- Mechanism of Polyphosphoric Acid and Phosphorus Pentoxide-Methanesulfonic Acid as Synthetic Reagents for Benzoxazole Formation
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The mechanism of 2-phenylbenzoxazole formation from benzoic acid and o-aminophenol in polyphosphoric acid (PPA) is studied by NMR spectroscopy and chemical analysis. Benzoic acid reacts with PPA to form benzoic-phosphoric anhydride and benzoic-polyphosphoric anhydride. The ratio of mixed anhydride to free carboxylic acid increases dramatically as the P2O5 content of PPA increases, but this ratio is independent of reaction temperature and time. When o-aminophenol dissolves in PPA, part of the hydroxyl group is converted to phosphate ester, and only protonated amine is detected. Benzoic acid, mixed anhydride, and PPA are in dynamic equilibrium, and so are PPA, o-aminophenol, and its phosphate ester. The mixed anhydride and o-aminophenol react to form 2-aminophenyl benzoate as the first reaction intermediate which undergoes rapid acyl migration to generate 2-hydroxybenzanilide. Ring closure of 2-hydroxybenzanilide to form 2-phenylbenzoxazole is acid catalyzed. The reactive components in phosphorus pentoxide-methanesulfonic acid (P2O5-MSA) which is a convenient alternative to PPA are very similar to those present in PPA. Benzoic acid is also converted into mixed anhydride in P2O5-MSA.
- So, Ying-Hung,Heeschen, Jerry P.
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- Radical Organometallic Phase-transfer Reactions
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The phase-transfer catalysed coupling reactions of benzylic halides, in the presence of catalytic quantities of bis(dibenzylideneacetone)palladium(0) or cobalt carbonyl, proceed via radical pathways.
- Galamb, Vilmos,Alper, Howard
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Read Online
- Decarboxylative cross-nucleophile coupling via ligand-to-metal charge transfer photoexcitation of Cu(ii) carboxylates
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Reactions that enable carbon–nitrogen, carbon–oxygen and carbon–carbon bond formation lie at the heart of synthetic chemistry. However, substrate prefunctionalization is often needed to effect such transformations without forcing reaction conditions. The development of direct coupling methods for abundant feedstock chemicals is therefore highly desirable for the rapid construction of complex molecular scaffolds. Here we report a copper-mediated, net-oxidative decarboxylative coupling of carboxylic acids with diverse nucleophiles under visible-light irradiation. Preliminary mechanistic studies suggest that the relevant chromophore in this reaction is a Cu(ii) carboxylate species assembled in situ. We propose that visible-light excitation to a ligand-to-metal charge transfer (LMCT) state results in a radical decarboxylation process that initiates the oxidative cross-coupling. The reaction is applicable to a wide variety of coupling partners, including complex drug molecules, suggesting that this strategy for cross-nucleophile coupling would facilitate rapid compound library synthesis for the discovery of new pharmaceutical agents. [Figure not available: see fulltext.].
- Li, Qi Yukki,Gockel, Samuel N.,Lutovsky, Grace A.,DeGlopper, Kimberly S.,Baldwin, Neil J.,Bundesmann, Mark W.,Tucker, Joseph W.,Bagley, Scott W.,Yoon, Tehshik P.
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- Reactive separation of β-bromoethylbenzene from α-β-bromoethylbenzene mixtures: a Zn2+-mediated radical polymerization mechanism
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A Zn2+-induced reactive separation method for the purification of β-bromoethylbenzene from α-β-bromoethylbenzene mixtures is discovered, where the selective decomposition of α-bromoethylbenzene follows a radical mechanism. Zn2+ facilitates the homolysis of the C-Br bond of halohydrocarbons with benzyl bromide, enabling the separation of the corresponding isomers with almost identical physical properties.
- Deng, Tianyu,Tian, Jiaming,Yan, Binhang,Zhu, Junqiu
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p. 1219 - 1222
(2022/02/03)
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- Decatungstate Catalyzed Synthesis of Trifluoromethylthioesters from Aldehydes via a Radical Process
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Here we report a mild and general method for the trifluoromethylthiolation of aldehydes using N-trifluoromethylthiosaccharin as the CF3S radical source and sodium decatungstate (NaDT) as the photocatalyst. This reaction proceeds via hydrogen at
- Ye, Zhegao,Lei, Ziran,Ye, Xiaodong,Zhou, Liejin,Wang, Yanan,Yuan, Zheliang,Gao, Feng,Britton, Robert
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supporting information
p. 765 - 775
(2021/12/17)
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- Molybdenum-Catalyzed Deoxygenation Coupling of Lignin-Derived Alcohols for Functionalized Bibenzyl Chemicals
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With the growing demand for sustainability and reducing CO2 footprint, lignocellulosic biomass has attracted much attention as a renewable, carbon-neutral and low-cost feedstock for the production of chemicals and fuels. To realize efficient utilization of biomass resource, it is essential to selectively alter the high degree of oxygen functionality of biomass-derivates. Herein, we introduced a novel procedure to transform renewable lignin-derived alcohols to various functionalized bibenzyl chemicals. This strategy relied on a short deoxygenation coupling pathway with economical molybdenum catalyst. A well-designed H-donor experiment was performed to investigate the mechanism of this Mo-catalyzed process. It was proven that benzyl carbon-radical was the most possible intermediate to form the bibenzyl products. It was also discovered that the para methoxy and phenolic hydroxyl groups could stabilize the corresponding radical intermediates and then facilitate to selectively obtain bibenzyl products. Our research provides a promising application to produce functionalized aromatics from biomass-derived materials.
