- In-situ facile synthesis novel N-doped thin graphene layer encapsulated Pd@N/C catalyst for semi-hydrogenation of alkynes
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Transition metal-catalyzed semi-hydrogenation of alkynes has become one of the most popular methods for alkene synthesis. Specifically, the noble metal Pd, Rh, and Ru-based heterogeneous catalysts have been widely studied and utilized in both academia and industry. But the supported noble metal catalysts are generally suffering from leaching or aggregation during harsh reaction conditions, which resulting low catalytic reactivity and stability. Herein, we reported the facile synthesis of nitrogen doped graphene encapsulated Pd catalyst and its application in the chemo-selective semi-hydrogenation of alkynes. The graphene layer served as “bulletproof” over the active Pd Nano metal species, which was confirmed by X-ray and TEM analysis, enhanced the catalytic stability during the reaction conditions. The optimized prepared Pd@N/C catalyst showed excellent efficiency in semi-hydrogenation of phenylacetylene and other types of alkynes with un-functionalized or functionalized substituents, including the hydrogenation sensitive functional groups (NO2, ester, and halogen).
- Lin, Shanshan,Liu, Jianguo,Ma, Longlong,Sun, Jiangming
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- Palladium Nanoparticle-Catalyzed Stereoselective Domino Synthesis of 3-Allylidene-2(3 H)-oxindoles and 3-Allylidene-2(3 H)-benzofuranones
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A single-step, stereoselective protocol for the synthesis of unsymmetrically substituted (E)-3-allylideneoxindole and (E)-3-allylidenebenzofuran from readily accessible starting materials using palladium binaphthyl nanoparticles (Pd-BNPs) has been developed. Pd-BNP showing a wide range of functional group tolerance and an immense array of substrate scope have been explored with the successful synthesis of the drug molecule "tubulin polymerization inhibitor" free from trace metal impurities. The model reaction is extended to a gram-scale synthesis, and one of the products is utilized for derivatization. The Pd-BNP has been recycled up to 5 catalytic cycles without any loss in reaction yields and particle size of nanoparticles.
- Parveen, Naziya,Sekar, Govindasamy
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p. 4682 - 4694
(2020/05/08)
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- Method for synthesizing olefin compound by photo-induced one-pot process
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The invention discloses a method for synthesizing an olefin compound by a photo-induced one-pot process. The method comprises the following step of subjecting a halohydrocarbon and an aldehyde compound to a reaction under the condition of irradiation in an inert atmosphere by taking alkali metal carbonate as a base, taking an organic phosphine compound as an adjuvant and taking a photosensitizer as a catalyst, thereby obtaining the olefin compound. According to the method disclosed by the invention, the olefin compound is produced from the halohydrocarbon and the aldehyde compound in a high-yield manner under the condition of irradiation in the inert atmosphere under normal-temperature reaction conditions by taking acetonitrile, DMF (N,N-dimethylformamide) or DMA (N,N-dimethylacetamide) asa solvent, taking an organic phosphine reagent as a reaction adjuvant, taking the alkali metal carbonate as the base and taking the photosensitizer as the catalyst. Compared with the conventional olefin synthesis methods, the method disclosed by the invention has the obvious advantages that the reaction raw materials are readily available, the tolerance to a variety of functional groups on halohydrocarbons and aldehydes is high, the yield is high, the separation and purification of a product are simple and convenient, and the like.
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Paragraph 0061-0063
(2018/11/03)
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- Electronically Mismatched Cycloaddition Reactions via First-Row Transition Metal, Iron(III)-Polypyridyl Complex
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The iron(III)-polypyridyl complex and its derivatives showed sufficient oxidizing potential to act as a one-electron oxidant, producing radical cations from olefins and promoting the efficient radical cation [2 + 2] and [2 + 4] cycloaddition reactions. Subsequent chain propagation afforded trisubstituted cyclobutane or cyclohexene derivatives, and this facile route enables the replacement of rare metals with sustainable, green, and inexpensive iron in radical cation cycloadditions.
- Shin, Jung Ha,Seong, Eun Young,Mun, Hyeon Jin,Jang, Yu Jeong,Kang, Eun Joo
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supporting information
p. 5872 - 5876
(2018/09/25)
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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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- Chemoselectivity in the Kosugi-Migita-Stille coupling of bromophenyl triflates and bromo-nitrophenyl triflates with (ethenyl)tributyltin
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Kosugi-Migita-Stille cross coupling reactions of (ethenyl)tributyltin with all isomeric permutations of bromophenyl triflate and bromo-nitrophenyl triflate were examined in order to determine the chemoselectivity of carbon-bromine versus carbon-triflate bond coupling under different reaction conditions. In general, highly selective carbon-bromine bond cross couplings were observed using for example bis(triphenylphosphine)palladium dichloride (2 mol-%) in 1,4-dioxane at reflux. In contrast, reactions using the same pre-catalyst but in the presence of a three-fold excess of lithium chloride in N,N-dimethylformamide at ambient temperature were in most cases selective for coupling at the carbon-triflate bond. Overall, isolated yields and the selectivity for carbon-bromine bond coupling were significantly higher compared to carbon-triflate bond coupling.
