- Facile Synthesis of Polysubstituted 2-Pyrones via TfOH-Mediated Ring Expansion of 2-Acylcyclopropane-1-carboxylates
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A facile route to polysubstituted 2-pyrones from readily available 2-acylcyclopropane-1-aryl-1-carboxylates mediated by TfOH is reported. The strongly donating 1-aryl group is important for directing the C-C bond cleavage of the donor-acceptor cyclopropane ring, which then leads to the formation of the 2-pyrone ring through lactonization.
- Shao, Jiru,An, Caiyun,Wang, Sunewang R.
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p. 4030 - 4041
(2021/07/19)
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- Enantioselective Construction of Quaternary Stereogenic Centers by the Addition of an Acyl Anion Equivalent to 1,3-Dienes
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We report the enantioselective formation of quaternary stereogenic centers by the intermolecular addition of malononitrile, an acyl anion equivalent, and related pronucleophiles to several 1,3-disubstituted acyclic 1,3-dienes in the presence of a Pd-PHOX catalyst. Products are obtained in up to 88% yield and 99:1 er and in most cases are formed as a single regioisomer. The products' malononitrile unit undergoes oxidative functionalization to afford β,γ-unsaturated carbonyls bearing internal olefins and α-quaternary stereogenic centers.
- Adamson, Nathan J.,Malcolmson, Steven J.,Nguyen, Andrew L.,Park, Sangjune,Zhou, Pengfei
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supporting information
(2020/03/04)
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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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- Method for synthesizing aryl ketone compound by taking TBADT as photocatalyst
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The invention provides a method for synthesizing an aryl ketone compound by taking TBADT as a photocatalyst. The method comprises the following steps: with TBADT as a photocatalyst, under the conditions of a palladium catalyst, a phosphine ligand, weak base and an organic solvent, irradiating the reactants under a 380-400 nm photocatalysis lamp at the room temperature under the inert protective atmosphere, so that an aldehyde group-containing compound reacts with Ar-X, wherein the Ar-X is aryl halide or aryl trifluoromethanesulfonate, and the aryl halide is aryl bromide or aryl iodide; the aldehyde group-containing compound is one of aryl aldehyde, alkyl aldehyde, linear primary aldehyde, acyclic secondary aldehyde and N-methylformamide. According to the invention, the tetrabutylammonium sebacate (TBADT)HAT photocatalyst and palladium catalysis are combined for use, and aldehyde C-H arylation and alkenylation reactions can be directly carried out to synthesize ketone. The method has the advantages of mild reaction conditions, high yield and wide substrate application range, and can be used for synthesizing natural products in medicinal plants.
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Paragraph 0040-0044; 0091-0098
(2020/09/21)
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- Electrochemical 1,4-reduction of α,β-unsaturated ketones with methanol and ammonium chloride as hydrogen sources
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A sustainable, chemoselective 1,4-reduction of α,β-unsaturated ketones by means of an electrochemical method is presented, wherein the extremely inexpensive ammonium chloride (NH4Cl) is applied as the only additive. The reaction proceeds smoothly in the air at ambient temperature. Mechanistic studies reveal that both NH4Cl and solvent methanol work as hydrogen donors.
- Huang, Binbin,Li, Yanan,Yang, Chao,Xia, Wujiong
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supporting information
p. 6731 - 6734
(2019/06/17)
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- Carboxylic phosphoric anhydrides as a new coupling partner in Pd-catalyzed coupling reactions: A new ketone synthesis
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The Pd-catalyzed cross-coupling reactions of carboxylic phosphoric anhydrides with organoboronic acids or organostannanes afforded the corresponding ketones. The intramolecular Heck reaction was successful with carboxylic phosphoric anhydrides as a coupling partner. Georg Thieme Verlag Stuttgart.
- Lim, Kyoung-Chan,Hong, Young-Taek,Kim, Sunggak
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p. 1851 - 1854
(2008/02/09)
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