- Jiang, Huifang,Lu, Rui,Luo, Xiaolin,Si, Xiaoqin,Xu, Jie,Lu, Fang
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supporting information
p. 1292 - 1296
(2020/12/09)
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- Reactivity of (bi-Oxazoline)organonickel Complexes and Revision of a Catalytic Mechanism
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Bi-Oxazoline (biOx) has emerged as an effective ligand framework for promoting nickel-catalyzed cross-coupling, cross-electrophile coupling, and photoredox-nickel dual catalytic reactions. This report fills the knowledge gap of the organometallic reactivity of (biOx)Ni complexes, including catalyst reduction, oxidative electrophile activation, radical capture, and reductive elimination. The biOx ligand displays no redox activity in (biOx)Ni(I) complexes, in contrast to other chelating imine and oxazoline ligands. The lack of ligand redox activity results in more negative reduction potentials of (biOx)Ni(II) complexes and accounts for the inability of zinc and manganese to reduce (biOx)Ni(II) species. On the basis of these results, we revise the formerly proposed “sequential reduction” mechanism of a (biOx)Ni-catalyzed cross-electrophile coupling reaction by excluding catalyst reduction steps.
- Ju, Luchuan,Lin, Qiao,LiBretto, Nicole J.,Wagner, Clifton L.,Hu, Chunhua Tony,Miller, Jeffrey T.,Diao, Tianning
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p. 14458 - 14463
(2021/09/18)
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- Enantioselective Reductive Cross-Coupling of Aryl/Alkenyl Bromides with Benzylic Chlorides via Photoredox/Biimidazoline Nickel Dual Catalysis
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The asymmetric reductive arylation and alkenylation of benzylic chloride under photoredox/nickel dual catalysis using chiral biimidazoline (BiIm) ligand is reported to access 1,1-diaryl alkanes and aryl allylic compounds with good yield as well as stereo-
- Cheng, Xiaokai,Fang, Qun,Li, Tongtong,Lu, Jiamin,Lu, Zhan,Wang, Huifeng
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supporting information
(2022/02/07)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Synthesis of dimeric molecules via ag-catalyzed electrochemical homocoupling of organic bromides paired with electrooxidation of urea
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We present a sacrificial anode-free approach to reductive homocoupling of organohalides that does not require a co-catalyst. In this approach, a divided electrochemical cell with aprotic and aqueous compartments separated by an anion exchange membrane enables coupling of the cathodic homocoupling reaction with anodic oxidation of urea. We show that, in contrast with traditional one-compartment cells relying on sacrificial anodes, the proposed cell configuration maintains stable cell voltage in the course of galvanostatic electrolysis. A synthetic potential of this method was assessed using a series of 13 organic bromides that demonstrated a strong dependence of the reaction outcome on the structure of the organic substrate, more specifically, the dissociation energy of the C–Br bond and the redox properties of formed radicals, which are discussed in detail. While not being suitable for the synthesis of byarylstructures, this method is excellent for C(sp3)-C(sp3) coupling to corresponding dimeric products with up to quantitative yields. Simultaneous electrochemical treatment of nitrogenous waste in the adjacent half-cell provides an additional incentive for wide adaptation of this sustainable synthetic approach.
- Klinkova, Anna,Krivoshapkina, Elena F.,Medvedev, Jury J.,Medvedeva, Xenia V.,Pivovarova, Yekaterina,Steksova, Yulia P.
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- Asymmetric Hydrogenation of Unfunctionalized Tetrasubstituted Acyclic Olefins
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Asymmetric hydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetric hydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio- and diastereoselective hydrogenation of such olefins and the mechanistic insights of the reaction. The power of this chemistry is demonstrated by the successful hydrogenation of a wide variety of electronically and sterically diverse olefins in excellent yield and high enantio- and diastereoselectivity.
- Bachmann, Stephan,Bigler, Raphael,Denmark, Scott E.,Gosselin, Francis,Han, Chong,Hildbrand, Stefan,Mack, Kyle A.,Pfaltz, Andreas,Scalone, Michelangelo,Shen, Jeff,Tosatti, Paolo,Zhang, Haiming
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p. 2844 - 2849
(2020/02/05)
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- Iron-catalysed enantioconvergent Suzuki-Miyaura cross-coupling to afford enantioenriched 1,1-diarylalkanes
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The first stereoconvergent Suzuki-Miyaura cross-coupling reaction was developed to afford enantioenriched 1,1-diarylalkanes. An iron-based complex containing a chiral cyanobis(oxazoline) ligand framework was best to obtain enantioenriched 1,1-diarylalkanes from cross-coupling reactions between unactivated aryl boronic esters and benzylic chlorides. Enhanced yields were obtained when 1,3,5-trimethoxybenzene was used as an additive, which is hypothesized to extend the lifetime of the iron-based catalyst. Exceptional enantioselectivities were obtained with challenging ortho-substituted benzylic chlorides. This journal is
- Tyrol, Chet C.,Yone, Nang S.,Gallin, Connor F.,Byers, Jeffery A.
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p. 14661 - 14664
(2020/12/02)
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- Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.
- Banert, Klaus,Hagedorn, Manfred,Heck, Manuel,Hertel, Raphael,Ihle, Andreas,Müller, Ioana,Pester, Tom,Shoker, Tharallah,Rablen, Paul R.
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p. 13630 - 13643
(2020/11/13)
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- Photoinduced Copper-Catalyzed Asymmetric Decarboxylative Alkynylation with Terminal Alkynes
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We describe a photoinduced copper-catalyzed asymmetric radical decarboxylative alkynylation of bench-stable N-hydroxyphthalimide(NHP)-type esters of racemic alkyl carboxylic acids with terminal alkynes, which provides a flexible platform for the construction of chiral C(sp3)?C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo- and cross-coupling catalyst but also tuning of the NHP-type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP-type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl-, allyl-, and aminocarbonyl-substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method.
