- Influence of β-Silyl Groups in Cycloalkanones on the Norrish Type I and Type II Cleavages
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The Norrish type I cleavage overwhelms the type II cleavage in the photolysis of α-alkylcycloalkanones bearing an SiMe3, SiMe2Ph, SiMePh2, or SiPh3 group at the β-position, of which the quantum yields are often greater than those of the non-silylated cycl
- Hwu, Jih Ru,Chen, Buh-Luen,Huang, Li Wen,Yang, Tu-Hsin
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- EVIDENCE FOR INTERMIDIATE ?-COMPLEXES IN THE ADDITION OF TRIALKYLSILYL AND TRIALKYLSTANNYLCUPRATES TO α,β-UNSATURATED ENONES
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Low temperature 13C NMR spectra of solutions generated during the addition of metallocuprates (PhMe2Si)3CuLi2, PhMe2Si(Me)Cu(CN)Li2, (Me3Sn)3CuLi2 and Mesu
- Sharma, Sunaina,Oehlschlager, Allan C.
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- Total Synthesis of Talatisamine
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Talatisamine (1) is a member of the C19-diterpenoid alkaloid family, and exhibits K+ channel inhibitory and antiarrhythmic activities. The formidable synthetic challenge that 1 presents is due to its highly oxidized and intricately fused hexacyclic 6/7/5/6/6/5-membered-ring structure (ABCDEF-ring) with 12 contiguous stereocenters. Here we report an efficient synthetic route to 1 by the assembly of two structurally simple fragments, chiral 6/6-membered AE-ring 7 and aromatic 6-membered D-ring 6. AE-ring 7 was constructed from 2-cyclohexenone (8) through fusing an N-ethylpiperidine ring by a double Mannich reaction. After coupling 6 with 7, an oxidative dearomatization/Diels–Alder reaction sequence generated fused pentacycle 4 b. The newly formed 6/6-membered ring system was then stereospecifically reorganized into the 7/5-membered BC-ring of 3 via a Wagner–Meerwein rearrangement. Finally, Hg(OAc)2 induced an oxidative aza-Prins cyclization of 2, thereby forging the remaining 5-membered F-ring. The total synthesis of 1 was thus accomplished by optimizing and orchestrating 33 transformations from 8.
- Kamakura, Daiki,Todoroki, Hidenori,Urabe, Daisuke,Hagiwara, Koichi,Inoue, Masayuki
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supporting information
p. 479 - 486
(2019/11/25)
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- Basic Copper Carbonate-Catalyzed Silyl Conjugate Additions to α,β-Unsaturated Carbonyls in Water
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We report here the silylation of α,β-unsaturated acceptors in water at room temperature using a copper catalyst. A broad substrate scope, including chalcone derivatives, esters, nitrile, and dienones, has been explored. In all cases, the reaction proceede
- Wang, Wei,Li, Bo-Jie,Xiao, Zu-Feng,Yan, Feng,Wei, Peng-Ren,Wang, Lian-Sheng,Zhu, Lei
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- [(18-C-6)K][(NC)CuI-SiMe2Ph], a Potassium Silylcyanocuprate as a Catalyst Model for Silylation Reactions with Silylboranes: Syntheses, Structures, and Catalytic Properties
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CuI-catalyzed silylation reactions involving silylboranes (in particular, pinB-SiMe2Ph (1)) as silyl sources have recently gained considerable attention. One of the most efficient and versatile and yet simplest catalyst systems consi
- Plotzitzka, Jacqueline,Kleeberg, Christian
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supporting information
p. 6671 - 6680
(2017/06/13)
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- 1,3-γ-Silyl-elimination in electron-deficient cationic systems
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Placement of an electron-withdrawing trifluoromethyl group (-CF 3) at a putative cationic centre enhances γ-silyl neighbouring-group participation (NGP). In stark contrast to previously studied γ-silyl-substituted systems, the preferred reaction pathway is 1,3-γ-silyl elimination, giving ring closure over solvent substitution or alkene formation. The scope of this cyclopropanation reaction is explored for numerous cyclic and acyclic examples, proving this method to be a viable approach to preparing CF3-substituted cyclopropanes and bicyclic systems, both containing quaternary centres. Rate-constants, kinetic isotope effects, and quantum mechanical calculations provided evidence for this enhancement and further elaborated the disparity in the reaction outcome between these systems and previously studied γ-silyl systems.
