- Design, Synthesis, and Implementation of Sodium Silylsilanolates as Silyl Transfer Reagents
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There is an increasing demand for facile delivery of silyl groups onto organic bioactive molecules. One of the common methods of silylation via a transition-metal-catalyzed coupling reaction employs hydrosilane, disilane, and silylborane as major silicon sources. However, the labile nature of the reagents or harsh reaction conditions sometimes render them inadequate for the purpose. Thus, a more versatile alternative source of silyl groups has been desired. We hereby report a design, synthesis, and implementation of storable sodium silylsilanolates that can be used for the silylation of aryl halides and pseudohalides in the presence of a palladium catalyst. The developed method allows a late-stage functionalization of polyfunctionalized compounds with a variety of silyl groups. Mechanistic studies indicate that (1) a nucleophilic silanolate attacks a palladium center to afford a silylsilanolate-coordinated arylpalladium intermediate and (2) a polymeric cluster of silanolate species assists in the intramolecular migration of silyl groups, which would promote an efficient transmetalation.
- Yamagishi, Hiroki,Saito, Hayate,Shimokawa, Jun,Yorimitsu, Hideki
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p. 10095 - 10103
(2021/08/18)
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- Sodium silylsilanolate enables nickel-catalysed silylation of aryl chlorides
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Structurally diverse aryl chlorides were silylated with sodium silylsilanolate reagents in the presence of a Ni(cod)2catalyst complexed with a phosphine ligand; PMe2Ph for electron-rich substrates, and PCy2Ph for electron-deficient ones. The mild reaction conditions allowed the silylation of various aryl chlorides including functionalised drug molecules.
- Hitoshio, Kenshiro,Yamagishi, Hiroki,Shimokawa, Jun,Yorimitsu, Hideki
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supporting information
p. 6867 - 6870
(2021/07/19)
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- Nickel-Catalyzed Decarbonylation of Acylsilanes
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Nickel-catalyzed decarbonylation of acylsilanes is developed. In sharp contrast to cross-coupling reactions of acylsilanes, in which the silyl group serves as a leaving group, the silyl group is retained in the product in this decarbonylation reaction. Although the strong binding of the dissociated CO to the nickel center frequently hinders catalyst turnover in nickel-mediated decarbonylative reactions, this reaction can be catalyzed by nickel complexes bearing a CO ligand.
- Ito, Yuri,Kodama, Takuya,Nakatani, Syun,Sakurai, Shun,Tobisu, Mamoru
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p. 7588 - 7594
(2020/06/27)
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- Sterically facilitated meta-lithiation of arenes, containing electron-donating groups
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The influence of the bulky trimethylsilyl substituent on the selectivity of metallation of dimethylaniline, anisole and 1-dimethylaminonaphthalene is studied. The neighboring SiMe3 group forces dimethylamino and methoxy groups to occupy a confo
- Antonov, Alexander S.,Bardakov, Victor G.,Mulloyarova, Valeriia V.
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supporting information
(2019/12/11)
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- Direct ortho Arylation of Anisoles via the Formation of Four-Membered Lithiumcycles/Palladacycles
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We report here our latest discovery on the directed lithiation and palladium-catalyzed arylation of anisoles. During this research, the formation of a four-membered lithiumcycle followed by transmetalation to the corresponding palladacycle has been achieved, which is difficult to be obtained from palladium-catalyzed C-H activation processes. This approach has provided an alternative way of introducing functionalities to arenes such as anisoles, thioanisoles, and anilines. This approach also features an excellent monoselectivity compared with reactions under transition-metal-catalyzed conditions.
- Xiong, Xiaoyu,Zhu, Ranran,Huang, Lin,Chang, Shuqin,Huang, Jianhui
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supporting information
p. 2046 - 2050
(2017/09/13)
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- Deprotonative metalation of functionalized aromatics using mixed lithium-cadmium, lithium-indium, and lithium-zinc species
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In situ mixtures of CdCl2TMEDA (0.5 equiv; TMEDA = N,N,N',N'-tetramethylethylenediamine) or InCl3 (0.33 equiv) with [Li(tmp)] (tmp = 2,2,6,6-tetramethylpiperidino; 1.5 or 1.3 equiv, respectively) were compared with the previously described mixture of ZnCl2-TMEDA (0.5 equiv) and [Li(tmp)] (1.5 equiv) for their ability to deprotonate anisole, benzothiazole, and pyrimidine. [(tmp)3CdLi] proved to be the best base when used in tetrahydrofuran at room temperature, as demonstrated by subsequent trapping with iodine. The Cd-Li base then proved suitable for the metalation of a large range of aromatics including benzenes bearing reactive functional groups (CONEt2, CO2Me, CN, COPh) or heavy halogens (Br, I), and heterocycles (from the furan, thiophene, pyrrole, oxazole, thiazole, pyridine, and diazine series). Fivemembered heterocycles benefiting from doubly activated positions were similarly dideprotonated at room temperature. The aromatic lithium cadmates thus obtained were involved in palladium-catalyzed cross-coupling reactions or simply quenched with acid chlorides.
