- Deoxygenative Amination of Azine-N-oxides with Acyl Azides via [3 + 2] Cycloaddition
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A transition-metal-free deoxygenative C-H amination reaction of azine-N-oxides with acyl azides is described. The initial formation of an isocyanate from the starting acyl azide via a Curtius rearrangement can trigger a [3 + 2] dipolar cycloaddition of polar N-oxide fragments to generate the aminated azine derivative. The applicability of this method is highlighted by the late-stage and sequential amination reactions of complex bioactive compounds, including quinidine and fasudil. Moreover, the direct transformation of aminated azines into various bioactive N-heterocycles illustrates the significance of this newly developed protocol.
- Ghosh, Prithwish,Han, Sang Hoon,Han, Sangil,Kim, Dongeun,Kim, In Su,Kim, Saegun,Kwon, Na Yeon,Mishra, Neeraj Kumar
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p. 2476 - 2485
(2020/03/13)
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- Co(III)-Catalyzed C-H Amidation of Nitrogen-Containing Heterocycles with Dioxazolones under Mild Conditions
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A cobalt(III)-catalyzed C-8 selective C-H amidation of quinoline N-oxide using dioxazolone as an amidating reagent under mild conditions is disclosed. The reaction proceeds efficiently with excellent functional group compatibility. The utility of the current method is demonstrated by gram scale synthesis of C-8 amide quinoline N-oxide and by converting this amidated product into functionalized quinolines. Furthermore, the developed catalytic method is also applicable for C-7 amidation of N-pyrimidylindolines and ortho-amidation of benzamides.
- Dhiman, Ankit Kumar,Thakur, Ankita,Kumar, Inder,Kumar, Rakesh,Sharma, Upendra
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p. 9244 - 9254
(2020/08/14)
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- Rh/O2-Catalyzed C8 Olefination of Quinoline N-Oxides with Activated and Unactivated Olefins
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The rhodium/O2 system-catalyzed distal C(sp2)-H olefination of quinoline N-oxides is developed. Molecular oxygen has been explored as an economic and clean oxidant, an alternative to inorganic oxidants. A wide substrate scope with respect to quinoline N-oxides and olefins (activated acrylates and styrenes; unactivated aliphatic olefins) demonstrates the robustness of the developed catalytic method. Interestingly, 2-substituted quinoline N-oxides also afforded good yields of the corresponding C8-olefinated products. Kinetic isotope studies and deuterium-labeling experiments have been performed to understand the preliminary mechanistic pathway. The applicability of the developed method is demonstrated by utilizing natural product-derived substrates and by converting the C8-olefinated quinoline N-oxides into various other useful molecules.
- Sharma, Ritika,Kumar, Rakesh,Sharma, Upendra
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p. 2786 - 2797
(2019/02/26)
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- Catalyst-Free Synthesis of 2-Anilinoquinolines and 3-Hydroxyquinolines via Three-Component Reaction of Quinoline N-Oxides, Aryldiazonium Salts, and Acetonitrile
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A rapid microwave-assisted, catalyst-free, three-component synthesis of various 2-anilinoquinolines from quinoline N-oxides and aryldiazonium salts in acetonitrile under microwave irradiation is reported. This reaction utilizes acetonitrile as a single nitrogen source and involves the formation of two new C-N bonds via the formal [3 + 2] cycloaddition reaction. In the case of 2-substituted quinolines, 3-hydroxyquinoline was observed as the main product via a 1,3 shift of the oxygen atom from N-oxide to the C3 position of quinolines.
- Dhiman, Ankit Kumar,Chandra, Devesh,Kumar, Rakesh,Sharma, Upendra
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p. 6962 - 6969
(2019/06/14)
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- 2-Position-Selective Trifluoromethylthiolation of Six-Membered Heteroaromatic Compounds
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The regioselective C-H trifluoromethylthiolation of six-membered heteroaromatic compounds via nucleophilic attack of a CF3S source on the electrophilically activated six-membered heteroaromatic ring was developed. The reaction proceeds in good yield with good functional group tolerance, even on a gram-scale. The key to the successful regioselective transformation is the presence of an additive (2,4-dinitrobenzenesulfonyl chloride). The regioselective trifluoromethylthiolation of quinidine derivative is also demonstrated. Trifluoromethylthiolation, followed by S-oxidation, affords the corresponding sulfones.
- Muta, Ryuhei,Torigoe, Takeru,Kuninobu, Yoichiro
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supporting information
(2019/06/13)
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- Synthesis of heteroaromatic trifluoromethyl ethers with trifluoromethyl triflate as the source of the trifluoromethoxy group
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A series of nitrogen-heterocycles have been transformed to the corresponding trifluoromethyl or higher perfluoroalkyl ethers by reaction of the corresponding N-oxides with trifluoromethyl or higher perfluoroalkyl triflate. Trifluoromethyl triflate, which has generally been used as a precursor to [OCF3]?, is used here as a bifunctional reagent to render the heteroarene more electrophilic and to deliver the trifluoromethoxy group. This reagent was easily prepared on a large scale (>100 grams) and is stable in either pure form or as a stock solution. Applications and limitations of this method are reported.