- Mercadante, Michael A.,Kelly, Christopher B.,Hamlin, Trevor A.,Delle Chiaie, Kayla R.,Drago, Michael D.,Duffy, Katherine K.,Dumas, Megan T.,Fager, Diana C.,Glod, Bryanna L. C.,Hansen, Katherine E.,Hill, Cameron R.,Leising, Rebecca M.,Lynes, Catherine L.,Macinnis, Allyson E.,McGohey, Madeline R.,Murray, Stephanie A.,Piquette, Marc C.,Roy, Shaina L.,Smith, Ryan M.,Sullivan, Katherine R.,Truong, Bao H.,Vailonis, Kristina M.,Gorbatyuk, Vitaliy,Leadbeater, Nicholas E.,Tilley, Leon J.
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p. 3983 - 3994
(2014/10/15)
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- CuI-catalyzed conjugate addition of silyl boronic esters: Retracing catalytic cycles using isolated copper and boron enolate intermediates
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Copper(I)-catalyzed conjugate additions of silyl boronic esters to α,β-unsaturated aldehydes, ketones, and esters are synthetically well-established reactions. For the first time central reactive intermediates as well as the boron enolates as the primary
- Plotzitzka, Jacqueline,Kleeberg, Christian
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p. 6915 - 6926
(2015/02/05)
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- Copper(II)-catalyzed silyl conjugate addition to α,β-unsaturated conjugated compounds: Bronsted base-assisted activation of Si-b bond in water
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A mild method for the installation of the dimethylphenylsilyl group on the β-carbon of electron-deficient olefins is reported. In the presence of a catalytic amount of copper(II) (1 mol %) and amine base (5 mol %) at rt, the transformation proceeds effici
- Calderone, Joseph A.,Santos, Webster L.
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experimental part
p. 2090 - 2093
(2012/06/18)
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- Metal-free catalytic C-Si bond formation in an aqueous medium. enantioselective NHC-catalyzed silyl conjugate additions to cyclic and acyclic α,β-unsaturated carbonyls
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A metal-free method for enantioselective conjugate addition of a dimethylphenylsilyl group to α,β-unsaturated carbonyls is reported. Transformations are catalyzed by a chiral N-heterocyclic carbene (NHC), performed in an aqueous solution (3:1 mixture of water and tetrahydrofuran) and are operationally simpler to perform than the NHC-Cu-catalyzed variant. The chiral catalyst is generated from an enantiomerically pure imidazolinium salt (prepared in three steps) and a common organic amine base (dbu). NHC-catalyzed processes proceed with 5.0-12.5 mol % catalyst loading at 22 °C within 1-12 h, affording the desired β-silyl carbonyls in 85:15 to >98:2 enantiomeric ratio and in 50% to >98% yield. Cyclic enones or lactones and acyclic α,β-unsaturated ketones, esters, and aldehydes can be used as substrates.
- O'Brien, Jeannette M.,Hoveyda, Amir H.
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scheme or table
p. 7712 - 7715
(2011/07/09)
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- Rhodium(I)-catalyzed enantioselective 1,4-addition of nucleophilic silicon
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A rhodium(I)-catalyzed activation of a silicon-boron linkage, that is, the transmetalation of silicon from boron to rhodium(I) by means of an RhI-OH complex, enables the conjugate transfer of nucleophilic silicon onto α,β-unsaturated acceptors. Pre- or in situ formed cationic rhodium(I)-binap complexes catalyze this novel carbon-silicon bond formation with exceptional enantiocontrol, 92 to >99% ee for cyclic carbonyl and carboxyl compounds as well as >99% ee for acyclic carboxyl compounds.
- Walter, Christian,Fr?hlich, Roland,Oestreich, Martin
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scheme or table
p. 5513 - 5520
(2009/12/09)
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- Organo[2-(hydroxymethyl)phenyl]dimethylsilanes as mild and reproducible agents for rhodium-catalyzed 1,4-addition reactions
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Stable and reusable tetraorganosilicon reagents, alkenyl-, aryl-, and silyl[2-(hydroxymethyl)phenyl]-dimethylsilanes, undergo 1,4-addition reactions to α,β-unsaturated carbonyl acceptors under mild rhodium-catalysis. The reaction tolerates a diverse range of functional groups and is applicable to gram-scale synthesis. Use of a chiral diene ligand allows the achievement of the corresponding enantioselective transformations using the tetraorganosilicon reagents, providing the silicon-based approach to optically active ketones and substituted piperidones that serve as synthetic intermediates of pharmaceuticals. A rhodium alkoxide species is suggested to be responsible for a transmetalation step on the basis of the observed kinetic resolution of a racemic chiral phenylsilane in the enantioselective 1,4-addition reaction under the rhodium-chiral diene catalysis.
