- Synergistic Activation of Amides and Hydrocarbons for Direct C(sp3)–H Acylation Enabled by Metallaphotoredox Catalysis
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The utilizations of omnipresent, thermodynamically stable amides and aliphatic C(sp3)?H bonds for various functionalizations are ongoing challenges in catalysis. In particular, the direct coupling between the two functional groups has not been realized. Here, we report the synergistic activation of the two challenging bonds, the amide C?N and unactivated aliphatic C(sp3)?H, via metallaphotoredox catalysis to directly acylate aliphatic C?H bonds utilizing amides as stable and readily accessible acyl surrogates. N-acylsuccinimides served as efficient acyl reagents for the streamlined synthesis of synthetically useful ketones from simple C(sp3)?H substrates. Detailed mechanistic investigations using both computational and experimental mechanistic studies were performed to construct a detailed and complete catalytic cycle. The origin of the superior reactivity of the N-acylsuccinimides over other more reactive acyl sources such as acyl chlorides was found to be an uncommon reaction pathway which commences with C?H activation prior to oxidative addition of the acyl substrate.
- Baik, Mu-Hyun,Choi, Seulhui,Hong, Soon Hyeok,Lee, Geun Seok,Won, Joonghee
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p. 16933 - 16942
(2020/08/03)
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- Direct C-H Arylation of Aldehydes by Merging Photocatalyzed Hydrogen Atom Transfer with Palladium Catalysis
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Herein, we report that merging palladium catalysis with hydrogen atom transfer (HAT) photocatalysis enabled direct arylations and alkenylations of aldehyde C-H bonds, facilitating visible light-catalyzed construction of a variety of ketones. Tetrabutylammonium decatungstate and anthraquinone were found to act as synergistic HAT photocatalysts. Density functional theory calculations suggested a Pd0-PdII-PdIII-PdI-Pd0 pathway and revealed that regeneration of the Pd0 catalyst and the photocatalyst occurs simultaneously in the presence of KHCO3. This regeneration features a low energy barrier, promoting efficient coupling of the palladium catalytic cycle with the photocatalytic cycle. The work reported herein suggests great promise for further applications of HAT photocatalysis in palladium-catalyzed cross-coupling and C-H functionalization reactions to be successful.
- Chen, Guangying,Cheng, Gui-Juan,Guo, Bin,Li, Xiaobao,Ran, Chongzhao,Wang, Lu,Wang, Ting,Wei, Jun-Jie,Zheng, Caijuan,Zheng, Chao
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p. 7543 - 7551
(2020/08/21)
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- Redox-Neutral ortho Functionalization of Aryl Boroxines via Palladium/Norbornene Cooperative Catalysis
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Palladium/norbornene (Pd/NBE) cooperative catalysis, also known as the Catellani reaction, has become an increasingly useful method for site-selective arene functionalization; however, certain constraints still exist because of its intrinsic mechanistic pathway. Herein, we report a redox-neutral ortho functionalization of aryl boroxines via Pd/NBE catalysis. An electrophile, such as carboxylic acid anhydrides or O-benzoyl hydroxylamines, is coupled at the boroxine ortho position, and a proton as the second electrophile is introduced at the ipso position. This reaction does not require extra oxidants or reductants and avoids stoichiometric bases or acids, thereby tolerating a wide range of functional groups. In particular, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated, which could be used to control reaction sequences. Finally, a deuterium-labeling study supports the ipso protonation pathway. This unique mechanistic feature could inspire the development of a new class of Pd/NBE-catalyzed transformations.Poly-substituted aromatics are ubiquitously found in drugs and agrochemicals. To realize streamlined synthesis, it is highly attractive if functional groups can be site-selectively introduced at unactivated positions with common arene starting materials. Here, a method is developed to directly introduce acyl and amino groups at unactivated ortho positions of readily available aryl boron compounds. Compared with the known ortho functionalization approaches, this method does not require stoichiometric bases, external oxidants, or reductants. Consequently, the reaction is chemoselective: a wide range of functional groups, including highly reactive aryl iodides, can be tolerated. The primary innovation lies in the use of a proton to terminate the ipso aryl intermediate and regenerate the active palladium catalyst. This unique mode of reactivity in the palladium/norbornene catalysis should open the door for developing new redox-neutral methods for site-selective arene functionalization.A redox-neutral ortho functionalization of aryl boroxines via palladium/norbornene cooperative catalysis is developed. The ortho amination and acylation are achieved with carboxylic acid anhydrides and O-benzoyl hydroxylamines as an electrophile, respectively, whereas protonation occurs at the ipso position. This transformation avoids using either extra oxidants and reductants or stoichiometric bases and acids. In addition, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated for pathway divergence.
