes.
- Siehl, Hans-Ullrich,Brixner, Sandra,Coletti, Cecilia,Re, Nazzareno,Chiavarino, Barbara,Crestoni, Maria Elisa,De Petris, Alberto,Fornarini, Simonetta
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- Diastereoselective protonation on a radical anion in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane
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Diastereoselectivity in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane in the presence of phenanthrene was dependent on the structures and stoichiometry of the added carboxylic acids. Diastereoselectivity increased up to 72% by the addition of equimolar amount of L-lactic acid based on the alkene. Springer Science+Business Media B.V. 2010.
- Maeda, Hajime,Nishitsuji, Nana,Mizuno, Kazuhiko
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experimental part
p. 577 - 585
(2011/11/30)
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- Insight into cis-to-trans olefin isomerisation catalysed by group 4 and 6 cyclopentadienyl compounds
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Intramolecular isomerisation of the pendant allyl unit present in the model compound [MoH(eta;5-C5H4SiMe 2CH2CH=CH2)- (CO)3] reported before was investigated by DFT calculations.
- Chahboun, Ghaita,Petrisor, Cristina E.,Gomez-Bengoa, Enrique,Royo, Eva,Cuenca, Tomas
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experimental part
p. 1514 - 1520
(2009/07/10)
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- Selective mono- and di-allylation and allenylation of chlorosilanes using indium
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Allyl and allenyl groups have been introduced into silicon systems by the allylation and allenylation of chlorosilanes using allyl bromide or propargyl bromide with indium. The allylation of chlorosilanes afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. By applying this method, the reactions of 1-bromo-3-methylbut-2-ene, 3-bromo-2-methylprop-1-ene and 3-bromobut-1-ene with chlorosilanes also proceed smoothly to give regioselectively allylic rearrangement products in good yields. Mediated by indium, dichlorosilanes (R2SiCl2) and trichlorosilanes (RSiCl3) can either afford monoallylated silanes or diallylated silanes depending on the amount of allyl bromide and indium used.
- Li, Zhifang,Yang, Chenjun,Zheng, Hongfang,Qiu, Huayu,Lai, Guoqiao
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scheme or table
p. 3771 - 3779
(2009/02/08)
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- Polymer supported naphthalene-catalysed sodium reactions
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Arene-catalysed sodium reactions have been utilised in the generation of organosodium complexes, from a variety of organochloride complexes, in high yield. Phenyltrimethylsilane, benzene and 2-methyl-1-phenyl-1-propanol were prepared in yields >80%, using polymer supported naphthalene-catalysed sodium reactions, whereby phenylsodium, prepared from the reaction of chlorobenzene, sodium powder and polymer-supported naphthalene (5-100%), was quenched with chlorotrimethylsilane, water or PriCHO respectively. The Royal Society of Chemistry.
- Van Den Ancker, Tania R.,Love, Cameron J.
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p. 3520 - 3523
(2008/09/19)
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- Controlled introduction of allylic group to chlorosilanes
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Allylation of chlorosilanes has been achieved with allylsamarium bromide, especially in a controlled manner. Thus allylation of trisubstituted chlorosilanes (R3SiCl) afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. Dichlorosilanes (R2SiCl2) can either afford monoallylated silanes or diallylated silanes depending on the amount of allylsamarium bromide used. Similarly, trichlorosilanes (RSiCl3) can selectively afford mono-, di-, and tri-allylation products. Finally, perchlorosilane (SiCl4) was allylated stepwise and the corresponding silanes containing one, two, three or four allylic groups, respectively, were obtained in satisfactory yields.
- Li, Zhifang,Cao, Xiaojun,Lai, Guoqiao,Liu, Jinhua,Ni, Yong,Wu, Jirong,Qiu, Huayu
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p. 4740 - 4746
(2007/10/03)
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- Evaluation of β- and γ-Effects of Group 14 Elements Using Intramolecular Competition
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To evaluate β-effects and γ-effects of group 14 elements, we have devised a system in which the intramolecular competition between γ-elimination of tin and β-elimination of silicon, germanium, and tin can be examined. Thus, the reactions of α-acetoxy(arylmethyl)stannanes with allylmetals (metal = Si, Ge, Sn) in the presence of BF3·OEt2 were carried out. The reactions seem to proceed by the initial formation of an α-stannyl-substituted carbocation, which adds to an allylmetal to give the carbocation that is β to the metal and γ to tin. The β-elimination of the metal gives the corresponding allylated product, and the γ-elimination of tin gives the cyclopropane derivative. In the case of allylsilane, the cyclopropane derivative was formed as a major product, whereas in the case of allylgermane the allylated product was formed predominantly. In the case of the allystannane the allylated product was formed exclusively. These results indicate that the y-elimination of tin is faster than the β-elimination of silicon, but slower than the β-elimination of germanium and tin. The theoretical studies using ab initio molecular orbital calculations of the carbocation intermediates are consistent with the experimental results. The effect of substituents on silicon was also studied. The introduction of sterically demanding substituents on silicon disfavored the β-elimination of silicon probably because of the retardation of nucleophilic attack on silicon to cleave the carbon-silicon bond.
