- Continuous Flow Process for the Synthesis of Betahistine via Aza-Michael-Type Reaction in Water
-
A continuous flow process for the preparation of betahistine with a 90% isolated yield has been reported. 2-Vinylpyridine and saturated methylamine hydrochloride aqueous solution were used as starting materials to achieve excellent results in the silicon carbide flow reactor, which can tolerate the corrosion of chloride ions at high temperature (170 °C) and pressure (25 bar). In the continuous flow process, the product can be obtained in 2.4 min with excellent conversion (>99%) and product selectivity (94%). The throughput can reach 1.06 kg h-1, and the purity of the final product was greater than 99.9% by distillation, which were in accordance with the needs of production. This new process using environmentally friendly water as the solvent is energy-efficient, time- and cost-economic, and offers a 50% reduction in process mass intensity compared to the batch process.
- Sun, Maolin,Yang, Jingxin,Fu, Youtian,Liang, Chaoming,Li, Hong,Yan, Guoming,Yin, Chao,Yu, Wei,Ma, Yueyue,Cheng, Ruihua,Ye, Jinxing
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p. 1160 - 1166
(2021/05/06)
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- Construction of α-Amino Azines via Thianthrenation-Enabled Photocatalyzed Hydroarylation of Azine-Substituted Enamides with Arenes
-
α-Amino azines are widely found in pharmaceuticals and ligands. Herein, we report a practical method for accessing this class of compounds via photocatalyzed hydroarylation of azine-substituted enamides with the in situ-generated aryl thianthrenium salts as the radical precursor. This reaction features a broad substrate scope, good functional group tolerance, and mild conditions and is suitable for the late-stage installation of α-amino azines in complex structures.
- Zhang, Yu-Lan,Wang, Gang-Hu,Wu, Yichen,Zhu, Chun-Yin,Wang, Peng
-
supporting information
p. 8522 - 8526
(2021/11/13)
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- KO-t-Bu Catalyzed Thiolation of β-(Hetero)arylethyl Ethers via MeOH Elimination/hydrothiolation
-
Herein, we describe a KO-t-Bu catalyzed thiolation of β-(hetero)arylethyl ethers through MeOH elimination to form (hetero)arylalkenes followed by anti-Markovnikov hydrothiolation to afford linear thioethers. The system works well with a variety of β-(hetero)arylethyl ethers, including electron-deficient, electron-neutral, electron-rich, and branched substrates and a range of aliphatic and aromatic thiols.
- Shigeno, Masanori,Shishido, Yoshiteru,Hayashi, Kazutoshi,Nozawa-Kumada, Kanako,Kondo, Yoshinori
-
supporting information
p. 3932 - 3935
(2021/08/24)
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- Preparation method of 2-vinylpyridine
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The invention discloses a preparation method of 2-vinylpyridine. The invention discloses a preparation method of 2-vinylpyridine, which comprises the following steps: under 2-5Mpa, in a polar protic solvent, under the action of a weak acid, carrying out the following reaction process on 2-methylpyridine and formaldehyde to obtain 2-vinylpyridine. According to the preparation method disclosed by the invention, the 2-vinylpyridine is synthesized in one step by taking the 2-methylpyridine as a raw material, the single-pass conversion rate of the 2-methylpyridine is greatly improved, the reactiontime is also remarkably shortened, side reactions are few, the purity is high, and the preparation method is suitable for industrial production.
- -
-
Paragraph 0064-0121
(2020/12/15)
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- Piperazine-promoted gold-catalyzed hydrogenation: The influence of capping ligands
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Gold nanoparticles (NPs) combined with Lewis bases, such as piperazine, were found to perform selective hydrogenation reactions via the heterolytic cleavage of H2. Since gold nanoparticles can be prepared by many different methodologies and using different capping ligands, in this study, we investigated the influence of capping ligands adsorbed on gold surfaces on the formation of the gold-ligand interface. Citrate (Citr), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), and oleylamine (Oley)-stabilized Au NPs were not activated by piperazine for the hydrogenation of alkynes, but the catalytic activity was greatly enhanced after removing the capping ligands from the gold surface by calcination at 400 °C and the subsequent adsorption of piperazine. Therefore, the capping ligand can limit the catalytic activity if not carefully removed, demonstrating the need of a cleaner surface for a ligand-metal cooperative effect in the activation of H2 for selective semihydrogenation of various alkynes under mild reaction conditions.
- Barbosa, Eduardo C. M.,Camargo, Pedro H. C.,Fiorio, Jhonatan L.,Hashmi, A. Stephen K.,Kikuchi, Danielle K.,Rossi, Liane M.,Rudolph, Matthias
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p. 1996 - 2003
(2020/04/22)
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- Creation of Redox-Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO-66 with Unique Semihydrogenation Catalytic Properties
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Semihydrogenation of alkynes to produce alkenes is very important in the industry; however, over-hydrogenation heavily complicates the postprocesses, which are highly energy consuming and not environmentally friendly. One of the most efficient pathways to solve this challenging issue is to develop highly selective catalysts that could only hydrogenate alkynes and are inactive in hydrogenation of alkenes. This work presents herein an efficient catalyst, consisting of in situ created PdS0.53 nanoparticles as the redox-active sites inside the defect pores of metal–organic framework UiO-66, which demonstrates very high alkene selectivity (up to 99.5%) in semihydrogenation of easily over-hydrogenated terminal alkynes. In contrast to the traditional catalysts, strict control over the reaction time becomes the nonessential condition because the catalyst system is almost inactive in hydrogenation of alkenes. Therefore, this paradigm work provides a practically applicable pathway for the development of efficient catalysts with unique catalytic properties for selective semihydrogenation reactions.