- Snegaroff, Katia,L'Helgoual'ch, Jean-Martial,Bentabed-Ababsa, Ghenia,Nguyen, Tan Tai,Chevallier, Floris,Yonehara, Mitsuhiro,Uchiyama, Masanobu,Derdour, Aicha,Mongin, Florence
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experimental part
p. 10280 - 10290
(2010/04/24)
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- Process for performing an in-situ-quench reaction
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Method for carrying out in-situ quench (ISQ) reaction, by producing reactive intermediate in presence of reaction partner comprises (a) supplying a mixture of a precursor(PR), RP and optionally inert diluent to microreactor; (b) mixing in reactor with highly reactive reagent (RR) which converts PR into RI; and (c) isolating final product formed by reaction of RI with RP (optionally after flowing through a residence time unit). A method for carrying out an in-situ quench (ISQ) reaction, by producing a reactive intermediate (RI) in presence of a reaction partner (RP), involves: (a) supplying a mixture of a precursor(PR), RP and optionally an inert diluent to a microreactor; (b) mixing in the reactor with a highly reactive reagent (RR) which converts PR into RI; and (c) isolating the final product formed by the reaction of RI with RP (optionally after flowing through a residence time unit). An independent claim is included for use of a microreactor for carrying out an ISQ reaction, by supplying a mixture of PR, RP and optionally an inert diluent to the microreactor and mixing with RR.
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Page/Page column 9
(2008/06/13)
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- Syndiospecific living propylene polymerization catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands
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The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy-imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a β-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C2 symmetry, they are capable of producing highly syndiotactic polypropylenes. 13C NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exclusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. 13C NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block structures. Substitutions on the phenoxy-imine ligands have profound effects on catalytic behavior of the Ti complexes. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization. Over a temperature range of 0-50 °C, Ti complex having a trimethylsilyl group ortho to the phenoxy oxygen forms highly syndiotactic, nearly monodisperse polypropylenes (94-90% rr) with extremely high peak melting temperatures (Tm = 156- 149 °C). The polymerization behavior of the Ti complexes can be explained well by the recently proposed site-inversion mechanism for the formation of syndiotactic polypropylene by a Ti complex having a pair of fluorine-containing phenoxy-imine ligands.
- Mitani, Makoto,Furuyama, Rieko,Mohri, Jun-ichi,Saito, Junji,Ishii, Seiichi,Terao, Hiroshi,Nakano, Takashi,Tanaka, Hidetsugu,Fujita, Terunori
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p. 4293 - 4305
(2007/10/03)
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- Fluorine- and trimethylsilyl-containing phenoxy-imine Ti complex for highly syndiotactic living polypropylenes with extremely high melting temperatures
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A fluorine- and trimethylsilyl-containing phenoxy-imine titanium complex was synthesized and the structure was determined by an X-ray analysis. The complex on activation with MAO initiates highly controlled syndiospecific living propylene polymerization to form extremely high Tm syndiotactic polypropylenes (Mw/Mn = 1.05-1.08, Tm = 156-152 °C) at 0 or 25 °C. Moreover, at 50 °C, the complex afforded monodisperse syndiotactic polypropylene with very high Tm's of 149, 150 °C. In contrast, complexes having a t-Bu group instead of the silyl group provided lower tacticity polymers with much lower Tm's. In addition, we revealed the substituent effect that plays a key role for the highly controlled syndiospecific polymerization displayed by the catalyst. Copyright
- Mitani, Makoto,Furuyama, Rieko,Mohri, Jun-ichi,Saito, Junji,Ishii, Seiichi,Terao, Hiroshi,Kashiwa, Norio,Fujita, Terunori
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p. 7888 - 7889
(2007/10/03)
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- Increasing enantioselectivities and reactivities by stereochemical tuning: Fenchone-based catalysts in dialkylzinc additions to benzaldehyde
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Trimethylsilyl substitutions of the fenchyl alcohols [(1R,2R,4S)-exo-(2- Ar)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, Ar = 2-methoxyphenyl (1) and Ar = 2-(dimethylaminomethyl)phenyl (2)] yield the chiral ligands 3 [Ar = 2- methoxy-3(trimethylsilyl)phenyl
- Goldfuss, Bernd,Steigelmann, Melanie,Rominger, Frank
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p. 1785 - 1792
(2007/10/03)
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- Kinetic Control in the Cleavage of Unsymmetrical Disilanes
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A series of 12 phenyl-substituted arylpentamethyldisilanes 1a-1 have been synthesized in order to examine the regioselectivity of their nucleophilic Si,Si bond cleavage reactions under Still's conditions (MeLi/HMPA/0°C). It has been found that the sensitivity of these reactions to the electronic effects of the substituents in the phenyl ring could be described by the Hammett-type equation log(kA/kB) = 0.4334 + 2.421(Σσ); (correlation coefficient R = 0.983). The kA/kB ratio represents the relative rate of attack at silicon atom A (linked to the aryl ring) or at silicon atom B (away from the aryl ring) of the unsymmetrical disilanes. Thus, the present investigation shows that the earlier belief according to which the nucleophilic cleavage of unsymmetrical disilanes always produces the more stable silyl anionic species (thermodynamic control) should be abandoned, or at least seriously amended: kinetic factors appear to exert a primary influence on the regioselectivity of such reactions. Since the two major kinetic factors (i.e., electrophilic character of and steric hindrance at a given silicon atom) have opposite effects on the orientation of the reaction, it may happen that kinetic and thermodynamic control lead to the same result. For some of the unsymmetrical disilanes studied, the major reaction path was not the Si,Si bond cleavage; instead, Si-aryl bond breaking occurred, producing the corresponding aryl anions.
