- De novo Design of Organic Photocatalysts: Bithiophene Derivatives for the Visible-light Induced C?H Functionalization of Heteroarenes
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Herein, we report the de novo synthesis and characterization of a series of substituted bithiophene derivatives as novel and inexpensive organic photocatalysts. DFT calculations were used to predict a priori their absorption spectra and redox potentials, which were then confirmed with empirical data. The photocatalytic activity of this novel class of organic photoredox catalyst was demonstrated in two visible-light mediated strategies for the C?H functionalization of heteroarenes. The implementation of these strategies in a continuous-flow photo-microreactor afforded moderate to excellent yields within few minutes of reaction time. Due to their straightforward synthesis, low cost and good photocatalytic properties we believe that the proposed bithiophene derivatives could be employed as a new class of organic photoredox catalysts. (Figure presented.).
- Bottecchia, Cecilia,Martín, Raúl,Abdiaj, Irini,Crovini, Ettore,Alcazar, Jesús,Orduna, Jesús,Blesa, María Jesús,Carrillo, José R.,Prieto, Pilar,No?l, Timothy
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supporting information
p. 945 - 950
(2019/01/25)
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- C(sp3)-F bond activation of CF3-substituted anilines with catalytically generated silicon cations: Spectroscopic evidence for a hydride-bridged Ru-S dimer in the catalytic cycle
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Heterolytic splitting of the Si-H bond mediated by a Ru-S bond forms a sulfur-stabilized silicon cation that is sufficiently electrophilic to abstract fluoride from CF3 groups attached to selected anilines. The ability of the Ru-H complex, generated in the cooperative activation step, to intramolecularly transfer its hydride to the intermediate carbenium ion (stabilized in the form of a cationic thioether complex) is markedly dependent on the electronic nature of its phosphine ligand. An electron-deficient phosphine thwarts the reduction step but, based on the Ru-S catalyst, half of an equivalent of an added alkoxide not only facilitates but also accelerates the catalysis. The intriguing effect is rationalized by the formation of a hydride-bridged Ru-S dimer that was detected by 1H NMR spectroscopy. A refined catalytic cycle is proposed.
- Stahl, Timo,Klare, Hendrik F. T.,Oestreich, Martin
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supporting information
p. 1248 - 1251
(2013/03/29)
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- Selective N-alkylation of amines using nitriles under hydrogenation conditions: Facile synthesis of secondary and tertiary amines
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Nitriles were found to be highly effective alkylating reagents for the selective N-alkylation of amines under catalytic hydrogenation conditions. For the aromatic primary amines, the corresponding secondary amines were selectively obtained under Pd/C-catalyzed hydrogenation conditions. Although the use of electron poor aromatic amines or bulky nitriles showed a lower reactivity toward the reductive alkylation, the addition of NH4OAc enhanced the reactivity to give secondary aromatic amines in good to excellent yields. Under the same reaction conditions, aromatic nitro compounds instead of the aromatic primary amines could be directly transformed into secondary amines via a domino reaction involving the one-pot hydrogenation of the nitro group and the reductive alkylation of the amines. While aliphatic amines were effectively converted to the corresponding tertiary amines under Pd/C-catalyzed conditions, Rh/C was a highly effective catalyst for the N-monoalkylation of aliphatic primary amines without over-alkylation to the tertiary amines. Furthermore, the combination of the Rh/C-catalyzed N-monoalkylation of the aliphatic primary amines and additional Pd/C-catalyzed alkylation of the resulting secondary aliphatic amines could selectively prepare aliphatic tertiary amines possessing three different alkyl groups. According to the mechanistic studies, it seems reasonable to conclude that nitriles were reduced to aldimines before the nucleophilic attack of the amine during the first step of the reaction.
