- Silicon Grignard Reagents as Nucleophiles in Transition-Metal-Catalyzed Allylic Substitution
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A broad range of transition-metal catalysts is shown to promote allylic substitution reactions of allylic electrophiles with silicon Grignard reagents. The procedure was further elaborated for CuI as catalyst. The regioselectively is independent of the leaving group for primary allylic precursors, favoring α over γ. The stereochemical course of this allylic transposition was probed with a cyclic system, and anti -dia-stereoselectivity was obtained.
- Xue, Weichao,Oestreich, Martin
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p. 233 - 239
(2019/01/04)
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- Fe and Co Complexes of Rigidly Planar Phosphino-Quinoline-Pyridine Ligands for Catalytic Hydrosilylation and Dehydrogenative Silylation
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Co and Fe dihalide complexes of a new rigidly planar PNN ligand platform are prepared and examined as precatalysts for hydrosilylation of alkenes. Lithiation of Thummel's 8-bromo-2-(pyrid-2′-yl)quinoline followed by treatment with (i-Pr)2PCl and (C6F5)2PCl afforded the phosphine-quinoline-pyridine ligands, abbreviated RPQpy for R = i-Pr and C6F5, respectively. These ligands form 1:1 adducts with the dichlorides and dibromides of iron and cobalt. Crystallographic characterization of FeBr2(iPrPQpy), FeBr2(ArFPQpy), CoCl2(iPrPQpy), CoBr2(iPrPQpy), and CoCl2(ArFPQpy) confirmed that the M-P-C-C-N-C-C-N portion of these complexes is planar within 0.078 ? unlike previous generations of PNN complexes where deviations from planarity were ~0.35 ?. Bond distances as well as magnetism indicate that the Fe complexes are high spin and the cobalt complexes are high spin or participate in spin equilibria. Also investigated were the NNN analogues of the RPQpy ligands, wherein the phosphine group was replaced by the mesityl ketimine. The complexes FeBr2(MesNQpy) and CoCl2(MesNQpy) were characterized crystallographically. Reduction of MX2(RPQpy) complexes with NaBHEt3 generates catalysts active for anti-Markovnikov silylation of simple and complex 1-alkenes with a variety of hydrosilanes. Catalysts derived from MesNQpy exhibited low activity. Fe-RPQpy derived catalysts favor hydrosilylation, whereas Co-RPQpy based catalysts favor dehydrogenative silylation. Catalysts derived from CoX2(iPrPQpy) convert hydrosilanes and ethylene to vinylsilanes. Related experiments were conducted on propylene to give propenylsilanes.
- Basu, Debashis,Gilbert-Wilson, Ryan,Gray, Danielle L.,Rauchfuss, Thomas B.,Dash, Aswini K.
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p. 2760 - 2768
(2018/09/10)
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- Hydroaminoalkylation of Allylsilanes and a One-Pot Procedure for the Synthesis of 1,5-Benzoazasilepines
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Allylsilanes undergo highly regioselective intermolecular alkene hydroaminoalkylation with secondary amines in the presence of a titanium mono(formamidinate) catalyst. Corresponding reactions of a suitable allyl(2-bromophenyl)silane which exclusively deliver the branched hydroaminoalkylation products combined with a subsequent Buchwald–Hartwig amination result in the development of an elegant one-pot procedure for the synthesis of literature-unknown silicon analogues of 1,5-benzodiazepines, the so-called 1,5-benzoazasilepines.
- Lühning, Lars H.,Strehl, Julia,Schmidtmann, Marc,Doye, Sven
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supporting information
p. 4197 - 4202
(2017/03/31)
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- Zinc mediated allylations of chlorosilanes promoted by ultrasound: Synthesis of novel constrained sila amino acids
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A simple, fast and efficient method for allylation and propargylation of chlorosilanes through zinc mediation and ultrasound promotion is reported. As a direct application of the resulting bis-allylsilanes, three novel, constrained sila amino acids are prepared for the first time. The design and synthesis of the constrained sila analogue of GABA (γ-amino butyric acid) is a highlight of this work. This journal is the Partner Organisations 2014.
