- Tunable and Practical Homogeneous Organic Reductants for Cross-Electrophile Coupling
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The syntheses of four new tunable homogeneous organic reductants based on a tetraaminoethylene scaffold are reported. The new reductants have enhanced air stability compared to current homogeneous reductants for metal-mediated reductive transformations, such as cross-electrophile coupling (XEC), and are solids at room temperature. In particular, the weakest reductant is indefinitely stable in air and has a reduction potential of -0.85 V versus ferrocene, which is significantly milder than conventional reductants used in XEC. All of the new reductants can facilitate C(sp2)-C(sp3) Ni-catalyzed XEC reactions and are compatible with complex substrates that are relevant to medicinal chemistry. The reductants span a range of nearly 0.5 V in reduction potential, which allows for control over the rate of electron transfer events in XEC. Specifically, we report a new strategy for controlled alkyl radical generation in Ni-catalyzed C(sp2)-C(sp3) XEC. The key to our approach is to tune the rate of alkyl radical generation from Katritzky salts, which liberate alkyl radicals upon single electron reduction, by varying the redox potentials of the reductant and Katritzky salt utilized in catalysis. Using our method, we perform XEC reactions between benzylic Katritzky salts and aryl halides. The method tolerates a variety of functional groups, some of which are particularly challenging for most XEC transformations. Overall, we expect that our new reductants will both replace conventional homogeneous reductants in current reductive transformations due to their stability and relatively facile synthesis and lead to the development of novel synthetic methods due to their tunability.
- Barth, Emily L.,Charboneau, David J.,Germe, Cameron C.,Hazari, Nilay,Huang, Haotian,Mercado, Brandon Q.,Uehling, Mycah R.,Zultanski, Susan L.
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p. 21024 - 21036
(2021/12/14)
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- Dual Nickel- And Photoredox-Catalyzed Reductive Cross-Coupling of Aryl Halides with Dichloromethane via a Radical Process
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The first catalytic strategy to harness a new chloromethane radical from dichloromethane under dual Ni/photoredox catalytic conditions has been developed. Compared with traditional two-electron reductive process associated with metallic reductants, this method via a single-electron approach can proceed under exceptionally mild conditions (visible light, ambient temperature, no strong base) and exhibits complementary reactivity patterns. It affords a broad scope of many functional groups, including alkenyl, which suffers cyclopropanation in previous routes. The diarylmethane-d2 compounds can be readily available with this transformation.
- Xu, Tao,Xu, Wenhao,Zheng, Purui
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supporting information
(2020/11/13)
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- Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
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The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
- Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
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supporting information
p. 5599 - 5602
(2019/05/21)
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- Thermally Stable Half-Sandwich Benzhydryl Ln(II) (Ln = Sm, Yb) Complexes Supported by Sterically Demanding Carbazolyl and Fluorenyl Ligands
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A series of new isolable and thermally stable half-sandwich Ln(II) benzhydryl complexes coordinated by the sterically demanding ligands tert-butylcarbazol-9-yl [tBu4Carb]Ln[(p-tBu-C6H4)2CH](L) (Ln = Sm, L = DME (4); Ln = Yb, L = DME (5); Ln = Yb, L = TMEDA (6)) and 2,7-di-tert-butyl-fluoren-9-trimethylsilylyl [2,7-tBu2-9-Me3Si-C13H6]Yb[(p-tBu-C6H4)2CH](DME) (7) were synthesized by the alkane elimination reaction of [(p-tBu-C6H4)2CH]2Ln(Ln) (Ln = Sm, Yb) with tBu4CarbH and 2,7-tBu2-9-Me3Si-C13H7. X-ray analysis revealed that in 4, 5, and 7 the benzhydryl ligand is coordinated to the metal ion in an ν3 coordination mode, while in 6 it is ν1-bound. The type of coordination of the benzhydryl ligands in diamagnetic 5-7 is retained in their C6D6 solutions. Complexes 4-7 demonstrated unprecedented thermal stability and do not undergo decomposition after heating their solutions in C6D6 or toluene at 100 °C for 72 h. The reactions of [tBu4Carb]Ln[(p-tBu-C6H4)2CH](DME) (Ln = Sm (4), Ln = Yb (5)) with an excess of DME led to the formation of the symmetrical bis(carbazolyl) complex products [tBu4Carb]2Ln(DME)4 (Ln = Sm (8), Yb (9)) isolated in the form of separated ion pairs.