- Dong, Ming-Jie,Wang, Xuan,Wu, Chuan-De
-
-
- 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
-
supporting information
p. 21170 - 21175
(2020/09/11)
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- Selective Semi-Hydrogenation of Terminal Alkynes Promoted by Bimetallic Cu-Pd Nanoparticles
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The selective semi-hydrogenation of terminal alkynes was efficiently performed, under mild reaction conditions (H 2 balloon, 110 °C), promoted by a bimetallic nanocatalyst composed of copper and palladium nanoparticles (5:1 weight ratio) supported on mesostructured silica (MCM-48). The Cu-PdNPS@MCM-48 catalyst, which demonstrated to be highly chemoselective towards the alkyne functionality, is readily prepared from commercial materials and can be recovered and reused after thermal treatment followed by reduction under H 2 atmosphere.
- Buxaderas, Eduardo,Volpe, María Alicia,Radivoy, Gabriel
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p. 1466 - 1472
(2019/03/07)
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- Design and characterization of a heterocyclic electrophilic fragment library for the discovery of cysteine-targeted covalent inhibitors
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A fragment library of electrophilic small heterocycles was characterized through cysteine-reactivity and aqueous stability tests that suggested their potential as covalent warheads. The analysis of theoretical and experimental descriptors revealed correlations between the electronic properties of the heterocyclic cores and their reactivity against GSH that are helpful in identifying suitable fragments for cysteines with specific nucleophilicity. The most important advantage of these fragments is that they show only minimal structural differences from non-electrophilic counterparts. Therefore, they could be used effectively in the design of targeted covalent inhibitors with minimal influence on key non-covalent interactions.
- Keeley,ábrányi-Balogh,Keseru
-
supporting information
p. 263 - 267
(2019/03/05)
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- Accessing Frustrated Lewis Pair Chemistry through Robust Gold@N-Doped Carbon for Selective Hydrogenation of Alkynes
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Pyrolysis of Au(OAc)3 in the presence of 1,10-phenanthroline over TiO2 furnishes a highly active and selective Au nanoparticle (NP) catalyst embedded in a nitrogen-doped carbon support, Au@N-doped carbon/TiO2 catalyst. Parameters such as pyrolysis temperature, type of support, and nitrogen ligands as well as Au/ligand molar ratios were systematically investigated. Highly selective hydrogenation of numerous structurally diverse alkynes proceeded in moderate to excellent yield under mild conditions. The high selectivity toward the industrially important alkene substrates, functional group tolerance, and the high recyclability makes the catalytic system unique. Both high activity and selectivity are correlated with a frustrated Lewis pairs interface formed by the combination of gold and nitrogen atoms of N-doped carbon that, according to density functional theory calculations, can serve as a basic site to promote the heterolytic activation of H2 under very mild conditions. This "fully heterogeneous" and recyclable gold catalyst makes the selective hydrogenation process environmentally and economically attractive.
- Fiorio, Jhonatan Luiz,Gon?alves, Renato Vitalino,Teixeira-Neto, Erico,Ortu?o, Manuel A.,López, Núria,Rossi, Liane Marcia
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p. 3516 - 3524
(2018/04/14)
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- Preparation method of orthographic optimizing betahistine hydrochloride
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The invention discloses a preparation method of orthographic optimizing betahistine hydrochloride, and relates to the field of drug preparation. The preparation method includes the steps: adding raw materials into a reaction bottle according to the feeding ratio (molar ratio) of 2-methylpyridine to paraformaldehyde of 1:0.57, leading in nitrogen, stirring mixture for 20 hours at the temperature of125 DEG C and at 4 barometric pressure, performing reduced pressure distillation, and collecting distillation cut at the temperature of 130-145 DEG C and under the pressure of 16mm mercury columns toobtain light-yellow oily 2-hydroxyethyl pyridine; adding the 2-hydroxyethyl pyridine into a three-opening bottle, adding sodium hydroxide according to the feeding ratio of 2-(2-Hydroxyethyl)pyridineto sodium hydroxide of 1:0.05, heating the mixture to reach 95-100 DEG C, stirring the mixture for 2 hours, removing a water layer, performing reduced pressure distillation on an oil layer, and collecting the distillation cut at the temperature of 65-70 DEG C and under the pressure of 17mm mercury columns to obtain 2-vinylpyridine. The preparation method is simple in technological process, safe tooperate and mild in reaction, production efficiency and product quality can be greatly improved, and production cost is reduced.
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- Ru-Catalyzed Completely Deoxygenative Coupling of 2-Arylethanols through Base-Induced Net Decarbonylation
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Substituted arylethanols can be coupled by using a readily available Ru catalyst in a fully deoxygenative manner to produce hydrocarbon chains in one step. Control experiments indicate that the first deoxygenation occurs through an aldol condensation, whereas the second occurs through a base-induced net decarbonylation. This double deoxygenation enables further development in the use of alcohols as versatile and green alkylating reagents, as well as in other fields, such as deoxygenation and upgrading of overfunctionalized biomass to produce hydrocarbons.
