- C(sp3)-H Bond Acylation with N -Acyl Imides under Photoredox/ Nickel Dual Catalysis
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A novel Ni/photoredox-catalyzed acylation of aliphatic substrates, including simple alkanes and dialkyl ethers, has been developed. The method combines C-N bond activation of amides with a radical relay mechanism involving hydrogen-atom transfer. The protocol is operationally simple, employs bench-stable N -acyl imides as acyl-transfer reagents, and permits facile access to alkyl ketones under very mild conditions.
- Kerackian, Taline,Reina, Antonio,Krachko, Tetiana,Boddaert, Hugo,Bouyssi, Didier,Monteiro, Nuno,Amgoune, Abderrahmane
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supporting information
p. 1531 - 1536
(2020/10/21)
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- 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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- Photocatalytic α-Acylation of Ethers
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Direct coupling of ethers and acyl halides was promoted by a binary catalytic system comprising an Ir-based photocatalyst and a Ni complex under blue-light irradiation. Photocatalysts with high triplet energy directed the catalysis, and the reaction likely proceeded by triplet-triplet energy transfer from the excited photocatalysts. Chlorine radicals generated from an excited Ni complex bearing a Ni-Cl bond would be responsible for generating α-oxy radicals leading to the α-acylated ethers.
- Sun, Zhongdong,Kumagai, Naoya,Shibasaki, Masakatsu
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supporting information
p. 3727 - 3730
(2017/07/26)
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- Sodium iodide-catalyzed direct α-alkoxylation of ketones with alcohols via oxidation of α-iodo ketone intermediates
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The direct α-alkoxylation of ketones with alcohols via a sodium iodide-catalyzed oxidative cross-coupling has been developed. This protocol enables a range of alkyl aryl ketones to cross couple with an array of alcohols in synthetically useful yields. The mechanistic studies provided solid evidence supporting that an α-iodo ketone was a key reaction intermediate, being converted into an α-alkoxylated ketone via further oxidation to a hypervalent iodine species rather than a common nucleophilic substitution, and was generated from the ketone starting material via a radical intermediate. These new mechanism insights should have an effect on the design of iodide-catalyzed oxidative cross-coupling reactions between nucleophiles.
- Zhu, Cuiju,Zhang, Yuanfei,Zhao, Huaiqing,Huang, Shijun,Zhang, Min,Su, Weiping
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supporting information
p. 331 - 338
(2015/02/19)
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- A facile synthesis of secondary α-alkoxy or α-acetoxy aromatic ketones
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The treatment of HNIB with aromatic ketones and subsequent solvolysis using alcohol or acetic acid in one-pot system makes it possible to give corresponding secondary α-alkoxy or α-acetoxy ketones in high yields.
- Lee, Jong Chan,Hong, Taiyoung
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p. 4085 - 4090
(2007/10/03)
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- Competing, kc, Borderline, ks, and Carbonyl Addition Processes in Solvolyses of α-Keto Mesylates and Triflates. α-Keto Cations. 5
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Solvolysis studies on tertiary α-keto mesylates show quite varying responses in rate to solvent ionizing power.The m values are 1.01 for 2-benzoyl-2-adamantyl mesylate (12), 0.66 for the mesylate derivative of 2-hydroxy-2,4,4-trimethyl-3-pentanone (4), and 0.63 for the mesylate derivative of 2-hydroxy-2-methylpropiophenone (3).The mesylate derivative of methyl α-hydroxyisobutyrate (5) does not correlate well with YOTs values, but instead it gives behavior that parallels that of isopropyl tosylate.Mesylates 3-5 solvolyze giving varying ratios of elimination and substitution products at rates comparable to that of isopropyl mesylate. β-d6 isotope effects for 3 and 4 range from 1.69 to 2.08 and are consistent with the intermediacy of α-keto cations. β-Deuterium isotope effects for 5 are quite variable (1.40-2.52) and parallel the amount of elimination product formed (22-94percent).This is consistent with the intermediacy of a reversibly formed ion-pair intermediate which can suffer proton loss.However, the SN2 (intermediate) mechanism remains a possibility in solvolyses of 5.Mesylate 3 solvolyzed in trifluoroethanol with added triethylamine to give an alkoxyoxirane.With small amounts of added 2,6-lutidine the 1,2-elimination product was major , while with added methanesulfonic acid the rearranged trifluoroethyl ester of dimethylphenyl acetic acid was major.These variable products were interpreted in terms of competing carbonyl addition processes and processes involving the α-keto cation.Secondary triflates derived from α-hydroxypropiophenone, 2,2-dimethyl-4-hydroxy-3-pentanone, and ethyl lactate solvolyzed giving the simple substitution product.Rates parallel solvent nucleophilicity and suggest a ks process involving negligible cationic character at the carbon α to the carbonyl group. kΔ processes are also not involved in solvolyses of these secondary triflates.
- Creary, Xavier
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p. 5568 - 5577
(2007/10/02)
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- Chemistry of O-Alkyl Selenoesters. Reaction with Triethylphosphine
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The reaction between triethylphosphine and a number of aliphatic and aromatic selenoesters under oxygen-free conditions have been investigated.The purple intermediate formed in the reaction with the aliphatic selenoesters was quenched with atmospheric oxygen and gave the corresponding esters, whereas quenching with methyl iodide gave the corresponding 1-alkoxy-1-iodoalkyltriethylphosphonium iodides (13)-(16).The 1-alkoxy-1-iodoalkyltriethylphosphonium iodides gave the 1-alkoxyalkyltriethylphosphonium iodides (17)-(20) upon treatment with methanol, and treatment with benzaldehyde at -70 deg C gave α-alkoxyalkyl phenyl ketones (22)-(25).The reaction between the selenobenzoates and triethylphosphine gave α-dialkoxy-stilbenes and -dibenzyls.When the reaction was carried out in cyclohexene 7-alkoxy-7-phenylbicycloheptanes were formed.The presence of benzaldehyde in the reaction mixture led to α-alkoxystilbenes.An explanation for these different reactions is presented.
- Hansen, Per-Egil
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p. 1627 - 1634
(2007/10/02)
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