- High Ethylene Selectivity in Methanol-to-Olefin (MTO) Reaction over MOR-Zeolite Nanosheets
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Precisely controlled crystal growth endows zeolites with special textural and catalytic properties. A nanosheet mordenite zeolite with a thickness of ca. 11 nm, named as MOR-NS, has been prepared using a well-designed gemini-type amphiphilic surfactant as
- Guan, Yejun,Hu, Bingwen,Huang, Ju,Jiang, Jingang,Li, Chao,Lu, Kun,Ma, Yanhang,Ren, Li,Wu, Peng,Xu, Hao
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- Investigation of the catalytic activity of niobium phosphates for liquid phase alkylation of anisole with benzyl chloride
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In this work crystalline niobium phosphate with different degrees of crystallinity was synthesized by two different methods as catalysts for benzylation of anisole with benzyl chloride. The catalysts were characterized by XRD, N2 physisorption, solid state 31P and 93Nb NMR, structural FTIR and FTIR after adsorption of pyridine. The catalytic activities were measured in the benzylation of anisole with benzyl chloride. The NMR technique seems to be more sensitive in evaluating the presence of amorphous phase, compared with DRX data. The crystalline niobium phosphate prepared by recrystallization of a commercial sample presented activity comparable to its parent compound, in contrast with the crystalline catalyst prepared from niobic acid. The activity was attributed to the Lewis sites present mostly on the amorphous phase of the catalysts.
- De La Cruz, Marcus Henrique C.,Rocha, ?ngela S.,Lachter, Elizabeth R.,Forrester, Aline M.S.,Reis, Michele Castro,San Gil, Rosane A.S.,Caldarelli, Stefano,Farias, Andrea D.,Gonzalez, Wilma A.
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- Nanocrystals of zeolite ZSM-5 as catalysts for the liquid phase benzylation of anisole with benzyl alcohol
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The current paper reports the application of nanocrystalline form of zeolite ZSM-5 in lieu of Friedel Crafts catalysts in the benzylation of anisole using benzyl alcohol. There are many problems associated with the use and disposal of conventional catalys
- Radhika,Selvin, Rosilda,Kakkar, Rita,Hsu, Hsiu-Ling
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- Electron Impact Induced Cyclization of ortho-Substituted Diphenylmethanes
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Mass spectra of 2-hydroxydiphenylmethane and its derivatives are characterized in the upper mass region by an abundant ion m/z 165.Metastable ion measurements reveal that this ion is formed from the molecular ion of the parent compound by elimination of H2O and hydrogen.A fluorenyl cation structure is proposed for this ion on the basis of identity of collision induced mass analyzed ion kinetic energy spectra of ion m/z 165 generated from 2-hydroxydiphenylmethane and from fluorene.Four different pathways of formation of a fluorenyl cation are discussed.The contribution of each of these to the genesis of fragment m/z 165 was monitored in a reversed geometry instrument by measuring the first fragmentation in the first field free region and the second fragmentation in the second field free region.
- Liehr, Joachim G.,Brenton, A. Gareth,Beynon, John H.,Richter, Wilhelm J.
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- Plasmon heating mediated Friedel-Crafts alkylation of anisole using supported AuNP@Nb2O5catalysts
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Two different hybrid materials composed of gold nanoparticles (AuNPs) supported on either commercial niobium oxide HY 340 or mesoporous niobium oxide catalyzed the Friedel-Crafts alkylation of anisole by benzyl chloride. Excitation of the surface plasmon of the supported AuNPs allowed the reaction to occur at lower temperatures by acting as an alternative heat source. The localized heating produced via plasmon excitation permitted the acid catalyzed reaction to occur - at the Lewis acid sites on the Nb2O5support - at 80?°C while thermal-dark reactions using a conventional heat source, required temperatures of 120?°C or higher. The catalytic activity of the tested hybrid materials decreased with storage time. However, the deactivation showed to be reversible upon lyophilisation indicating that the nature of the deactivation could be due to water adsorption.
- Dos Santos, Carolina G.,Marquez, Daniela T.,Crites, Charles-Oneil L.,Netto-Ferreira, Jose Carlos,Scaiano, Juan C.
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- Deoxygenation of tertiary and secondary alcohols with sodium borohydride, trimethylsilyl chloride, and potassium iodide in acetonitrile
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The deoxygenation of tertiary and secondary alcohols to give the corresponding alkanes is conventionally performed using an organosilane and a strong acid. In this study, a deoxygenation method was developed for tertiary and secondary alcohols, using trimethylsilane and trimethylsilyl iodide generated in situ from sodium borohydride and trimethylsilyl chloride, and trimethylsilyl chloride and potassium iodide, respectively. With our method, tertiary and secondary alcohols, which provided stable carbocations, were converted into the corresponding alkanes. This paper also presents the optimization of the reaction conditions, the reaction mechanism, as well as the scope and limitations of the method.
