- Heck reactions in hydrothermal, sub-critical water: Water density as an important reaction variable
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Heck coupling reactions of iodobenzene and cyclohexene in sub-critical water illustrate the importance of water density as a reaction variable. Altering the water density from 0.03 to 0.84 g/mL and the reaction pressure from 30 to greater than 213 bar at 225°C changed both product and isomer yields. The multiple physical effects of water density were also explored by the addition of ionic salts. Changing the isothermal state of the liquid water, measurably altered coupling reaction pathways suggesting that changes in solvent-solute interactions can influence transition states favoring some configurations and disfavoring others.
- Gron, Liz U,LaCroix, Jeanna E,Higgins, Cortney J,Steelman, Karen L,Tinsley, Amanda S
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Read Online
- Photosensitized (electron-transfer) deconjugation of 1-arylcyclohexenes
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(equation presented) A series of 1-arylcyclohexenes have been deconjugated to the corresponding 3-arylcyclohexenes via a photosensitized electron-transfer reaction. The introduction of substituents on the aryl group has provided insight into the underlyin
- Mangion, Dino,Kendall, Jamie,Arnold, Donald R.
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Read Online
- A Change from Kinetic to Thermodynamic Control Enables trans-Selective Stereochemical Editing of Vicinal Diols
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Here, we report the selective, catalytic isomerization of cis-1,2-diols to trans-diequatorial-1,2-diols. The method employs triphenylsilanethiol (Ph3SiSH) as a catalyst and proceeds under mild conditions in the presence of a photoredox catalyst and under
- Gu, Xin,Wendlandt, Alison E.,Zhang, Yu-An
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supporting information
p. 599 - 605
(2022/01/03)
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- Efficient functionalization of olefins by arylsilanes catalyzed by palladium anionic complexes
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The coupling of organosilanes and different olefins was performed efficiently in the presence of anionic complexes, [CA]2[PdX4] and [CA]2[Pd2X6], where CA?=?imidazolium or pyridinium cation. The reaction proceeds according to a Pd(II)-mediated pathway, and Cu(OAc)2 acts as the re-oxidant of Pd(0) formed during the catalytic process. High product yields were obtained for differently substituted olefins at 80?°C in 4?h. Styrylsilanes reacted in the same conditions giving unsymmetrical 1,3-dienes.
- Silarska,Majchrzak,Marciniec,Trzeciak
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p. 458 - 464
(2016/12/16)
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- Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides
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The direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides proceeded in the absence of coordinating ethereal solvents at ambient temperature without the addition of a catalyst. The C(sp2)-C(sp3) cross-coupling showed excellent functional-group tolerance, and products were isolated in high yields, generally without the requirement for purification by chromatography. This process represents an expedient, operationally simple method for the construction of new C(sp2)-C(sp3) bonds. Zinc and you'll miss it. Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with alkyl halides proceeded rapidly at ambient temperature without a coordinating ethereal solvent or an added catalyst (see scheme). This versatile, operationally simple approach to C(sp2)-C(sp3) bond formation enables the expedient construction of a diverse array of carbon-based structural motifs.
- Dunsford, Jay J.,Clark, Ewan R.,Ingleson, Michael J.
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supporting information
p. 5688 - 5692
(2015/05/19)
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- A palladium NNC-pincer complex: An efficient catalyst for allylic arylation at parts per billion levels
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Allylic arylation of allylic acetates by sodium tetraarylborates in the presence of ppb to ppm (molar) loadings of a palladium NNC-pincer complex catalyst in methanol at 50°C gave the corresponding arylated products in excellent yields. Total turnover numbers of up to 500 000 000 and turnover frequencies of up to 11 250 000 h-1 were achieved.