- Sugawara, Masanobu,Yoshida, Jun-Ichi
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p. 3135 - 3142
(2007/10/03)
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- Infrared and nuclear magnetic resonance spectroscopic studies of the structure and dynamics of allylic magnesium compounds
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The infrared spectra of allyl- and methallyl-d2-magnesium bromides have two double bond stretching bands, corresponding to C=CH2 and C=CD2 groups in equilibrating allylic isomers. The methylene resonances in the 13C NMR spectra of allylmagnesium bromide and chloride and methallylmagnesium bromide are broadened at low temperatures by an exchange process which appears to be the interconversion between the classical unsymmetrical allylic structures. Analogous changes are seen in the spectrum of 1,3-dimethylallylmagnesium chloride and in the proton NMR spectrum of allylmagnesium bromide. Rate constants and activation parameters for the exchange have been determined from the line broadenings. Unlike the Grignard reagent, the methylene resonances of diallylmagnesium in tetrahydrofuran are not significantly broadened at reduced temperature, and the deuterated reagent does not have two distinct double bond stretching bands in the IR spectrum.
- Hill, E. Alexander,Boyd, Winston A.,Desai, Hemnalini,Darki, Amir,Bivens, Lymel
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- Chemistry of organosilicon compounds. CC. Allyl coupling reactions of allylsilanes and allylstannanes with allylic halides, ethers and acetates promoted by a Lewis acid
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Facile allyl couplings between allylsilanes or allylstannanes and various allylic substrates such as halides, ethers or acetates promoted by a Lewis acid, leading to 1,5-dienes with regiospecific transposition in the allylic part of allylmetallics have been observed. The combination of allylstannanes with allylic acetates promoted by bis(diethylaluminum) sulfate gives the most satisfactory results. The factors influencing the regioselectivity with respect to allylic substrates are discussed.
- Hosomi, Akira,Imai, Takafumi,Endo, Masahiko,Sakurai, Hideki
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- SYNTHESIS AND THERMAL REACTIONS OF 3-TRIMETHYLSILYL-1-PYRAZOLINE
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The compound 3-trimethylsilyl-1-pyrazoline has been synthesized by addition of diazomethane to vinyltrimethylsilane at room temperature.In contrast, addition of trimethylsilyldiazomethane to ethylene at 55 deg C yields 1-trimethylsilyl-2-pyrazoline exclusively.The thermal isomerization of 3-trimethylsilyl-1-pyrazoline to 1-trimethylsilyl2-pyrazoline has been followed kinetically by proton NMR spectroscopy and the reverse reaction has been detected by gas phase pyrolysis.Thermal elimination of nitrogen from either pyrazoline leads to cyclopropyltrimethylsilane, allyltrimethylsilane and E- and Z-1-propenyltrimethylsilane.The relative rates of methylene-H migration to radical centers α and γ to silicon are approximately equal.
- Conlin, Robert T.,Kwak, Young-Woo
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p. 177 - 184
(2007/10/02)
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- Catalytic Conversion of Allylic Esters to Corresponding Allylic Silanes with Hexamethyldisilane and Palladium(0) or Rhodium(I) Complexes
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Treatment of allylic esters (R1CH=CR2CH2OCOR3:R1=H,Ar;R2=H, alkyl; and R3=Me,Ph) with hexamethyldisilane in the presence of catalytic amounts of PdL4 (L=PPh3 or P(OPh)3) or RhCl(PPh3)3 gives the corresponding allylic silanes in the excellent yield.