- Selikhov, Alexander N.,Shavyrin, Andrey S.,Cherkasov, Anton V.,Fukin, Georgy K.,Trifonov, Alexander A.
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p. 4615 - 4624
(2019/12/24)
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- Thermally Stable Ln(II) and Ca(II) Bis(benzhydryl) Complexes: Excellent Precatalysts for Intermolecular Hydrophosphination of C-C Multiple Bonds
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A series of Ln(II) and Ca(II) bis(alkyl) complexes with bulky benzhydryl ligands, [(p-tBu-C6H4)2CH]2M(Ln) (M = Sm, L = DME, n = 2 (1); M = Sm, Yb, Ca, L = TMEDA, n = 1 (2, 3, 4), were synthesized by t
- Selikhov, Alexander N.,Plankin, Gleb S.,Cherkasov, Anton V.,Shavyrin, Andrey S.,Louyriac, Elisa,Maron, Laurent,Trifonov, Alexander A.
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p. 5325 - 5334
(2019/04/17)
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- Mixed er-NHC/phosphine Pd(ii) complexes and their catalytic activity in the Buchwald-Hartwig reaction under solvent-free conditions
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A series of novel (NHC)PdCl2-PR3 complexes were synthesized and fully characterized by 1H, 13C, 31P NMR and FT-IR spectroscopy. These complexes showed high catalytic activity toward solvent-free Buchwald-Hartwig amination. Both primary and secondary amines were efficiently utilized under the same reaction conditions. The solvent-free synthesis of valuable N-aryl carbazoles and similar N-heterocyclic systems was described.
- Ageshina, Alexandra A.,Sterligov, Grigorii K.,Rzhevskiy, Sergey A.,Topchiy, Maxim A.,Chesnokov, Gleb A.,Gribanov, Pavel S.,Nechaev, Mikhail S.,Asachenko, Andrey F.,Bermeshev, Maxim V.,Melnikova, Elizaveta K.
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supporting information
p. 3447 - 3452
(2019/04/30)
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- Facile Hydrogenolysis of C(sp3)–C(sp3) σ Bonds
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The modification of benzylic quaternary, tertiary, and secondary carbon centers through palladium-catalyzed hydrogenolysis of C(sp3)–C(sp3) σ bonds is presented. When benzyl Meldrum's acid derivatives bearing quaternary benzylic centers are treated under mild hydrogenolysis conditions – palladium on carbon and atmospheric pressure of hydrogen – aromatics substituted with tertiary benzylic centers and Meldrum's acid are obtained with good to excellent yield. Analogously, substrates containing tertiary or secondary benzylic centers yield aromatics substituted with secondary benzylic centers or toluene derivatives, respectively. Furthermore, this strategy is used for the high yielding synthesis of diarylmethanes. The scope of the reductive dealkylation reaction is explored and the limitations with respect to steric and electronic factors are determined. A mechanistic analysis of the reaction is described that consisted of deuterium labelling experiments and hydrogenolysis of enantioenriched derivatives. The investigation shows that the C(sp3)–C(sp3) σ bond-cleaving events occur through a hybrid SN1/SN2 mechanism, in which the palladium center displaces a carbon-based leaving group, namely Meldrum's acid, with inversion of configuration, followed by reductive elimination of palladium to furnish a C?H bond. (Figure presented.).