- Dong, Xiao-Yang,Du, Xuan-Yi,Fang, Jia-Heng,Gu, Qiang-Shuai,Li, Zhong-Liang,Liu, Xin-Yuan,Wang, Li-Lei,Xia, Hai-Dong
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supporting information
p. 16926 - 16932
(2020/08/25)
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- Dehydrogenative Coupling of Benzylic and Aldehydic C-H Bonds
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A photoinduced dehydrogenative coupling reaction between benzylic and aldehydic C-H bonds is reported. When a solution of an alkylbenzene and an aldehyde in ethyl acetate is irradiated with visible light in the presence of iridium and nickel catalysts, a coupled α-aryl ketone is formed with evolution of dihydrogen. An analogous C-C bond forming reaction occurs between a C-H bond next to the nitrogen of an N-methylamide and an aldehydic C-H bond to produce an α-amino ketone. These reactions provide a straightforward pathway from readily available materials leading to valued structural motifs of pharmacological relevance.
- Ishida, Naoki,Kawasaki, Tairin,Murakami, Masahiro
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supporting information
p. 3366 - 3370
(2020/03/06)
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- Vanadium Pyridonate Catalysts: Isolation of Intermediates in the Reductive Coupling of Alcohols
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The reductive coupling of alcohols using vanadium pyridonate catalysts is reported. This attractive approach for C(sp3)-C(sp3) bond formation uses an oxophilic, earth-abundant metal for a catalytic deoxygenation reaction. Several pyridonate complexes of vanadium were synthesized, giving insight into the coordination chemistry of this understudied class of compounds. Isolated intermediates provide experimental mechanistic evidence that complements reported computational mechanistic proposals for the reductive coupling of alcohols. In contrast to previous mononuclear vanadium(V)/vanadium(III)/vanadium(IV) cycles, this pyridonate catalyst system is proposed to proceed by a vanadium(III)/vanadium(IV) cycle involving bimetallic intermediates.
- Griffin, Samuel E.,Schafer, Laurel L.
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supporting information
(2020/04/15)
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- Synthesis of unsymmetrical ketones by applying visible-light benzophenone/nickel dual catalysis for direct benzylic acylation
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Herein, we report a dual catalytic system for the direct benzylic C-H acylation reaction furnishing a variety of unsymmetrical ketones. A benzophenone-derived photosensitizer combined with a nickel catalyst has been established as the catalytic system. Both acid chlorides and anhydrides are able to acylate the benzylic position of toluene and other methylbenzenes. The method offers a valuable alternative to late transition metal catalyzed C-H acylation reactions.
- Krach, Patricia E.,Dewanji, Abhishek,Yuan, Tingting,Rueping, Magnus
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supporting information
p. 6082 - 6085
(2020/06/18)
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- Ni(II)/Al(0) mediated benzylic Csp 3 - Csp 3 coupling in aqueous media
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Abstract : The reaction of benzyl bromides and chlorides with aluminium metal powder or foil (1.2 eqv.) in the presence of catalytic nickel nitrate (10 mol%) in water at room temperature resulted in homocoupling to the corresponding bibenzyl products which were isolated in moderate to good yields. In sharp contrast, the same reaction in organic solvents like dichloromethane, dimethylformamide, acetonitrile, methanol and toluene yielded only a trace amount of the desired product. The scope of the reaction was tested with substituents on the aromatic ring such as Me-, Cl-, CN-, F-, NO 2-, Ph- as well as 2 ° benzyl halides. Graphical abstract: The reagent combination of aluminium metal and catalytic Ni(NO3)2 promotes the homocoupling of benzyl bromides and chlorides giving rise to the corresponding bibenzyl products in good to excellent yields. The reaction is greatly facilitated in water and showed good functional group tolerance. Besides the mild reaction condition and bench-friendliness, the present reaction constitutes the first example of aluminium-mediated homocoupling of a halide in water. [Figure not available: see fulltext.].
- Nayak, Mukesh Kumar,Mukhi, Priyabrata,Mohanty, Anuradha,Rana, Sohel Samim,Arora, Rajat,Narjinari, Himani,Roy, Sujit
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- Carboxylation of benzylic and aliphatic C-H bonds with CO2 induced by light/ketone/nickel
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A photoinduced carboxylation reaction of benzylic and aliphatic C-H bonds with CO2 is developed. Toluene derivatives capture gaseous CO2 at the benzylic position to produce phenylacetic acid derivatives when irradiated with UV light in the presence of an aromatic ketone, a nickel complex, and potassium tert-butoxide. Cyclohexane reacts with CO2 to furnish cyclohexanecar-boxylic acid under analogous reaction conditions. The present photoinduced carboxylation reaction provides a direct access from readily available hydrocarbons to the corresponding carboxylic acids with one carbon extension.