- Ansari, Nurul N.,Cummings, Matthew M.,S?derberg, Bj?rn C.G.
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p. 2547 - 2560
(2018/04/20)
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- Copper-Catalyzed Oxidative Difunctionalization of Terminal Unactivated Alkenes
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The copper(II)-promoted free-radical oxidative difunctionalization of terminal alkenes to access ketoazides by utilizing molecular oxygen has been reported. A series of styrene derivatives have been evaluated and were found to be compatible to give the desired difunctionalized products in moderate to good yields. The role of molecular oxygen both as an oxidant and oxygen atom source in this catalytic transformation has been unquestionably demonstrated by 18O-labeling studies and a radical mechanistic pathway involving the oxidative formation of azidyl radicals is also designed. This environment-friendly catalytic oxidative protocol can transform aldehyde to nitrile.
- Hussain, Muhammad Ijaz,Feng, Yangyang,Hu, Liangzhen,Deng, Qingfu,Zhang, Xiaohui,Xiong, Yan
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p. 7852 - 7859
(2018/05/30)
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- α-Alkylidene-γ-butyrolactone Formation via Bi(OTf)3-Catalyzed, Dehydrative, Ring-Opening Cyclizations of Cyclopropyl Carbinols: Understanding Substituent Effects and Predicting E/Z Selectivity
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A Bi(OTf)3-catalyzed ring-opening cyclization of (hetero)aryl cyclopropyl carbinols to form α-alkylidene-γ-butyrolactones (ABLs) is reported. This transformation represents different chemoselectivity from previous reports that demonstrated formation of (hetero)aryl-fused cyclohexa-1,3-dienes upon acid-promoted cyclopropyl carbinol ring opening. ABLs are obtained in up to 89% yield with a general preference for the E-isomers. Mechanistically, Bi(OTf)3 serves as a stable and easy to handle precursor to TfOH. TfOH then catalyzes the formation of cyclopropyl carbinyl cations, which undergo ring opening, intramolecular trapping by the neighboring ester group, subsequent hydrolysis, and loss of methanol resulting in the formation of the ABLs. The nature and relative positioning of the substituents on both the carbinol and the cyclopropane determine both chemo- and stereoselective outcomes. Carbinol substituents determine the extent of cyclopropyl carbinyl cation formation. The cyclopropane donor substituents determine the overall reaction chemoselectivity. Weakly stabilizing or electron-poor donor groups provide better yields of the ABL products. In contrast, copious amounts of competing products are observed with highly stabilizing cyclopropane donor substituents. Finally, a predictive model for E/Z selectivity was developed using DFT calculations.
- Sandridge, Matthew J.,McLarney, Brett D.,Williams, Corey W.,France, Stefan
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p. 10883 - 10897
(2017/10/27)
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- Lewis base-assisted Lewis acid-catalyzed selective alkene formation via alcohol dehydration and synthesis of 2-cinnamyl-1,3-dicarbonyl compounds from 2-aryl-3,4-dihydropyrans
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Acid-catalyzed dehydration of alcohols has been widely employed for the synthesis of alkenes. However, activated alcohols when employed as substrates in dehydration reactions are often plagued by the lack of alkene selectivity. In this work, the reaction system can be significantly improved through enhancing the performance of Lewis acid catalysts in the dehydration of activated alcohols by combining with a Lewis base. Observations of the reaction mechanism revealed that the Lewis base component might have changed the reaction rate order. Although both the principal and side reaction rates decreased, the effect was markedly more observed on the latter reaction. Therefore, the selectivity of the dehydration reaction was improved. On the basis of this observation, a new route to synthesize 2-cinnamyl-1,3-dicarbonyl compounds was developed by using 2-aryl-3,4-dihydropyran as a starting substrate in the presence of a Lewis acid/Lewis base combined catalyst system.
- Liu, Changhui,Pan, Bin,Gu, Yanlong
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p. 979 - 986
(2016/07/06)
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- Synthesis of 1,3-Substituted Cyclobutanes by Allenoate-Alkene [2 + 2] Cycloaddition
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A method for the [2 + 2] cycloaddition of terminal alkenes with allenoates is presented. This process allows for the rapid synthesis of 1,3-substituted cyclobutanes in high yield under simple and robust reaction conditions.
- Conner, Michael L.,Brown, M. Kevin
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p. 8050 - 8060
(2016/09/09)
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- Oxidative trifluoromethylation and fluoroolefination of unactivated olefins
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Fluorine-containing organic compounds are gaining increasing importance in medicinal chemistry. Described herein is a mild and efficient method for the radical addition of olefins with TMSCF3 and TMSCF2R (R = COOEt or CF3) to deliver various α-trifluoromethylated ketones and α-fluoroolefinated ketones.