- Li, Renhe,Liu, Feipeng,Dong, Guangbin
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supporting information
p. 929 - 939
(2019/04/10)
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- Palladium and visible-light mediated carbonylative Suzuki-Miyaura coupling of unactivated alkyl halides and aryl boronic acids
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Herein, a simple and efficient method for the palladium-catalyzed carbonylation of aryl boronic acids with unactivated alkyl iodides and bromides under visible-light irradiation, ambient temperature and low CO-pressure is presented. Notably, the procedure uses readily available equipment and an inexpensive palladium catalyst to generate the key alkyl radical intermediate. These mild conditions enabled the synthesis of a range of functionalized aryl alkyl ketones including the antipsychotic drug, melperone.
- Roslin, Sara,Odell, Luke R.
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supporting information
p. 6895 - 6898
(2017/07/10)
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- Palladium-Catalyzed Environmentally Benign Acylation
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Recent trends in research have gained an orientation toward developing efficient strategies using innocuous reagents. The earlier reported transition-metal-catalyzed carbonylations involved either toxic carbon monoxide (CO) gas as carbonylating agent or functional-group-assisted ortho sp2 C-H activation (i.e., ortho acylation) or carbonylation by activation of the carbonyl group (i.e., via the formation of enamines). Contradicting these methods, here we describe an environmentally benign process, [Pd]-catalyzed direct carbonylation starting from simple and commercially available iodo arenes and aldehydes, for the synthesis of a wide variety of ketones. Moreover, this method comprises direct coupling of iodoarenes with aldehydes without activation of the carbonyl and also without directing group assistance. Significantly, the strategy was successfully applied to the synthesis n-butylphthalide and pitofenone.
- Suchand, Basuli,Satyanarayana, Gedu
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p. 6409 - 6423
(2016/08/16)
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- Catalytic decarboxylative cross-ketonisation of aryl- and alkylcarboxylic acids using iron catalysts
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In the presence of catalytic amounts of magnetite nanopowder, mixtures of aromatic and aliphatic carboxylic acids are converted selectively into the corresponding aryl alkyl ketones. As by-products, only carbon dioxide and water are released. This catalytic cross-ketonisation allows the regioselective acylation of aromatic systems and, thus, represents a sustainable alternative to Friedel-Crafts acylations.
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Page/Page column 4
(2012/07/03)
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- Catalytic Decarboxylative Cross-Ketonisation of Aryl- and Alkylcarboxylic Acids using Magnetite Nanoparticles
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In the presence of catalytic amounts of magnetite nanopowder, mixtures of aromatic and aliphatic carboxylic acids are converted selectively into the corresponding aryl alkyl ketones. As by-products, only carbon dioxide and water are released. This catalytic cross-ketonisation allows the regioselective acylation of aromatic systems and, thus, represents a sustainable alternative to Friedel-Crafts acylations.
- Goossen, Lukas J.,Mamone, Patrizia,Oppel, Christoph
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supporting information; experimental part
p. 57 - 63
(2011/03/22)
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- Friedel-Crafts acylation reaction using carboxylic acids as acylating agents
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Dehydrative Friedel-Crafts acylation reaction of aromatic compounds with carboxylic acids as acylating agents was investigated in the presence of Lewis acid- or Br?nsted acid-catalyst. Various metal triflates and bis(trifluoromethanesulfonyl)amides showed catalytic activity at high temperature, among which Eu(NTf2)3 proved to be the most effective and efficiently catalyzed the acylation reaction of alkyl- and alkoxybenzenes with aliphatic and aromatic carboxylic acids at 250 °C. Bi(NTf2)3 was more effective than Eu(NTf2)3 at lower temperature, but proved to be hydrolyzed in the presence of a small amount of water to give HNTf2 and [Bi6O4(OH)4(H2O)6](NTf2)6. The structure of the latter compound was confirmed by a single crystal X-ray analysis. Among five Br?nsted acids, HOTf, HNTf2, HCTf3, TsOH, and Nafion SAC-13, HNTf2 has proved to be the most efficient catalyst and more effective than Eu(NTf2)3 for the acylation of p-xylene with heptanoic acid at 220 °C or lower temperature. HNTf2 catalyzed the acylation of anisole with carboxylic acids in high yields in refluxing toluene with azeotropic removal of water.