- Manojveer, Seetharaman,Forrest, Sebastian J. K.,Johnson, Magnus T.
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supporting information
p. 803 - 807
(2018/01/27)
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- A vinyl pyridine production process (by machine translation)
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Vinyl pyridine is an important chemical products. The production flow: (1) 2 - hydroxy ethyl pyridine synthesis; (2) dehydration reaction; (3) the essence steams. (by machine translation)
- -
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Page/Page column 3
(2017/07/20)
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- Photoinduced, copper-catalyzed three components cyanofluoroalkylation of alkenes with fluoroalkyl iodides as fluoroalkylation reagents
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In the past few years, Ru and Ir catalyzed photoredox radical coupling reactions have been widely applied in organic synthesis. In contrast, the applications of Cu catalysts in photoredox organic transformations were limited. We here report the first example of photoinduced, Cu-catalyzed three component cyanofluoroalkylation of alkenes by directly using fluoroalkyl iodides as fluoroalkylation reagents.
- Guo, Quanping,Wang, Mengran,Wang, Yanfang,Xu, Zhaoqing,Wang, Rui
-
supporting information
p. 12317 - 12320
(2017/11/20)
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- Ligand-free nickel-catalyzed semihydrogenation of alkynes with sodium borohydride: A highly efficient and selective process for: Cis -alkenes under ambient conditions
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We report a low-cost and efficient catalytic system, involving in situ generated ligand-free Ni NPs, methanol and sodium borohydride, for the semihydrogenation of alkynes under ambient conditions. This catalytic system exhibits remarkably high activity, satisfactory cis-selectivity for internal alkynes, good stability and general applicability.
- Wen, Xin,Shi, Xiaozhen,Qiao, Xianliang,Wu, Zhilei,Bai, Guoyi
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supporting information
p. 5372 - 5375
(2017/07/06)
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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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- Supported gold nanoparticles catalyzed: Cis -selective semihydrogenation of alkynes using ammonium formate as the reductant
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TiO2 supported gold nanoparticles with low loading (0.5 mol%) are able to semihydrogenate non-fluorinated and gem-difluorinated alkynes to cis-alkenes with high selectivity, using cost-effective and easy-to-handle ammonium formate as the reductant. No over-reduction was observed. The good recyclability of Au/TiO2 allows for "green" semireduction of alkynes. A difluorinated pyran and α,β-unsaturated δ-lactone were easily prepared from the obtained gem-difluoro alkene building blocks.
- Liang, Shengzong,Hammond, Gerald B.,Xu, Bo
-
supporting information
p. 6013 - 6016
(2016/05/24)
-
- Heterogeneous Gold-Catalyzed Selective Semireduction of Alkynes using Formic Acid as Hydrogen Source
-
A convenient and robust protocol for the selective transfer semireduction of alkynes was developed, using bio-renewable formic acid as the hydrogen source and easily handled supported gold nanoparticles as the catalyst. The catalytic system showed several attractive features such as high activity and selectivity, recyclability, scalability and adaptability to continuous operation under mild reaction conditions, thus providing a practical alternative to current methods for alkyne semireduction.
- Li, Shu-Shuang,Tao, Lei,Wang, Fu-Ze-Rong,Liu, Yong-Mei,Cao, Yong
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supporting information
p. 1410 - 1416
(2016/05/19)
-
- Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations
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New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h-1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy?-)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.
- Zhang, Teng,Manna, Kuntal,Lin, Wenbin
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supporting information
p. 3241 - 3249
(2016/03/19)
-
- Silica supported palladium phosphine as a robust and recyclable catalyst for semi-hydrogenation of alkynes using syngas
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This work reports a chemo-selective semi-hydrogenation of alkynes to alkenes using silica supported palladium phosphine catalyst with syngas (CO/H2). This developed methodology is an alternative to classical Lindlar catalyst for chemo-selective semi-hydrogenation of alkynes to alkenes. Various alkynes were smoothly convert to alkenes in 60-97% conversion with 85-98% selectivity. The prepared catalyst was well characterized by Field Emmission Gun Scanning Electron Microscopy (FEG-SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma- Atomic Emmission Spectroscopy (ICP-AES) analysis techniques. In addition, catalyst was effectively recycled up to four consecutive run without significant loss in its catalytic activity and selectivity.
- Jagtap, Samadhan A.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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- Cooperative C(sp3)-H and C(sp2)-H Activation of 2-Ethylpyridines by Copper and Rhodium: A Route toward Quinolizinium Salts
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A method for the synthesis of substituted quinolizinium salts from 2-ethylpyridines and alkynes is demonstrated. The transformation is conveniently achieved using 1 mol % of a Rh(III) catalyst along with an excess amount of copper(II) salt. The reaction gives high product yields with broad substrate scope and functional group tolerance. Detailed mechanistic studies suggest that 2-vinylpyridine is formed in situ from 2-ethylpyridine by a copper-promoted C(sp3)-H hydroxylation, followed by dehydration. Later, a Rh(III)-catalyzed pyridine-directed vinylic C(sp2)-H activation and annulation with alkynes provided the final product. (Chemical Equation Presented).
