- OXIDATIVE DEHYDROGENATION OF ALKYLHETEROAROMATIC COMPOUNDS. 2. DEHYDROGENATION OF ALKYLTHIOPHENES
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The dehydrogenation of a series of alkylthiophenes has been studied on vanadium-magnesium systems in the presence of atmospheric oxygen, and zinc-chromium oxide catalysts in the absence of oxygen.Optimum conditions heve been determined for bringing this about enabling vinylthiophenes to be obtained in high yield and with high selectivity.The advantages of the oxidative dehydrogenation method have been shown in the synthesis of vinyl derivatives of thiophene.
- Belomestnykh, I.P.,Rozhdestvenskaya, N.N.,Isagulyants, G.V.
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- Stereoselective Gold(I)-Catalyzed Vinylcyclopropanation via Generation of a Sulfur-Substituted Vinyl Carbene Equivalent
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A stereoselective gold(I)-catalyzed vinylcyclopropanation of alkenes has been developed. A gold-coordinated cationic vinyl carbene species, readily generated via a rearrangement of the ethylenedithioacetal of propargyl aldehyde, reacts with a wide range of alkenes to afford thio-substituted vinylcyclopropanes. The gold-catalyzed vinyl cyclopropanation proceeds under mild conditions at room temperature and is generally selective for the formation of cis-substituted cyclopropanes. The reaction allows the formal introduction of a “naked” vinyl carbene, by subsequent chemoselective hydrodesulfurisation of the ethylenedithio-bridge. The synthetic utility of the new method is demonstrated by a short, racemic formal synthesis of the alkaloid cephalotaxin, hinging on a key vinyl cyclopropane-cyclopentene rearrangement.
- Yuan, Tengrui,Ryckaert, Bram,Van Hecke, Kristof,Hullaert, Jan,Winne, Johan M.
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- Tertiary arsine ligands for the Stille coupling reaction
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The Stille coupling reaction is one of the most important coupling reactions. It is well known that the triphenylarsine ligand can accelerate the reaction rate of Stille coupling. However, other arsine ligands have never been investigated for the Stille c
- Chishiro, Akane,Imoto, Hiroaki,Inaba, Ryoto,Konishi, Masafumi,Naka, Kensuke,Yumura, Takashi
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- Br?nsted Acid Catalyzed Peterson Olefinations
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A mild and facile Peterson olefination has been developed employing low catalyst loading of the Br?nsted acid HNTf2. The reactions are typically performed at room temperature, with the reaction tolerant to a range of useful functionalities. Furthermore, we have extended this methodology to the synthesis of enynes.
- Britten, Thomas K.,McLaughlin, Mark G.
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p. 301 - 305
(2019/12/25)
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- Selective Transfer Semihydrogenation of Alkynes with H2O (D2O) as the H (D) Source over a Pd-P Cathode
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We reported a selective semihydrogenation (deuteration) of numerous terminal and internal alkynes using H2O (D2O) as the H (D) source over a Pd-P alloy cathode at a lower potential. P-doping caused the enhanced specific adsorption of alkynes and the promoted intrinsic activity for producing adsorbed atomic hydrogen (H*ads) from water electrolysis. The semihydrogenation of alkynes could be accomplished at a lower potential with up to 99 % selectivity and 78 % Faraday efficiency of alkene products, outperforming pure Pd and commercial Pd/C. This electrochemical semihydrogenation of alkynes might proceed via a H*ads addition pathway rather than a proton-coupled electron transfer process. The decreased amount of H*ads at a lower potential and the more preferential adsorption of the Pd-P to C≡C π bond than C=C moiety resulted in the excellent alkene selectivity. This method was capable of producing mono-, di-, and tri-deuterated alkenes with up to 99 % deuterium incorporation.
- Liu, Cuibo,Lu, Siyu,Wang, Changhong,Wu, Yongmeng,Zhang, Bin
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supporting information
p. 21170 - 21175
(2020/09/11)
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- Iron-Catalyzed Direct Julia-Type Olefination of Alcohols
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Herein, we report an iron-catalyzed, convenient, and expedient strategy for the synthesis of styrene and naphthalene derivatives with the liberation of dihydrogen. The use of a catalyst derived from an earth-abundant metal provides a sustainable strategy to olefins. This method exhibits wide substrate scope (primary and secondary alcohols) functional group tolerance (amino, nitro, halo, alkoxy, thiomethoxy, and S- A nd N-heterocyclic compounds) that can be scaled up. The unprecedented synthesis of 1-methyl naphthalenes proceeds via tandem methenylation/double dehydrogenation. Mechanistic study shows that the cleavage of the C-H bond of alcohol is the rate-determining step.
