- Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium saltsviaregioselective Heck arylation at room temperature
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Preparation of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described. The reaction is catalyzed by palladium acetate at room temperature in the absence of ligand and base. The developed method is highly attractive in terms of reaction conditions, substrate scope, functional group tolerance and yields. Synthetic applications of the present method are demonstrated by preparing α-aryl indoles and 3-aryl isocoumarin from styryl ethers.
- Kandasamy, Jeyakumar,Lee, Yong Rok,Singh, Adesh Kumar,Venkatesh, Rapelly
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supporting information
p. 7832 - 7837
(2021/09/28)
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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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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- Diarylrhodates as promising active catalysts for the arylation of vinyl ethers with grignard reagents
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Anionic diarylrhodium complexes, generated by reacting [RhCl(cod)] 2 with 2 equiv of aryl Grignard reagents, were found to be effective active catalysts in cross-coupling reactions of vinyl ethers with aryl Grignard reagents, giving rise to the production of vinyl arenes. In this catalytic system, vinyl-O bonds were preferably cleaved over Ar-O or Ar-Br bonds. A lithium rhodate complex was isolated, and its crystal structure was determined by X-ray crystallography.
- Iwasaki, Takanori,Miyata, Yoshinori,Akimoto, Ryo,Fujii, Yuuki,Kuniyasu, Hitoshi,Kambe, Nobuaki
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supporting information
p. 9260 - 9263
(2014/07/21)
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- Pyrolysis of azetidinone derivatives: A versatile route towards electron-rich alkenes, C-1 allylation and/or homologation of aldehydes
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Pyrolysis of β-lactams and β-thiolactams led essentially to stereoselective synthesis of the high energy electron-rich Z-alkenes. Extension of this methodology to the pyrolysis of 3-allyloxy derivatives gave a simple direct route to the synthetically important 4-pentenal. These pyrolytic transformations convert aldehydes to aryloxyalkenes (a protected homologation) and 4-pentenal (a C-1 allylation and homologation). The starting 3-aryloxy and 3-allyloxy-β-lactams were synthesized by the standard Staudinger ketene-imine [2 + 2] cycloaddition. The corresponding β-thiolactams have readily been obtained in good yields by thiation of β-lactams with Lawesson's reagent. This journal is the Partner Organisations 2014.
- Al-Hamdan, Nouf S.,Habib, Osama M.,Ibrahim, Yehia A.,Al-Awadi, Nouria A.,El-Dusouqui, Osman M. E.
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p. 21023 - 21031
(2014/06/09)
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- Regioselective and stereoselective entry to β,β-disubstituted vinyl ethers via the sequential hydroboration/Suzuki-Miyaura coupling of ynol ethers
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A highly regio- and stereoselective synthesis of stereodefined β,β-disubstituted alkenyl ethers featuring the sequential hydroboration/Suzuki-Miyaura coupling of ynol ethers has been described. A number of functional groups, including OMe, Ac, CO2Et, CN, halides, and alkyl, (hetero)aryl, and alkenyl groups, are well-tolerated under the reaction conditions. Furthermore, it allows a facile entry to the labile diarylacetaldehydes by TFA-mediated hydrolysis of β,β-disubstituted vinyl ethers.
- Cui, Weijian,Mao, Mengyi,He, Zuying,Zhu, Gangguo
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p. 9815 - 9821
(2013/10/22)
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- Chemo-selective copper-catalyzed C-O coupling reactions of phenols with aryl/vinyl halides using enaminone as efficient ligand
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The copper-catalyzed Ullmann C-O coupling reactions between phenols and aryl/vinyl halides have been efficiently performed by employing (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one, an easily available enaminone, as ligand. This new ligand is advantageous for its easy availability, broad applicability and good efficiency. Copyright 2012 John Wiley & Sons, Ltd. Copyright
- Wan, Jie-Ping,Wang, Chunping,Liu, Yunyun
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experimental part
p. 445 - 447
(2012/09/25)
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- Three component reaction of arynes with cyclic ethers and active methines: Synthesis of ω-trichloroalkyl phenyl ethers
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Synthesis of ω-chlorinated alkyl phenyl ethers by tandem reaction of arynes with cyclic ethers and active methines was achieved. Reaction of benzenediazonium 2-carboxylate with tetrahydropyran or tetrahydrofuran in refluxing chloroform afforded 6,6,6-trichlorohexyl phenyl ether or 5,5,5-trichloropentyl phenyl ether in 40% and 61% yields, respectively. When dichloroacetonitrile was used as a reactant, 5,5-dichloro-5-cyanopentyl phenyl ether was obtained in 61% yield. While benzenediazonium carboxylate did not react with epoxides, reaction of benzyne derived from 2-(trimethylsilyl)phenyl triflate with epoxides afforded 3,3,3-trichloropropyl phenyl ethers in good yields as isomeric mixtures. The reaction of oxetanes with benzyne was also reported.
