- Highly chemoselective deoxygenation of N-heterocyclic: N -oxides under transition metal-free conditions
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Because their site-selective C-H functionalizations are now considered one of the most useful tools for synthesizing various N-heterocyclic compounds, the highly chemoselective deoxygenation of densely functionalized N-heterocyclic N-oxides has received much attention from the synthetic chemistry community. Here, we provide a protocol for the highly chemoselective deoxygenation of various functionalized N-oxides under visible light-mediated photoredox conditions with Na2-eosin Y as an organophotocatalyst. Mechanistic studies imply that the excited state of the organophotocatalyst is reductively quenched by Hantzsch esters. This operationally simple technique tolerates a wide range of functional groups and allows high-yield, multigram-scale deoxygenation. This journal is
- Kim, Se Hyun,An, Ju Hyeon,Lee, Jun Hee
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supporting information
p. 3735 - 3742
(2021/05/04)
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- Methanol as a formylating agent in nitrogen heterocycles
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A radical mediated C-H direct formylation of N-heteroarenes with methanol is reported. The reaction features a novel iron-catalyzed Minisci oxidative coupling process using commercially available methanol as a formylating reagent. It effectively solved the long-standing problems associated with using methanol as a formylating reagent in these types of reactions. Compared to the traditional Minisci C-H formylation methods, this protocol is highly atom-economical, simple to operate, and environmentally friendly and shows good functional group tolerance. This Minisci formylation strategy is a straightforward approach for the late-stage functionalization of N-heteroarenes. This journal is
- Xu, Zhengbao,Zhang, Lizhi
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p. 9476 - 9482
(2021/11/17)
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- Nickel-catalyzed electrochemical Minisci acylation of aromatic N-heterocycles with α-keto acids via ligand-to-metal electron transfer pathway
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A nickel-catalyzed electrochemical methodology for the Minisci acylation of aromatic electron-deficient heterocycles with α-keto acids has been developed. The reaction is performed in an undivided cell under constant current conditions, featuring broad scope of substrates and avoiding the conventional utilization of silver-based catalysts in conjunction with excess amount of oxidants. Cyclic voltammetric analysis disclosed that a ligand-to-metal electron transfer process may be involved in the generation of the key acyl radicals.
- Ding, Hang,Xu, Kun,Zeng, Cheng-Chu
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- Metal-free C-H methylation and acetylation of heteroarenes with PEG-400
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The generation of a methyl carbon source from renewable and cheap sources is challenging. Herein, we describe a novel and an efficient route for methylation and acetylation of aza-heteroarenes using PEG-400 under O2and TsOH·H2O for the first time by tuning the reaction conditions using a different set of starting materials. The key features of the current protocol are oxidative C-O and C-C bond scission under metal-free conditions with good functional group tolerance, and a broad substrate scope. The potential applicability of the designed methodology was demonstrated for the synthesis of central nervous system (CNS) depressant and anticonvulsant drug molecules by a one-pot strategy.
- Kudale, Vishal Suresh,Wang, Jeh-Jeng
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supporting information
p. 3506 - 3511
(2020/06/25)
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- Iron-catalyzed Minisci acylation of N-heteroarenes with α-keto acids
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An efficient and mild protocol has been developed for the Minisci acylation reactions of nitrogen-containing heteroarenes with α-keto acids. Distinct from the conventional Minisci acylation conditions, the chemistry was performed using non-noble metal Fe(II), instead of expensive Ag(I) salt, as catalyst. A wide range of substrates, including aliphatic or aromatic α-keto acids, as well as various N-heteroarenes, proved to be compatible with the protocol. Scale-up experiment also demonstrates the practicality of the approach.
- Wang, Xiu-Zhi,Zeng, Cheng-Chu
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supporting information
p. 1425 - 1430
(2019/02/01)
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- Iron-Catalyzed Minisci Type Acetylation of N-Heteroarenes Mediated by CH(OEt)3/TBHP
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Iron-catalyzed acetylation of electron deficient N-heteroarenes has been reported using triethylorthoformate as robust and inexpensive acetyl source. This new method is successfully applied for the acetylation of quinolines, isoquinoline, quinoxalines, arylpyridines, bipyridines, and benzothiazole.