- Nakao, Yoshiaki,Chen, Jinshui,Imanaka, Hidekazu,Hiyama, Tamejiro,Ichikawa, Yoshitaka,Duan, Wei-Liang,Shintani, Ryo,Hayashi, Tamio
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p. 9137 - 9143
(2008/02/09)
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- Copper-free and copper-promoted conjugate addition reactions of bis(triorganosilyl) zincs and tris(triorganosilyl) zincates
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In the course of our investigations directed towards an asymmetric copper-catalyzed silyl transfer from bis(triorganosilyl) zincs onto α,β-unsaturated carbonyl compounds, the presence of Lewis acidic lithium cations and the uncatalyzed background reaction
- Auer, Gertrud,Weiner, Barbara,Oestreich, Martin
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p. 2113 - 2116
(2008/02/03)
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- Rhodium-catalyzed enantioselective conjugate silyl transfer: 1,4-Addition of silyl boronic esters to cyclic enones and lactones
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(Chemical Equation Presented) Missing linkage: A chiral cationic rhodium complex catalyzes the enantioselective conjugate addition of silyl anion equivalents to cyclic α,β-unsaturated ketones (X = CH2) and esters (X = O; see scheme). This unpre
- Walter, Christian,Auer, Gertrud,Oestreich, Martin
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p. 5675 - 5677
(2008/02/03)
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- Copper-catalyzed conjugate addition of a bis(triorganosilyl) zinc and a methyl(triorganosilyl) magnesium
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A practical copper-catalyzed conjugate silylation of α,β- unsaturated carbonyl compounds 4 utilizing bis(triorganosilyl) zinc reagent 3 is described. Moreover, mixed methyl(triorganosilyl) magnesium 7 also transfers its silyl ligand to simple enones 4 und
- Oestreich, Martin,Weiner, Barbara
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p. 2139 - 2142
(2007/10/03)
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- Electronic and steric effects of silyl groups in silicon-directed Norrish type cleavages
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Sterically congested cis-2-(t-butyl)-3-(organosilyl)cyclohexanones were irradiated with UV light to give a mixture of Norrish type I and II products, as well as the corresponding trans-2-(t-butyl)-3- (organosilyl)cyclohexanones. In comparison with the trans isomers, the quantum yields and rate constants of the photolytic reactions were greater for the cis isomers.
- Hwu, Jih Ru,Chen, Buh-Luen,Lin, Chien-Fu,Murr, Brown L.
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p. 198 - 201
(2007/10/03)
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- Palladium/Me3SiOTf-catalyzed bis-silylation of α,β-unsaturated carbonyl compounds without involving oxidative addition of disilane
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In the presence of a catalytic amount of Me3SiOTf and palladium(0), the addition of disilane to α,β-unsaturated carbonyl compounds proceeds under very mild conditions via η3-siloxyallylpalladium generated by the reaction of enone, en
- Ogoshi, Sensuke,Tomiyasu, Sadayuki,Morita, Masaki,Kurosawa, Hideo
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p. 11598 - 11599
(2007/10/03)
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- Conjugate addition of dimethylphenylsilyllithium to α,β-unsaturated carbonyl compounds mediated by sub-stoichiometric quantities of dimethylzinc
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Dimethylphenylsilyllithium undergoes conjugate addition to a variety of α,β-unsaturated enones in the presence of sub-stoichiometric amounts of dimethylzinc. Down to 10 mol % of Me2Zn facilitates these reactions to afford good to excellent yields of β-silylated products. This catalytic behavior is displayed when the Me2Zn used is generated in situ, from the addition of methyllithium to zinc (II) iodide or when used directly from a commercial source. This methodology in which sub-stoichiometric quantities of the reactive organometallic reagent are present at a given time may provide a route for catalytic enantioselective conjugate addition of trialkylsilyl moieties to enones.
- MacLean, Bonnie L.,Hennigar, Kimberlea A.,Kells, Kevin W.,Singer, Robert D.