- Ikawa, Takashi,Fujita, Yuki,Mizusaki, Tomoteru,Betsuin, Sae,Takamatsu, Haruki,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
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p. 293 - 304
(2012/02/01)
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- Bi(CF3)3/Cu(OCOCH3)2 - A new system for the synthesis of 2-trifluoromethylcycloalkan-1-ones, trifluoromethylanilines and phenyl(trifluoromethyl)sulfane
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Bi(CF3)3 reacts in the presence of equimolar amounts of Cu(OCOCH3)2 and 1-morpholinocyclopentene to give 1-morpholino-2-trifluoromethylcyclopentene in 83% yield. This compound as well as intermediately formed 1-morpholino-2-trifluoromethylcyclohexene can easily be converted into the corresponding cycloketones (78 and 41% yield) using the Swarts procedure. In absence of a copper(II) source, no reactions were observed. The reaction of the system Bi(CF3)3/Cu(OCOCH3)2 with N,N-diethylaniline gave an 1.7: 1 isomer mixture of 2-trifluoromethyl and 4-trifluormethyl-N,N-diethylanilines in 48% yield. With tetrabutylammonium thiophenolate, mixtures of phenyl(trifluoromethyl)sulfane and diphenyldisulfane were obtained. Mechanisms are discussed.
- Kirij,Pasenok,Yagupolskii,Tyrra,Naumann
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p. 217 - 221
(2007/10/03)
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- Palladium-catalyzed amination of aryl bromides utilizing arene-chromium complexes as ligands
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The arene - chromium complexes of o-diphenylphosphino α- phenylethylamine or α-phenylethyl methyl ether derivatives were examined with regard to their activity as ligands for palladium(0)-catalyzed aryl amination of aryl bromides with a variety of amines. Both steric and electronic factors were found to be significant for the efficient palladium- catalyzed aryl amination reactions. Modulation of the inductive capacity of the arylphosphine atom was achieved by photoinduced ligand exchange of one carbonyl of the chromium tripode in the presence of electron-donating triphenylphosphine or phosphite. Among these arene - chromium ligands, the use of the monophosphineor monophosphite-(dicarbonyl)chromium of N,N- dimethyl α-(o-diphenylphosphino)phenylethylamine and methyl α-(o- diphenylphosphino)phenylethyl ether produced the palladium(0)-catalyzed aryl amination products with cyclic amines or acyclic secondary amines in high yields; the corresponding strong electron-withdrawing tricarbonylchromium complex resulted in a modest yield of the aryl amination.
- Kamikawa, Ken,Sugimoto, Suguru,Uemura, Motokazu
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p. 8407 - 8410
(2007/10/03)
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- Palladium-Catalyzed Synthesis of Arylamines from Aryl Halides. Mechanistic Studies Lead to Coupling in the Absence of Tin Reagents
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The reaction of aryl halides with secondary amines in the presence of silylamide base and tri-o-tolyphopshine palladium complexes gives arylamine products.This process provides a convenient method for performing these heterocross coupling reactions without the necessity for forming tin amides and disposing of tin halides.This reaction follows from a mechanistic analysis of the coupling reaction with tin amides and occurs as a result of the cleavage of palladium aryl halide dimers with secondary amines.
- Louie, Janis,Hartwig, John F.
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p. 3609 - 3612
(2007/10/02)
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- TRIFLUOROMETHYLATION OF AROMATIC AMINO AND THIO COMPOUNDS BY BISTRIFLUOROMETHYL TELLURIDE
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The reaction of aromatic and heterocyclic amines with (CF3)2Te gave the products from trifluoromethylation in the aromatic ring.The reaction with the corresponding thiols gave S-trifluoromethyl derivatives.
- Naumann, D.,Pazenok, S. V.,Turra, V.
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p. 128 - 130
(2007/10/02)
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- Reactions of Trifluoromethyl Bromide and Related Halides: Part 10. Perfluoroalkylation of Aromatic Compounds induced by Sulphur Dioxide Radical Anion Precursors
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Perfluoroalkylation of electron-rich aromatic compounds with trifluoromethyl bromide, or long-chain perfluoroalkyl iodides, was performed in the presence of sodium dithionite or zinc-sulphur dioxide.This alkylation occurred at the ortho and para positions relative to the amino or hydroxy substitutent.Pyrroles were perfluoroalkylated regioselectively at the 2-position.This alkylation was interpreted as a radical aromatic substitution; the formation of the perfluoroalkyl radical can be induced by a single-electron transfer from sulphur dioxide radical anion to the perfluoroalkyl halide.
- Tordeux, Marc,Langlois, Bernard,Wakselman, Claude
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p. 2293 - 2299
(2007/10/02)
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