- Urata, Hisao,Suzuki, Hiroharu,Moro-oka, Yoshihiko,Ikawa, Tsuneo
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p. 607 - 608
(2007/10/02)
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- Regioselective Synthesis of Allyltrimethylsilanes from Allylic Halides and Allylic Sulfonates. Application to the Synthesis of 2,3-Bis(trimethylsilyl)alk-1-enes
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The preparation of allyltrimethylsilanes by regioselective pathways is described.Treatment of (E)-1-chloro-2-alkenes with a reagent prepared from 1 equiv each of trimethylsilyllithium and copper(I) iodide in hexamethylphosphoramide to presumably form a (trimethylsilyl)copper reagent affords 3-(trimethylsilyl)-1-alkenes in good to excellent yields with a high regioselectivity.Treatment of these same 1-chloro-2-alkenes with (trimethylsilyl)lithium alone without added copper(I) iodide yields only (E)-1-(trimethylsilyl)-2-alkenes.A single allylic halide thus yields two regioisomeric allyltrimethylsilanes by proper choice of reaction conditions.The reaction of a variety of allylic sulfonates with (trimethylsilyl)copper has also been investigated.The mesylates of 2 deg and 3 deg allylic alcohols yield mixtures of isomeric allyltrimethylsilanes in which the 1-(trimethylsilyl)-2-alkenes predominate.With geraniol, the mesylate was prepared in situ and allowed to react with (trimethylsilyl)copper to afford two isomeric allyltrimethylsilanes in which the 3-(trimethylsilyl)-1-alkene predominates.Finally, these reactions have also been used to prepare a variety of 2,3-bis(trimethylsilyl)alk-1-enes, a class of unsaturated organosilanes which has received little attention in the literature.
- Smith, Janice Gorzynski,Drozda, Susan E.,Petraglia, Susan P.,Quinn, Nina R.,Rice, Elizabeth M.,et al.
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p. 4112 - 4120
(2007/10/02)
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- Regiochemical Convergence in the Reaction of Heterosubstituted Allylic Carbanions via Allylic Aluminum and Boron "Ate" Complexes
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The regiochemistry in reactions of heterosubstituted allylic carbanions (1) is highly controlled via allylic aluminum or boron "ate" complexes which direct both carbonyl compounds and reactive halides to the α-position with high regioselectivity.For example, carbonyl compounds react with the oxygen- (3), sulfur- (12), selenium- (20), and silicon- (25) substituted allylic carbanions at the α-position via the ate complexes.Although the reactions of the ate complexes (2) with aldehydes generally produce a mixture of erythro and threo isomers, the aluminum ate comlex of 3b gives the erythro isomer (5) with very high stereoselectivity.This procedure is applied to the stereoselective synthesis of exo-brevicomin (9).With allylic halides, the oxygen- (3a) and sulfur- (12) substituted allylic carbanions again react at the α-position via the ate complexes.However, the coupling mode is entirely different; the α-α' coupling product (10) is obtained from 3a, while the α-γ' coupling product (15) is produced from 12.
- Yamamoto, Yoshinori,Yatagai, Hidetaka,Saito, Yoshikazu,Maruyama, Kazuhiro
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p. 1096 - 1104
(2007/10/02)
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- SYNTHESIS OF ALLYL SILANES USING TRIMETHYLSILYLLITHIUM IN THE PRESENCE OF COPPER(I) IODIDE
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Allyl silanes have been prepared by reaction of allylic halides with trimethylsilyllithium in the presence of copper(I) iodide.
- Smith, Janice Gorzynski,Quinn, Nina R.,Viswanathan, Malini
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- Reaction of Allylic and Benzylic Methyl Ethers with Sodium and Trimethylchlorosilane. Evidence for the Intermediacy of Allylic Radicals and Anions
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Allyl methyl ether and benzyl methyl ether react with sodium and trimethylchlorosilane to yield, respectively, allyltrimethylsilane and benzyltrimethylsilane. α,α-Dimethylallyl methyl ether and γ,γ-dimethylallyl methyl ether react with sodium and trimethylchlorosilane to yield γ,γ-dimethylallyltrimethylsilane. α-Methylallyl methyl ether and trans-γ-methylallyl methyl ether react with trimethylchlorosilane and sodium to yield similar product mixtures of α-methylallyltrimethylsilane and cis- and trans-γ-methylallyltrimethylsilane.These results are discussed in ter ms of a mechanism involving electron transfer to yield allylic radicals and allylic anion intermediates.
- Tzeng, Dongjaw,Weber, William P.