- Landge, Vinod G.,Babu, Reshma,Yadav, Vinita,Subaramanian, Murugan,Gupta, Virendrakumar,Balaraman, Ekambaram
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p. 9876 - 9886
(2020/09/03)
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- Hydrazide-Catalyzed Polyene Cyclization: Asymmetric Organocatalytic Synthesis of cis-Decalins
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Polyene cyclizations offer rapid entry into terpenoid ring systems. Although enantioselective cyclizations of (E)-polyenes to form trans-decalin ring systems are well precedented, highly enantioselective cyclizations of (Z)-polyenes to form the correspond
- Plamondon, Samuel J.,Warnica, Josephine M.,Kaldre, Dainis,Gleason, James L.
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supporting information
p. 253 - 258
(2019/11/28)
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- Biocatalytic asymmetric ring-opening of dihydroisoxazoles: a cyanide-free route to complementary enantiomers of β-hydroxy nitriles from olefins
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By combination of the cyanide-free synthesis of chiral nitriles and the Kemp elimination reaction catalyzed by aldoxime dehydratases, we herein report a new application of aldoxime dehydratase in the asymmetric ring-opening of 5-sub-4,5-dihydroisoxazoles
- Asano, Yasuhisa,Zheng, Daijun
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supporting information
p. 4930 - 4936
(2020/08/25)
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- Efficient and Practical Transfer Hydrogenation of Ketones Catalyzed by a Simple Bidentate Mn?NHC Complex
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Catalytic reductions of carbonyl-containing compounds are highly important for the safe, sustainable, and economical production of alcohols. Herein, we report on the efficient transfer hydrogenation of ketones catalyzed by a highly potent Mn(I)?NHC complex. Mn?NHC 1 is practical at metal concentrations as low as 75 ppm, thus approaching loadings more conventionally reserved for noble metal based systems. With these low Mn concentrations, catalyst deactivation is found to be highly temperature dependent and becomes especially prominent at increased reaction temperature. Ultimately, understanding of deactivation pathways could help close the activity/stability-gap with Ru and Ir catalysts towards the practical implementation of sustainable earth-abundant Mn-complexes.
- van Putten, Robbert,Benschop, Joeri,de Munck, Vincent J.,Weber, Manuela,Müller, Christian,Filonenko, Georgy A.,Pidko, Evgeny A.
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p. 5232 - 5235
(2019/07/18)
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- Terminal Alkenes from Acrylic Acid Derivatives via Non-Oxidative Enzymatic Decarboxylation by Ferulic Acid Decarboxylases
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Fungal ferulic acid decarboxylases (FDCs) belong to the UbiD-family of enzymes and catalyse the reversible (de)carboxylation of cinnamic acid derivatives through the use of a prenylated flavin cofactor. The latter is synthesised by the flavin prenyltransferase UbiX. Herein, we demonstrate the applicability of FDC/UbiX expressing cells for both isolated enzyme and whole-cell biocatalysis. FDCs exhibit high activity with total turnover numbers (TTN) of up to 55000 and turnover frequency (TOF) of up to 370 min?1. Co-solvent compatibility studies revealed FDC's tolerance to some organic solvents up 20 % v/v. Using the in-vitro (de)carboxylase activity of holo-FDC as well as whole-cell biocatalysts, we performed a substrate profiling study of three FDCs, providing insights into structural determinants of activity. FDCs display broad substrate tolerance towards a wide range of acrylic acid derivatives bearing (hetero)cyclic or olefinic substituents at C3 affording conversions of up to >99 %. The synthetic utility of FDCs was demonstrated by a preparative-scale decarboxylation.
- Aleku, Godwin A.,Prause, Christoph,Bradshaw-Allen, Ruth T.,Plasch, Katharina,Glueck, Silvia M.,Bailey, Samuel S.,Payne, Karl A. P.,Parker, David A.,Faber, Kurt,Leys, David
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p. 3736 - 3745
(2018/08/03)
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- Additive-modulated switchable reaction pathway in the addition of alkynes with organosilanes catalyzed by supported Pd nanoparticles: Hydrosilylation: versus semihydrogenation
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We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.
