- Ligand-accelerated non-directed C-H functionalization of arenes
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The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.
- Wang, Peng,Verma, Pritha,Xia, Guoqin,Shi, Jun,Qiao, Jennifer X.,Tao, Shiwei,Cheng, Peter T. W.,Poss, Michael A.,Farmer, Marcus E.,Yeung, Kap-Sun,Yu, Jin-Quan
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p. 489 - 493
(2017/11/28)
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- S,O-Ligand-Promoted Palladium-Catalyzed C-H Functionalization Reactions of Nondirected Arenes
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Pd(II)-catalyzed C-H functionalization of nondirected arenes has been realized using an inexpensive and easily accessible type of bidentate S,O-ligand. The catalytic system shows high efficiency in the C-H olefination reaction of electron-rich and electron-poor arenes. This methodology is operationally simple, scalable, and can be used in late-stage functionalization of complex molecules. The broad applicability of this catalyst has been showcased in other transformations such as Pd(II)-catalyzed C-H acetoxylation and allylation reactions.
- Naksomboon, Kananat,Valderas, Carolina,Gómez-Martínez, Melania,álvarez-Casao, Yolanda,Fernández-Ibá?ez, M. ángeles
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p. 6342 - 6346
(2017/09/15)
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- Synthesis, structure and catalytic activity of a gold(i) complex containing 1,2-bis(diphenylphosphino)benzene monoxide
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The gold(i) complex [Au(dppbO)Cl] was synthesized by reaction of Na[AuCl4]·2H2O with 1,2-bis(diphenylphosphino)benzene (dppb) in the presence of water. This is a new method for the synthesis of a bisphosphine monoxide gold(i) complex. The new gold(i) complex was characterized by NMR spectroscopy and X-ray crystal structure analysis. In the solid state structure a relatively short contact between the oxygen atom of the phosphine oxide group and the gold center was observed. The catalytic activity of [Au(dppbO)Cl] was tested for three different intermolecular alkyne hydrofunctionalization reactions. Silver tetrafluoroborate was used as co-catalyst for halide abstraction. While the bisphosphine monoxide gold(i) complex showed moderate activity for the hydration of various alkynes and the hydroamination of phenyl acetylene, high activity was observed for the hydroarylation of ethylpropiolate. Electron-rich arenes add very fast to the C-C triple bond but with relatively low selectivity.
- Hahn, Christine,Cruz, Leticia,Villalobos, Amanda,Garza, Liliana,Adeosun, Samuel
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p. 16300 - 16309
(2015/01/09)
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- Reactivity of electron-deficient alkynes on gold nanoparticles
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Propiolates cyclotrimerize in the presence of catalytic amounts of gold nanoparticles to give aryl benzoates in high yields and with turnover frequencies of thousands per hour. Types of alkynes other than propiolates do not react, and, if molecular oxygen
- Leyva-Perez, Antonio,Oliver-Meseguer, Judit,Cabrero-Antonino, Jose R.,Rubio-Marques, Paula,Serna, Pedro,Al-Resayes, Saud I.,Corma, Avelino
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p. 1865 - 1873
(2013/09/02)
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- A catalyst-free one-pot construction of skeletons of 5-methoxyseselin and alloxanthoxyletin in water
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In refluxing water and without an additional catalyst, electron-rich phenols could react with alkynoic acids or alkynoates to provide coumarin structures. The skeletons of two natural pyranocoumarins, 5-methoxyseselin and alloxanthoxyletin, could be constructed (total yield up to 76%) in an aqueous multicomponent reaction in which isoprenyl acetate, propiolic acid, and phloroglucinol were simply mixed and refluxed in water.
- Cao, Jin-Li,Shen, Su-Li,Yang, Peng,Qu, Jin
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supporting information
p. 3856 - 3859
(2013/09/02)
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- Update: An efficient synthesis of poly(ethylene glycol)-supported iron(II) porphyrin using a click reaction and its application for the catalytic olefination of aldehydes
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The facile synthesis of polyethylene glycol (PEG)-immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2] cycloaddition "click" reaction is reported. The prepared complex 5 (PEG-C 51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine, and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration, and was recycled through ten runs without significant activity loss. Copyright
- Chinnusamy, Tamilselvi,Rodionov, Valentin,Kuehn, Fritz E.,Reiser, Oliver
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supporting information; experimental part
p. 1827 - 1831
(2012/08/08)
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- Organocatalytic decarboxylative Doebner-Knoevenagel reactions between arylaldehydes and monoethyl malonate mediated by a bifunctional polymeric catalyst
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A bifunctional polystyrene bearing both DMAP and piperidine groups has been prepared and used as an organocatalyst for decarboxylative Doebner-Knoevenagel reactions of arylaldehydes and monoethyl malonate. Isolated yields of the resulting cinnamates were very high, and in all cases only the E-isomer was detected. When a polystyrene catalyst functionalized with only DMAP or piperidine groups was used in these reactions, catalysis was much less efficient. Furthermore, catalysis using a combination of the monofunctional polymers was also less efficient than with the bifunctional polystyrene. Thus, it appears that there is a synergistic effect obtained by co-locating the two different catalytic amine groups on the same polymer backbone. Georg Thieme Verlag Stuttgart · New York.
- Lu, Jinni,Toy, Patrick H.
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supporting information; experimental part
p. 1723 - 1726
(2011/09/12)
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- An efficient synthesis of poly(ethylene glycol)-supported iron(II) porphyrin using a click reaction and its application for the catalytic olefination of aldehydes
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The first successful synthesis of poly(ethylene glycol) (PEG) immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2] cycloaddition is reported. In contrast to the existing methods for the synthesis of PEG-immobilized metalloporphyrins, the click method offers better catalyst loading under comparatively mild reaction conditions. The prepared complex 5 (PEG-C51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration and was recycled for up to ten runs without significant loss of activity.
- Jain, Suman L.,Joseph, Jomy K.,Kuehn, Fritz E.,Reiser, Oliver
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supporting information; experimental part
p. 230 - 234
(2009/09/06)
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- Efficient functionalization of aromatic C-H bonds catalyzed by gold(III) under mild and solvent-free conditions
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A gold(III)-catalyzed carbon-carbon bond formation reaction between arenes and electron-deficient alkynes or alkenes is described. Electron-rich arenes can be efficiently functionalized with the alkyne or alkene substrates. This reaction can be run with neat reactants at ambient temperature. Under the solventless conditions, clean product was obtained from a reaction of equal molar amounts of arene and alkyne substrates. The mild conditions and potential tolerance to different functional groups make this method practical for arene functionalization and for constructing complicated molecules. Efficient preparation of various coumarins from aryl alkynoates was demonstrated. Preliminary mechanistic studies were performed to probe the pathway of this reaction.
- Shi, Zhangjie,He, Chuan
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p. 3669 - 3671
(2007/10/03)
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- Substituent Effects in the Reaction of t-Butylmagnesium Chloride with Substituted Ethyl Cinnamates. A Correlation with 13C NMR Chemical Shifts
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The reaction of t-butylmagnesium chloride with some substituted ethyl (E)-cinnamates gave mainly 1,3-, 1,4-, 1,2- and 1,4-addition products and minor amounts of 1,2- and 1,3-addition products.The relative amounts of 1,3-addition products has been shown to correlate with 13C NMR chemical shifts of C-α of the ethyl cinnamates.The correlation indicates that the regio selectivity of the reactions is to a great extent dependent of polar effects and that the t-butyl radical has a nucleophilic character.
- Jalander, Lars
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p. 419 - 428
(2007/10/02)
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