- Luo, Ching-Zong,Gandeepan, Parthasarathy,Wu, Yun-Ching,Tsai, Chia-Hung,Cheng, Chien-Hong
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p. 4837 - 4841
(2015/08/18)
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- One-step Synthesis of Core-Gold/Shell-Ceria Nanomaterial and Its Catalysis for Highly Selective Semihydrogenation of Alkynes
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We report a facile synthesis of new core-Au/shell-CeO2 nanoparticles (Au@CeO2) using a redox-coprecipitation method, where the Au nanoparticles and the nanoporous shell of CeO2 are simultaneously formed in one step. The Au@CeO2 catalyst enables the highly selective semihydrogenation of various alkynes at ambient temperature under additive-free conditions. The core-shell structure plays a crucial role in providing the excellent selectivity for alkenes through the selective dissociation of H2 in a heterolytic manner by maximizing interfacial sites between the core-Au and the shell-CeO2.
- Mitsudome, Takato,Yamamoto, Masaaki,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 13452 - 13455
(2015/11/10)
-
- cis-Semihydrogenation of alkynes with amine borane complexes catalyzed by gold nanoparticles under mild conditions
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Supported gold nanoparticles catalyze the semihydrogenation of alkynes to alkenes with ammonia borane or amine borane complexes in excellent yields and under mild conditions. Internal alkynes provide cis-alkenes, making this protocol an attractive alternative of the classical Lindlar's hydrogenation.
- Vasilikogiannaki, Eleni,Titilas, Ioannis,Vassilikogiannakis, Georgios,Stratakis, Manolis
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supporting information
p. 2384 - 2387
(2015/02/05)
-
- 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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- Room temperature hydrophosphination using a simple iron salen pre-catalyst
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Phosphines are fundamentally important to the fine chemicals, pharmaceutical and agrochemical industries. Reported is the first example of alkene hydrophosphination using a designed iron pre-catalyst which yields the anti-Markovnikov products in high yield at room temperature. The phosphine products are excellent pro-ligands for Fe-catalyzed Negishi cross-coupling. This journal is
- Gallagher,Webster
-
supporting information
p. 12109 - 12111
(2015/01/08)
-
- Triazolopyridines. Part 30.1 Hydrogen transfer reactions; Pyridylcarbene formation
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The transfer hydrogenation reaction of [1,2,3]triazolo[1,5-a]pyridines with Pd/C/Zn or Pd(OH)2/C/Zn in water, ethanol or water/ethanol mixture has been explored. 4,5,6,7-Tetrahydrotriazolopyridines were obtained in good to medium yields. In addition, under the same conditions 2-substituted pyridines were also formed as a result of intermediate pyridylcarbene formation, by triazole ring opening and loss of nitrogen.
- Abarca, Belen,Adam, Rosa,Alom, Shamim,Ballesteros, Rafael,Lopez-Molina, Sonia
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p. 175 - 186
(2014/03/21)
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- Stereoselective nitration of olefins with tBuONO and TEMPO: Direct access to nitroolefins under metal-free conditions
-
Nitroolefins are essential elements for both synthetic chemistry and medicinal research. Despite significant improvements in nitration of olefin an efficient metal-free synthesis remains elusive so far. Herein, we disclose a new set of reagents to access nitroolefins in a single step under metal-free conditions. A wide range of olefins with diverse functionalities has been nitrated in synthetically useful yields. This transformation is operationally simple and exhibits excellent E-selectivity. Furthermore, site selective nitration in a complex setup makes this method advantageous.
- Maity, Soham,Naveen, Togati,Sharma, Upendra,Maiti, Debabrata
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supporting information
p. 3384 - 3387
(2013/07/26)
-
- Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
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Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid-liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid-liquid separator both play an essential role in enabling these telescoped flow processes.
- Bourne, Samuel L.,O'Brien, Matthew,Kasinathan, Sivarajan,Koos, Peter,Tolstoy, Paeivi,Hu, Dennis X.,Bates, Roderick W.,Martin, Benjamin,Schenkel, Berthold,Ley, Steven V.
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p. 159 - 172
(2013/03/13)
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- Ruthenium-catalyzed conversion of sp3 C-O bonds in ethers to C-C bonds using triarylboroxines
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Catalytic conversion of unreactive sp3 C-O bonds in alkyl ethers to C-C bonds is described. Alkyl ethers bearing 2- or 4-pyridyl groups were coupled with triarylboroxines in the presence of a ruthenium catalyst. Triarylboroxines bearing a variety of functional groups including electron-withdrawing and -donating groups can be used for the reaction. No additional base was required for the coupling with the organoboron reagents, and base-sensitive groups can be tolerated. The reaction is considered to proceed via dehydroalkoxylation followed by addition of triarylboroxines to form C-C bonds.
- Ogiwara, Yohei,Kochi, Takuya,Kakiuchi, Fumitoshi
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body text
p. 3254 - 3257
(2011/08/02)
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- Highly active and recyclable silica gel-supported palladium catalyst for mild cross-coupling reactions of unactivated heteroaryl chlorides
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Silica gel-supported β-ketoiminatophosphane-Pd complex (Pd@SiO 2) was shown to be a highly active and long-lived catalyst for aqueous Suzuki, Stille and Sonogashira coupling reactions of heteroaryl chlorides. A wide range of heteroaryl chlorides could be efficiently coupled with different nucleophilic partners in the presence of only 0.5 mol% catalyst and under mild conditions. This is one of the most powerful heterogeneous catalysts for the couplings of diverse heteroaryl chlorides. Furthermore, the catalyst could be reused with almost consistent activity. The Royal Society of Chemistry 2010.