- Duan, Yanan,Ji, Guijie,Zhang, Shaochun,Chen, Xiufang,Yang, Yong
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p. 1039 - 1050
(2018/03/05)
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- Model Guided Development of a Simple Catalytic Method for the Synthesis of Unsymmetrical Stilbenes by Sequential Heck Reactions of Aryl Bromides with Ethylene
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Stilbenes are important and useful structural moieties, but methods for their preparation typically possess numerous inefficiencies. Presented here is a methodology for the two-step, one pot preparation of unsymmetrical stilbenes via sequential Heck reactions. The first Heck reaction with ethylene gas was analysed as a function of temperature and pressure for electronically differentiated naphthyl bromides and model-aided reaction optimization was utilized to define the system. In addition, reactNMR was utilized to determine ethylene solubility in common organic solvents useful for Heck reactions. Finally, an optimized sequential Heck reaction process was developed and applied to a range of substrates allowing for efficient preparation of unsymmetrical stilbenes, including the natural antioxidant, pterostilbene. (Figure presented.).
- Barlow, Helen,Buser, Jonas Y.,Glauninger, Hendrik,Luciani, Carla V.,Martinelli, Joseph R.,Oram, Niall,Thompson-Van Hook, Nichole,Richardson, Jeffery
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p. 2678 - 2690
(2018/06/04)
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- Catalytic Asymmetric Dearomatization by Visible-Light-Activated [2+2] Photocycloaddition
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A novel method for the catalytic asymmetric dearomatization by visible-light-activated [2+2] photocycloaddition with benzofurans and one example of a benzothiophene is reported, thereby providing chiral tricyclic structures with up to four stereocenters including quaternary stereocenters. The benzofurans and the benzothiophene are functionalized at the 2-position with a chelating N-acylpyrazole moiety which permits the coordination of a visible-light-activatable chiral-at-rhodium Lewis acid catalyst. Computational molecular modeling revealed the origin of the unusual regioselectivity and identified the heteroatom in the heterocycle to be key for the regiocontrol.
- Hu, Naifu,Jung, Hoimin,Zheng, Yu,Lee, Juhyeong,Zhang, Lilu,Ullah, Zakir,Xie, Xiulan,Harms, Klaus,Baik, Mu-Hyun,Meggers, Eric
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supporting information
p. 6242 - 6246
(2018/05/03)
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- Palladium-catalyzed convenient one-pot synthesis of multi-substituted 2-pyrones via transesterification and alkenylation of enynoates
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An efficient one-pot protocol for the synthesis of multi-substituted 2-pyrone derivatives from internal alkynes and unactivated alkenes is reported. The methodology involves difunctionalization of internal alkynes by using Pd(II) as a catalyst alongwith X-Phos as ligand via 6-endo transesterification and subsequent alkenylation pathway. Notable features include simple and easily available starting materials, including a range of unactivated alkenes, reduced synthetic steps and mild reaction conditions with high efficiency.
- Pathare, Ramdas S.,Sharma, Shivani,Gopal, Kandasamy,Sawant, Devesh M.,Pardasani, Ram T.
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supporting information
p. 1387 - 1389
(2017/03/17)
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- Selective Semihydrogenation of Alkynes Catalyzed by Pd Nanoparticles Immobilized on Heteroatom-Doped Hierarchical Porous Carbon Derived from Bamboo Shoots
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Highly dispersed palladium nanoparticles (Pd NPs) immobilized on heteroatom-doped hierarchical porous carbon supports (N,O-carbon) with large specific surface areas are synthesized by a wet chemical reduction method. The N,O-carbon derived from naturally abundant bamboo shoots is fabricated by a tandem hydrothermal–carbonization process without assistance of any templates, chemical activation reagents, or exogenous N or O sources in a simple and ecofriendly manner. The prepared Pd/N,O-carbon catalyst shows extremely high activity and excellent chemoselectivity for semihydrogenation of a broad range of alkynes to versatile and valuable alkenes under ambient conditions. The catalyst can be readily recovered for successive reuse with negligible loss in activity and selectivity, and is also applicable for practical gram-scale reactions.