- Hamasaka, Go,Sakurai, Fumie,Uozumi, Yasuhiro
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supporting information
p. 3886 - 3888
(2015/03/04)
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- A vesicular self-assembled amphiphilic palladium NNC-pincer complex-catalyzed allylic arylation of allyl acetates with sodium tetraarylborates in water
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Abstract The allylic arylation of various allyl acetates with sodium tetraarylborates proceeded in water in the presence of a vesicular self-assembled amphiphilic palladium NNC-pincer complex to give the corresponding arylated products in high yield, wher
- Hamasaka, Go,Sakurai, Fumie,Uozumi, Yasuhiro
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p. 6437 - 6441
(2015/08/18)
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- Cobalt-Catalyzed Cross-Coupling of Grignards with Allylic and Vinylic Bromides: Use of Sarcosine as a Natural Ligand
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Sarcosine was discovered to be an excellent ligand for cobalt-catalyzed carbon-carbon cross-coupling of Grignard reagents with allylic and vinylic bromides. The Co(II)/sarcosine catalytic system is shown to perform efficiently when phenyl and benzyl Grignards are coupled with alkenyl bromides. Notably, previously unachievable Co-catalyzed coupling of allylic bromides with Grignards to linearly coupled α-products was also realized with Co(II)/sarcosine catalyst. This method was used for efficient preparation of the key intermediate in an alternative synthesis of the antihyperglycemic drug sitagliptin.
- Frlan, Rok,Sova, Matej,Gobec, Stanislav,Stavber, Gaj,?asar, Zdenko
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p. 7803 - 7809
(2015/08/18)
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- A mild method for eliminating alkyl ethers to alkenes
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A method for the conversion of methyl ethers into alkenes is described. In a one-step and mild procedure, both conjugated and isolated cyclic alkenes are accessible in mostly good yields using triflic anhydride in combination with triethylamine. This elimination procedure can also be applied to ethyl and benzyl ethers.
- Lindner, Stephanie,Braese, Stefan
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p. 29439 - 29442
(2014/08/05)
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- Cycloalkyl-based unsymmetrical unsaturated (U2)-NHC ligands: Flexibility and dissymmetry in ruthenium-catalysed olefin metathesis
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Air-stable Ru-indenylidene and Hoveyda-type complexes bearing new unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands combining a mesityl unit and a flexible cycloalkyl moiety as N-substituents were synthesised. Structural features, chemical stabilities and catalytic profiles in olefin metathesis of this new library of cycloalkyl-based U2-NHC Ru complexes were studied and compared with their unsymmetrical saturated NHC-Ru homologues as well as a set of commercially available Ru-catalysts bearing either symmetrical SIMes or IMes NHC ligands.
- Rouen, Mathieu,Borre, Etienne,Falivene, Laura,Toupet, Loic,Berthod, Mikael,Cavallo, Luigi,Olivier-Bourbigou, Helene,Mauduit, Marc
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supporting information
p. 7044 - 7049
(2014/05/06)
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- Selective arylation at the vinylic site of cyclic olefins
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Cyclic olefins usually give Heck products having an aryl ring residing at the allylic or homoallylic position. We describe herein a new method that allows arylation at the vinylic position of various cyclic olefins.
- Wu, Xiaojin,Zhou, Jianrong
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p. 4794 - 4796
(2013/06/05)
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- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
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In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
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supporting information
p. 6014 - 6020
(2013/06/26)
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- Alder-ene reaction of aryne with olefins
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A novel intermolecular Alder-ene reaction based on aryne and olefins was developed. We performed this transformation under mild conditions such as at room temperature, and this reaction displayed high selectivity and good yields only in the presence of CsF. Hence, the intermolecular Alder-ene reaction of aryne with olefins provides an effective route to synthesize derivatives of olefins.
- Chen, Zhao,Liang, Jinhua,Yin, Jun,Yu, Guang-Ao,Liu, Sheng Hua
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supporting information
p. 5785 - 5787
(2013/10/01)
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- Iron-catalyzed allylic arylation of olefins via C(sp3)-H activation under mild conditions
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An aryl Grignard reagent in the presence of mesityl iodide converts an allylic C-H bond of a cycloalkene or an allylbenzene derivative into a C-C bond in the presence of a catalytic amount of Fe(acac)3 and a diphosphine ligand at 0 C. The stereo- and regioselectivity of the reaction, together with deuterium labeling experiments, suggest that C-H bond activation is the slow step in the catalytic cycle preceding the formation of an allyliron intermediate.
- Sekine, Masaki,Ilies, Laurean,Nakamura, Eiichi
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supporting information
p. 714 - 717
(2013/04/10)
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- Selective cross-coupling of organic halides with allylic acetates
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A general protocol for the coupling of haloarenes with a variety of allylic acetates is presented. Strengths of the method are a tolerance for electrophilic (ketone, aldehyde) and acidic (sulfonamide, trifluoroacetamide) substrates and the ability to couple with a variety of substituted allylic acetates. Secondary alkyl bromides can also be allylated under slightly modified conditions, demonstrating the generality of the approach. Finally, the coupling of a reactive vinyl halide could be achieved by the use of a very hindered ligand and more reactive, branched allylic acetates.