- Kato, Yuichi,Inoue, Tomoka,Furuyama, Yuuki,Ohgane, Kenji,Sadaie, Mahito,Kuramochi, Kouji
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supporting information
(2021/11/16)
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- Nickel-Catalyzed Electrochemical C(sp3)?C(sp2) Cross-Coupling Reactions of Benzyl Trifluoroborate and Organic Halides**
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Reported here is the redox neutral electrochemical C(sp2)?C(sp3) cross-coupling reaction of bench-stable aryl halides or β-bromostyrene (electrophiles) and benzylic trifluoroborates (nucleophiles) using nonprecious, bench-stable NiCl2?glyme/polypyridine catalysts in an undivided cell configuration under ambient conditions. The broad reaction scope and good yields of the Ni-catalyzed electrochemical coupling reactions were confirmed by 50 examples of aryl/β-styrenyl chloride/bromide and benzylic trifluoroborates. Potential applications were demonstrated by electrosynthesis and late-stage functionalization of pharmaceuticals and natural amino acid modification, and three reactions were run on gram-scale in a flow-cell electrolyzer. The electrochemical C?C cross-coupling reactions proceed through an unconventional radical transmetalation mechanism. This method is highly productive and expected to find wide-spread applications in organic synthesis.
- Luo, Jian,Hu, Bo,Wu, Wenda,Hu, Maowei,Liu, T. Leo
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supporting information
p. 6107 - 6116
(2021/02/01)
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- Photoredox Heterobimetallic Dual Catalysis Using Engineered Covalent Organic Frameworks
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The functionalization of an imine-based layered covalent organic framework (COF), containing phenanthroline units as ligands, has allowed the obtention of a heterobimetallated material. Photoactive Ir and Ni fragments were immobilized within the porous structure of the COF, enabling heterogeneous light-mediated Csp3-Csp2cross-couplings. As radical precursors, potassium benzyl- and alkoxy-trifluoroborates, organic silicates, and proline derivatives were employed, which brings out the good versatility ofIr,Ni@Phen-COF. Moreover, in all the studied cases, an enhanced activity and stability have been observed in comparison with analogous homogenous systems.
- Alemán, José,Imaz, Inhar,López-Magano, Alberto,Mas-Ballesté, Rubén,Maspoch, Daniel,Ortín-Rubio, Borja
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p. 12344 - 12354
(2021/10/12)
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- In SituAnodically Oxidized BMIm-BF4: A Safe and Recyclable BF3Source
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The anodic oxidation of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF4) efficiently generates BF3from BF4-. This Lewis acid, strongly bound to the ionic liquids, can be efficiently used in classical BF3-catalyzed reactions. We demonstrated the BF3/BMIm-BF4reactivity in four reactions, namely, a domino Friedel-Crafts/lactonization of phenols, the Povarov reaction, the Friedel-Crafts benzylation of anisole, and the multicomponent synthesis of tetrahydro-11H-benzo[a]xanthen-11-ones. In comparison with literature data using BF3-Et2O in organic solvents, in all the presented cases, analogous or improved results were obtained. Moreover, the noteworthy advantages of the developed method are thein situgeneration of BF3(no storing necessity) in the required amount, using only the electron as redox reagent, and the recycling of BMIm-BF4for multiple subsequent runs.
- Bortolami, Martina,Mattiello, Leonardo,Scarano, Vincenzo,Vetica, Fabrizio,Feroci, Marta
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p. 16151 - 16157
(2021/07/26)
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- Development of highly efficient Friedel-Crafts alkylations with alcohols using heterogeneous catalysts under continuous-flow conditions
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The development of Friedel-Crafts alkylations with alcohols under continuous-flow conditions using heterogeneous catalysts is reported. The reactivities and durabilities of the examined catalysts were systematically investigated, which showed that montmorillonite clay is the best catalyst for these reactions. A high turnover frequency of 9.0 × 102h?1was recorded under continuous-flow conditions, and the continuous operation was successfully maintained over one week.
- Kobayashi, Shū,Koumura, Nagatoshi,Masuda, Koichiro,Okamoto, Yukiko,Onozawa, Shun-Ya
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p. 24424 - 24428
(2021/07/29)
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- Multifunctional oxygen vacancies in WO3–x for catalytic alkylation of C–H by alcohols under red-light
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Surface reaction kinetics and light absorption properties of a photocatalyst are essential demands for efficiently solar to chemical energy converting. In this study, plasmonic WO3–x was firstly applied to photocatalytic alkylation of arenes under red light irradiation. The oxygen vacancies, both on the surface and in the bulk of WO3–x, allow abundant free electrons to increase carrier densities and support its LSPR using low energy photons. The surface oxygen vacancies have more functions: they not only release surface tungsten sites which ensure the chemisorption of alcohols due to the coordianation ability but also promote the activation of alcohols via an efficient transport of the holes on the neighbouring O sites to chemisorption alcohol species. In brief, the bulk oxygen vacancies provide abundant charges and the surface vacancies promote the bond adsorption and activation abilities, which ensure the high efficiency of photocatalytic alkylation of C–H.
- Gu, Xianmo,Sun, Xichen,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
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p. 208 - 217
(2021/09/06)
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- METHOD FOR PRODUCING ARENE COMPOUNDS AND ARENE COMPOUNDS PRODUCED BY THE SAME
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Provided is a method for producing (alkyl)arene compounds represented by Formulae 3-1, 3-2, and 3-3 by the Friedel-Crafts alkylation reaction of alkyl halide compounds and arene compounds using organic phosphine compounds as a catalyst.