- Ji, Guijie,Duan, Yanan,Zhang, Shaochun,Fei, Benhua,Chen, Xiufang,Yang, Yong
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p. 3427 - 3434
(2017/09/15)
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- Carboxylation of styrenes with CBr4 and DMSO via cooperative photoredox and cobalt catalysis
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Cooperative photoredox and cobalt catalyzed carboxylation of styrenes with CBr4 to afford the corresponding α,β-unsaturated carboxylic acids has been realized through radical addition and Kornblum (DMSO) oxidation. DMSO serves as the oxidant, oxygen source and solvent under these photocatalytic conditions.
- Song, Cai-Xia,Chen, Ping,Tang, Yu
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p. 11233 - 11243
(2017/02/26)
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- Enantioselective Reaction of 2H-Azirines with Phosphite Using Chiral Bis(imidazoline)/Zinc(II) Catalysts
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The first highly enantioselective nucleophilic addition reaction of phosphites with 2H-azirines has been developed. The reaction was applied to various 3-substituted 2H-azirines using novel chiral bis(imidazoline)/ZnII catalysts to afford produ
- Nakamura, Shuichi,Hayama, Daiki
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supporting information
p. 8785 - 8789
(2017/07/17)
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- Towards nitrile-substituted cyclopropanes-a slow-release protocol for safe and scalable applications of diazo acetonitrile
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Diazo acetonitrile has long been neglected despite its high value in organic synthesis due to a high risk of explosions. Herein, we report our efforts towards the transient and safe generation of this diazo compound, its applications in iron catalyzed cyclopropanation and cyclopropenation reactions and the gram-scale synthesis of cyclopropyl nitriles.
- Hock, Katharina J.,Spitzner, Robin,Koenigs, Rene M.
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supporting information
p. 2118 - 2122
(2017/07/24)
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- Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
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Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
- Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
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p. 6111 - 6119
(2016/04/26)
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- (E)-Specific direct Julia-olefination of aryl alcohols without extra reducing agents promoted by bases
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An unprecedented base-promoted direct olefination of aryl alcohols with sulfones via a Julia-type reaction has been described. No extra reductants are needed for Julia reaction since alcohols work as double sources of aldehydes and the hydride. Generally high yields were given for both terminal and highly (E)-selective internal olefins.
- Yao, Chuan-Zhi,Li, Qiang-Qiang,Wang, Mei-Mei,Ning, Xiao-Shan,Kang, Yan-Biao
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supporting information
p. 7729 - 7732
(2015/05/12)
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- Efficient E-Selective Transfer Semihydrogenation of Alkynes by Means of Ligand-Metal Cooperating Ruthenium Catalyst
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The manuscript describes an efficient protocol for the E-selective transfer semihydrogenation of internal alkynes employing a previously described bifunctional ruthenium-based PC(sp3)P complex, 20'mol% of sodium formate and nearly stoichiometric formic acid. Semihydrogenation of the terminal alkynes results in the formation of the corresponding styrenes. The mechanism of the reaction includes stepwise transfer of both the hydride and the proton of the formic acid to the substrate. This fact allowed for the development of a facile protocol for the synthesis of monodeuterated alkenes by simply applying formic acid/sodium formate/D2O mixture as a hydrogen source. High yields, selectivity and functional group compatibility have been generally achieved.
- Musa, Sanaa,Ghosh, Amrita,Vaccaro, Luigi,Ackermann, Lutz,Gelman, Dmitri
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supporting information
p. 2351 - 2357
(2015/07/27)
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- Immobilized Pd complexes over HMMS as catalysts for Heck cross-coupling and selective hydrogenation reactions
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High-performance Pd(0) on the surface of hollow magnetic mesoporous spheres (HMMS), with Fe3O4 nanoparticles embedded in the mesoporous shell was prepared. The catalyst was characterized by TEM, XRD, VSM and ICP. It showed high activity for selective hydrogenation of alkynes to alkenes and the Heck coupling reaction. The catalyst could be recovered in a facile manner from the reaction mixture and recycled six times without loss in activity.