- Anka-Lufford, Lukiana L.,Prinsell, Michael R.,Weix, Daniel J.
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supporting information
p. 9989 - 10000
(2013/01/15)
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- Enantioselective synthesis of chiral sulfones by ir-catalyzed asymmetric hydrogenation: A facile approach to the preparation of chiral allylic and homoallylic compounds
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A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg-Baecklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%).
- Zhou, Taigang,Peters, Byron,Maldonado, Matias F.,Govender, Thavendran,Andersson, Pher G.
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p. 13592 - 13595
(2012/10/08)
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- Self-assembled poly(imidazole-palladium): Highly active, reusable catalyst at parts per million to parts per billion levels
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Metalloenzymes are essential proteins with vital activity that promote high-efficiency enzymatic reactions. To ensure catalytic activity, stability, and reusability for safe, nontoxic, sustainable chemistry, and green organic synthesis, it is important to develop metalloenzyme-inspired polymer-supported metal catalysts. Here, we present a highly active, reusable, self-assembled catalyst of poly(imidazole-acrylamide) and palladium species inspired by metalloenzymes and apply our convolution methodology to the preparation of polymeric metal catalysts. Thus, a metalloenzyme-inspired polymeric imidazole Pd catalyst (MEPI-Pd) was readily prepared by the coordinative convolution of (NH4)2PdCl4 and poly[(N-vinylimidazole)-co-(N- isopropylacrylamide)5] in a methanol-water solution at 80 °C for 30 min. SEM observation revealed that MEPI-Pd has a globular-aggregated, self-assembled structure. TEM observation and XPS and EDX analyses indicated that PdCl2 and Pd(0) nanoparticles were uniformly dispersed in MEPI-Pd. MEPI-Pd was utilized for the allylic arylation/alkenylation/vinylation of allylic esters and carbonates with aryl/alkenylboronic acids, vinylboronic acid esters, and tetraaryl borates. Even 0.8-40 mol ppm Pd of MEPI-Pd efficiently promoted allylic arylation/alkenylation/vinylation in alcohol and/or water with a catalytic turnover number (TON) of 20 000-1 250 000. Furthermore, MEPI-Pd efficiently promoted the Suzuki-Miyaura reaction of a variety of inactivated aryl chlorides as well as aryl bromides and iodides in water with a TON of up to 3 570 000. MEPI-Pd was reused for the allylic arylation and Suzuki-Miyaura reaction of an aryl chloride without loss of catalytic activity.
- Yamada, Yoichi M. A.,Sarkar, Shaheen M.,Uozumi, Yasuhiro
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supporting information; experimental part
p. 3190 - 3198
(2012/04/10)
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- Cross-coupling of N-allylic sulfonimides with organozinc reagents at room temperature
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An efficient cross-coupling reaction of N-allylic sulfonimides with organozinc reagents has been developed. In the presence of 1 mol-% of Pd 2(dba)3, a range of N-allylic sulfonimides smoothly couple with various organozinc reagents at room temperature to give the corresponding (E)-alkene products in moderate to excellent yields and with good to exclusive α-selectivity. It is noteworthy that allyl ether, benzyl ether, and ester are tolerated under the reaction conditions. A range of N-allylic sulfonimides smoothly couple with various organozinc reagents in the presence of 1 mol-% of Pd2(dba)3 at room temperature to give the corresponding (E)-alkene products in moderate to excellent yields and with good to exclusive α-selectivity.
- Tang, Xiang-Ling,Wu, Zhao,Li, Man-Bo,Gu, Yonghong,Tian, Shi-Kai
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supporting information; experimental part
p. 4107 - 4109
(2012/09/08)
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- A highly active and reusable self-assembled poly(imidazole/palladium) catalyst: Allylic arylation/alkenylation
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Gobs of globules: A polymeric imidazole/acrylamide palladium catalyst, MPPI-Pd (M=PdIICl and Pd0), was utilized for the allylic arylation/alkenylation of allylic esters with aryl/alkenylboronic acids and tetraaryl borates. Low catalyst loadings efficiently promoted the reaction with a catalytic turnover number of 20000-1250000. The catalyst can be reused without loss of catalytic activity.
- Sarkar, Shaheen M.,Uozumi, Yasuhiro,Yamada, Yoichi M. A.