- Lee, Dong-Hwan,Jung, Ji-Young,Jin, Myung-Jong
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experimental part
p. 2024 - 2029
(2011/02/22)
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- Structure-activity relationships of adenine and deazaadenine derivatives as ligands for adenine receptors, a new purinergic receptor family
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Adenine derivatives bearing substituents in the 2-, N6-, 7-, 8-, and/or 9-position and a series of deazapurines were synthesized and investigated in [3H]adenine binding studies at the adenine receptor in rat brain cortical membrane preparations (rAde1R). Steep structure-activity relationships were observed. Substitution in the 8-position (amino, dimethylamino, piperidinyl, piperazinyl) or in the 9-position (2-morpholinoethyl) with basic residues or introduction of polar substituents at the 6-amino function (hydroxy, amino, acetyl) represented the best modifications. Functional evaluation of selected adenine derivatives in adenylate cyclase assays at 1321N1 astrocytoma cells stably expressing the rAde1R showed that all compounds investigated were agonists or partial agonists. A subset of compounds was additionally investigated in binding studies at human embryonic kidney (HEK293) cells, which also express a high-affinity adenine binding site. Structure-affinity relationships at the human cell line were similar to those at the rAde1R, but not identical. In particular, N 6-acetyladenine (25, Ki rat: 2.85 μM; Ki human: 0.515 μM) and 8-aminoadenine (33, Ki rat: 6.51 μM; Ki human: 0.0341 μM) were much more potent at the human as compared to the rat binding site. The new AdeR ligands may serve as lead structures and contribute to the elucidation of the functions of the adenine receptor family. 2009 American Chemical Society.
- Borrmann, Thomas,Abdelrahman, Aliaa,Volpini, Rosaria,Lambertucci, Catia,Alksnis, Edgars,Gorzalka, Simone,Knospe, Melanie,Schiedel, Anke C.,Cristalli, Gloria,Müller, Christa E.
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scheme or table
p. 5974 - 5989
(2010/03/24)
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- Gold and palladium combined for cross-coupling
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Gold and palladium-a unique liason: A study of the transmetalation abilities of organogold compounds builds the basis for a new class of cross-coupling reactions. Stable intermediates of gold catalysis deliver new complex products by a palladium-catalyzed coupling reaction, (see Scheme)
- Hashmi, A. Stephen K.,Lothschuetz, Christian,Doepp, Rene,Rudolph, Matthias,Ramamurthi, Tanuja D.,Rominger, Frank
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supporting information; experimental part
p. 8243 - 8246
(2010/02/27)
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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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- Copper-carbene complexes as catalysts in the synthesis of functionalized styrenes and aliphatic alkenes
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(NHC)-Cu (NHC = N-heterocyclic carbene) complexes efficiently catalyzed the methylenation of a variety of aliphatic and aromatic aldehydes and ketones in the presence of trimethylsilyldiazomethane, triphenylphosphine, and 2-propanol. The copper catalysts are not only inexpensive compared to rhodium complexes, but they also exhibit better functional group compatibility with aromatic aldehydes and ketones. Indeed very high yields were obtained for the formation of styrenes containing nitro, trifluoromethyl, amino, and ester groups, as well as for pyridine-, pyrrole-, and indole-substituted alkenes.
- Lebel, Helene,Davi, Michael,Diez-Gonzalez, Silvia,Nolan, Steven P.
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p. 144 - 149
(2007/10/03)
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- Palladium-catalyzed 2-pyridylmethyl transfer from 2-(2-pyridyl)-ethanol derivatives to organic halides by chelation-assisted cleavage of unstrained Csp3-Csp3 bonds
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(Chemical Equation Presented) Making a break for it: Treatment of 2-(2-pyridyl)ethanol derivatives with aryl chlorides in the presence of a palladium catalyst results in the transfer of the pyridylmethyl moiety of the alcohol to yield the corresponding (2-pyridyl-methyl)arene. The reaction proceeds by chelation-assisted cleavage of an Csp3-C5p3 bond (see scheme) followed by formation of a carbon-carbon bond.