- Ramesh, Remya,Reddy, D. Srinivasa
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supporting information
p. 4093 - 4097
(2014/06/10)
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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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- 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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- Pd-catalyzed coupling reaction of allyl and propargyl ethers with chlorosilanes
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Pd-catalyzed synthesis of allylsilanes from chlorosilanes and allyl ethers is described. The reaction proceeds efficiently at room temperature by the use of phenyl or vinyl Grignard reagent in the presence of palladium catalysts. The present method can also be applied to synthesis of propargylsilanes by the use of propargyl ethers. Copyright
- Naitoh, Yoshitaka,Bando, Fumiaki,Terao, Jun,Otsuki, Kazutaka,Kuniyasu, Hitoshi,Kambe, Nobuaki
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p. 236 - 237
(2008/02/04)
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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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- Cross-coupling of triallyl(aryl)silanes with aryl bromides and chlorides: An alternative convenient biaryl synthesis
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Cross-coupling of a diverse range of aryl bromides with triallyl(aryl)silanes is effective in the presence of PdCl2/PCy 3 and tetrabutylammonium fluoride (TBAF) in DMSO-H2O to give various biaryls in good yields. It is worthwhile to note that the all-carbon-substituted arylsilanes, stable towards moisture, acid, and base and easily accessible, serve as a highly practical alternative to their aryl(halo)silane counterparts. A catalyst system consisting of [η3-C3H5)PdCl]2 and 2-[2,4,6-(i-Pr)3C6Ha]-C6H4PCy 2 and use of TBAF· 3 H2O in THF-H2O are effective especially for the cross-coupling with aryl chlorides. Both of the catalyst systems tolerate a broad spectrum of common functional groups. The high efficiency of reactions is presumably due to the ready cleavage of the allyl groups upon treatment with TBAF·3 H2O and an appropriate amount of water. Diallyl(diphenyl)silane also cross-couples with various aryl bromides and chlorides in good yields, whereas allyl(triphenyl)silane gives the cross-coupled products in only moderate yields. Through sequential cross-coupling of bromochlorobenzenes with different arylsilanes, a range of unsymmetrical terphenyls are accessible in good overall yields.
- Sahoo, Akhila K.,Oda, Takuro,Nakao, Yoshiaki,Hiyama, Tamejiro
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p. 1715 - 1727
(2007/10/03)
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- Novel nickel-catalyzed coupling reaction of allyl ethers with chlorosilanes, alkyl tosylates, or alkyl halides promoted by vinyl-Grignard reagent leading to allylsilanes or alkenes
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A new method for a carbon-silicon or carbon-carbon bond forming reaction between allyl ethers and chlorosilanes, alkyl tosylates, or alkyl halides giving rise to allylsilanes or alkenes has been developed. This reaction proceeds efficiently at ambient temperature by the combined use of nickel catalysts and a vinyl-Grignard reagent. A possible reaction pathway involving the formation of allyl-Grignard reagents via transmetallation of π-allylnickel complexes with the vinyl-Grignard reagent and subsequent trapping of the thus formed allyl-Grignard reagents with electrophiles is proposed.
- Terao, Jun,Watabe, Hiroyasu,Watanabe, Hiroyuki,Kambe, Nobuaki
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p. 1674 - 1678
(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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- Highly stereoselective synthesis of bicyclo[n.3.0]alkanes by titanium tetrachloride promoted [3 + 2] cycloaddition of allylsilanes and 1-acetylcycloalkenes
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The titanium tetrachloride promoted reaction of allylsilanes 1 with 1-acetylcyclohexene is shown to afford the silylbicyclo[4.3.0]nonanes 9 ([3 + 2] cycloaddition products) along with the 1-acetyl-2-allylcyclohexane 4 (Hosomi-Sakurai product). Here we report that systematic variation of the substituents at the silicon atom of 1 allows suppression of the classical Hosomi Sakurai reaction in favor of the [3+2] cycloaddition. Cycloaddition of the allylsilanes 1d, 1i, and 1k with 1-acetylcycloalkenes 10, containing a 5-, 6-, 7-, 8-, or 12-membered ring, gives rise to the corresponding silylbicyclo[n.3.0]alkanes 11-13. The cycloaddition of allyltriisopropylsilane (1k) and 1-acetyl-2-methylcycloalkenes 15 provides silylbicyclo[n.3.0]alkanes 16 with two contiguous quaternary carbon centers. The stereochemistry of the silylbicyclo[n.3.0]alkanes 11a-c and 14 is unambiguously determined by X-ray analysis and 13C NMR spectroscopy.
- Knoelker, Hans-Joachim,Foitzik, Norbert,Goesmann, Helmut,Graf, Regina,Jones, Peter G.,Wanzl, Guenter
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p. 538 - 551
(2007/10/03)
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- Concave reagents. 20. Sterically shielded m-terphenyls as selective agents in general protonations
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New m-terphenyls with acidic substituants in the 2′-position have been used in general protonations leading to reagent-controlled selectivity enhancements: up to 96:4 for the γ/α-protonation of unsymmetrically substituted allyl anions, up to 97:3 for the protonation of cyclohexyl anions generating preferentially the thermodynamically less stable cis-products. In order to allow a general, reagent-controlled protonation the acidity of the protonating agent should be as low as possible.