- Ishida, Naoki,Masuda, Yusuke,Imamura, Yuuya,Yamazaki, Katsushi,Murakami, Masahiro
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supporting information
p. 19611 - 19615
(2019/12/24)
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- Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene
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Divergent synthesis that enables a catalytic reaction to selectively produce different products from common substrates will allow the charting of wider chemical space and the unveiling of distinct mechanistic paradigms. A common strategy for it employs different ligands to modulate organometallic catalysts. Dramatic developments in photocatalysis have enabled previously inaccessible transformations. In particular, photoredox catalysis modulates the oxidation state of transition-metal complexes, offering enormous opportunities for methodology development. Herein, we developed a photo-mediated divergent ethylene difunctionalization via modulating oxidation states of the nickel catalyst by using different photoredox catalysts. This work will inspire new perspectives for value-added chemical synthesis using ethylene as a feedstock and shed light on photoredox-catalyst-based divergent synthesis, which fundamentally differs from ligand-controlled transition-metal catalysis.Divergent synthesis represents a powerful strategy for directly accessing different molecular scaffolds originating from the same starting materials. Access to different end products via transition-metal catalysis is conventionally achieved by ligand control. We herein demonstrate the use of ethylene feedstock and commercially available aryl halides to accomplish the divergent synthesis of 1,2-diarylethanes, 1,4-diarylbutanes, or 2,3-diarylbutanes in a highly selective fashion through the synergistic combination of nickel and photoredox catalysis. Mechanistic studies suggest that the observed selectivity was due to different active states of Ni(I) and Ni(0) modulated by Ru- and Ir-based photoredox catalysts, respectively. The ability to access different organometallic oxidation states via photoredox catalysis promises to inspire new perspectives for synergistic transition-metal-catalyzed divergent synthesis.Functionalization of ethylene without polymerization is challenging under photo-irradiation conditions. We have demonstrated that the photo-transformation of ethylene can be controllable by merging photoredox and transition-metal catalysis. In our study, the use of different photoredox catalysts was able to modulate the oxidation state of the nickel catalyst. Through different oxidation states, the nickel-catalyzed couplings proceeded via distinct pathways to generate divergent ethylene difunctionalization products selectively from the same feedstock.
- Li, Jiesheng,Luo, Yixin,Cheo, Han Wen,Lan, Yu,Wu, Jie
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supporting information
p. 192 - 203
(2019/01/21)
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- Synthesis of α-Substituted Primary Benzylamines through Copper-Catalyzed Cross-Dehydrogenative Coupling
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A copper-catalyzed route to α-substituted, primary benzylamines by C-H functionalization of alkylarenes is described. The method directly affords the amine hydrochloride salt. Catalyst loadings down to 0.1 mol % in combination with scalability, insensitivity to air and moisture, and no need for column chromatography makes the procedure highly practical. The facile synthesis of the racemate of a blockbuster drug highlights the relevance for the development of pharmaceuticals. Preliminary mechanistic data are also included.
- Kramer, S?ren
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supporting information
p. 65 - 69
(2019/01/04)
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- Oxovanadium(v)-catalyzed deoxygenative homocoupling reaction of alcohols
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Oxovanadium(v)-catalyzed transformation of alcohols in the presence of hydrazine derivatives was demonstrated. The direct hydrazination reaction of 1,3-diphenylprop-2-en-1-ol with 1,1-diphenylhydrazine in the presence of VO(OSiPh3)3 as a catalyst and MS3A as a dehydrating reagent proceeded to afford the corresponding hydrazination product. On the contrary, the utilization of 1,1-dimethylhydrazine instead of 1,1-diphenylhydrazine was found to induce the deoxygenative homocoupling reaction of the allyl alcohol to give the corresponding 1,5-diene as a major product. In addition to the deoxygenative homocoupling product, the allyl amine into which aniline was introduced was also obtained by using 1,2-diphenylhydrazine in the reaction of 1,3-diphenyl-2-methylprop-2-en-1-ol. Oxovanadium(v)-catalyzed deoxygenative homocoupling reaction of benzyl alcohols could also be performed in the presence of 1,1-dimethylhydrazine.
- Sakuramoto, Takashi,Donaka, Yosuke,Tobisu, Mamoru,Moriuchi, Toshiyuki
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p. 17571 - 17576
(2019/11/25)
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- Method for preparation of bibenzyl compounds by photocatalytic one-step process
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The invention relates to a brand new low-cost method for synthesis of bibenzyl compounds. The method adopts green and clean light energy as the reaction energy, and takes toluene or a toluene derivative as the raw material to prepare bibenzyl compounds under the catalysis of a solid photocatalyst. The method is carried out at room temperature, and can prepare bibenzyl compounds directly by illumination. The reaction process includes: mixing a toluene derivative, a catalyst and a solvent, then putting the mixture into a pressure-resistant quartz container (larger than 1MPa), and performing replacement with inert gas, conducting illumination stirring at room temperature, and carrying out reaction for 1 or more hour. At the end of the reaction, the catalyst can be easily separated from the reaction system and can be recycled repeatedly, the reaction product can be separated by crystallization, and the yield of bibenzyl compounds can reach 3.21g (g catalyst)h. The method can be used for direct preparation of 1, 2-diphenylethane and natural bibenzyl drugs.
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Paragraph 0064-0065
(2019/07/04)
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- Iron-Catalyzed Suzuki-Miyaura Cross-Coupling Reactions between Alkyl Halides and Unactivated Arylboronic Esters
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An iron-catalyzed cross-coupling reaction between alkyl halides and arylboronic esters was developed that does not involve activation of the boronic ester with alkyllithium reagents nor requires magnesium additives. A combination of experimental and theoretical investigations revealed that lithium amide bases coupled with iron complexes containing deprotonated cyanobis(oxazoline) ligands were best to obtain high yields (up to 89%) in catalytic cross-coupling reactions. Mechanistic investigations implicate carbon-centered radical intermediates and highlight the critical importance of avoiding conditions that lead to iron aggregates. The new iron-catalyzed Suzuki-Miyaura reaction was applied toward the shortest reported synthesis of the pharmaceutical Cinacalcet.
- Crockett, Michael P.,Tyrol, Chet C.,Wong, Alexander S.,Li, Bo,Byers, Jeffery A.
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supporting information
p. 5233 - 5237
(2018/09/12)
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- Generation and Confinement of Long-Lived N-Oxyl Radical and Its Photocatalysis
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Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C-H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 s as measured by in situ electron paramagnetic resonance (EPR) after the light being turned off. This allows the long-lived N-oxyl radical to abstract the H from C-H bond to form a carbon radical that reacts with molecular oxygen to form R3C-OO· species, decomposition of which leads to oxygenated products.