- Niwa, Takashi,Yorimitsu, Hideki,Oshima, Koichiro
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p. 2643 - 2645
(2008/02/13)
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- Structure and reactivity of trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1). A study on the elimination reaction of 1 and 2-(2-chloroethyl) pyridine induced by quinuclidine in acetonitrile
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The trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1) has been prepared and structurally characterized by X-ray spectroscopy and computational study. The X-ray structure of 1 is consistent with the trans isomer (with respect to Pd). The NMR spectrum and the computational study are in agreement with an equilibrium in CD3CN solution between two isomers of the trans structure. The reaction of the palladium complex with quinuclidine in CH3CN, at 25 °C, leads to competing elimination and displacement reactions with formation of vinylpyridine and chloroethylpyridine in a ratio of 1.5:1. However, the rate constant for formation of uncoordinated (vinyl)pyridine monitored by HPLC (k;QHPLC = 2.3 × 10-3 M-1 s-1) is nearly 3 times slower than a rate constant monitored spectrophotometrically (kQ = 6.5 × 10-3 M-1 s-1). This suggests that the initial product of elimination is a palladium complex of vinylpyridine and that displacement from this complex is partially rate determining in the formation of the uncoordinated product. A study by UV spectroscopy at λ = 295 nm of trans-bis[2-(2-chloroethyl)pyridine-d2]palladium chloride with quinuclidine (Q) has shown the presence of a significant primary kinetic isotope effect, k Q(H)/kQ(D) = 1.8, for the elimination reaction within the Pd complex, 1. The second-order rate constant for the β-elimination reaction from 2-(2-chloroethyl)pyridine induced by quinuclidine in CH 3CN at 25 °C is kQFREE = 6.2 × 10-6 M-1 s-1. It can be observed as a significant activation (about 3 orders of magnitude) of the β-elimination reaction within the complex 1 with respect to the free 2-(2-chloroethyl) pyridine. The possible mechanism in agreement with these results is discussed.
- Alunni, Sergio,Bellachioma, Gianfranco,Clot, Eric,Giacco, Tiziana Del,Ottavi, Laura,Zuccaccia, Daniele
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p. 10688 - 10692
(2007/10/03)
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- Separating material
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The present invention provides a separating material producable by a) providing a solid substrate, having amino-functional groups coupled to the substrate surface, b) covalently coupling of the amino-functional groups with a thermally labile radical initiator, c) contacting the substrate surface with a solution of polymerizable monomers under conditions, where thermally initiated graft copolymerization of the monomers takes place, to form a structure of adjacent functional polymer chains on the surface of the substrate. The present invention further provides a method for the production of a separating material by a) providing a solid substrate, having amino-functional groups coupled to the substrate surface, b) covalently coupling of the amino-functional groups with a thermally labile radical initiator, c) contacting the substrate surface with a solution of polymerizable monomers under conditions, where thermally initiated graft copolymerization of the monomers takes place, to form a structure of adjacent functional polymer chains on the surface of the substrate.
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- 4,4,6-Trimethyl-2-vinyl-1,3,2-dioxaborinane: An efficient and selective 2-carbon building block for vinylboronate Suzuki-Miyaura coupling reactions
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An extremely simple and efficient palladium-catalyzed coupling procedure for the synthesis of functionalized styrenes and dienes is utilized to demonstrate how 4,4,6-trimethyl-2-vinyl-1,3,2-dioxaborinane can be employed to selectively undergo Suzuki-Miyaura coupling with a range of halide substrates. Georg Thieme Verlag Stuttgart.
- Lightfoot, Andrew P.,Twiddle, Steven J. R.,Whiting, Andrew
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p. 529 - 531
(2007/10/03)
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- PROCESS FOR THE PREPARATION OF VINYLPYRIDINE FROM PICOLINE OVER MODIFIED ZEOLITES
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The present invention relates to an improved eco-friendly process for the preparation of vinylpyridine from corresponding picoline over modified zeolite catalyst in vapour phase which comprises reacting picoline with formaldehyde with a molar ratio of formaldehyde to picoline in the range of 1:1 to 4:1, at a temperature ranging between 200°C to 450°C, at a weight hourly space velocity in the range of 0.25 hr?-1? - 1.00 hr?-1? over a modified commercial zeolite catalyst to obtain a high yield and selectivity of the desired product.
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Page 6; 7; 8
(2008/06/13)
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- Metal Ion Catalysis in the β-Elimination Reactions of N-[2-(4-Pyridyl)ethyl]quinuclidinium and N-[2-(2-Pyridyl)ethyl]quinuclidinium in Aqueous Solution
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Catalysis of the β-elimination reaction of N-[2-(4-pyridyl)ethyl]quinuclidinium (1) and N-[2-(2-pyridyl)ethyl]quinuclidinium (2) by Zn2+ and Cd2+ in OH-/H2O (pH = 5.20-6.35, 50 °C, and μ = 1 M KCl) has been studied. In the presence of Zn2+, the elimination reactions of both isomers occur from the Zn2+-complexed substrates (C). The equilibrium constants for the dissociation of the Zn 2+-complexes are as follows: Kd = 0.012 ± 0.003 M (isomer 1) and Kd = 0.065 ± 0.020 M (isomer 2). The value of kH2OC for isomer 1 is 4.81 × 10-6 s -1. For isomer 2 both the rate constants for the water and OH--induced reaction of the Zn2+-complexed substrate could be measured, despite the low concentration of OH- in the investigated reaction mixture [kH2OC 0 = 1.97 × 10-6 s-1 and kOH-C = 21.9 M -1 s-1, respectively]. The measured metal activating factor (MetAF), i.e., the reactivity ratio between the complexed and the uncomplexed substrate, is 8.1 × 104 for the OH--induced elimination of 2. This high MetAF can be compared with the corresponding proton activating factor (Alunni, S.; Conti, A.; Palmizio Errico, R. J. Chem. Soc., Perkin Trans. 2 2000, 453), PAF = 1.5 × 106 and is in agreement with an E1cb irreversible mechanism (AxhD E* + DN) (Guthrie, R. D.; Jencks, W. P. Acc. Chem. Res. 1989, 22, 343). A value of kH2OC ≥ 23 × 10 -7 s-1 is estimated for the Cd2+-complexed isomer 2, while catalysis by Cd2+ has not been observed for isomer 1.