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supporting information; experimental part
p. 9437 - 9441
(2011/11/06)
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- Copper-catalyzed asymmetric allylic alkylation of racemic cyclic substrates: Application of dynamic kinetic asymmetric transformation (DYKAT)
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The copper-catalyzed asymmetric allylic alkylation (AAA) is of great interest in organic synthesis. This reaction was extensively studied using a broad range of substrates, ligands and organometallic reagents. However, the use of racemic substrates was still limited. Although some processes of kinetic resolution are reported in the literature, no examples of quantitative deracemization are described as is the case for the Pd-catalyzed allylic alkylation. We present here a full account of our investigations through the development of the first example of such a process in copper-catalyzed AAA. High enantioselectivities (up to 99% ee), scope of the reaction and mechanistic considerations are reported herein.
- Langlois, Jean-Baptiste,Alexakis, Alexandre
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supporting information; scheme or table
p. 447 - 457
(2010/06/13)
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- Selective heck arylation of cyclohexene with homogeneous and heterogeneous palladium catalysts
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Palladium catalysts containing Pd(II) supported on Al2O 3 and alumina-based mixed oxides, Al2O3- ZrO2, Al2O3-CeO2, and Al 2O3-Fe2O3, are very effective in the Heck coupling of iodobenzene with cyclohexene in DMF solution. The best results, up to 81% of monoarylated products with a selectivity to 4-phenylcyclohexene (3) close to 90% were obtained with KOH as a base. The catalytic activity of palladium supported on aluminabased oxides was compared with that of homogeneous precursors, such as Pd(OAc)2 and PdCl 2(PhCN)2, used in [Bu4N]Br as the reaction medium. Under such conditions homogeneous systems were more selective and produced up to 60% of monoarylated products with a selectivity to 3 close to 60%. Copyright
- Mieczynska, Ewa,Trzeciak, Anna M.
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scheme or table
p. 2166 - 2177
(2010/08/04)
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- Copper-catalyzed γ-selective and stereospecific allyl-aryl coupling between (Z)-acyclic and cyclic allylic phosphates and arylboronates
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A Cu-catalyzed allyl-aryl coupling reaction between (Z)-acyclic or cyclic allylic phosphates and arylboronates proceeds with excellent γ-E-selectivity and 1,3-anti chirality transfer, which gives the corresponding coupling products with benzylic and allylic stereogenic centers. The wide availability and easy-to-handle nature of arylboronates, the inexpensiveness of the Cu catalyst system, and the high regio- and stereoselectivities are attractive features of this protocol.
- Ohmiya, Hirohisa,Yokokawa, Natsumi,Sawamura, Masaya
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supporting information; experimental part
p. 2438 - 2440
(2010/07/10)
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- Dynamic kinetic asymmetric transformation in copper catalyzed allylic alkylation
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The first dynamic kinetic asymmetric transformation in copper catalyzed allylic alkylation is reported, with enantioselectivities up to 92%.
- Langlois, Jean-Baptiste,Alexakis, Alexandre
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supporting information; experimental part
p. 3868 - 3870
(2010/01/06)
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- Ion-tagged π-acidic alkene ligands promote Pd-catalysed allyl-aryl couplings in an ionic liquid
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Ionic π-acidic alkene ligands based on chalcone and benzylidene acetone frameworks have been ?doped? into ionic liquids to provide functional reaction media for Pd-catalysed cross-couplings of a cyclohexenyl carbonate with aryl siloxanes that allow simple product isolation, free from Pd (50 ppm) and ligand contamination.
- Baeuerlein, Patrick S.,Fairlamb, Ian J. S.,Jarvis, Amanda G.,Lee, Adam F.,Mueller, Christian,Slattery, John M.,Thatcher, Robert J.,Vogt, Dieter,Whitwood, Adrian C.
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supporting information; experimental part
p. 5734 - 5736
(2010/01/31)
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- Direct coupling of alcohols with alkenylsilanes catalyzed by indium trichloride or bismuth tribromide
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Indium halides or bismuth halides catalyzed the coupling of various alcohols with alkenylsilanes to give the corresponding alkenes stereospecifically without any other activators. The Royal Society of Chemistry 2008.