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Paragraph 0075
(2021/06/26)
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- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
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We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
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p. 13337 - 13347
(2021/11/20)
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- Mixed Alkyl/Aryl Diphos Ligands for Iron-Catalyzed Negishi and Kumada Cross Coupling Towards the Synthesis of Diarylmethane
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Mixed alkyl/aryl diphos ligands have been prepared and their application in iron-catalyzed cross coupling of benzylic chlorides with diaryl zinc (Negishi) or aryl Grignard reagents (Kumada) towards the synthesis of diarylmethane has been evaluated. The iron?diphos catalytic system exhibited the enhanced activity and selectivity in the two coupling reactions. The electron-rich mixed PPh2/PCy2 ligands outperformed their symmetrical PPh2 congeners, and led to decreased homocoupling byproduct formation. It indicates that the electronic effect of the ligands plays an important role in the catalytic performance. The Fe catalyst supported by L8 bearing an electron-rich PCy2 substituent and a sterically demanding tert-butyl on ethene backbone exhibited the best catalytic performance and good functional group tolerance in the two cross coupling reactions.
- Ma, Xufeng,Wang, Han,Liu, Yao,Zhao, Xing,Zhang, Jun
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p. 5134 - 5140
(2021/11/16)
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- Palladium-Catalyzed Cross-Coupling of Superbase-Generated C(sp3) Nucleophiles
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A range of methods has been investigated recently for the arylation of weakly acidic C(sp3)-H bonds, primarily exploiting directed metalation with a transition metal catalyst or radical formation via hydrogen atom transfer. In this work, a classical base-mediated approach is taken, exploiting the ability of organometallic superbases to metalate very weakly acidic (pKa> 40) C-H bonds. Conditions are developed with eithern-BuLi/diamine orn-BuLi/KOtBu superbases to enable metalation to occur with high selectivity. Organolithium nucleophiles can be directly used in cross-coupling, or organozincs can be formed to enable reactions with functional group-dense organohalides.
- Freure, Garrett P. R.,Lavertu, Jean-Danick E.,Newman, Stephen G.,Skrotzki, Eric A.
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p. 12258 - 12263
(2021/10/26)
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- Dynamic Kinetic Cross-Electrophile Arylation of Benzyl Alcohols by Nickel Catalysis
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Catalytic transformation of alcohols via metal-catalyzed cross-coupling reactions is very important, but it typically relies on a multistep procedure. We here report a dynamic kinetic cross-coupling approach for the direct functionalization of alcohols. The feasibility of this strategy is demonstrated by a nickel-catalyzed cross-electrophile arylation reaction of benzyl alcohols with (hetero)aryl electrophiles. The reaction proceeds with a broad substrate scope of both coupling partners. The electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles (e.g., Ar-OTf, Ar-I, Ar-Br, and inert Ar-Cl) all coupled well. Most of the functionalities, including aldehyde, ketone, amide, ester, nitrile, sulfone, furan, thiophene, benzothiophene, pyridine, quinolone, Ar-SiMe3, Ar-Bpin, and Ar-SnBu3, were tolerated. The dynamic nature of this method enables the direct arylation of benzylic alcohol in the presence of various nucleophilic groups, including nonactivated primary/secondary/tertiary alcohols, phenols, and free indoles. It thus offers a robust alternative to existing methods for the precise construction of diarylmethanes. The synthetic utility of the method was demonstrated by a concise synthesis of biologically active molecules and by its application to peptide modification and conjugation. Preliminary mechanistic studies revealed that the reaction of in situ formed benzyl oxalates with nickel, possibly via a radical process, is an initial step in the reaction with aryl electrophiles.
- Guo, Peng,Wang, Ke,Jin, Wen-Jie,Xie, Hao,Qi, Liangliang,Liu, Xue-Yuan,Shu, Xing-Zhong
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supporting information
p. 513 - 523
(2021/01/12)
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- Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides
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As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp2)-C(sp3) bonds, in which free alcohols and aryl bromides - both readily available chemicals - can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage arylation of several structurally complex natural products and pharmaceuticals.
- Li, Zijian,Sun, Wenxuan,Wang, Xianxu,Li, Luyang,Zhang, Yong,Li, Chao
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supporting information
p. 3536 - 3543
(2021/03/08)
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- Nickel-Catalyzed Negishi-Type Arylation of Trialkylsulfonium Salts
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Negishi-type arylation of trialkylsulfonium salts with arylzinc reagents has been accomplished under nickel catalysis. The use of cyclohexanethiol as an additional ligand was found to be particularly important to promote C-S cleavage. The present reaction accommodates one-pot arylation of dialkyl sulfides by combining with S -methylation with MeOTf. Mechanistic experiments suggest that C-S cleavage would proceed via single-electron transfer (SET) to generate the most stable carbon-centered radical and that the thiolate ligand would promote the C-S cleavage and radical recombination step.
- Minami, Hiroko,Nogi, Keisuke,Yorimitsu, Hideki
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supporting information
p. 1542 - 1546
(2021/09/06)
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- Photo-Ni-Dual-Catalytic C(sp2)-C(sp3) Cross-Coupling Reactions with Mesoporous Graphitic Carbon Nitride as a Heterogeneous Organic Semiconductor Photocatalyst
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The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp2)-C(sp3) cross-co
- Antonietti, Markus,Ghosh, Indrajit,K?nig, Burkhard,Khamrai, Jagadish,Savateev, Aleksandr
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p. 3526 - 3532
(2020/04/09)
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- Enhanced Friedel-Crafts benzylation activity of bimetallic WSn-KIT-6 catalysts
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A series of W and Sn-containing KIT-6 mesoporous silicates (designated as WxSn5) with similar Sn (~5 wtpercent) and varying W (x = 3–23 wtpercent) loadings were prepared by a one-pot hydrothermal synthesis method. No detectable bulk WO3 species were observed for W loading up to 14 wtpercent with preferential dispersion of WOx species near SnO2 sites. The WxSn5 materials exhibited superior performance for Friedel-Crafts anisole benzylation with intrinsic rate constants for all WxSn5 catalysts being greater than those without Sn. Based on results from DR-UV–Vis, XRD, XPS, EXAFS techniques, we postulate that the WxSn5 materials contain both isolated [WO4]2-/SnO2 and isolated [WO4]2-/SiO2 as active species, with the former being more active. The relative populations of these two highly dispersed species dictate the overall catalyst activity. The intrinsic activities of the WxSn5 catalysts are found to scale linearly with total acidity but are mainly dictated by the Lewis acid sites.