- Zhang, Chaofeng,Huang, Zhipeng,Lu, Jianmin,Luo, Nengchao,Wang, Feng
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supporting information
p. 2032 - 2035
(2018/02/19)
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- Nondirecting Group sp3 C?H Activation for Synthesis of Bibenzyls via Homo-coupling as Catalyzed by Reduced Graphene Oxide Supported PtPd@Pt Porous Nanospheres
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The use of heterogeneous bimetallic Pd-based nanocatalyst for directing the inactivated sp3 C?H coupling has been scarcely explored. This work reported the formation of symmetrical C?C bonds from the inactivated sp3 C?H bonds catalyzed by employing reduced graphene oxide supported PtPd@Pt porous nanospheres. The reaction of sp3 C?H activation proceeded under mild conditions without any solvent, ligand or directing group. It is a higher atom-, step- and cost-effectiveness strategy for developing heterogeneous catalysts in the synthesis of bibenzyls with various functional groups (e. g. aryl, alkyl, methoxyl, halogen, ester, and pyridyl). (Figure presented.).
- Wang, Zheng-Jun,Lv, Jing-Jing,Yi, Rong-Nan,Xiao, Min,Feng, Jiu-Ju,Liang, Zhi-Wu,Wang, Ai-Jun,Xu, Xinhua
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supporting information
p. 932 - 941
(2018/01/05)
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- Method for synthesizing 1,2-diphenylethane derivative by catalyzing coupling of sp3C-H bond through graphene-loaded palladium/platinum
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The invention provides a novel method for catalyzing activation of an sp3C-H bond to build a 1,2-diphenylethane compound by developing a novel graphene-loaded bimetal palladium/platinum catalyst whichis simple, convenient and efficient, is free of guide groups and free of participation of solvents and can be reused, so as to increase the yield of the target product, simplify operation steps and improve an atom utilization ratio and the recovery of the catalyst. The invention provides an economical, efficient and green method for preparing the compound. The method has the main advantages thatexperiment operation is simple and convenient, guide groups are not needed, the participation of other solvents is not needed, and the catalyst can be repeatedly recycled.
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Paragraph 0015; 0016
(2018/07/15)
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- Liquid-phase oxidation of alkylaromatics to aromatic ketones with molecular oxygen over a Mn-based metal-organic framework
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Liquid-phase oxidation of alkylaromatics with molecular O2 was examined using a microporous Mn-based metal-organic framework (Mn-MOF-74). Mn-MOF-74 consisting of trimeric Mn clusters and 2,5-dihydroxyterephthalate (dhtp) linkers exhibits superior catalytic activity with good ketone selectivity compared to conventional oxide-supported Mn catalysts without showing any lengthy induction period. Combined analyses by means of XRD, FE-SEM, N2 physisorption and Mn K-edge XAFS reveal that the superior catalytic performance is attributed to the inherently-formed Mn(iii)2(dhtp) moieties embedded in the Mn-MOF-74 framework rather than structural factors associated with the MOF. The catalyst is reusable over multiple catalytic runs along with retaining its original catalytic activity due to the ability of the dhtp ligand to stabilize active Mn(iii) atoms. Owing to high activity, reusability and nontoxicity, Mn-MOF-74 can offer a simple, inexpensive and efficient protocol for the oxidation of some important alkylaromatics, such as ethylbenzene and diphenylmethane to produce the corresponding aromatic ketones.
- Kuwahara, Yasutaka,Yoshimura, Yukihiro,Yamashita, Hiromi
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supporting information
p. 8415 - 8421
(2017/07/12)
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- Cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds
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A protocol for the cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds with carboxylic acids was developed in this work. Mechanistic studies revealed that C(sp3)–H bond activation in the hydrocarbon was the turnover-limiting step and the in-situ formed [Co(III)]Ot-Bu did not engage in hydrogen atom abstraction (HAA) of a C–H bond. This protocol was successfully incorporated into a synthetic pathway to β-damascenone that avoided the use of NBS.
- Ren, Tian-Lu,Xu, Bao-Hua,Mahmood, Sajid,Sun, Ming-Xue,Zhang, Suo-Jiang
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supporting information
p. 2943 - 2948
(2017/04/26)
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- A well-defined low-valent cobalt catalyst Co(PMe3)4 with dimethylzinc: a simple catalytic approach for the reductive dimerization of benzyl halides
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Herein, we report the first catalytic version of a cobalt-catalysed reductive homocoupling of benzyl halides which proceeds with low catalyst loadings (0.5 to 5 mol%). By synthetizing each cobalt intermediate we demonstrate that reaction proceeds through two single electron transfers (SET) and that dimethylzinc is only involved in the regeneration of the catalytic species.
- Fallon, Brendan J.,Corcé, Vincent,Amatore, Muriel,Aubert, Corinne,Chemla, Fabrice,Ferreira, Franck,Perez-Luna, Alejandro,Petit, Marc
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p. 9912 - 9916
(2016/12/07)
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- Oxo-rhenium catalyzed reductive coupling and deoxygenation of alcohols
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Representative benzylic, allylic and α-keto alcohols are deoxygenated to alkanes and/or reductively coupled to alkane dimers by reaction with PPh3 catalyzed by (PPh3)2ReIO2 (1). The newly discovered catalytic reductive coupling reaction is a rare C-C bond-forming transformation of alcohols.
- Kasner, Gabrielle R.,Boucher-Jacobs, Camille,Michael McClain,Nicholas, Kenneth M.