- Nishimoto, Yoshihiro,Kajioka, Masayuki,Saito, Takahiro,Yasuda, Makoto,Baba, Akio
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supporting information; body text
p. 6396 - 6398
(2009/04/13)
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- Cobalt-catalyzed regioselective dehydrohalogenation of alkyl halides with dimethylphenylsilylmethylmagnesium chloride
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Cobalt-catalyzed reactions of haloalkanes with dimethylphenylsilylmethylmagnesium chloride result in highly regioselective dehydrohalogenation. The reaction does not follow the conventional E2 elimination mechanism but includes β-hydride elimination from the corresponding alkylcobalt intermediate. The interesting reaction mechanism of the cobalt-catalyzed dehydrohalogenation offered unique transformations that are otherwise difficult to attain. Copyright
- Kobayashi, Tsuneyuki,Ohmiya, Hirohisa,Yorimitsu, Hideki,Oshima, Koichiro
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supporting information; scheme or table
p. 11276 - 11277
(2009/02/05)
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- Cross-coupling reaction of allylic and benzylic carbonates with organo[2-(hydroxymethyl)phenyl]dimethylsilanes
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The title reaction is found to proceed in the presence of a palladium catalyst and in the absence of any activator. Various functional groups are tolerated to give a diverse range of 1,4-diene and diarylmethane products, which are ubiquitous units of natural products and pharmaceuticals. Copyright
- Nakao, Yoshiaki,Ebata, Shiro,Chen, Jinshui,Imanaka, Hidekazu,Hiyama, Tamejiro
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p. 606 - 607
(2008/02/07)
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- Efficient palladium-catalyzed nucleophilic addition of triorganoindium reagents to carbocyclic derivatives
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Palladium (0)-catalyzed allylic substitution reactions employing triorganoindium reagents have been investigated. In situ generated vinyl- and arylindiums react with substituted and unsubstituted cyclohex-2-enyl esters in the presence of 1-3 mol % Pd2(dba)3 to produce vinyl- or arylcyclohexenes in moderate to excellent yields. The stereoselectivity of this process was also examined, and evidence is presented that the reaction proceeds with inversion of stereochemical configuration.
- Baker, Lucas,Minehan, Thomas
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p. 3957 - 3960
(2007/10/03)
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- Oxygen-promoted Pd(II) catalysis for the coupling of organoboron compounds and olefins
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(Matrix presented) Reported herein is a mild and efficient Pd(ll) catalysis, leading to the formation of carbon-carbon bonds between a broad spectrum of organoboron compounds and alkenes. Molecular oxygen was employed to reoxidize the resultant Pd(0) species back to Pd(ll) during catalytic cycles. This oxygen protocol promoted the desired Pd(ll) catalysis, whereas it retarded competing Pd(0) catalytic pathways such as Heck or Suzuki couplings.
- Jung, Young Chun,Mishra, Rajesh Kumar,Yoon, Cheol Hwan,Jung, Kyung Woon
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p. 2231 - 2234
(2007/10/03)
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- Hypervalent silane and siloxane derivatives and the use thereof
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Hypervalent silane and siloxane reagents (preformed or generated in situ) for transmetalation in palladium catalyzed reactions with derivatives of allylic alcohols, aryl halides, electron-withdrawing aryl bromides, and aryl triflates derived from phenols are disclosed. Also disclosed are methods of preparing glycosyl azides by reaction of an azide with a silyl ester in the presence of a phoshine.
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- A novel palladium catalyst for cross-coupling of allyl acetates with arylboronic acids
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The palladium-catalyzed coupling reactions of various arylboronic acids and allylic acetates take place readily under mild conditions. The choice of ligand in the palladium catalyst and the solvent are critical to the yields of coupled products. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Bouyssi, Didier,Gerusz, Vincent,Balme, Genevieve
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p. 2445 - 2448
(2007/10/03)
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- Palladium-catalyzed arylation of allylic benzoates using hypervalent siloxane derivatives
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Palladium-catalyzed cross-coupling of hypervalent arylsiloxane derivatives proceeded in good to excellent yields with allylic benzoates. Arylation occurred with complete inversion of configuration. The scope and limitations of this reaction, an alternative to the Stille coupling, is summarized.