- Wang, Peng,Liu, Hengzhi,Liu, Mengmeng,Li, Rong,Ma, Jiantai
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p. 1138 - 1143
(2014/03/21)
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- Concise synthesis of vinylheterocycles through β-elimination under solventless phase transfer catalysis conditions
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Various vinylheterocycles compounds have been prepared in excellent yields through β-elimination of the corresponding sulfonate esters with 50% aq NaOH under phase transfer catalysis conditions without organic solvent. The new approach provides an economic and environmentally friendly solution to removal of hazardous bases as well as toxic and expensive dipolar aprotic solvents.
- Albanese, Domenico,Ghidoli, Cristina,Zenoni, Maurizio
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p. 736 - 739
(2013/01/03)
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- Suzuki-Miyaura cross-coupling reactions of potassium vinyltrifluoroborate with aryl and heteroaryl electrophiles
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We have previously reported that the palladium-catalyzed cross-coupling reaction of potassium vinyltrifluoroborate with aryl electrophiles proceeds with good yields. Herein, we describe recent progress in optimizing the reaction, as well as outlining the scope and limitations of the reaction. The cross-coupling reaction can generally be effected using 2 mol % of PdCl2 and 6 mol % of PPh3 as a catalyst system in THF/H2O with Cs 2CO3 as a base. Moderate to good yields are obtained in the presence of a variety of functional groups.
- Molander, Gary A.,Brown, Adam R.
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p. 9681 - 9686
(2007/10/03)
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- Hydrazines and azides via the metal-catalyzed hydrohydrazination and hydroazidation of olefins
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The discovery, study, and implementation of the Co- and Mn-catalyzed hydrohydrazination and hydroazidation reactions of olefins are reported. These reactions are equivalent to direct hydroaminations of C-C double bonds with protected hydrazines or hydrazoic acid but are based on a different concept in which the H and the N atoms come from two different reagents, a silane and an oxidizing nitrogen source (azodicarboxylate or sulfonyl azide). The hydrohydrazination reaction using di-tert-butyl azodicarboxylate is characterized by its ease of use, large functional group tolerance, and broad scope, including mono-, di-, tri-, and tetrasubstituted olefins. Key to the development of the hydroazidation reaction was the use of sulfonyl azides as nitrogen sources and the activating effect of tert-butyl hydroperoxide. The reaction was found to be efficient for the functionalization of mono-, di-, and trisubstituted olefins, and only a few functional groups are not tolerated. The alkyl azides obtained are versatile intermediates and can be transformed to the free amines or triazoles without isolation of the azides. Preliminary mechanistic investigations suggest a rate-limiting hydrocobaltation of the alkene, followed by an amination reaction. Radical intermediates cannot be ruled out and may be involved.
- Waser, Jerome,Gaspar, Boris,Nambu, Hisanori,Carreira, Erick M.
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p. 11693 - 11712
(2007/10/03)
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- ORGANIC TELLURIUM COMPOUND, PROCESS FOR PRODUCING THE SAME, LIVING RADICAL POLYMERIZATION INITIATOR, PROCESS FOR PRODUCING POLYMER WITH THE SAME, AND POLYMER
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An organotellurium compound of the formula (1) is useful as a living radical polymerization initiator and makes possible precision control of molecular weights and molecular weight distributions under mild conditions wherein R1 is C1-C8 alkyl, R2 and R3 are each a hydrogen atom or C1-C8 alkyl, and R4 is aryl, substituted aryl, aromatic heterocyclic group, hydroxycarbonyl or cyano.
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Page/Page column 8
(2010/02/11)
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- New polymer-supported organosilicon reagents
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New polymer-supported organosilanes have been prepared using two different strategies. These involved the synthesis of soluble and insoluble supports through the copolymerization of styrene and monomers containing a thiophene ring. Selective metallation o
- Fauvel, Anne,Deleuze, Herve,Landais, Yannick
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p. 3900 - 3910
(2007/10/03)
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- Low-coordinated diphosphinidenecyclobutene ligands: A new entry for Stille cross-coupling of aryl bromides
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A sterically protected diphosphinidenecyclobutene/palladium system has been used to mediate the catalytic cross-coupling of aryl bromides with organostannanes. An air- and moisture-stable diphosphinidenecyclobutene ligand proved the efficiency and generality of this class of ligand for cross-coupling reactions.