- Alunni, Sergio,Del Giacco, Tiziana,De Maria, Paolo,Fifi, Giorgia,Fontana, Antonella,Ottavi, Laura,Tesei, Ilaria
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p. 3276 - 3281
(2007/10/03)
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- A study of the OH--induced β-elimination reactions of 2-(4-chloroethyl)pyridine, 2-(2-chloroethyl)pyridine, 1-methyl-2-(4-chloroethyl) pyridinium iodide and 1-methyl-2-(2-chloroethyl)pyridinium iodide in acetonitrile/water
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Second-order rate constants have been determined for the title reactions in OH-/H2O and in OH-/ (CH3CN/H 2O) [30/70, 60/40, and 85/15 (v/v) mixtures]. A relatively small increase in reactivity is observed for the four substrates upon increasing the percentage of CH3CN in the solvent mixture. The methyl activating factors (kOH-NCH3/kOH-N) are also slightly affected by the solvent composition. On the other hand, the high acceleration of the reaction by methylation of the pyridine ring amounts to 104-106 according to an E1cb mechanism.
- Alunni, Sergio,Del Giacco, Tiziana,De Maria, Paolo,Fontana, Antonella,Gasbarri, Carla,Ottavi, Laura
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p. 6121 - 6123
(2007/10/03)
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- Mechanisms of Acid-Base Catalysis of β-Elimination Reactions in Systems Activated by a Pyridine Ring
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β-Elimination reactions from 1 (in quinuclidine/quinuclidinium chloride, imidazole/imidazolium, and acetate/acetic acid buffers) and from 2 (in imidazole/imidazolium and acetate/acetic acid buffers) with formation of 4-vinylpyridine and 2-vinylpyridine, respectively, were studied. The results of a kinetic study of acid-base catalysis and H/D exchange are consistent with NH+, the protonated substrate, as the species that undergoes carbon deprotonation with an E1cb mechanism. The comparison with previously studied reactions in acetohydroxamate/acetohydroxamic acid buffer confirms this assignment. The high proton activating factor, PAF, value observed (PAF = 1.2 × 10 6 with isomer 1 in quinuclidine/quinuclidinium buffer) can be explained with the high stability by the resonance of the intermediate carbanion.
- Alunni, Sergio,Ottavi, Laura
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p. 2272 - 2283
(2007/10/03)
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- Process for the preparation of vinylpyridine from picoline over modified zeolites
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The present invention relates to an improved eco-friendly process for the preparation of vinylpyridine from corresponding picoline over modified zeolite catalyst in vapour phase which comprises reacting picoline with formaldehyde with a molar ratio of formaldehyde to picoline in the range of 1:1 to 4:1, at a temperature ranging between 200° C. to 450° C., at a weight hourly in the range of 0.25 hr?1-1.00 hr?1over a modified commercial zeotlite catalyst to obtain a high yield and selectivity of the desired product.
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Page column 5
(2008/06/13)
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- Catalysis of the β-elimination of HF from isomeric 2-fluoroethylpyridines and 1-methyl-2-fluoroethylpyridinium salts. Proton-activating factors and methyl-activating factors as a mechanistic test to distinguish between concerted E2 and E1cb irreversible mechanisms
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Second-order rate constants, kOHN, M-1 s-1, for the β-elimination reactions of HF with 2-(2-fluoroethyl)pyridine (2), 3-(2-fluoroethyl)pyridine (3), and 4-(2-fluoroethyl)pyridine (4) in OH-/H2O, at 50°C and μ = 1 M KCl, are kOHN = 0.646 × 10-4 M-1 s-1, kOHN = 2.97 × 10-6 M-1 s-1, and kOHN = 5.28 × 10-4 M-1 s-1, respectively. When compared with the second-order rate constants for the same processes with the nitrogen-methylated substrates 1-methyl-2-(2-fluoroethyl)pyridinium iodide (5), 1-methyl-3-(2-fluoroethyl)pyridinium iodide (6), and 1-methyl-4-(2-fluoroethyl)pyridinium iodide (7), the methyl-activating factor (MethylAF) can be calculated from the ratio kOHNCH3/kOHN, and a value of 8.7 × 105 is obtained with substrates 5/2, a value of 1.6 × 103 with 6/3, and a value of 2.1 × 104 with 7/4. The high values of MethylAF are in agreement with an irreversible E1cb mechanism (ANDE* + DN) for substrates 5 and 7 and with the high stability of the intermediate carbanion related to its enamine-type structure. In acetohydroxamate/acetohydroxamic acid buffers (pH 8.45-9.42) and acetate/acetic acid buffers (pH 4.13-5.13), the β-elimination reactions of HF, with substrates 2 and 4, occur at NH+, the substrates protonated at the nitrogen atom of the pyridine ring, even when the [NH+] is much lower than the [N], the unprotonated substrate, due to the high proton-activating factor (PAF) value observed: 3.6 × 105 for 2 and 6.5 × 104 for 4 with acetohydroxamate base. These high PAF values are indicative of an irreversible E1cb mechanism rather than a concerted E2 (ANDEDN) mechanism. Finally, the rate constant for carbanion formation from NH+ with 2 is kBNH+ = 0.35 M-1 s-1, which is lower than when chlorine is the leaving group (kBNH+ = 1.05 M-1 s-1; Alunni, S.; Busti, A. J. Chem. Soc., Perkin Trans. 2 2001, 778). This is direct experimental evidence that some lengthening of the carbon-leaving group bond can occur in the intermediate carbanion. This is a point of interest for interpreting a heavy-atom isotope effect.