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p. 7313 - 7316
(2007/10/03)
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- Conjugate Addition of Zinc Halide Derived Trialkylsilyl(dialkyl)zincate Reagents to α,β-Unsaturated Carbonyl Compounds
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Trialkylsilyl(dialkyl)zincate reagents, PhMe2SiZnR2Li, (R = Alkyl), are easily prepared in THF solutions via the addition of two equivalents of methyllithium and one equivalent of dimethylphenylsilyllithium to zinc halides (ZnI2 or ZnCl2).The resulting zi
- Vaughan, Andrew,Singer, Robert D.
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p. 5683 - 5686
(2007/10/02)
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- Conjugate Addition of the Phenyldimethylsilyl Group to αβ-Unsaturated Carbonyl Compounds Using a Silylzincate in Place of the Silylcuprate
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Lithium phenyldimethylsilyl(dialkyl)zincates add to a number of αβ-unsaturated carbonyl compounds to give, in most cases, higher yields of the conjugate addition product than we had achieved with the corresponding silylcuprate.
- Crump, Roger A. N. C.,Fleming, Ian,Urch, Christopher J.
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p. 701 - 706
(2007/10/02)
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- Composition and Chemistry of the Mixed Higher Order Cuprates (PhMe2Si)m(CH3)nCu(CN)Lim+n
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Low-temperature 29Si, 13C, and 1H NMR spectroscopic techniques were used to probe the nature of THF solutions of cuprates derived from PhMe2SiLi, MeLi, and CuCN in the stoichiometric ratios 1:1:1, 2:1:1, and 1:2:1 (Si:Me:Cu).Unlike the corresponding mixed stannyl systems that yield R3Sn(R)2CuLi2 when the ratio of stannyl anion:alkyl anion:cuprous ion is 1:2:1, these mixed silyl systems only form R3Si(R)Cu(CN)Li2.Solutions wherein the ratio of silyl anion and alkyl anion to cuprous ion is greater than 2:1 contain alkyllithium uncoordinated with cuprous ion.The most striking result is the preferential displacement of RLi when R3SiLi is added to solutions of R3Si(R)Cu(CN)Li2 or R2Cu(CN)Li2.These mixed metallocuprate solutions preferentially transfer the PhMe2Si moiety in reactions with α,β-unsaturated enones and other unsaturated organic substrates.However, the mixed alkylsilylcuprate (PhMe2Si)(CH3)Cu(CN)Li2 reacts with 1,2-epoxyoctane to afford up to 31percent of the methylated alcohol.Frontier orbital analysis of both the predominant cuprates species and preferential ligand transfer provides a rationale for the observed behavior.
- Singer, Robert D.,Oehlschlager, Allan C.
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p. 3510 - 3514
(2007/10/02)
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- Synthetic and Mechanistic Implications of Ligand Mixing in Higher Order Mixed (Trialkylsilyl)- and (Trialkylstannyl)cuprates
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Low-temperature 119Sn, 29Si, 13C, and 1H NMR spectroscopic techniques were used to probe the nature of cuprates derived from CuCN, MeLi, and R3MLi (M = Si or Sn) in THF.These studies conclusively demonstrate facile dissociation-reassociation of R3M and al
- Sharma, Sunaina,Oehlschlager, Allan C.
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p. 770 - 776
(2007/10/02)
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- Catalytic asymmetric synthesis of β-hydroxy ketones by palladium-catalyzed asymmetric 1,4-disilylation of α,β-unsaturated ketones
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1,4-Disilylation of β,β-unsaturated ketones with 1,1-dichloro-1-phenyl-2,2,2-trimethyldisilane proceeded in the presence of phosphine-palladium catalysts in benzene. High enantio-selectivity (up to 92%) was observed in the disilylation with dichloro[(R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl] palladium(II) as a catalyst (0.5 mol %). The disilylation products, 1-(trimethyisilyloxy)-3-(dichlorophenylsilyl)propenes, were readily converted into optically active α-unsubstituted or anti α-substituted β-(phenyldimethylsilyl) ketones, the oxidation of which gave the corresponding optically active β-hydroxy ketones in high yields.
- Matsumoto, Yonetatsu,Hayashi, Tamio,Ito, Yoshihiko
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p. 335 - 346
(2007/10/02)
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- CHEMICAL AND SPECTROSCOPIC INVESTIGATIONS OF TRIALKYLSILYLCUPRATES DERIVED FROM CuCN.