- Hevesi, Laszlo,Dehon, Michael,Crutzen, Raphael,Lazarescu-Grigore, Adriana
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p. 2011 - 2017
(2007/10/03)
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- Media effects in directed ortho metalation
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Rates and extents of directed ortho metalation (DoM) of anisole and p-methylanisole (p-MA) with n-BuLi have been measured in THF/n-hexane. About a 14% (v/v) solution of THF in the hydrocarbon provides an extent of metalation which exceeds that in neat THF
- Slocum,Reed,Jackson III,Friesen
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p. 265 - 267
(2007/10/03)
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- A PREDICATIVE MODEL FOR CERTAIN DIRECTED METALATIONS, I; APPLICATIONS TO THE BEHAVIOUR OF ANISOLE
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A model whereby the relative ability of the methoxy group to direct metalations in aromatic systems is described.Evidence is presented for a dramatic acceleration of the rate of metalation of anisole provided by the presence of TMEDA resulting in the larg
- Scolum, D. W.,Moon, R.,Thompson, J.,Coffey, D. S.,Li, J. D.,et al.
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p. 385 - 388
(2007/10/02)
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- Multinuclear NMR spectroscopic studies of aryltrimethylsilanes and aryldimethylphosphaneboranes
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Proton, boron-11, carbon-13, silicon-29, and phosphorus-31 NMR chemical shifts and coupling constants are reported for nine ortho- and 2,6-disubstituted aryltrimethylsilanes and five similarly substituted aryldimethylphosphaneboranes.Resonances in the natural-abundance carbon-13 NMR spectra for both sets of derivatives are assigned on the basis of additivity relationships, proton-coupled spectra, and relative magnitudes of 31P-13C)> coupling constants.Carbon-13 chemical shifts and 1J(13C-1H)> coupling constants indicate that the P(BH3)(CH3)2 group is electron-withdrawing.The 13C chemical shifts of aryl C(5) carbons can be attributed to steric inhibition of resonance of about the same magnitude as that produced by ortho-Si(CH3)3.Chemical shift and coupling constant data from previous work are expanded in terms of Taft's dual substituent constants ?1 and ?R0.Least squares solutions of these equations for aryldimethylphosphaneborane derivatives provide values of 0.41 for ?1 and 0.04 for ?R0 for the P(BH3)(CH3)2 group.These constants produce reasonable agreement wit observed 13C chemical shifts and coupling constants in the ortho derivatives.
- Albanese, Joseph A.,Gingrich, Diane E.,Schaeffer, Charles D. Jr.,Coley, Suzanne M.,Otter, Julie C.,et al.
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- Dilithiation of Aromatic Ethers
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The lithiations of anisole and all the isomeric dimethoxy- and trimethoxybenzenes with 2-5 equiv of n-butyllithium/TMEDA complex have been investigated under a variety of reaction conditions.Anisole and m-dimethoxybenzene do not undergo dilithiatian, but
- Crowther, G. P.,Sundberg, Richard J.,Sarpeshkar, Ashok M.
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p. 4657 - 4663
(2007/10/02)
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- Organo-metallic compounds
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Organometallic compounds of the general formula Lr M(CH2 SiR1 R2 R3)m (1) where M is a transition metal of Groups IIIA to VIA of the Periodic Table of Elements, m is an integer from 1 to the prevailing valency of the metal M, Lr represents the sum of any other incidental ligands attached to the metal M, r being 0 or an integer, and R1, R2 and R3 represent substituted or unsubstituted hydrocarbyl groups or hydrogen atoms, at least one of said groups having the general formula SPC1 Where n is an integer from 1 to 5 and Y is a group capable of donating electrons to the metal M are useful as catalysts for olefin polymerization. The compounds may be used as catalysts alone or when supported upon a matrix for example of alumina. Particularly useful compounds are those in which the transition metal M has a valency lower than the maximum valency for that metal.
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