- Correia,DeShong
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p. 7159 - 7165
(2007/10/03)
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- The photochemistry of the 4-cyanobenzoic acid esters of trans- and cis-2-phenylcyclohexanol
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Irradiation of trans-2-phenylcyclohexyl 4-cyanobenzoate (4) in methanol results in formation of the 1-phenylcyclohexene and 4-cyanobenzoic acid as the major products. The mechanism proposed for this example of the Norrish Type II-like reaction, normally inefficient for the π,π*state of esters, begins with intramolecular electron transfer in the excited singlet state. The next step, intramolecular proton transfer, is highly exergonic as a result of the increased acidity of the benzylic hydrogen of the radical cation and the increased basicity of the carbonyl oxygen of the radical anion. The final step is cleavage of the 1,4-biradical. This mechanism is proposed on the basis of product studies, absorption spectra, fluorescence spectra, oxidation and reduction potentials, and nanosecond laser flash photolysis spectra. The stereochemical requirements for the process have also been examined using solution NMR, the X-ray structure, and MM3 calculations. The stereoisomer, cis-2-phenylcyclohexyl 4-cyanobenzoate (5), undergoes cis to trans isomerization before photofragmentation. Photolysis of the cis isomer in methanol-OD demonstrated that the cis to trans isomerization occurred by inversion at C1.
- Pincock,Rifai,Stefanova
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- Allyl alcohols and organocerium reagents, II. - Mechanism and extensibility of the reaction
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Alkylcerium reagents add to the multiple bonds of allyl and propargyl alcohols in good yields and under mild conditions. The double bond can be reduced with lithium aluminum hydride in the presence of cerium trichloride. The regiochemistry of the attack depends on electronic factors.
- Bartoli, Giuseppe,Bellucci, M. Cristina,Bosco, Marcella,Dalpozzo, Renato,De Nino, Antonio,Sambri, Letizia,Tagarelli, Antonio
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- Cross-coupling reactions of hypervalent siloxane derivatives: An alternative to stille and Suzuki couplings
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Palladium-catalyzed cross-coupling of phenyl, vinyl, and allyl siloxane derivatives proceeded in good to excellent yield with aryl iodides, electron-deficient aryl bromides, and allylic benzoates. Methyl and 2,2,2-trifluoroethyl siloxane derivatives can be employed in the coupling reaction. Electron-donating and -withdrawing groups are tolerated on the aryl halide without affecting the coupling. The scope and limitations of this alternative to Stille and Suzuki couplings is outlined.
- Mowery, Molly E.,DeShong, Philip
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p. 1684 - 1688
(2007/10/03)
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- Highly selective palladium-catalyzed Heck reactions of aryl bromides with cycloalkenes
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Formula presented The influence of palladium catalysts and reaction conditions on the selectivity of Heck reactions of aryl bromides with cyclohexene and cyclopentene has been investigated. It is shown that the addition of DMSO as a cosolvent leads to improved selectivities of nonconjugated aryl olefins. On the other hand, high selectivities for conjugated arylcyclopentenes have been obtained with the catalytic system DMA/Na2-CO3/Pd2(dba) 3·dba/PCy3.
- Hartung, Christian G.,Koehler, Klaus,Beller, Matthias
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p. 709 - 711
(2008/02/11)
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- Cyclization and fluorination of 5-hexenols with boron trifluoride etherate. Stereoselective synthesis of (optically active) fluorinated cyclohexane derivatives by cyclization of ω-pentenyl pentadienol tricarbonyl iron complexes
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Monofluorinated cyclohexane derivatives are obtained by treatment of ω-pentenyl pentadienol tricarbonyl iron complexes with boron trifluoride etherate. The reaction is stereoselective, so that optically active fluorocyclohexanes can be obtained from readily available enantiomerically pure starting complexes. This fluorocyclization reaction with the cheap reagent BF3.Et2O is not restricted to transition-metal coordinated substrates, working also with simple ω-pentenyl benzylic alcohols.
- Franck-Neumann, Michel,Geoffroy, Philippe,Hanss, David
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p. 8487 - 8490
(2007/10/03)
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- Tailoring aqueous solvents for organic reactions: Heck coupling reactions in high temperature water
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High temperature water is demonstrated to be an effective solvent for Heck coupling reactions of aromatic halides with cyclic alkenes without the addition of co-solvents or specialized ligands. Reactions in the presence of LiCl and quaternary ammonium salts indicate that the reaction takes place in the aqueous phase.