- Kawamura, Masato,Cui, Dong-Mei,Shimada, Shigeru
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p. 9201 - 9209
(2007/10/03)
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- Structure-activity relationship of trihexyphenidyl analogs with respect to the dopamine transporter in the on going search for a cocaine inhibitor
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A series of trihexyphenidyl (THP) analogs were used to search for a derivative that could serve as a cocaine inhibitor. A compound that blocks binding of the cocaine analog carboxyfluorotropane (CFT), allows dopamine uptake and exhibits low side effects could serve as a good candidate for that purpose. All analogs were tested for the extent to which they inhibit CFT binding, dopamine uptake and n-methyl scopolamine (NMS) binding. Several structure-function relationships emerged. Methylation/halogenation of THP's benzene ring enhanced the compound's ability to block CFT binding in comparison to its ability to block dopamine uptake (5a-e). Replacement of the cyclohexyl ring with a benzene ring tended to create compounds that had lower affinities to the dopamine transporter (7b compared to THP, 7d compared to 5h, 7c compared to 8c) and modification of THP's piperidine ring tended to enhance affinity to the dopamine transporter (5f-h, 8a, 8c). One analog (5f) that showed little muscarinic activity indicating that it would probably have few side effects was investigated for its effects as an in vivo cocaine inhibitor. However, it showed few antagonistic effects in vivo. Nevertheless, this work greatly elucidates the structure-function relationships required for potential cocaine inhibitors and so lays out promising directions for future research.
- Dar,Thiruvazhi,Abraham,Kitayama,Kopajtic,Gamliel,Slusher,Carroll,Uhl
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p. 1013 - 1021
(2007/10/03)
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- Friedel-Crafts Acylation of Arenes Catalysed by Bromopentacarbonylrhenium(I)
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The intermolecular Friedel-Crafts acylation of aromatic compounds (such as toluene, m-xylene, and anisole) with various acid chlorides proceeds by using a catalytic amount of bromopentacarbonylrhenium(I) to afford aryl ketones.Intramolecular acylation is also catalyzed by the above-mentioned catalyst to give indanone and tetralone derivatives.
- Kusama, Hiroyuki,Narasaka, Koichi
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p. 2379 - 2384
(2007/10/03)
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- Ruthenium Complex Catalyzed Intermolecular Hydroacylation and Transhydroformylation of Olefins with Aldehydes
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Low-valent ruthenium complexes such as dodecacarbonyltriruthenium (Ru3(CO)12), (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium (Ru(COD)(COT)) and bis(η5-cyclooctadienyl)ruthenium showed high catalytic activity for the intermolecular hydroacylation of olefins with various aromatic and heteroaromatic aldehydes at 180-200 deg C for 24-48 h under an initial carbon monoxide pressure of 20 kg cm-2 to give unsymmetric ketones in moderate to good yields.In the reaction of 2-thiophenecarbaldehyde with cyclohexene, cyclohexyl 2-thienyl ketone was obtained in 62 percent yield.On the other hand, when the aliphatic aldehyde, heptanal, was treated with cyclohexene, the corresponding ketone was not obtained at all, and a transhydroformylation reaction proceeded; i.e., the formyl group of heptanal was apparently transformed to cyclohexene to give cyclohexanecarbaldehyde in 29 percent yield, together with their Tishchenko-type reaction products.
- Kondo, Teruyuki,Akazome, Motohiro,Tsuji, Yasushi,Watanabe, Yoshihisa
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p. 1286 - 1291
(2007/10/02)
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