- (Feng) Tao, Franklin,Araújo do Nascimento Araújo, Aline,Chapman, Clint,Maheswari, Rajamanickam,Ramanathan, Anand,Subramaniam, Bala,Tang, Yu,Zhu, Hongda
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p. 657 - 666
(2020/07/31)
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- Synthesis of fluoride-containing high dimensionally structured nb oxide and its catalytic performance for acid reactions
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High dimensionally structured niobium oxide (HDS-NbO) containing fluoride (F-) was prepared by a hydrothermal synthesis. F- could be introduced into HDS-NbO by replacing lattice oxygen up to a solid F-/Nb ratio of 0.55. The introduction of an appropriate
- Hiyoshi, Norihito,Ishikawa, Satoshi,Kimura, Momoka,Motoki, Yuta,Shinoda, Mai,Tsurumi, Shota,Ueda, Wataru,Yoshida, Akihiro
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supporting information
(2020/07/13)
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- Visible Light-Catalyzed Benzylic C-H Bond Chlorination by a Combination of Organic Dye (Acr+-Mes) and N-Chlorosuccinimide
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By combining "N-chlorosuccinimide (NCS)"as the safe chlorine source with "Acr+-Mes"as the photocatalyst, we successfully achieved benzylic C-H bond chlorination under visible light irradiation. Furthermore, benzylic chlorides could be converted to benzylic ethers smoothly in a one-pot manner by adding sodium methoxide. This mild and scalable chlorination method worked effectively for diverse toluene derivatives, especially for electron-deficient substrates. Careful mechanistic studies supported that NCS provided a hydrogen abstractor "N-centered succinimidyl radical,"which was responsible for the cleavage of the benzylic C-H bond, relying on the reducing ability of Acr?-Mes.
- Xiang, Ming,Zhou, Chao,Yang, Xiu-Long,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
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p. 9080 - 9087
(2020/08/14)
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- Alumina grafted SBA-15 sustainable bifunctional catalysts for direct cross-coupling of benzylic alcohols to diarylmethanes
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AlSBA-15 catalysts possessing Br?nsted acid and Lewis acid-base bifunctionalities catalyze the direct arylation of benzyl alcohols to diarylmethanes with an 85% product yield through C-O bond activation. 2 and 4wt%AlSBA-15 catalysts have been synthesised by adopting a simple and efficient post-synthetic metal implantation route. The synthesised catalysts were characterized using XRD, N2 adsorption and desorption, 27Al MAS NMR, XPS, HR-TEM, NH3 and CO2-temperature-programmed desorption (TPD) and pyridine-transmission-FTIR spectroscopy techniques to confirm the existence of Br?nsted acid and Lewis acid-base bifunctionalities. Through various control experiments, it is verified that Br?nsted acid sites activate the benzyl alcohol and Lewis base sites interact with phenylboronic acid concurrently to accomplish the coupling reaction. In the recyclability study, 4wt%AlSBA-15 preserves its activity and stability up to 5 cycles. The 4wt%AlSBA-15 catalyst unlike homogeneous catalysts does not require additives, long reaction time and expensive metals.
- Rajendran, Chandran,Satishkumar, Govindaswamy,Lang, Charlotte,Gaigneaux, Eric M.
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p. 2583 - 2592
(2020/05/14)
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- Mild Deprotection of Dithioacetals by TMSCl/NaI Association in CH3CN
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A mild process using a combination of TMSCl and NaI in acetonitrile is used to regenerate carbonyl compounds from a variety of dithiane and dithiolane derivatives. This easy to handle and inexpensive protocol is also efficient to deprotect oxygenated and mixed acetals as 1,3-dioxanes, 1,3-dioxolanes and 1,3-oxathianes quantitatively. As a possible extension of this method, it was also shown that nitrogenated substrates such as hydrazones, N-tosylhydrazones, and ketimines reacted well under these conditions to give the expected ketones in high yields. The methodology proposed herein is a good alternative to the existing methods since it does not use metals, oxidants, reducing agents, acidic or basic media, and keto-products were obtained in high to excellent yields.
- Yao, Yunxin,Zhao, Guangkuan,Hamze, Abdallah,Alami, Mouad,Provot, Olivier
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p. 5775 - 5779
(2020/08/17)
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- Nickel catalysis enables convergent paired electrolysis for direct arylation of benzylic C-H bonds
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Convergent paired electrosynthesis is an energy-efficient approach in organic synthesis; however, it is limited by the difficulty to match the innate redox properties of reaction partners. Here we use nickel catalysis to cross-couple the two intermediates
- Hu, Xile,Zhang, Lei
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p. 10786 - 10791
(2020/10/26)
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- Phosphonic acid mediated practical dehalogenation and benzylation with benzyl halides
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For the first time, by using H3PO3/I2 system, various benzyl chlorides, bromides and iodides were dehalogenated successfully. In the presence of H3PO3, benzyl halides underwent electrophilic substitution reactions with electron-rich arenes, leading to a broad range of diarylmethanes in good yields. These transformations feature green, cheap reducing reagents and metal-free conditions. A possible mechanism was proposed.