- Gron,Tinsley
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p. 227 - 230
(2007/10/03)
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- A Surprising Solid-Phase Effect: Development of a Recyclable "Traceless" Linker System for Reactions on Solid Support
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Keywords: arenes; asymmetric synthesis; C-C coupling; solid-phase synthesis; triazenes
- Braese, Stefan,Enders, Dieter,Koebberling, JOhannes,Avamaria, Frank
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p. 3413 - 3415
(2007/10/03)
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- The Palladium-Catalyzed Cross-Coupling Reaction of Organosilicon Compounds with Allylic Carbonates or Diene Monoxides
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The cross-coupling reaction of allylic carbonates with organosilanes was found to proceed without fluoride ion activation under mild conditions by using a coordinatively unsaturated palladium complex as a catalyst.The reaction was assumed to proceed through an allylpalladium alkoxide derived from the allylic carbonate substrate and a palladium(0) species, the alkoxo ligand activating the organosilicon reagent.Likewise, diene monoxides also underwent cross-coupling with alkenyl- and arylfluorosilanes in moderate to high yields.
- Matsuhashi, Hayao,Asai, Satoshi,Hirabayashi, Kazunori,Hatanaka, Yasuo,Mori, Atsunori,Hiyama, Tamejiro
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p. 1943 - 1952
(2007/10/03)
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- Diastereoselectivity in the epoxidation of substituted cyclohexenes by dimethyldioxirane
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Three series of compounds based on the cyclohexene framework have been epoxidized by dimetbyldioxirane. A pronounced dependence of epoxide diastereoselectivity on substituent has been observed. In addition there is a solvent influence on this stereoselectivity. The results have been explained by invoking steric, H-bonding, and dipole - dipole influences on the epoxide stereochemistry.
- Murray, Robert W.,Singh, Megh,Williams, Brian L.,Moncrieff, Hazel M.
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p. 1830 - 1841
(2007/10/03)
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- Mechanistic pathways in phosphate ester photochemistry
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Initial bond breaking processes (homolysis vs heterolysis) of phosphate ester photosolvolysis were probed by chemically trapping the reactive intermediates with a tethered 5-hexenyl group. The resulting mechanistic picture is a blend of homolytic and heterolytic pathways, where the heterolytic cleavage is dominant.
- Givens, Richard S.,Singh, Rominder
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p. 7013 - 7016
(2007/10/02)
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- Hydroboration. 86. Convenient Conversion of Aldehydes and Ketones into the Corresponding Alkenes via Hydroboration of their Enamines. A Remarkably Simple Synthesis of Either (Z)- or (E)-Alkenes
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Aldehydes and ketones are converted into the corresponding alkenes via hydroboration of their enamines.Hydroboration of aldehyde enamines by 9-borabicyclononane (9-BBN), followed by methanolysis, affords the corresponding terminal alkenes in 75-90percent yields.Unsaturated aldehyde enamines produce the corresponding dienes under these conditions.Enamines derived from substituted cyclic ketones and heterocyclic ketones are readily accommodated in this reaction to afford the corresponding alkenes in very good yields.The synthesis of pure (Z)- or (E)-alkenes is readily achieved from the same acyclic ketone enamine by modification of the hydroboration-elimination procedure: (A) hydroboration by 9-BBN followed by methanolysis or (B) hydroboration by borane methyl sulfide (BMS) followed by methanolysis and hydrogen peroxide oxidation.Mechanistic rationale is provided.
- Singaram, Bakthan,Rangaishenvi, Milind V.,Brown, Herbert C.,Goralski, Christian G.,Hasha, Dennis L.
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p. 1543 - 1549
(2007/10/02)
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- Reactions of Azo and Azoxy Sulphones with Transition Metal Complexes. Part 7. Arylation of Olefins with Arylazoxy Aryl Sulphones Catalysed by a Palladium(0) Phosphine Complex
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The arylation of acyclic and cyclic olefins by arylazoxy aryl sulphones has been investigated in the presence of a palladium(0) catalyst in benzene.Both of the aryl groups of the arylazoxy aryl sulphones are found to participate in the arylation.Two equivalents of aryl-substituted olefins were obtained when the reactions were carried out at 80 deg C, whereas one equivalent of olefin was arylated at 120 deg C.A plausible catalytic cycle involving a diarylpalladium(II) species is proposed.