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supporting information
p. 7257 - 7260
(2016/06/09)
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- Cyclopentadienyl nickel(ii) N, C-chelating benzothiazolyl NHC complexes: Synthesis, characterization and application in catalytic C-C bond formation reactions
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Cyclopentadienyl (Cp) Ni(ii) complexes [CpNiL][PF6] containing hybrid N,C chelating benzothiazolyl NHC ligands (L1 = 1-(2-benzothiazolyl)-3-methylimidazol-2-ylidene, 3a; L2 = 1-(2-benzothiazolyl)-3-allylimidazol-2-ylidene, 3b; L3 = 1-(2-benzothiazolyl)-3-benzylimidazol-2-ylidene, 3c) have been synthesized and fully characterized. The catalytic activity of 3a-3c in some C-C bond formation reactions has been examined. They are efficient catalysts for the homo-coupling of benzyl bromide in the presence of MeMgCl at r.t. with good functional group tolerance. Complex 3a is active in the catalytic oxidative homo-coupling of Grignard reagents with 1,2-dichloroethane as an oxidant at r.t.
- Teo, Wei Jie,Wang, Zhe,Xue, Fei,Andy Hor,Zhao, Jin
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p. 7312 - 7319
(2016/06/01)
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- B12-TiO2 Hybrid Catalyst for Light-Driven Hydrogen Production and Hydrogenation of C-C Multiple Bonds
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The B12-TiO2 hybrid catalyst mediates H2O reduction to form hydrogen under UV irradiation (turnover number of one per hour). The catalyst also mediates reductions of alkenes such as styrene derivatives and alkylacrylates (maximum turnover number of 100 per hour) under mild conditions of room temperature, ordinary pressure, and water or alcohol as solvent.
- Shimakoshi, Hisashi,Hisaeda, Yoshio
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p. 1250 - 1253
(2016/02/18)
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- Nickel-catalyzed asymmetric reductive cross-coupling between vinyl and benzyl electrophiles
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A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preclude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic arylation.
- Cherney, Alan H.,Reisman, Sarah E.
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p. 14365 - 14368
(2014/12/11)
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- Stoichiometric reactions of acylnickel(II) complexes with electrophiles and the catalytic synthesis of ketones
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Acylnickel(II) complexes feature prominently in cross-electrophile coupling (XEC) reactions that form ketones, yet their reactivity has not been systematically investigated. We present here our studies on the reactivity of acylnickel(II) complexes with a series of carbon electrophiles. Bromobenzene, α-chloroethylbenzene, bromooctane, and iodooctane were reacted with (dtbbpy)NiII(C(O)C5H11)(Br) (1b) and (dtbbpy)NiII(C(O)tolyl)(Br) (1c) to form a variety of organic products. While reactions with bromobenzene formed complex mixtures of ketones, reactions with α-chloroethylbenzene were highly selective for the cross-ketone product. Reactions with iodooctane and bromooctane also produced the cross-ketone product, but in intermediate yield and selectivity. In most cases the presence or absence of a chemical reductant (zinc) had only a small effect on the selectivity of the reaction. The coupling of 1c with iodooctane (60% yield) was translated into a catalytic reaction, the carbonylative coupling of bromoarenes with primary bromoalkanes (six examples, 60% average yield).
- Wotal, Alexander C.,Ribson, Ryan D.,Weix, Daniel J.
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supporting information
p. 5874 - 5881
(2015/01/09)
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- Synthesis of Ni(II) complexes with unsymmetric [O,N,O′]-pincer ligands and their use as precatalysts in carbon-carbon bond formations to access diarylmethanes
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1-Acetyl-[1a,3,5-CF3,1-C(=O)CH3] and 1-benzoyl-5-hydroxypyrazolines [1b, 3,5-CF3, 1-C(=O)C 6H5] have been synthesized and reacted with Ni(OAc) 2·4H2O in the presence of PPh3 to form square planar nickel complexes, which revealed a O,N,O′-coordination. An additional coordination site on the nickel center is occupied by one triphenylphosphane ligand. After having investigated the properties of the complexes, catalytic experiments have been carried out to synthesize diarylmethanes. Applying the complexes in the nickel-catalyzed carbon-carbon cross coupling of aryl halides with benzylzinc bromide excellent yields and selectivities of the corresponding diarylmethane have been obtained. Moreover, various experiments have been performed to shed light on the underlying reaction mechanism.
- Someya, Chika I.,Irran, Elisabeth,Enthaler, Stephan
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p. 136 - 144
(2014/07/08)
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- Convenient synthesis of monobenzylated hydrazides via aqueous zinc-mediated addition reactions
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Addition of substituted benzyl bromides to dialkyl azodicarboxylates under aqueous zinc-mediated addition conditions occurs readily to afford monobenzylated hydrazides in good to excellent yields. The reaction is tolerant of a variety of substituents on the benzyl bromide ring. Several dialkyl azodicarboxylates were successfully tested under the reaction conditions. The limitations of the reaction are also addressed.
- Breton, Gary W.
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supporting information
p. 1128 - 1136
(2014/04/03)
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- Asymmetric electrocarboxylation of 1-phenylethyl chloride catalyzed by electrogenerated chiral [CoI(salen)]- complex
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The feasibility of asymmetric electrocarboxylation of 1-phenylethyl chloride catalyzed by the electrogenerated chiral [CoI(salen)] - complex has been investigated for the first time. Using this system, optically active 2-phenylpropionic acid in 37% yield and 83% ee is synthesized from 1-phenylethyl chloride and CO2. The electrochemical behavior of the catalyst and the optimization of synthesis conditions are discussed. This study provides a new procedure for the asymmetric synthesis of a chiral compound and expands the applications of chiral CoII(salen) in the electrochemical asymmetric fixation of CO2.
