- Cleavage of the Carbon–Carbon Triple Bonds of Arylacetylenes for the Synthesis of Arylnitriles without a Metal Catalyst
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Cleavage of the carbon–carbon triple bonds of alkynes was achieved, which led to the synthesis of arylnitriles under transition-metal-free conditions. A vast range of terminal alkyne substrates underwent this reaction to provide the corresponding nitriles in moderate to good yields with good functional group tolerance.
- Lin, Yuanguang,Song, Qiuling
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p. 3056 - 3059
(2016/07/12)
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- A Homogeneous Method for the Conveniently Scalable Palladium- and Nickel-Catalyzed Cyanation of Aryl Halides
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Homogeneous conditions for the palladium-catalyzed cyanation of aryl halides were developed. This new system features a broad scope of aryl chlorides and bromides, uses 2-propanol or 1-butanol as solvent, and is readily scalable. The same conditions can also provide simple benzonitriles using the recently developed (TMEDA)NiCl(o-tolyl) precatalyst in conjunction with 1,1′-bis(diphenylphosphino)ferrocene (dppf) as a ligand.
- Burg, Finn,Egger, Julian,Deutsch, Johannes,Guimond, Nicolas
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p. 1540 - 1545
(2016/08/30)
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- Electron-deficient heteroarenium salts: An organocatalytic tool for activation of hydrogen peroxide in oxidations
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A series of monosubstituted pyrimidinium and pyrazinium triflates and 3,5-disubstituted pyridinium triflates were prepared and tested as simple catalysts of oxidations with hydrogen peroxide, using sulfoxidation as a model reaction. Their catalytic efficiency strongly depends on the type of substituent and is remarkable for derivatives with an electron-withdrawing group, showing reactivity comparable to that of flavinium salts which are the prominent organocatalysts for oxygenations. Because of their high stability and good accessibility, 4-(trifluoromethyl)pyrimidinium and 3,5-dinitropyridinium triflates are the catalysts of choice and were shown to catalyze oxidation of aliphatic and aromatic sulfides to sulfoxides, giving quantitative conversions, high preparative yields and excellent chemoselectivity. The high efficiency of electron-poor heteroarenium salts is rationalized by their ability to readily form adducts with nucleophiles, as documented by low pKR+ values (pKR+ red > -0.5 V). Hydrogen peroxide adducts formed in situ during catalytic oxidation act as substrate oxidizing agents. The Gibbs free energies of oxygen transfer from these heterocyclic hydroperoxides to thioanisole, obtained by calculations at the B3LYP/6-311++g(d,p) level, showed that they are much stronger oxidizing agents than alkyl hydroperoxides and in some cases are almost comparable to derivatives of flavin hydroperoxide acting as oxidizing agents in monooxygenases.
- ?turala, Ji?í,Bohá?ová, Soňa,Chudoba, Josef,Metelková, Radka,Cibulka, Radek
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p. 2676 - 2699
(2015/03/18)
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- Effect of reaction medium on the composition of vanadium-titanium catalyst in oxidative ammonolysis of alkylpyridines
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The influence exerted by the concentration of alkylpyridines on the chemical composition of a vanadium-titanium catalyst under oxidative ammonolysis conditions was subjected to a comparative study.
- Saurambaeva,Sembaev
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p. 1104 - 1107
(2007/10/03)
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- REGIOSELECTIVE CYANATION OF 3-SUBSTITUTED PYRIDINE 1-OXIDES
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Cyanation of 3-X-pyridine 1-oxides with trimethylsilanecarbonitrile and dimethylcarbamoyl chloride occurs quantitatively to give 3-X-pyridinecarbonitriles in > 90percent isolated yields when X = -CH3, -OCH3, -OH and -Cl, and approximately equal amounts of the 3- and 5-X derivatives when X = -CN and -COOCH3.
- Fife, Wilmer K.
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