- Gajare, Anil S.,Jensen, Rader S.,Toyota, Kozo,Yoshifuji, Masaaki,Ozawa, Fumiyuki
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p. 144 - 148
(2007/10/03)
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- Urokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Ukokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Nickel-Catalyzed Olefination of Cyclic Benzylic Dithioacetals by Grignard Reagents. Scope and Mechanism
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The details of the first nickel-catalyzed olefination of cyclic dithioacetals to form substituted styrenes and aryl-substituted 1,4-pentadienes are described.The reaction represents a new synthetic use of the dithioacetal functionality.Only nickel complexes catalyzes these cross-coupling reactions; palladium complexes displayed no catalytic activity under the reaction conditions employed.Selective coupling occurred.A mechanism for the reaction is proposed.The experimental evidence indicates that, in these nickel-catalyzed couplings, cyclic dithioacetals are more reactive than their acyclic analogues.This increased reactivity appears to be the result of maintaining the two sulfur atoms in close proximity to each other by the use of a short chain of methylene groups.
- Ni, Zhi-Jie,Mei, Nai-Wen,Shi, Xian,Tzeng, Yih-Ling,Wang, Maw Cherng,Luh, Tien-Yau
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p. 4035 - 4042
(2007/10/02)
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- A Quick Procedure for the Partial Reduction of Triple Bonds
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Regio- as well as stereospecific cis-reductions of a wide variety of acetylenic derivatives can be carried out in absolute ethanol with zinc powder activated with 1,2-dibromoethane and with zinc power treated successively with dibromoethane and lithium bromocuprate, the first reagent being less powerful and more selective than the second one.
- Aerssens, M.H.P.J.,Heiden, R. van der,Heus, M.,Brandsma, L.
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p. 3421 - 3425
(2007/10/02)
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- CYCLOADDITION REACTIONS OF 2-VINYLTHIOPHEN
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Cycloaddition reactions between 2-vinylthiophen and the dienophiles maleic anhydride, dimethyl acetylenedicarboxylate, methyl propiolate, and methyl acrylate, are reported.Products include simple benzotiophen carboxylates (6, 13, 17) and reduced derivatives (3, 4, 18).The acetylenic dienophiles also gave a dihydrobenzthienyl-acrylate (16) or -fumarate (11), and the dithienylcyclohexene esters (7) and (14).
- Abarca, Belen,Ballesteros, Rafael,Enriquez, Emilio,Jones, Gurnos
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p. 2435 - 2440
(2007/10/02)
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- Regio- and Stereo-specific Reduction of Conjugated and Non-conjugated Triple Bonds by Activated Zinc Powder
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Regio- as well as stereo-specific reductions of a wide variety of acetylenic derivatives have been carried out in absolute ethanol with zinc powder activated with 1,2-dibromoethane, and with zinc powder activated successively with dibromoethane and copper(I) bromide, the first reagent being less powerful and more selective than the second one.
- Aerssens, Marc H. P. J.,Brandsma, Lambert
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p. 735 - 736
(2007/10/02)
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- A REGIOSPECIFIC SYNTHESIS OF CARBOSUBSTITUTED HETEROAROMATIC DERIVATIVES VIA Pd-CATALYZED CROSS COUPLING
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The Pd-catalyzed cross-coupling reaction of either heteroarylzinc derivatives with unsaturated organic halides or heteroaryl halides with organometallic reagents containing Zn or Al can produce cleanly and regiospecifically the corresponding carbo-substituted heteroatomic compounds in high yields.
- Negishi, Ei-ichi,Luo, Fen-Tair,Frisbee, Roger,Matsushita, Hajime
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p. 117 - 122
(2007/10/02)
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- NICKEL-PHOSPHINE COMPLEX-CATALYZED GRIGNARD COUPLING-II; GRIGNARD COUPLING OF HETEROCYCLIC COMPOUNDS
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A general, versatile method for alkylation and arylation of haloheterocyclic compounds is reported.In the presence of a catalytic quantity of , where dppp stands for Ph2P(CH2)3PPh2, bromothiophenes, halopyridines, haloquinoline, and haloisoquinolines reacted with alkyl and aryl Grignard reagents at room temperature or at ether refluxing temperature to give the cross-coupling products.The coupling reactions has been applied to the synthesis of isoquinoline alkaloids.Reactivities of 2-thienyl and 2-pyridyl Grignard reagents have also been examined.
- Tamao, K.,Kodama, S.,Nakajima, I.,Kumada, M.,Minato, A.,Suzuki, K.
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p. 3347 - 3354
(2007/10/02)
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