- Gao, Jing,Han, Li-Biao,Ma, Yonghao,Tang, Zilong,Wu, Xiaofang,Xiao, Jing
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p. 22343 - 22347
(2019/07/31)
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- Green, Mild, and Efficient Friedel–Crafts Benzylation of Scarcely Reactive Arenes and Heteroarenes under On-Water Conditions
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Metal-free Friedel–Crafts benzylation (FCB) of scarcely reactive arenes and heteroarenes was performed under on-water conditions by an environmentally sustainable procedure. The catalytic strategy exploits the hydrophobicity of the resorcinarene macrocycle 1 a. The proposed mechanism is based on the activation of benzyl chloride by H-bonding interactions with catalyst 1 a. In fact, under on-water conditions the hydrophobic amplification of the strength of the H-bonding interactions between the OH groups of the resorcinarene catalyst and the chlorine atom of benzyl chloride leads to polarization of the C?Cl bond, which consequently promotes electrophilic attack of the π nucleophile. Thus, many arenes and heteroarenes were efficiently benzylated under mild on-water conditions by using resorcinarene 1 a as catalyst. The FCB of benzene is industrially relevant for the synthesis of diphenylmethane, and hence the on-water procedure was extended to the gram-scale synthesis of diphenylmethane, starting from benzene and benzyl chloride in the presence of resorcinarene catalyst 1 a.
- La Manna, Pellegrino,Soriente, Annunziata,De Rosa, Margherita,Buonerba, Antonio,Talotta, Carmen,Gaeta, Carmine,Neri, Placido
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p. 1673 - 1683
(2019/03/26)
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- CEREBLON BINDERS FOR THE DEGRADATION OF IKAROS
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The present invention provides cereblon binders for the degradation of Ikaros or Aiolos by the ubiquitin proteasome pathway along with their use in therapeutic applications as described herein.
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Page/Page column 342; 343
(2019/10/23)
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- +: A Masked Potent Boron Lewis Acid
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The chemistry of the boron cation has been revitalized in the past decade due to its newfound application in stoichiometric and catalytic organic reactions. To extend the frontier of boron cation catalysis, we came to discover that a mesityl-substituted η5-Cp*-coordinated boron cation could serve as a powerful Lewis acid for organic catalytic transformations. The boron cation [Cp*B-Mes][B(C6F5)4] ([1][B(C6F5)4]) stabilized in a boronium-like electronic structure binds to Et3PO readily and displays an acceptor number exceeding that of B(C6F5)3 on the Gutmann-Beckett acidity scale. The steric and electronic stabilization exerted by the electron-donating Cp? renders the highly Lewis acidic boron cation an easy-to-handle catalyst for hydrodeoxygenation of aryl ketones at ambient temperature. The exceptional catalytic performance of [1]+ implies that the incorporation of a coordinatively flexible substituent at boron is critical in bringing catalytic activity and stability to boron cation catalysts.
- Tseng, Hsi-Ching,Shen, Chao-Tang,Matsumoto, Kentaro,Shih, Ding-Nan,Liu, Yi-Hung,Peng, Shie-Ming,Yamaguchi, Shigehiro,Lin, Ya-Fan,Chiu, Ching-Wen
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supporting information
p. 4516 - 4521
(2019/11/14)
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- Electrochemical Hydrogenation with Gaseous Ammonia
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As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.
- Li, Jin,He, Lingfeng,Liu, Xu,Cheng, Xu,Li, Guigen
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supporting information
p. 1759 - 1763
(2019/01/16)
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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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- Super electron donor-mediated reductive desulfurization reactions
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The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
- Nozawa-Kumada, Kanako,Ito, Shungo,Noguchi, Koto,Shigeno, Masanori,Kondo, Yoshinori
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p. 12968 - 12971
(2019/11/05)
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- Cross coupling of benzylammonium salts with boronic acids using a well-defined N-heterocyclic carbene-palladium(ii) precatalyst
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N-heterocyclic carbene-palladium(ii)-catalyzed cross-coupling of benzylammonium salts with arylboronic acids for the synthesis of diarylmethane derivatives via C-N bond activation has been developed. Notably, in the presence of the easily prepared and bench-stable Pd-PEPPSI precatalyst, the Csp3-N bond activation of the benzylammonium salt even proceeded smoothly in isopropanol at room temperature.
- Wang, Tao,Guo, Jiarui,Wang, Xiaojuan,Guo, Han,Jia, Dingli,Wang, Hengjin,Liu, Lantao
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p. 5738 - 5741
(2019/03/02)
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- Preparation and application of blended nickel (II) complex with bisoxazoline derived azacyclo-carbene ligand and phosphite ester ligand
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The invention discloses a blended nickel (II) complex with a bisoxazoline derived azacyclo-carbene ligand and a phosphite ester ligand and application of the blended nickel (II) complex. The blended nickel (II) complex has a chemical formula of Ni(NHC)[P(OR)3]X2, in the formula, R is one of ethyl or isopropyl; X is one of bromine atoms or helium atoms; and NHC is the bisoxazoline derived azacyclo-carbene ligand. In the presence of magnesium chips, the blended nickel (II) complex with the bisoxazoline derived azacyclo-carbene ligand and the phosphite ester ligand, which is disclosed by the invention, is capable of catalyzing aromatic hydrocarbon or fluoro-aromatic hydrocarbon with low activity to have a reduction cross coupling reaction with a benzyl chloride type compound at a single temperature, then a diarylmethane compound can be generated at one step, and a novel method is provided for synthesizing diarylmethane compounds.