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We disclose that in THF addition of increasing amounts of ΦMe2SiLi (with LiCl) to CuCN gives sequentially ΦMe2SiCu(CN)Li (1:1), (ΦMe2Si)2Cu(CN)Li2 (2:1) and (ΦMe2Si)3CuLi2 (3:1).The formation of the latter species is corroborated with chemical tests on bo
- Sharma, Sunaina,Oehlschlager, Allan C.
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p. 557 - 568
(2007/10/02)
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- PALLADIUM-CATALYZED 1,4-DISILYLATION OF α,β UNSATURATED KETONES WITH 1,1-DICHLORO-1-PHENYL-2,2,2-TRIMETHYLDISILANE
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1,4-Disilylation of α,β-unsaturated ketones proceeded with 1,1-dichloro-1-phenyl-2,2,2-trimethyldisilane in the presence of a phosphine-palladium catalyst in benzene.Treatment of the disilylation products with an excess of methyllithium generated β-silyl lithium enolates, of which hydrolysis and alkylation gave β-(phenyldimethylsilyl) ketones and anti β-silyl α-alkyl ketones, respectively.
- Hayashi, Tamio,Matsumoto, Yonetatsu,Ito, Yoshihiko
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p. 4147 - 4150
(2007/10/02)
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- TRANSITION-METAL CATALYZED SILYLZINCATION AND SILYLALUMINATION OF ACETYLENIC COMPOUNDS
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Dialkyl(dimethylphenylsilyl)zinclithium and trialkyl(dimethylphenylsilyl)aluminiumlithium add effectively to internal acetylenes as well as terminal ones in the presence of transition-metal catalysts to provide vinylsilanes with high stereo- and regiosele
- Wakamatsu, Kuni,Nonaka, Tsuyoshi,Okuda, Yasuhiro,Tueckmantel, Werner,Oshima, Koichiro,et al.
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p. 4427 - 4436
(2007/10/02)
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- 1,4-Addition of Triorganozincates and Silyldiorganozincates to α,β-Unsaturated Ketones
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Lithium and magnesium triorganozincates, prepared by combination of ZnCl2(TMEDA) with 3 molar equivalents of RLi or RMgX, or from dialkylzinc and 1 molar equivalent of RLi or RMgX, react with 2-cyclohexen-1-one (1) under mild conditions to produce moderate to good yields of the 1,4-addition products 2.The approximate reactivity order obtained from the product distribution using unsymmetrical zincates is tBuCH2 tBu, Me Me2PhSi.The latter groups are transferred with good selectivity from mixed reagents derived from Me2Zn.This sequence differs strikingly from that exhibited by unsymmetrical cuprates which transfer neopentyl very easily, and also tert-butyl more easily than the corresponding zincates.The methylation with Me3ZnLi is catalyzed by cobalt complexes.Other enones (7-13) generally give poor yields, and the cobalt-catalyzed methylation of isophorone (3) is complicated by a Kharasch-type deconjugation.Mixed silyldialkylzincates, Me2PhSiZnR2Li, produce the β-silyl ketones from a variety of unhindered or moderately hindered enones in practically useful yields; one example of an α,β-unsaturated ester (12) is also included.
- Tueckmantel, Werner,Oshima, Koichiro,Nozaki, Hitosi
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p. 1581 - 1593
(2007/10/02)
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- COPPER CATALYZED SILYLZINCATION OF ACETYLENES
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Dialkyl(dimethylphenylsilyl)zinclithium adds effectively to internal acetylenes as well terminal acetylenes in the presence of CuCN catalyst.
- Okuda, Yasuhiro,Wakamatsu, Kuni,Tueckmantel, Werner,Oshima, Koichiro,Nozaki, Hitosi
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p. 4629 - 4632
(2007/10/02)
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- The Conjugate Addition of a Silyl Group to Enones and its Removal with Copper(II) Bromide: A Protecting Group for the αβ-Unsaturation of αβ-Unsaturated Ketones
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Silyl-lithium reagents mixed with copper(I) salts react with enones, including esters and aldehydes, to give β-silyl carbonyl compounds in good yield.The β-silylketones can be used in synthesis without risk to the silyl group and the enone group can be restored by bromination-desilylbromination with copper(II) bromide.The principle is illustrated with syntheses of carvone and dihydrojasmone.
- Ager, David J.,Fleming, Ian,Patel, Shailesh K.
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p. 2520 - 2526
(2007/10/02)
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