- Okuma, Kentaro,Fukuzaki, Yuta,Nojima, Akiko,Sou, Ayumi,Hino, Haruna,Matsunaga, Nahoko,Nagahora, Noriyoshi,Shioji, Kosei,Yokomori, Yoshinobu
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experimental part
p. 1238 - 1247
(2010/12/20)
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- Catalytic dehydrogenation of o-alkylated or o-alkoxylated iodoarenes with concomitant hydrogenolysis
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Palladium-catalyzed dehydrogenation of suitable chains bonded to an ortho position of an iodoarene has been achieved by two methods both involving oxidative addition of the iodoarene to palladium(0) and palladacycle formation under mild conditions.
- Motti, Elena,Catellani, Marta
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experimental part
p. 565 - 569
(2009/05/07)
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- Reaction of benzyne with styrene oxide: Insertion of arynes into a C-O bond of epoxides
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Benzyne inserts into one of the C-O bonds of styrene oxide to form a dihydrobenzofuran as the major product together with five other reaction products. A detailed study of the reaction mixture clarified an intriguing forty-year-old personal communication from Stiles and Haag. Georg Thieme Verlag Stuttgart.
- Beltrán-Rodil, Sandra,Pe?a, Diego,Guitián, Enrique
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p. 1308 - 1310
(2008/02/07)
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- CuI/N,N-dimethylglycine-catalyzed cross-coupling reaction of vinyl halides with phenols and its application to the assembly of substituted benzofurans
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CuI-catalyzed coupling reaction of vinyl halides and phenols occurs at 60-90 °C with N,N-dimethylglycine hydrochloride as the additive, giving vinyl aryl ethers in good yields. The cross-coupling products formed from o-iodophenols and vinyl iodides are co
- Ma, Dawei,Cai, Qian,Xie, Xiaoan
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p. 1767 - 1770
(2007/10/03)
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- Formation of disubstituted β-lactones using bifunctional catalysis
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(Chemical Equation Presented) Acid chlorides and aromatic aldehydes react in the presence of a stoichiometric amount of a tertiary amine and catalytic amounts of a cinchona alkaloid derivative and a Lewis acid to produce β-lactones in high diastereo- and
- Calter, Michael A.,Tretyak, Olexandr A.,Flaschenriem, Christine
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p. 1809 - 1812
(2007/10/03)
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- Diazo reactions with unsaturated compounds: V.1 reaction of phenyl vinyl ether with arenediazonium chlorides
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Phenyl vinyl ether reacts with arenediazonium chlorides in aqueous acetone at pH 3-4 in the presence of a catalytic amount of copper(II) chloride to give arylacetaldehydes and small amounts 1-aryl-2-phenoxyethenes. No reaction occurs between the same reactants in the presence of sulfur(IV) oxide. 2000 MAIK "Nauka/Interperiodica".
- Naidan
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p. 1600 - 1602
(2007/10/03)
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- PULSE RADIOLYSIS AND PRODUCT ANALYSIS OF 1,1-DIPHENYLETHYLENE AND RELATED COMPOUNDS IN METHANOL
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Pulse radiolysis of 1,1-diphenylethylene (DPE) in methanol in the presence of oxygen, as well as of 1,1-diphenyl-2-chloroethylene (DPE-2-Cl), 1,1-diphenyl-1-chloroethane (DP-1-Cl-Et) and 1,1-diphenyl-2-chloroethane (DP-2-Cl-Et) in methanol saturated with argon, was performed.The products formed under pulse-radiolysis conditions were also analysed.Spectroscopic and kinetic data of the corresponding transiets are presented.The reaction rate constants determined in methanol are .It has been established that the solutes are primarily attacked by e-s and H, whereas the CH2OH species (or O2) react with the intermediates thus produced.Reaction mechanisms consistent with the spectroscopic and kinetic data are presented.
- Getoff, Nikola,Ritter, Alfred,Schwoerer, Friedrich
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p. 2389 - 2404
(2007/10/02)
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