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Paragraph 0062-0063
(2019/10/17)
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- Post-synthesis deposition of mesoporous niobic acid with improved thermal stability by kinetically controlled sol-gel overcoating
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Niobia is a well-known solid acid catalyst owing to its intrinsic Br?nsted and Lewis acidity. However, catalyst development with this oxide has been limited by our ability to control its pore structure and thermal stability. Here we report a novel post-synthetic approach for preparing mesoporous niobia catalysts. This method relies on controlling the kinetics of niobium(v) ethoxide to deposit conformal Nb2O5 overcoats on SBA-15 in a typical St?ber solution. Full Nb2O5 coverage over the mesopores of SBA-15 was achieved by adding 4 monolayer equivalents of precursor (4Nb2O5?SBA-15), which was verified by X-ray photoelectron spectroscopy. This overcoated SBA-15 had a high surface area and retained a narrow as well as ordered pore size distribution. Importantly, the typical structural transition from the amorphous to pseudo-hexagonal Nb2O5 phase did not occur with the overcoat after calcination at 773 K. Limiting this crystallization imparts an unprecedented thermal stability to our niobia overcoat, which enables the acid sites to be well preserved after catalyst regeneration. Furthermore, 4Nb2O5?SBA-15 showed higher yields than commercial niobia (HY-340) and lab-synthesized bulk niobia in two probe reactions: xylose dehydration to furfural and Friedel-Crafts alkylation. In both cases, the improvement could be explained by the unique structural features of the niobia overcoat, including a favorable ratio of Br?nsted and Lewis acid sites in the case of xylose dehydration and a high proportion of isolated Nb-OH groups for the alkylation reaction. Such structural features and unprecedented thermal stability provide additional tools for synthetizing unique solid acid catalysts using a simple post-synthesis deposition method.
- Du, Yuan-Peng,Héroguel, Florent,Nguyen, Xuan Trung,Luterbacher, Jeremy S.
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p. 23803 - 23811
(2019/11/05)
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- N-heterocyclic carbene–palladium complexes for Suzuki–Miyaura coupling reaction with benzyl chloride and aromatic boronic acid leading to diarylmethanes
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A family of N-heterocyclic carbene–palladium(II)–N,N-dimethylbenzylamine complexes ((NHC)LPdCl2; L?=?N,N-dimethylbenzylamine) were synthesized as well as characterized using single-crystal X-ray diffraction and spectroscopic data. These complexes exhibited higher catalytic activities for the Suzuki reaction of benzyl chlorides to afford diarylmethanes under milder conditions than other efficient (NHC)LPdCl2 complexes. Using the optimum conditions, the expected coupling products were obtained in moderate to high yields. All reactions were carried out in air and all starting materials were used as supplied without purification.
- Chen, Ming-Tsz,Wang, Wan-Rong,Li, Yi-Jun
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- The Dual Role of Benzophenone in Visible-Light/Nickel Photoredox-Catalyzed C?H Arylations: Hydrogen-Atom Transfer and Energy Transfer
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A dual catalytic protocol for the direct arylation of non-activated C(sp3)?H bonds has been developed. Upon photochemical excitation, the excited triplet state of a diaryl ketone photosensitizer abstracts a hydrogen atom from an aliphatic C?H bond. This inherent reactivity was exploited for the generation of benzylic radicals which subsequently enter a nickel catalytic cycle, accomplishing the benzylic arylation.
- Dewanji, Abhishek,Krach, Patricia E.,Rueping, Magnus
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supporting information
p. 3566 - 3570
(2019/02/26)
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- Nickel-catalyzed cyanation of aryl halides and triflates using acetonitrile: Via C-CN bond cleavage assisted by 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine
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We developed a non-toxic cyanation reaction of various aryl halides and triflates in acetonitrile using a catalyst system of [Ni(MeCN)6](BF4)2, 1,10-phenanthroline, and 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine (Si-Me4-DHP). Si-Me4-DHP was found to function as a reductant for generating nickel(0) species and a silylation reagent to achieve the catalytic cyanation via C-CN bond cleavage.
- Ueda, Yohei,Tsujimoto, Nagataka,Yurino, Taiga,Tsurugi, Hayato,Mashima, Kazushi
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p. 994 - 999
(2019/02/03)
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- Ni(NIXANTPHOS)-Catalyzed Mono-Arylation of Toluenes with Aryl Chlorides and Bromides
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A nickel-catalyzed cross-coupling of toluene derivatives with both aryl bromides and chlorides using a NIXANTPHOS-ligated nickel(II) complex has been developed. The key factor to success is proposed to be the catalyst activation of toluene by a cation-π complex, enabling methyl arenes (pKa ≈ 43) to be deprotonated with the relatively mild base NaN(SiMe3)2. This method facilitates access to a variety of sterically and electronically diverse hetero- and nonheteroaryl-containing diarylmethanes.
- Jiang, Hui,Sha, Sheng-Chun,Jeong, Soo A,Manor, Brian C.,Walsh, Patrick J.
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supporting information
p. 1735 - 1739
(2019/03/20)
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- Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides
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This work describes Ni-catalyzed cross-electrophile coupling of benzyl chloroformate derivatives with aryl iodides that generates a wide range of diaryl methane products. The mild reaction conditions merit the C-O bond radical fragmentation of benzyl chloroformates via halide abstraction or a single electron reduction by a Ni catalyst. This work offers a new substrate type for cross-electrophile couplings.