- Fillion, Eric,Beaton, Eric,Nguyen, Yen,Wilsily, Ashraf,Bondarenko, Ganna,Jacq, Jér?me
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supporting information
p. 3422 - 3434
(2016/11/13)
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- Facile one-pot palladium-catalyzed sequential coupling to diarylmethanes by using aryl methyl ketones as the methylene donors
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A novel palladium-catalyzed coupling reaction of an aryl methyl ketone with two molecules of an aryl halide to yield symmetric diarylmethanes is described. In the facile one-pot reaction, the aryl methyl ketone acts as a formal methylene donor. The experimental facts, including TLC monitoring, speculated intermediates as the raw materials, analysis of the cesium benzoate coproduct by ex situ IR spectroscopy, and the cross-coupling reactions of two different aryl halides, indicate a mechanism involving a palladium-catalyzed sequential two-step coupling process, in which the presence of a trace amount of H 2O is indispensable. The reaction is applicable to a broad spectrum of substrates and delivers the products in good to excellent yields. Access to unsymmetrical diarylmethanes with this method is also explored and various factors are discussed. An aryl methyl ketone is used as the methylene donor to couple with two molecules of an aryl halide for the synthesis of various symmetric diarylmethanes under palladium catalysis. The mechanism involves a two-step coupling process in which the presence of a trace amount of H 2O is indispensable. The cross-coupling to unsymmetrical diarylmethanes with this method is also explored. Copyright
- Wang, Xing,Liu, Lian-Hua,Shi, Jin-Hua,Peng, Ji,Tu, Hai-Yang,Zhang, Ai-Dong
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p. 6870 - 6877
(2013/11/06)
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- SYNTHESIS OF SUBSTITUTED FLUORENE LIGANDS
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The present invention describes a cost-efficient method for preparing di-substituted fluorenes in high yield.
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Page/Page column 2
(2011/02/15)
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- SYNTHESIS OF SUBSTITUTED FLUORENES
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The present invention describes a cost-efficient method for preparing di-substituted fluorenes in high yield.
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Page/Page column 4
(2010/08/09)
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- Synthesis and characterization of teranthene: A singlet biradical polycyclic aromatic hydrocarbon having kekule structures
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A teranthene derivative has been successfully isolated in a crystalline form for the first time. Geometrical considerations and physical property investigations indicate that the molecule possesses prominent biradical character in the ground state.
- Konishi, Akihito,Hirao, Yasukazu,Nakano, Masayoshi,Shimizu, Akihiro,Botek, Edith,Champagne, Benoit,Shiomi, Daisuke,Sato, Kazunobu,Takui, Takeji,Matsumoto, Kouzou,Kurata, Hiroyuki,Kubo, Takashi
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supporting information; experimental part
p. 11021 - 11023
(2010/09/17)
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- New method for the reduction of benzophenones with Raney Ni-Al alloy in water
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Raney Ni-Al alloy in a dilute alkaline aqueous solution has been shown to be a powerful reducing agent, which is highly effective in the reduction of benzophenones to the corresponding hydrocarbon derivatives, in the absence of any organic solvents. Copyright Taylor & Francis Group, LLC.
- Liu, Guo-Bin,Zhao, Hong-Yun,Zhu, Jia-Da,He, Hong-Jie,Yang, Hong-Jie,Thiemann, Thies,Tashiro, Hideki,Tashiro, Masashi
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p. 1651 - 1661
(2008/09/20)
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- Process for the preparation of substituted fluorenes
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Methods for the preparation of fluorenyl-type ligand structures and substituted fluorenyl groups which may be employed in metallocene-type olefin polymerization catalysts. There is provided a 2,2′-dihalogen-diphenylmethylene having a methylene bridge conn
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Page/Page column 9; 19
(2008/06/13)
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- Catalytic asymmetric epoxidation
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The present invention relates to the synthesis of chiral epoxides via a catalytic asymmetric oxidation of olefins. Additionally, the methodology provides a method of asymmetrically oxidizing sulfides and phosphines. This asymmetric oxidation employs a catalyst system composed of a metal and a chiral bishydroxamic acid ligand, which, in the presence of a stoichiometric oxidation reagent, serves to asymmetrically oxidize a variety of substrates.