- Alunni, Sergio,Laureti, Valeria,Ottavi, Laura,Ruzziconi, Renzo
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p. 718 - 725
(2007/10/03)
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- Studies on the reactions of 2,3-diketopyrido[4,3,2-de] quinolines with aliphatic amines
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A reaction of 2,3-diketopyrido[4,3,2-de]quinolines with different amines is described. The aminative transfer is carried out in the presence of triethylamine in tetrahydrofuran under ambient conditions.
- Shao, Huawu,Ding, Qizhu,Lown, J. William
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p. 107 - 112
(2007/10/03)
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- Mechanism and proton activating factors in base-induced β-elimination reactions of 2-(2-chloroethyl)pyridine
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The substrate 2-(2-chloroethyl)pyridine reacts in OH-/H2O, 50 deg C, μ=1 M KCl by an elimination reaction with the formation of 2-vinylpyridine; the second order rate constant is kNOH=4.59x10-4 dm3 mol-1 s-1. In acetohydroxamate-acetohydroxamic acid buffers, The elimination reaction competes with the SN2 reaction of the acetohydroxamate nucleophile. Studies of acid-base catalysis at pH values ranging from 8.42 to 9.42 are in agreement with an E1cb irreversible mechanism, where carbon deprotonation occurs from the substrate protonated at the nitrogen of the pyridine ring (NH+), even if it is present at very low concentrations with respect to the unprotonated substrate (N) under the reaction conditions. The value for the reactivity ratio between NH+ and N is of the irder of 105. The strong reactivity of NH+ is attributed to the high stability of the carbanion intermediate formed; this intermediate has an enamine structure.
- Alummi, Sergio,Busti, Alessandra
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p. 778 - 781
(2007/10/03)
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- Mechanism and proton activating factors in base-induced β-elimination reactions of N-[2-(4-pyridyl)ethyl]quinuclidinium and N-[2-(2-pyridyl)ethyl]quinuclidinium salts
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β-Elimination reactions of N-[2-(4-pyridyl)ethyl]quinuclidinium and N-[2-(2-pyridyl)ethyl]quinuclidinium salts (N) in acetohydroxamate-acetohydroxamic acid buffer, H2O, μ = 1 M KCl, 50°C, with the formation of 4- or 2-vinylpyridine, respectively, proceed by an Elcb mechanism with carbon deprotonation occurring in the substrates protonated at the pyridine ring (NH+). The formation of the intermediate carbanion has a high degree of reversibility. The systems consistently present H/D exchange. NH+ is much more reactive than N; this can be attributed to the strong stabilization of the intermediate carbanion formed from NH+ due to resonance.
- Alunni, Sergio,Conti, Annarita,Errico, Rosa Palmizio
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p. 453 - 457
(2007/10/03)
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- Triazole antifungal agents
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An antifungal compound of formula (I): STR1 or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate of either entity, wherein X is CH or N; R1 is phenyl substituted with 1 to 3 substituents each independently selected from halo and CF3 ; R2 is (hydroxy)C1 -C4 alkyl, CONH2, S(O)m (C1 -C4 alkyl), Ar or Het; m is 1 or 2; Ar is phenyl optionally monosubstituted with halo or CF3 ; and Het is a C-linked 6-membered nitrogen-containing aromatic heterocyclic group containing 1 or 2 nitrogen atoms, or a C- or N-linked 5-membered nitrogen-containing aromatic heterocyclic group containing from 2 to 4 nitrogen atoms, wherein either of said heterocyclic groups is optionally substituted with C1 -C4 alkyl or (C1 -C4 alkoxy)methyl.
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- Mechanistic studies of the ring opening reactions of [1,2,3]triazolo[1,5-a]pyridines
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A mechanism with radical intervention is proposed for the opening of the triazole ring in [1,2,3] triazolo[1,5-a]pyridines which results in the production of 2- or 2,6-disubstituted pyridines.
- Abarca, Belen,Ballesteros, Rafael,Rodrigo, Gemma,Jones, Gurnos,Veciana, Jaume,Vidal-Gancedo, Jose
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p. 9785 - 9790
(2007/10/03)
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- Indole derivatives as 5-HT1-like agonists
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Compounds of formula (I) and pharmaceutically acceptable salts thereof, wherein R1 is a substituted alkylene; C3 -C7 cycloalkyl optionally substituted with HO; C3 -C6 alkenyl optionally substituted with aryl; C5 -C7 cycloalkenyl; or C3 -C6 alkynyl; R2 is H; halo; F3 C; NC; R8 R9 NOC; a substituted alkylene; R8 R9 NO2 S; R10 S(O)m ; R12 CON(R11); R10 SO2 N(R11); R8 R9 NOCN(R11); R10 O2 CN(R11); R13 (CH2)n CH=CH; or R7 O are selective 5-HT1 -like receptor agonists useful in the treatment of migraine, cluster headache, chronic paroxysmal hemicrania and headache associated with vascular disorders.
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