- Pan, Yingying,Gong, Yuxin,Song, Yanhong,Tong, Weiqi,Gong, Hegui
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supporting information
p. 4230 - 4233
(2019/05/06)
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- Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
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Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
- Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
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supporting information
p. 16490 - 16494
(2019/11/03)
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- Palladium-Catalyzed Hiyama Coupling of Benzylic Ammonium Salts via C-N Bond Cleavage
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The first palladium-catalyzed Hiyama cross-coupling of arylsilanes with benzyltrimethylammonium salts is reported. The reaction proceeds smoothly to facilitate C(sp2)-C(sp3) bond formation via cleavage of the C-N bond and provides a useful approach to various diarylmethanes with a broad substrate scope and excellent functional group tolerance in good to excellent yields.
- Han, Chunyu,Zhang, Zhenming,Xu, Silin,Wang, Kai,Chen, Kaiting,Zhao, Junfeng
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p. 16308 - 16313
(2019/12/25)
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- An Efficient Ga(OTf)3/Isopropanol Catalytic System for Direct Reduction of Benzylic Alcohols
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This study aims to report the first gallium-catalyzed direct reduction of benzylic alcohols using isopropanol as a reductant. The reaction proceeds via gallium catalyst-assisted hydride transfer of the in situ-generated benzylic isopropyl ether. The method generates only water and acetone as byproducts and thus provides an atom-economic and environmentally friendly approach to the synthesis of di- and triarylmethanes, which are important substructures in various bioactive compounds and functional materials. (Figure presented.).
- Sai, Masahiro
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supporting information
p. 4330 - 4335
(2018/10/15)
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- Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds
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Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step.
- Stache, Erin E.,Ertel, Alyssa B.,Rovis, Tomislav,Doyle, Abigail G.
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p. 11134 - 11139
(2018/11/21)
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- Cobalt-Catalyzed Formation of Functionalized Diarylmethanes from Benzylmesylates and Aryl Halides
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A simple cobalt-catalyzed reductive coupling protocol allowing the synthesis of functionalized diarylmethanes from benzyl mesylate is described. The possibility to directly use the benzyl alcohol as a result of a two-step reaction is also presented. This method tolerates a variety of functional groups. A benzyl radical is likely involved. (Figure presented.).
- Reddy, Bhoomireddy Rajendra Prasad,Chowdhury, Sushobhan,Auffrant, Audrey,Gosmini, Corinne
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p. 3026 - 3029
(2018/08/24)
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- Nickel-Catalyzed Cross-Electrophile Coupling between Benzyl Alcohols and Aryl Halides Assisted by Titanium Co-reductant
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A nickel-catalyzed cross-electrophile coupling reaction between benzyl alcohols and aryl halides has been developed using a homolytic C-O bond cleavage protocol that has recently been established. The treatment of a benzyl alcohol and aryl halide with a nickel catalyst and low-valent titanium reagent generated from TiCl4(lutidine) (lutidine = 2,6-lutidine) and manganese powder afforded the cross-coupled product in high yield. A mechanistic study indicated the intermediacy of the benzyl radicals that originate from the benzyl alcohols.
- Suga, Takuya,Ukaji, Yutaka
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supporting information
p. 7846 - 7850
(2019/01/14)
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- Unmodified Fe3O4 nanostructure promoted with external magnetic field: safe, magnetically recoverable, and efficient nanocatalyst for N- and C-alkylation reactions in green conditions
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Transition metal compounds have emerged as suitable catalysts for organic reactions. Magnetic compounds as soft Lewis acids can be used as catalysts for organic reactions. In this report, the Fe3O4 nanostructures were obtained from Fe2+ and Fe3+-salts, under an external magnetic field (EMF) without any protective agent. The X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy tools were used to characterize these magnetic compounds. The two-dimensional (2-D, it showed nanometric size in the two dimensions, nanorod structure) Fe3O4 compound showed high catalytic activity and stability in N- and C-alkylation reactions. A diverse range of N- and C-alkylation products were obtained in moderate to high yield under green and mild conditions in air. Also the N- and C-alkylation products can be obtained with different selectivity and yield by exposure reactions with EMF. Results of alkylation reactions showed that the presence of Fe(II) and Fe(III) species on the surface of magnetic catalysts (phase structure of magnetic compounds) are essential as very cheap active sites. Also, morphology of magnetic catalysts had influence on their catalytic performances. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The catalyst was reused at least four times without any loss of its high catalytic activity for N- and C-alkylation reactions.
- Rafiee, Ezzat,Joshaghani, Mohammad,Abadi, Parvaneh Ghaderi-Shekhi
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p. 2503 - 2522
(2018/01/04)
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- Substrate switchable Suzuki-Miyaura coupling for benzyl ester: Vs. benzyl halide
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Two reaction conditions were developed to accomplish the substrate switchable Suzuki-Miyaura coupling of benzyl derivatives and arylboronic acid derivatives. Under conditions for esters, benzyl esters such as carbonates and acetates reacted with arylboronic acids to afford the corresponding diarylmethanes. However, the benzyl halides did not react under the same conditions. On the other hand, benzyl halides such as bromides and chlorides furnished diarylmethanes under conditions for halides, under which benzyl ester substrates did not react, in which water was found to play an important role. This switching system was tested using the intermolecular/intramolecular competitive reactions, during which the desired products could be synthesized by selecting the appropriate reaction conditions.