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p. 265 - 267
(2007/10/02)
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- Mechanisms of Hydride Abstraction from Organometallic Compounds. Effects of Two β-Metal Substituents on the Kinetics of Dehydrometalation
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A series of 1,3-dimetallopropanes, Me3M(CH2)3M'Me3, in which M and M' are C, Si, Ge, Sn, and Pb, has been reacted with triphenylcarbenium ion to remove hydride and yield triphenylmethane.The rate constants for these reactions follow the Hammett-type relationship log k2 = ρΣ?+ + constant, where Σ?+ is the sum of ?+CH2MPh3 for both metal groups.This relationship leads to the conclusion that both metal groups simultaneously stabilize a carbocation intermediate by vertical stabilization through ?-? conjugation.
- Traylor, T.G.,Koermer, G.S.
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p. 3651 - 3657
(2007/10/02)
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- The Mechanism of the Protodesilylation of Allylsilanes and Vinylsilanes
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The protodesilylation of either 1-dimethyl(phenyl)silyl-3-trimethylsilylpropene (15) or its isomer, 1-trimethylsilyl-3-dimethyl(phenyl)silylpropene (16), gave the same, 4:1, mixture of allylsilanes, 3-dimethyl(phenyl)silylpropene (18) and 3-trimethylsilylpropene (19), showing that a cationic intermediate (17) is involved in both reactions.
- Fleming, Ian,Langley, Jennifer A.
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p. 1421 - 1423
(2007/10/02)
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- Regiospecific Synthesis of Allylic Dimethylmethoxysilanes
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Photochemically generated dimethylsilylene reacts regiospecifically with allylic methyl ethers to yield allylic dimethylmethoxysilanes.Reaction of allylic methyl ethers with dimethyldichlorosilane and sodium metal likewise gives allylic dimethylmethoxysilanes in preparatively useful yields.Regiospecificity, however, is not always observed in this latter reaction.Such allylic dimethylmethoxysilanes can be converted to allylic trimethylsilanes easily by reaction with methyllithium.
- Tzeng, Dongjaw,Weber, William P.
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p. 693 - 696
(2007/10/02)
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- DEOXYMETALATION REACTIONS. THE MECHANISMS OF DEOXYSILYLATION OF MONO-TRIMETHYLSILYL-AND BIS-TRIMETHYLSILYL-SUBSTITUTED ALCOHOLS AND A COMPARISON TO THE MECHANISM OF DEOXYSTANNYLATION AND DEOXYPLUMBYLATION
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The relative rates of acid-catalyzed deoxysilylation of 2-trimethylsilyl-1-hydroxyethane, 4, 1-trimethylsilyl-2-hydroxypropane, 5, 1,3-bis(trimethylsilyl)-2-hydroxypropane, 6, and 1-trimethylsilyl-2-methyl-2-hydroxypropane, 7, were found to be 1 : 103.30 : 105.92 : 106.77, respectively, in 9 vol percent aqueous-methanol at 40 deg C.These rates are directly proportional to the sum of the ?+ constants of the substituents on the carbon bearing the nucleofuge (ρ+ = -11).The additive rate-accelerating effect of two trimethylsilyl groups requires equal conjugativen bystabilization by each trimethylsilyl group, and a mechanism involving a hyperconjugatively-stabilized carbocation intermediate is proposed.In contrast, the deoxymetalation reactions of the triphenyltin-, triphenyllead-, and iodomercury-analogs exhibit very different structure-reactivity relationships and have been described as proceeding through concerted E2-like or bridged-ion mechanisms.These mechanistic regimes are reconciled by considering the conjugative interactions, electrofugalities and nucleophilic solvent assistance at the organometal-leaving groups in terms of Thornton's Reacting Bond Rules.This analysis suggests a spectrum of merging mechanisms, the acid-catalyzed deoxysilylation representing one extreme, the E1M (carbocation intermediate) mechanism and the other Group IV deoxymetalation reactions more nearly concerted E2M-paths.
- Davis, Dennis D.,Jacocks, Henry M.
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- Alkali Metal Hydrides: New Metallating Reagents at Silicon
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New procedures for the preparation of organo-silyl-sodium or potassium, which undergo coupling reactions with alkyl, allyl, and benzyl halides and α-enones, are reported.
- Corriu, Robert J. P.,Guerin, Christian
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p. 168 - 169
(2007/10/02)
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Brominations of triphenylallylsilane, methylphenyl-1-naphthylallylsilane, 2(1-naphthyl)-2-allyl-1,2,3,4-tetrahydro-2-silanaphthalene and triphenylallylgermane have been studied in carbon tetrachloride, acetic acid and methanol as solvents. Either cleavage
- Carre,Corriu,Henner
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p. 589 - 598
(2007/10/05)
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