- Covalent Triazine Framework Nanoparticles via Size-Controllable Confinement Synthesis for Enhanced Visible-Light Photoredox Catalysis
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For metal-free, organic conjugated polymer-based photocatalysts, synthesis of defined nanostructures is still highly challenging. Here, we report the formation of covalent triazine framework (CTF) nanoparticles via a size-controllable confined polymerization strategy. The uniform CTF nanoparticles exhibited significantly enhanced activity in the photocatalytic formation of dibenzofurans compared to the irregular bulk material. The optoelectronic properties of the nanometer-sized CTFs could be easily tuned by copolymerizing small amounts of benzothiadiazole into the conjugated molecular network. This optimization of electronic properties led to a further increase in observed photocatalytic efficiency, resulting in total an 18-fold enhancement compared to the bulk material. Full recyclability of the heterogeneous photocatalysts as well as catalytic activity in dehalogenation, hydroxylation and benzoimidazole formation reactions demonstrated the utility of the designed materials.
- Huang, Wei,Huber, Niklas,Jiang, Shuai,Landfester, Katharina,Zhang, Kai A. I.
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- Modulation of Acridinium Organophotoredox Catalysts Guided by Photophysical Studies
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Control over redox states and spin multiplicity of photocatalysts throughout a catalytic cycle is crucial for selective and efficient photocatalytic processes. However, the rational design of photocatalysts is often hampered by the mechanistic complexity
- Fischer, Christian,Kerzig, Christoph,Zilate, Bouthayna,Wenger, Oliver S.,Sparr, Christof
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p. 210 - 215
(2019/12/24)
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- Electrochemical Cross-Dehydrogenative Coupling between Phenols and β-Dicarbonyl Compounds: Facile Construction of Benzofurans
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Preparative electrochemical synthesis is an ideal method for establishing green, sustainable processes. The major benefits of an electro-organic strategy over that of conventional chemical synthesis are the avoidance of reagent waste and mild reaction conditions. Here, an intermolecular cross-dehydrogenative coupling between phenols and β-dicarbonyl compounds has been developed to build various benzofurans under undivided electrolytic conditions. Neither transition metals nor external chemical oxidants are required to facilitate the dehydrogenation and dehydration processes. The key factor in success was the use of nBu4NBF4 as the electrolyte and hexafluoroisopropanol as the solvent, which play key roles in the cyclocondensation step. This electrolysis is scalable and can be used as a key step in drug synthesis. On the basis of several experimental results, the mechanism, particularly of the remarkable anodic oxidation and cyclization process, was illustrated.
- Ding, Mengning,Shi, Zhuangzhi,Tian, Bailin,Wang, Yandong
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supporting information
(2020/03/23)
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- SMALL-MOLECULE ORGANIC DYES
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The present invention relates to compounds of formula (A), wherein Z is NR10 or O. These compounds represent novel acridinium and xanthylium salts having an unprecedented substituted heterocyclic core. They are useful as fluorescent dyes or pre
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Page/Page column 89; 90
(2019/04/16)
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- Photocatalytic synthesis of dihydrobenzofurans by oxidative [3+2] cycloaddition of phenols
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We report a protocol for oxidative [3+2] cycloadditions of phenols and alkenes applicable to the modular synthesis of a large family of dihydrobenzofuran natural products. Visible-light-activated transition metal photocatalysis enables the use of ammonium persulfate as an easily handled benign terminal oxidant. The broad range of organic substrates that are readily oxidized by photoredox catalysis suggests that this strategy may be applicable to a variety of useful oxidative transformations.
- Blum, Travis R.,Zhu, Ye,Nordeen, Sarah A.,Yoon, Tehshik P.
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p. 11056 - 11059
(2015/03/30)
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- Phenol and aniline oxidative coupling with alkenes by using hypervalent iodine dimer for the rapid access to dihydrobenzofurans and indolines
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A highly reactive hypervalent iodine dimer, [Ph(CF3COO)I]-O- [I(OCOCF3)Ph], is utilized as successful promoter in the oxidative phenolic coupling with styrenes leading to 2-aryldihydrobenzofurans. The extensions of the substrates in this study have led to the development of a new expeditious construction of the pyrroloindoline structure from aniline and enamide derivatives.
- Dohi, Toshifumi,Toyoda, Yosuke,Nakae, Tomofumi,Koseki, Daichi,Kubo, Hiroko,Kamitanaka, Tohru,Kita, Yasuyuki
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p. 631 - 644
(2015/03/04)
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- Br?nsted acid-controlled [3 + 2] coupling reaction of quinone monoacetals with alkene nucleophiles: A catalytic system of perfluorinated acids and hydrogen bond donor for the construction of benzofurans
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We have developed an efficient Br?nsted acid-controlled strategy for the [3 + 2] coupling reaction of quinone monoacetals (QMAs) with nucleophilic alkenes, which is triggered by the particular use of a specific acid promoter, perfluorinated acid, and a solvent, fluoroalcohol. This new coupling reaction smoothly proceeded with high regiospecificity in regard with QMAs for introducing π-nucleophiles to only the carbon α to the carbonyl group, thereby providing diverse dihydrobenzofurans and derivatives with high yields, up to quantitative, under mild conditions in short reaction times. The choice of Br?nsted acid enabled us to avoid hydrolysis of the QMAs, which gives quinones, and the formation of discrete cationic species from the QMAs. Notably, further investigations in this study with regard to the acid have led to the findings that the originally stoichiometrically used acid could be reduced to a catalytic amount of 5 mol % loading or less and that the stoichiometry of the alkenes could be significantly improved down to only 1.2 equiv. The facts that only a minimal loading (5 mol %) of perfluoroterephthalic acid is required, readily available substrates can be used, and the regioselectivity can be controlled by the acid used make this coupling reaction very fascinating from a practical viewpoint.
- Hu, Yinjun,Kamitanaka, Tohru,Mishima, Yusuke,Dohi, Toshifumi,Kita, Yasuyuki
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p. 5530 - 5543
(2013/07/26)
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- Iron-catalyzed oxidative cross-coupling of phenols and alkenes
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A novel bioinspired iron-catalyzed oxidative cross-coupling reaction between phenols and conjugated alkenes was developed. This method enables the direct coupling of phenols with styrene, α-alkyl- and α- arylstyrenes, β-alkyl styrenes, and stilbenes, thereby providing a new strategy for the preparation of the pharmacologically important 2,3-dihydrobenzofuran motif. In addition, this study revealed that under a different set of conditions an oxidative/addition dearomatization reaction of 1,1′-bi-2-naphthol (BINOL) with styrene can take place.
- Kshirsagar, Umesh A.,Regev, Clil,Parnes, Regev,Pappo, Doron
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supporting information
p. 3174 - 3177
(2013/07/26)
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- Mechanistic Aspects and Synthetic Applications of the Electrochemical and Iodobenzene Bis(trifluoroacetate) Oxidative 1,3-Cycloadditions of Phenols and Electron-Rich Styrene Derivatives
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Anodic oxidation of p-methoxy-substituted phenols and electron-rich styrene or propenylbenzene derivatives affords in good yield trans-dihydrobenzofurans derived from a formal 1,3-oxidative cycloaddition of the phenol to the styrene derivative.The yield o
- Gates, Bradley D.,Dalidowicz, Peter,Tebben, Andrew,Wang, Shaopeng,Swenton, John S.
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p. 2135 - 2143
(2007/10/02)
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