- Srinivasulu,Shantharjun,Vani,Ashalu, K. Chinna,Mohd,Wencel-Delord,Colobert,Reddy, K. Rajender
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supporting information
p. 1815 - 1819
(2019/02/20)
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- Chloroacetate-promoted selective oxidation of heterobenzylic methylenes under copper catalysis
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The efficient selective oxidation and functionalization of C-H bonds with molecular oxygen and a copper catalyst to prepare the corresponding ketones was achieved with ethyl chloroacetate as a promoter. In this transformation, various substituted N-heterocyclic compounds were well tolerated. Preliminary mechanistic investigations indicated that organic radical species were involved in the overall process. The N-heterocyclic compounds and ethyl chloroacetate work synergistically to activate C-H bonds in the methylene group, which results in the easy generation of free radical intermediates, thus leading to the corresponding ketones in good yields.
- Liu, Jianming,Zhang, Xin,Yi, Hong,Liu, Chao,Liu, Ren,Zhang, Heng,Zhuo, Kelei,Lei, Aiwen
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supporting information
p. 1261 - 1265
(2015/01/30)
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- AgNO2-mediated direct nitration of the quinoxaline tertiary benzylic C-H bond and direct conversion of 2-methyl quinoxalines into related nitriles
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A unique method for AgNO2-mediated direct nitration of the quinoxaline tertiary C-H bond and direct conversion of 2-methyl quinoxalines into 2-quinoxaline nitriles under oxidative conditions has been developed. This protocol provides an efficient way to access quinoxaline containing nitroalkanes and nitriles depending on different substrate selection. the Partner Organisations 2014.
- Wu, Degui,Zhang, Jian,Cui, Jianhai,Zhang, Wei,Liu, Yunkui
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p. 10857 - 10860
(2014/09/30)
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- SUBSTITUTED 8 - AMINO - IMIDAZO [1, 2-A] PYRAZ1NES AS ANTIBACTERIAL AGENTS
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The present invention relates to substituted imidazo[1,2-a]pyrazines of Formula (I) and their use as antibacterial agents.
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Page/Page column 86-87
(2013/02/27)
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- ANTIFUNGAL AGENTS
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Compounds of formula (I), and pharmaceutically acceptable salts thereof, may be used in therapy, for example as antifungal agents, wherein: R1, R2 and R3 are as defined herein. Certain compounds of formula (I) are also provided. Compounds of formula (I), and agriculturally acceptable salts thereof, may also be used as agricultural fungicides.
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Page/Page column 43-44
(2010/02/14)
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- Synthesis of (η 5-cyclopentadienyl)-1-(4-benzyloxycarbonyl-3,4-dihydroquinoxalin-2- yl)ethene-1,2-dithiolatocobalt(III) and (η 5-cyclopentadienyl)-1-[2-(N,N-dimethylaminomethyleneamino)-3-methyl- 4-oxopteridin-6-yl]ethene-1,2-dithiol
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Cobalt(III) complexes are reported in which (a) a dihydroquinoxalinylethenedithiolate ligand models the pyrazine ring oxidation level in Moco, and (b) a pteridinylethenedithiolate models the pteridine ligand in Moco.
- Dinsmore, Andrew,Birks, Jacqueline H.,Garner, C. David,Joule, John A.
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p. 801 - 807
(2007/10/03)
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- Homolytic Acylation of Protonated Pyridines and Pyrazines with α-Keto Acids: The Problem of Monoacylation
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The silver-catalyzed decarboxylation of α-keto acids by persulfate leads to acyl radicals, which can effect the selective homolytic acylation of pyridine and pyrazine derivatives.Compared with the previously developed source of acyl radicals by hydrogen abstraction from aldehydes, this procedure is more effective in monoacylation when multiple positions of high nucleophilic reactivity are available in the heterocyclic ring.Although the introduction of an acyl group strongly activates the heterocyclic ring toward further substitution, monoacylation can be achieved by taking advantage of the difference in basicity and lipophilicity between the starting base and the monoacylation products in a two-phase system.
- Fontana, Francesca,Minisci, Francesco,Barbosa, Maria Claudia Nogueira,Vismara, Elena
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p. 2866 - 2869
(2007/10/02)
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- SYNTHESIS AND PROPERTIES OF HETEROCYCLIC ANALOGS OF 4-AZIDOCHALCONE
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A study has been made of the spectral and photochemical properties of a series of heterocyclic analogs of 4-azidochalcone, specifically the pyridine, quinoline, isoquinoline, and quinoxaline derivatives.It has been shown that the absorption spectra of most of the 4-azidocinnamoylarenes are shifted bathochromically in comparison with 4-azidochalcone.The quantum yields of photodissociation of the compounds that were investigated were found to vary within the limits 0.70 +/- 0.15.With steric hindrance for the planar conformation of the molecule, a hypsochromic shift ofthe absorption spectra is observed, along with a slight decrease of the quantum yield.
- Budyka, M. F.,Kantor, M. M.,Alfimov, M. V.
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p. 1072 - 1075
(2007/10/02)
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