- Wu, Ye-Bin,Lu, Guo-Ping,Yuan, Tao,Xu, Zhu-Bing,Wan, Li,Cai, Chun
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supporting information
p. 13668 - 13670
(2016/11/29)
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- Benzocarbazoles dioxane derivatives, its preparation process and its use in medicine
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The invention relates to a benzodioxane derivative, a preparation method thereof and application of the derivative in medicines. Specifically, the invention relates to a novel benzodioxane derivative shown as a formula (I), medial salt thereof or a medicine composition containing the derivative, and a preparation method of the derivative. The invention further relates to a use of the benzodioxane derivative and the medial salt thereof or the medicine composition containing the derivative in preparing therapeutic agent, especially GPR 40 agonist, and a drug for treating the diseases such as diabetes, metabolic disorders and the like, wherein each substituent group in the formula (I) is as defined in the description.
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Paragraph 0207-0213
(2016/10/10)
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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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- 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
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supporting information
p. 12109 - 12111
(2015/01/08)
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- Aryl bromide/triflate selectivities reveal mechanistic divergence in palladium-catalysed couplings; the Suzuki-Miyaura anomaly
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In palladium-catalysed cross-coupling reactions, the outcome of competition between aryl bromides and aryl triflates depends on the nucleophilic partner; Suzuki couplings with R-B generally follow a different pattern from other R-M species. The Royal Society of Chemistry.
- Espino, Gustavo,Kurbangalieva, Almira,Brown, John M.
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p. 1742 - 1744
(2008/02/04)
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- A dehydrohalogenation methodology for synthesizing terminal olefins under mild conditions
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A new methodology for preparing terminal olefins in good yield by dehydrohalogenation of primary alkyl iodide with tetrabutylammonium fluoride in dimethyl sulfoxide at room temperature is presented. Optimization of the mild reaction conditions and assays on various alkyl iodides are described. Georg Thieme Verlag Stuttgart.
- Berube, Marie,Kamal, Fatima,Roy, Jenny,Poirier, Donald
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p. 3085 - 3091
(2008/02/08)
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- Iron-catalyzed cross-coupling between alkenyl and dienyl sulfonates and functionalized arylcopper reagents
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Functionalized arylcopper reagents react readily with alkenyl sulfonates in the presence of catalytic amounts of Fe(acac)3, (10 mol%) providing the expected cross-coupling products in good yields. Ester or cyano group are tolerated. This cross-coupling can be performed with dienyl sulfonates leading to the corresponding substituted dienes. Georg Thieme Verlag Stuttgart.
- Dunet, Guillaume,Knochel, Paul
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p. 407 - 410
(2007/10/03)
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- REACTIONS OF DIHALOCARBENES WITH SUBSTITUTED SPIROHEPTA-4,6-DIENES
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Reactions of dihalocarbenes with spirohepta-4,6-diene lead to the formation of 1-halo-3-(2-haloethyl)benzenes, which readily undergo dehydrohalogenation to 3-halostyrenes.From 1-arylspirohepta-4,6-dienes and dihalocarbenes 3-halostilbenes are obtained.
- Molchanov, A. P.,Kostikov, R. R.
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p. 935 - 937
(2007/10/02)
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- Concerted Bimolecular Substitution Reactions of 1-Phenylethyl Derivatives
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Substituted 1-phenylethyl derivatives with ?+ > -0.08 exhibit bimolecular substitution reactions with azide ion in 20percent acetonitrile in water.The reactions with 1-phenylethyl chlorides follow a Hammett correlation with ρ = -2.9, compared with ρ = -5.6 (r+ = 1.15) for solvolysis.Swain-Scott correlations give values of s = 0.46 and 0.22 for 1-(4-nitrophenyl)ethyl chloride and tosylate, respectively; there are large positive deviations for azide ion and water and negative deviations for cyanide ion.The value of βnuc is 0.09 for reactions of substituted acetates with the chloride.The reactions exhibit ''synergism'' between the nucleophile and leaving group that favors the bimolecular reaction with Me2S, Br- > Cl- > OTs- leaving groups.The bimolecular reaction with azide follows the Grunwald-Winstein Y correlation with m = 0.8 in methanol-water mixtures.Bimolecular reactions with less reactive nucleophiles in the series N3-, CN-, AcO-, and ROH appear at progressively larger ? values, as the carbocation becomes less stable.It is concluded that these reactions are SN2 displacements that proceed through an open, ''exploded'' transition state that closely resembles a carbocation.Specific salt effects are small in water but are significant in acetonitrile-water mixtures and could be mistaken for normal or induced common ion rate depressions.No evidence was obtained for nucleophilic assistance to the formation of a carbocation intermediate.Concurrent SN1 and SN2 pathways occur in the reactions with solvent and azide of dimethylsulfonium ion, 1-(4-fluorophenyl)ethyl chloride, 1-(3-methoxyphenyl)ethyl chloride, and, probably, 1-(3-nitro-4-methoxyphenyl)ethyl chloride.Crude estimates of the lifetime of the carbocation intermediate in the presence of the nucleophile are consistent with the hypothesis that the concerted reactions are enforced by the absence of a significant lifetime of the carbocation in the presence of the nucleophile and that stepwise mechanisms are followed when the intermediate has a significant lifetime; the change from a stepwise to a concerted mechanism occurs when the intermediate ceases to have a lifetime in the presence of a nucleophile.
- Richard, John P.,Jencks, William P.
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p. 1383 - 1396
(2007/10/02)
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