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Page/Page column 27
(2010/02/12)
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- METALLOCENE COMPOUND, PROCESS FOR PRODUCING METALLOCENE COMPOUND, OLEFIN POLYMERIZATION CATALYST, PROCESS FOR PRODUCING POLYOLEFIN, AND POLYOLEFIN
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The metallocene compound according to the invention and the olefin polymerization catalyst containing the compound are intended to produce a catalyst capable of preparing an isotactic polymer with a high polymerization activity. The metallocene compound contains a substituted cyclopentadienyl group and a (substituted) fluorenyl group and has a structure wherein these groups are bridged by a hydrocarbon group or the like. The process for preparing a metallocene compound according to the invention is intended to selectively prepare a specific metallocene compound so as not to produce an isomer, and in this process an intermediate product is synthesized by a specific method. The process for preparing a polyolefin according to the invention is intended to prepare a polyolefin having excellent impact resistance and transparency, and this process comprises homopolymerizing an α-olefin of 3 to 8 carbon atoms or copolymerizing an olefin of 3 to 8 carbon atoms and another α-olefin in the presence of an olefin polymerization catalyst containing the above-mentioned metallocene compound.
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- Structural requirements for decarbonylative α,α-diarylation reaction of 2-methoxyalkanoic acids in phosphorus pentoxide-methanesulfonic acid mixture yielding 1,1-diarylalkane homologs
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2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P2O5-MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.
- Yonezawa, Noriyuki,Hino, Tetsuo,Tokita, Yoshimi,Matsuda, Kazuhisa,Ikeda, Tomiki
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p. 14287 - 14296
(2007/10/03)
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- Diaryliodonium fluoroalkyl sulfonate salts and a method of making
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The present invention provides a convenient, simple, safe and efficient one-pot method for the synthesis of a number of diarlyiodonium triflate salts which does not involve sulfuric acid and which eliminates the need for any counter-ion exchange processes. The invention also provides a novel salt of the formula STR1
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- Organic Reactions Catalyzed by Solid Superacids. 9. Friedel-Crafts Cyclobenzylation of Benzene with Bis-(hydroxymethyl)diarylalkanes Catalyzed by a Perfluorinated Sulfonic Acid Resin (Nafion-H)
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Cyclobenzylation of benzene using bis(hydroxymethyl)diarylmethanes (6) and bis(hydroxymethyl)diarylaethanes (14) in the presence of solid perfluorinated sulfonic acid resin, Nafion-H, as a catalyst results in novel bridged aromatic compounds, 10,15-dihydro-5H-tribenzocyclononenes (15) and metacyclophanes (17), respectively.The reactions were clean, and water that was formed as a by-product did not deactivate the catalyst.It was also found that cyclobenzylation products, methacyclophanes were not formed via the isomerization of the corresponding orthomethacyclophane (19) under the reaction conditions used.The posible mechanism of the reaction is also discussed.
- Yamato, Takehiko,Sakaue, Naozumi,Furusawa, Takashi,Tashiro, Masahi,Prakash, G.K.Surya,Olah, George A.
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p. 2414 - 2438
(2007/10/02)
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- BESTIMMUNG DER IONENPAAR-BASIZITAT VON LITHIUM- UND KALIUMAMIDEN
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Ion pair basicities of lithio and potassio salts of some secondary amines were determined by equilibration with benzyl compounds.With these bases it is possible to span a range of about 19 pK-units from pK = 27 up to 46.The structural dependence of thermodynamic as well as kinetic basicity is discussed.Some new effective amide bases for preparative purposes are recommended.For the first time the pK-value of toluene has been determined by direct equilibration.It amounts to 40.7 in tetrahydrofuran.
- Ahlbrecht, Hubertus,Schneider, Gunther
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p. 4729 - 4742
(2007/10/02)
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