- Chen, Bao-Li,Zhu, Hong-Wei,Xiao, Yan,Sun, Qi-Long,Wang, Huan,Lu, Jia-Xing
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- Role of free space and conformational control on photoproduct selectivity of optically pure α-alkyldeoxybenzoins within a water-soluble organic capsule
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Optically pure α-alkyl deoxybenzoins resulting in products of Norrish Type I and Type II reactions upon excitation has been investigated within the octa acid (OA) capsule in water. The product distribution was different from that in an organic solvent and was also dependent on the length of the α-alkyl chain. Most importantly, a rearrangement product not formed in an organic solvent arising from the triplet radical pair generated by Norrish Type I reaction was formed, and its yield was dependent on the alkyl chain length. In an organic solvent, since the cage lifetime is shorter than the time required for intersystem crossing (ISC) of the triplet radical pair to the singlet radical pair the recombination with or without rearrangement of the primary radical pair (phenylacetyl and benzyl) does not occur. Recombination without rearrangement within the capsule as inferred from monitoring the racemization of the optically pure α-alkyl deoxybenzoins suggesting the capsule's stability for at least 10-8 s (the time required for ISC) is consistent with our previous photophysical studies that showed partial opening and closing of the capsule in the time range of microseconds.
- Kulasekharan, Revathy,Maddipatla, Murthy V. S. N.,Parthasarathy, Anand,Ramamurthy
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p. 942 - 949
(2013/04/10)
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- Homocoupling of benzyl halides catalyzed by POCOP-nickel pincer complexes
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Two types of POCOP-nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields.
- Chen, Tao,Yang, Limin,Li, Liang,Huang, Kuo-Wei
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experimental part
p. 6152 - 6157
(2012/08/29)
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- Transition Metal-Catalyzed C-H Amination Using Unactivated Amines
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One aspect of the invention relates to a method of animation or amidation, comprising the step of combining a substrate, comprising a reactive C—H bond, and an amine or amide, comprising a reactive N—H bond, in the presence of an oxidizing agent and a metal-containing catalyst, thereby forming a product with a covalent bond between the carbon of the reactive C—H bond and the nitrogen of the reactive N—H bond.
- -
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Page/Page column 3; 27
(2011/09/20)
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- Oxidative nucleophilic substitution: Transformation of alkylboronic derivatives
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An efficient amidation reaction is described in this paper. Potassium alkyltrifluoroborate salts can be transforming to amides from nitriles in the presence of copper acetate and boron trifluoride. An extension of this reaction allowed the formation of amines, ethers, and C-C bond.
- Cazorla, Clément,Métay, Estelle,Lemaire, Marc
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p. 8615 - 8621
(2011/11/30)
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- Synthesis, characterization and catalytic function of a B 12-hyperbranched polymer
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A new hybrid catalyst composed of a vitamin B12 derivative and a hyperbranched polymer (HBP) was synthesized and characterized by UV-vis and ESR spectroscopy as well as AFM. The B12-HBP showed good properties as a homogenous catalyst
- Tahara, Keishiro,Shimakoshi, Hisashi,Tanaka, Akihiro,Hisaeda, Yoshio
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experimental part
p. 3035 - 3042
(2010/06/14)
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- Synthesis and catalysis of B12-core-shell hyperbranched polymer
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A vitamin B12 derivative was immobilized on a core-shell hyperbranched polymer, and the hybrid polymer was characterized by GPC, UV-vis, IR as well as TEM analyses. The hybrid polymer exhibits catalysis for the dehalogenation of phenethyl bromi
- Shimakoshi, Hisashi,Nishi, Masashi,Tanaka, Akihiro,Chikama, Katsumi,Hisaeda, Yoshio
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scheme or table
p. 22 - 23
(2010/04/23)
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- Nickel-catalyzed, sodium iodide-promoted reductive dimerization of alkyl halides, alkyl pseudohalides, and allylic acetates
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The first general method for the reductive dimerization of alkyl halides, alkyl mesylates, alkyl trifluoroacetates, and allylic acetates is reported which proceeds with low catalyst loading (0.5 to 5 mol%), generally high yields (80% ave yield), and good functional-group tolerance.
- Prinsell, Michael R.,Everson, Daniel A.,Weix, Daniel J.
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supporting information; experimental part
p. 5743 - 5745
(2010/09/18)
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- Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
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Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
- Makhlynets, Olga V.,Rybak-Akimova, Elena V.
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supporting information; experimental part
p. 13995 - 14006
(2011/04/12)
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- The reaction of α-phenethyl radicals with 1,4-benzoquinone and 2,6-di-tert-butyl-1,4-benzoquinone
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The absolute rate constant for 1,4-benzoquinone (BQ) irreversibly trapping α-phenethyl radicals (3) has been determined as 4.4×106 M-1 s-1 at 43 °C using acyclic cis azoalkane 9c as a radical precursor. These reactants afford the hydroquinone mono ether 4 at 30 °C but a mixture of products at elevated temperature. 2,6-Di-tert-butyl-1,4- benzoquinone (DTBQ) also reacts with 3 but the cyclohexadienone products are thermally labile.