- Kamigata, Nobumasa,Fukushima, Takamasa,Satoh, Akira,Kameyama, Masayuki
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p. 549 - 553
(2007/10/02)
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- Regioselective Palladium-Catalyzed Tandem α-Arylation/Isomerization of Cyclic Enamides
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Palladium-catalyzed reactions of aryl iodides with the cyclic enamides 1-(methoxycarbonyl)-1,4,5,6-tetrahydropyridine (1), 1-formyl-1,4,5,6-tetrahydropyridine (2), and 1-formyl-2-pyrroline (3) result in regioselective α-arylation, with concomitant isomerization of the double bond into conjugation with the nitrogen atom.The new enamides 1-(methoxycarbonyl)-2-aryl-1,2,3,4-tetrahydropyridines (4), 1-formyl-2-aryl-1,2,3,4-tetrahydropyridines (5), and 1-formyl-5-phenyl-2-pyrroline (6a) were isolated in various yields.The migration of the double bond is affected (a) by an amino group in the ortho position of the aryl iodide; (b) by the presence of silver salts; and (c) partly by a 4-methyl group in the tetrahydropyridine ring.In these cases the allylic compounds 2-aryl-1,2,5,6-tetrahydropyridines (10a,b and 13) are formed.
- Nilsson, Kristina,Hallberg, Anders
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p. 2464 - 2470
(2007/10/02)
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- PALLADIUM-CATALYZED PHENYLATION OF ALLYLIC ACETATES BY TETRAPHENYLBORATE ANION
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Commercial sodium tetraphenylborate is a convenient phenylating reagent in the palladium(0)-catalyzed substitution of allylic acetates.Two phenyl groups of NaBPh4 are available for transfer.Triphenylboron is also a phenylating agent in this reaction.
- Legros, Jean-Yves,Fiaud, Jean-Claude
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p. 7453 - 7456
(2007/10/02)
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- The photochemical rearrangement of 1,2-dihydronaphthalenes into 1,4-dihydronaphthalenes induced by amines
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The synthetic usefulness of the deprotonation/protonation reaction of excited 1,2-dihydronaphthalenes into 1,4-dihydronaphthalenes induced by amines has been investigated using 13 different substituted 1,2-dihydronaphthalenes and related compounds.The yield of the rearrangement ranges from 5 to 96percent.The formation of side-products depends on the position of protons in the substrate, which can be abstracted by the amine, and on competitive photoreactions.
- Cuppen, Th. J. H. M.,Berendsen, N.,Laarhoven, W. H.
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p. 168 - 171
(2007/10/02)
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- Radical ions in photochemistry. 21. The photosensitized (electron transfer) tautomerization of alkenes; the phenyl alkene system
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Alkenes, conjugated with a phenyl group, can be converted to nonconjugated tautomers by sensitized (electron transfer) irradiation.For example, irradiation of an acetonitrile solution of the conjugated alkene 1-phenylpropene, the electron accepting photosensitizer 1,4-dicyanobenzene, the cosensitizer biphenyl, and the base 2,4,6-trimethylpiridine gave the nonconjugated tautomer 3-phenylpropene in good yield.Similarly, 2-methyl-1-phenylpropene gave 2-methyl-3-phenylpropene, and 1-phenyl-1-butene gave E- and Z-1-phenyl-2-butene.The reaction also works well with cyclic alkenes.For example, 1-phenylcyclohexene gave 3-phenylcyclohexene, and 1-(phenylmethylene)cyclohexane gave 1-(phenylmethyl)cyclohexene.The proposed mechanism involves the initial formation of the alkene radical cation and the sensitizer radical anion, induced by irradiation of the sensitizer and mediated by the cosensitizer.Deprotonation of the radical cation assisted by the base gives the ambident radical, which is then reduced to the anion by the sensitizer radical anion.Protonation of the ambident anion at the benzylic position completes the sequence.Reprotonation at the original position is an energy wasting step.Tautomerization is driven toward the isomer with the higher oxidation potential, which is, in the cases studied, the less thermodinamically stable isomer.The tautomerization of 2-methyl-1-phenylbutene gave both 2-phenylmethyl-1-butene and 2-methyl-1-phenyl-2-butene (E and Z isomers), while 2,3-dimethyl-1-phenylbutene gave only 3-methyl-2-phenylmethyl-1-butene.In the latter case, steric interaction of the methyls on the isopropyl group prevents effective overlap of the tertiary carbon-hydrogen bond with the singly occupied molecular orbital, thus inhibiting deprotonation from this site.Key words: photosensitized, electron transfer, alkene, tautomerization, radical cation.
- Arnold, Donald R.,Mines, Shelley A.
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p. 689 - 698
(2007/10/02)
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