- Luening,Baumgartner,Manthey,Meynhardt
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p. 7922 - 7926
(2007/10/03)
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- Regioselective Protonation of Allylithium Compounds
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By varying the general acid, the regioselectivity of the protonation of (triphenylsilyl)allyllithium (1) in diethyl ether in the presence of HMPT can be changed from 9:1 to 1:9 at room temperature.When other aprotic solvents are used, the nature of the lithium salt changes, and the selectivity decreases.The regioselectivity of the protonation of the dithio-stabilized allyllithium 4 by water is highly dependent on the age of the allyllithium solution with α/γ ratios varying from 2.7:1 to 1:3.5. - Key Words: Protonation, regioselective / Allyllithium compound / Allyl anion / General acid / Regioselectivity / Aging
- Luening, Ulrich,Wangnick, Carsten,Kuemmerlin, Martin
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p. 2431 - 2434
(2007/10/02)
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- PHOTORESIST MATERIALS BASED ON ORGANOMETALLIC-CONTAINING POLYSULFONES
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Soluble 1:1 alternating copolymers of p-tert-butylstyrene, p-(trimethylsilyl)styrene, p-(trimethylgermyl)styrene, and 3-vinylbenzyltrimethylsilane with sulfur dioxide have been synthesized by tert-butylhydroperoxide-initiated copolymerization at T -60 d
- Kim, Seong-Ju,Kim, Ji-Hong,Lee, Dae-Youp,Ko, Young-Hoon,Park, Byung-Sun,Park, Chun-Geun
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p. 317 - 324
(2007/10/02)
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- Ene Reactions of Allylic Derivatives of Silicon, Germanium, Tin and Lead with N-Phenyltriazolinedione: the Effect of Varying the Metal
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The compounds Ph3MCH2CH=CH2 and (M=Si, Ge, Sn or Pb) have been treated with 4-phenyl-1,2,4-triazoline-3,5-dione, and the relative yields of the products of the M-ene reaction, of the H-ene reaction, and of the reaction involving cycloaddition with shift of the organometallic substituent, have been determined.The silicon compounds react principally by the H-ene process.The cycloaddition process is at a maximum (50percent or 70percent) with the germanium compounds, and the tin compounds show mainly the M-ene reaction, with some cycloaddition but no H-ene reaction.Triphenylprop-2-enylplumbane show only the M-ene reaction.In trimethyl(1,1-dimethylprop-2-enyl)silane, in which the H-ene reaction is blocked, only cycloaddition with shift of the silyl group is observed.
- Cai, Jiaqiang,Davies, Alwyn G.
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p. 1743 - 1746
(2007/10/02)
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- A Synthesis of Various Substituted Naphthalenones by Additions to Naphthyloxazolines
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A series of synthetic manipulations on the naphthalene nucleus, containing a 1-(2-oxazolinyl) moiety, is described.Nucleophilic additions afford both regio- and stereoselective products in the 1- and 4-positions.The latter is oxidatively transformed in th
- Meyers, A. I.,Gant, Thomas G.
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p. 4225 - 4231
(2007/10/02)
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- Transition-metal complexes corresponding to the insertion into a group 4B element-carbon bond. 3. Reactivity of complexes with unsaturated carbon-carbon bonds. Crystal structure of (η5-cyclopentadienyl)(triphenylgermyl) (η3-hexenyl) nitrosylmolybdenum
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Anions of the type [(η5-C5H5)(CO)(L)(M4BPh 3)MT]- (L = CO, NO; M4B - Si, Ge, Sn; MT = Mn, Mo, W) react with allyl halides, affording neutral σ-bonded alkenyl derivatives. These new complexes can rearrange to η3-allyl complexes and also lose (allyl)M4B to give η2-allyl complexes. According to the nature of both the transition metal and the group 4B metal η1, η3, or η2 complexes are obtained. A mechanism for these successive reactions is proposed. Butenyl and hexenyl iodides also react with the anions, affording η1 complexes that can eliminate CO and rearrange to a η3 ligand as shown by X-ray structure determination.
- Carré, Francis,Colomer, Ernesto,Corriu, Robert J. P.,Vioux, André
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p. 970 - 977
(2008/10/08)
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- -
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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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