- Ohsumi, Masato,Ito, Akitaka,Nishiwaki, Nagatoshi
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p. 35056 - 35061
(2018/10/24)
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- Palladium-Catalysed Cross-Coupling of Benzylammonium Salts with Boronic Acids under Mild Conditions
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Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C-H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.
- Türtscher, Paul L.,Davis, Holly J.,Phipps, Robert J.
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p. 793 - 803
(2017/10/07)
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- Benzylation with Benzyl Alcohol Catalyzed By [ChCl][TfOH]2, a Br?nsted Acidic DES with Reaction Control Self-Separation Performance
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Abstract: A deep eutectic solvent with strong Br?nsted acidity was prepared easily by choline chloride and trifluoromethanesulfonic acid. The obtained [ChCl][TfOH]2 catalyst which was characterized by FT-IR, 1H NMR and TG, possessed greatly enhanced stability than trifluoromethanesulfonic acid, and exhibited excellent catalytic performance in benzylation with benzyl alcohol. Especially, the prepared [ChCl][TfOH]2 catalyst could dissolve into the reactants to realize homogeneous catalysis, and then self-separate from the organic phase after reaction due to the entire consumption of benzyl alcohol. As a result, the catalyst could be recovered and reused simply for six-runs without noticeable loss of catalytic performance. Graphical Abstract: [Figure not available: see fulltext.].
- Yuan, Bing,Li, Yinglian,Yu, Fengli,Li, Xiaoqiang,Xie, Congxia,Yu, Shitao
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p. 2133 - 2138
(2018/05/29)
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- Mild Friedel–Crafts Reactions inside a Hexameric Resorcinarene Capsule: C?Cl Bond Activation through Hydrogen Bonding to Bridging Water Molecules
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A novel catalytic feature of a hexameric resorcinarene capsule is highlighted. The self-assembled cage was exploited to promote the Friedel–Crafts benzylation of several arenes and heteroarenes with benzyl chloride under mild conditions. Calculations showed that there are catalytically relevant hydrogen-bonding interactions between the bridging water molecules of the capsule and benzyl chloride, which is fundamental for the activation of the C?Cl bond. The capsule controls the reaction outcome. Inside the inner cavity of the capsule, N-methylpyrrole is preferentially benzylated in the unusual β-position while mesitylene reacts faster than 1,3-dimethoxybenzene despite the greater π-nucleophilicity of the latter compound.
- La Manna, Pellegrino,Talotta, Carmen,Floresta, Giuseppe,De Rosa, Margherita,Soriente, Annunziata,Rescifina, Antonio,Gaeta, Carmine,Neri, Placido
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p. 5423 - 5428
(2018/04/09)
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- MoO3 supported on ordered mesoporous zirconium oxophosphate: An efficient and reusability solid acid catalyst for alkylation and esterification
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A series of molybdenum oxide supported on ordered mesoporous zirconium oxophosphate (MoO3/M-ZrPO) materials with different MoO3 loadings (0–20 wt%) and calcination temperatures (500–900 °C) have been designed, synthesized and employed as solid acid catalysts in alkylation and esterification. The XRD, TG-DSC, H2-TPR, N2-physisorption and TEM characterizations were taken to investigate the structural properties and states of introduced MoO3 species. The influence of MoO3 loadings and calcination temperatures in catalytic performance was detailedly investigated and optimal catalytic activity was reached at 10 wt% MoO3 loadings and treated at 700 °C. Moreover, MoO3/M-ZrPO catalysts exhibited outstanding catalytic performance in Friedel-Crafts alkylation of different aromatic compounds and esterification of levulinic acid with 1-butanol. Furthermore, it was noteworthy that the catalyst had superior reusability and no noticeable declines were observed in catalytic performance even after seven runs.
- Miao, Zhichao,Li, Zhenbin,Zhao, Jinping,Si, Weijiang,Zhou, Jin,Zhuo, Shuping
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- Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent-free reductive-deoxygenation of ketones with NaBH3CN
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NaBH3CN as a modified hydroborate agent and due to a strong withdrawing CN group does not show any reducing ability to reduce functional groups in the absence of acidic media (pH ~ 3–4). In this study, the immobilized sulfonic acid on silica, SiO2@SO3H, was prepared and applied as a new solid acid catalyst for extremely enhancing the reducing ability of NaBH3CN. The influence of SiO2@SO3H was highlighted by performing the quick and green reduction of structurally diverse carbonyl compounds involving aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones, and acyloins to the corresponding alcohols or alkanes with NaBH3CN. By the NaBH3CN/SiO2@SO3H system, aldehydes were reduced to the corresponding alcohols and ketonic compounds to alkanes as reductive-deoxygenation products. All reduction reactions were carried out within 3 min at room temperature and under solvent-free conditions to afford the products in high to excellent yields (90–98%).
- Zeynizadeh, Behzad,Kouhkan, Mehri
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p. 1521 - 1528
(2018/11/23)
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- Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
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A novel metal-free process allowing the reductive desulfurization of various benzylic dithioketals to afford diarylmethane and benzylester derivatives with good to excellent yields is reported. At room temperature, this mild reduction process requires only the use of TMSCl and NaI in CH2Cl2 and tolerates a large variety of functional groups. (Figure presented.).
- Zhao, Guangkuan,Yuan, Ling-Zhi,Alami, Mouad,Provot, Olivier
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p. 2522 - 2536
(2018/05/14)
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