- Engel, Paul S.,Park, Hee Jung,Mo, Hua,Duan, Shaoming
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experimental part
p. 8805 - 8814
(2011/01/04)
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- Nickel complexes of a pincer amidobis(amine) ligand: Synthesis, structure, and activity in stoichiometric and catalytic C-C bond-forming reactions of alkyl halides
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The synthesis, properties, and reactivity of nickel(II) complexes of a newly developed pincer amidobis(amine) ligand (McNN2) are described. Neutral or cationic complexes [(MeNN2)NiX] (X = OTf (6), OC(O)CH3 (7), CH3CN (8), OMe (9)) were prepared by salt metathesis or chloride abstraction from the previously reported [( MeNN2)NiCl] (1). The Lewis acidity of the {( McNN2)Ni) fragment was measured by the 1H NMR chemical shift of the coordinated CH3CN molecule in 8. Electrochemical measurements on 1 and 8 indicate that the electron-donating properties of NN2 are similar to those of the analogous amidobis(phosphine) (pnp) ligands. The solid-state structures of 6-8 were determined and compared to those of 1 and [(MeNN2)NiEt] (3). In all complexes, the MeNN2 ligand coordinates to the NiII ion in a mer fashion, and the square-planar coordination sphere of the metal is completed by an additional donor. The coordination chemistry of MeNN 2 thus resembles that of other three-dentate pincer ligands, for example, pnp and arylbis(amine) (ncn). Reactions of 2 with alkyl monohalides, dichlorides, and trichlorides were investigated. Selective C-C bond formation was observed in many cases. Based on these reactions, efficient Kumada-Corriu-Tamao coupling of unactivated alkyl halides and alkyl Grignard reagents with 1 as the precatalyst was developed. Good yields were obtained for the coupling of primary and secondary iodides and bromides. Double C-C coupling of CH2Cl2 with alkyl Grignard reagents by 1 was also realized. The scope and limitations of these transformations were studied. Evidence was found for a radical pathway in Ni-catalyzed C-C cross-coupling reactions, which involves NiIl alkyl intermediates.
- Vechorkin, Oleg,Csok, Zsolt,Scopelliti, Rosario,Hu, Xile
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scheme or table
p. 3889 - 3899
(2009/12/26)
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- Ritter-type amidation of alkylboron derivatives with nitriles
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A mild and facile synthesis of amides from alkylboron compounds and nitriles promoted by copper acetate and BF3·OEt2 at room temperature is disclosed.
- Cazorla, Clément,Métay, Estelle,Andrioletti, Bruno,Lemaire, Marc
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scheme or table
p. 6855 - 6857
(2010/05/03)
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- SmI2/H2O/amine promoted reductive cleavage of benzyl-heteroatom bonds: optimization and mechanism
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The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and found to be a viable alternative to the Birch reduction yielding the corresponding deoxygenated product in excellent yield. The reaction has been investigated by kinetic methods, and a mechanism involving a pre-complexation of the alcohol to SmI2 followed by an amine mediated electron transfer and subsequent bond cleavage and transfer of a second electron and proton to yield the toluene product has been proposed. The reaction is strongly inhibited at higher concentrations of water, indicating that it proceeds via an inner-sphere electron transfer from samarium(II) to the benzyl group, and excess of water prevents coordination of benzyl alcohol to samarium.
- Ankner, Tobias,Hilmersson, G?ran
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experimental part
p. 10856 - 10862
(2010/02/28)
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- Templation of the excited-state chemistry of α-(n-alkyl) dibenzyl ketones: how guest packing within a nanoscale supramolecular capsule influences photochemistry
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Excited-state behavior of eight α-alkyl dibenzyl ketones (alkyl = CH3 through n-C8H17) that are capable of undergoing type II and/or type I photoreactions has been explored in isotropic solution and within a water-soluble capsule. The study consisted of two parts: photochemistry that explored the excited-state chemistry and an NMR analysis that revealed the packing of each guest within the capsule. The NMR data (COSY, NOESY, and TOCSY experiments) revealed that ternary complexes between α-alkyl dibenzyl ketones and the capsule formed by two cavitands are kinetically stable, and the guests fall into three packing motifs modulated by the length of the α-alkyl chain. In essence, the host is acting as an external template to promote the formation of distinct guest conformers. The major products from all eight guests upon irradiation either in hexane or in buffer solution resulted from the well-known Norrish type I reaction. However, within the capsule the excited-state chemistry of the eight ketones was dependent on the alkyl chain length. The first group consisted of α-hexyl, α-heptyl, and α-octyl dibenzyl ketones that yielded large amounts of Norrish type II products within the host, while in solution the major products were from Norrish type I reaction. The second group consists of α-butyl and α-pentyl dibenzyl ketones that yield equimolar amounts of two rearranged starting ketones within the capsule (combined yield of ca 60%), while in solution no such products were formed. The third group consisted of α-methyl, α-ethyl, and α-propyl dibenzyl ketones that within the capsule yielded only one (not two) rearranged starting ketone in larger amounts (21-35%) while in solution no rearrangement product was obtained. Variation in the photochemistry of the guest within the capsule, with respect to the α-alkyl chain length of the guest, highlights the importance of how a small variation in supramolecular structure can influence the selectivity within a confined nanoscale reactor.
- Gibb, Corinne L. D.,Sundaresan, Arun Kumar,Ramamurthy,Gibb, Bruce C.
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p. 4069 - 4080
(2008/12/20)
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- Kinetics and mechanism of the reaction of benzyl bromide with copper in hexamethylphosphoramide
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The reaction of copper with benzyl bromides in hexamethylphosphoramide has been studied. The kinetic and thermodynamic parameters of the reaction have been obtained. Hammett plots of log (script k sign/script k sign°) vs the substituent constant σ gave good correlations (ρ = 0.15, S ρ = 0.02, r = 0.954). The structure of the organic group has little effect on the rate of reaction of benzyl bromide with copper. In the absence of atmospheric oxygen, the oxidative dissolution of copper occurred by the mechanism of single-electron transfer with the formation of 1,2-diphenylethane and copper(I) complexes. The stereochemistry and intermediates compound was also investigated. The reaction mechanism is discussed.
- Egorov, Anatoly M.,Matyukhova, Svetlana A.,Anisimov, Alexander V.
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p. 296 - 305
(2007/10/03)
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