- Zhang, Qing-Wei,Hartwig, John F.
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supporting information
p. 10124 - 10127
(2018/09/18)
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- RhIII-Catalyzed Direct C8-Arylation of Quinoline N-Oxides using Diazonaphthalen-2(1H)-ones: A Practical Approach towards 8-aza BINOL
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An efficient RhIII-catalyzed redox-neutral method for the direct C8-arylation of quinoline N-oxides using diazonaphthalen-2(1H)-one as coupling partner has been demonstrated. The developed method is simple, scalable and straightforward with a w
- Ghosh, Bidhan,Biswas, Aniruddha,Chakraborty, Soumen,Samanta, Rajarshi
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supporting information
p. 2388 - 2392
(2018/05/30)
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- Copper-Catalyzed Direct, Regioselective Arylamination of N-Oxides: Studies to Access Conjugated π-Systems
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An efficient copper(I)-catalyzed direct regioselective arylamination of various heterocyclic N-oxides was achieved successfully under redox-neutral conditions using anthranils as arylaminating reagents. The developed protocol is simple, straightforward, and economic with a broad range substrate scope. The dual functional groups in the final molecules were utilized to construct structurally and functionally diverse nitrogen-containing organic π-conjugated systems.
- Biswas, Aniruddha,Karmakar, Ujjwal,Nandi, Shiny,Samanta, Rajarshi
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p. 8933 - 8942
(2017/09/11)
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- Rhodium-Catalyzed Remote C-8 Alkylation of Quinolines with Activated and Unactivated Olefins: Mechanistic Study and Total Synthesis of EP4 Agonist
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Reported herein is a rhodium(III)-catalyzed regioselective distal C(sp2)-H bond alkylation of quinoline N-oxides using olefins as alkyl source and N-oxide as the traceless directing group. The reaction exhibits broad substrate scope with excellent selectivity for C-8 position and good yields of alkylated products. The usefulness of the developed catalytic protocol is established by synthesis of EP4 agonist. In mechanistic study, C-8 olefinated quinoline was identified as the reaction intermediate, which gets reduced to desired C-8 alkylated product in the presence of a rhodium(I) species (produced from rhodium(III) during reaction) and formic acid. Formic acid is produced from dimethylformamide in the presence of silver tetrafluoroborate. (Figure presented.).
- Sharma, Ritika,Kumar, Inder,Kumar, Rakesh,Sharma, Upendra
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supporting information
p. 3022 - 3028
(2017/09/08)
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- Catalyst and solvent-free alkylation of quinoline N-oxides with olefins: A direct access to quinoline-substituted α-hydroxy carboxylic derivatives
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A catalyst/solvent-free, one-pot and operationally simple method for the synthesis of quinoline-substituted α-hydroxy carboxylic derivatives by the hydroxyheteroarylation of olefins with quinoline N-oxides is reported. The reaction features a high atom-economy, mild and reagent/solvent-free conditions, broad substrate scope and good selectivity with high yields. A preliminary mechanistic study to shed light into the reaction pathway was also carried out.
- Kumar, Rakesh,Kumar, Inder,Sharma, Ritika,Sharma, Upendra
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supporting information
p. 2613 - 2617
(2016/03/05)
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- Copper-catalyzed oxygen atom transfer of N-oxides leading to a facile deoxygenation procedure applicable to both heterocyclic and amine N-oxides
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Deoxygenation of various types of N-oxides including both heterocyclic and alkyl(aryl)amine derivatives has successfully been developed by the copper-catalyzed oxygen atom transfer using diazo compounds as the oxygen acceptor. The reaction proceeds smoothly over a broad range of substrates with excellent functional group tolerance under mild conditions. This journal is
- Jeong, Jisu,Lee, Donggun,Chang, Sukbok
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supporting information
p. 7035 - 7038
(2015/04/22)
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- KINETICS OF N-OXIDATION OF COMPOUNDS OF THE QUINOLINE SERIES AND ISOMERIC BENZOQUINOLINES BY PERBENZOIC ACID IN CHLOROFORM AND AQUEOUS DIOXANE
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The kinetics of the N-oxidation with perbenzoic acid of 15 derivatives of quinoline and benzoquinoline in chloroform and 19 compounds in 50percent aqueous dioxane at 20, 25, 30, and 35 deg C were subjected to a comparative study.The rate constants, parameters of Arrhenius equation, and the activation energies for the N-oxidation of the indicated monoazines were determined.A scale of the reactivities of derivatives of the quinoline series and benzoquinolines was calculated within the framework of general perturbation theory.
- Lokhov, R. E.
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