- Rh/TiO2-Photocatalyzed Acceptorless Dehydrogenation of N-Heterocycles upon Visible-Light Illumination
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TiO2 is an effective and extensively employed photocatalyst, but its practical use in visible-light-mediated organic synthesis is mainly hindered by its wide band gap energy. Herein, we have discovered that Rh-photodeposited TiO2 nanoparticles selectively dehydrogenate N-heterocyclic amines with the concomitant generation of molecular hydrogen gas in an inert atmosphere under visible light (λmax = 453 nm) illumination at room temperature. Initially, a visible-light-sensitive surface complex is formed between the N-heterocycle and TiO2. The acceptorless dehydrogenation of N-heterocycles is initiated by direct electron transfer from the HOMO energy level of the amine via the conduction band of TiO2 to the Rh nanoparticle. The reaction condition was optimized by examining different photodeposited noble metals on the surface of TiO2 and solvents, finding that Rh0 is the most efficient cocatalyst, and 2-propanol is the optimal solvent. Structurally diverse N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, indolines, and others bearing electron-deficient as well as electron-rich substituents underwent the dehydrogenation in good to excellent yields. The amount of released hydrogen gas evinces that only the N-heterocyclic amines are oxidized rather than the dispersant. This developed method demonstrates how UV-active TiO2 can be employed in visible-light-induced synthetic dehydrogenation of amines and simultaneous hydrogen storage applications.
- Bahnemann, Detlef W.,Balayeva, Narmina O.,Dillert, Ralf,Mamiyev, Zamin,Zheng, Nan
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p. 5542 - 5553
(2020/08/25)
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- Optimizing ligand structure for low-loading and fast catalysis for alkynyl-alcohol and-amine cyclization
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A series of [Ru(Cp/Cp?)(PR2NR′2)(MeCN)]PF6 complexes were prepared, in which the steric and electronic properties of the primary coordination sphere were varied (R = Ph, t-Bu, Bn; and Cp vs. Cp?). These complexes were catalytically active in the cyclization of alkyne substrates with an intramolecular nucleophile (amine or alcohol) to produce 5-and 6-membered heterocycles. The effect of the 1° coordination sphere structure on catalyst performance was evaluated. Steric bulk around the metal centre was a key feature to achieve rapid catalysis at low temperatures. The catalyst [Ru(Cp)(Pt-Bu2NPh2)(MeCN)]PF6 gave a turnover number that was >1 order of magnitude more active than previous catalysts in the cyclization of the benchmark substrate 2-ethynylaniline. This catalyst is tolerant of a diversity of functional groups and is competent at the formation of various substituted indoles.
- Stubbs, James M.,Bridge, Benjamin J.,Blacquiere, Johanna M.
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p. 7928 - 7937
(2019/06/13)
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- Active and Recyclable Catalytic Synthesis of Indoles by Reductive Cyclization of 2-(2-Nitroaryl)acetonitriles in the Presence of Co-Rh Heterobimetallic Nanoparticles with Atmospheric Hydrogen under Mild Conditions
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A cobalt-rhodium heterobimetallic nanoparticle-catalyzed reductive cyclization of 2-(2-nitroaryl)acetonitriles to indoles has been achieved. The tandem reaction proceeds without any additives under the mild conditions (1 atm H2 and 25 °C). This procedure could be scaled up to the gram scale. The catalytic system is significantly stable under these reaction conditions and could be reused more than ten times without loss of catalytic activity.
- Choi, Isaac,Chung, Hyunho,Park, Jang Won,Chung, Young Keun
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supporting information
p. 5508 - 5511
(2016/11/17)
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- N-(2-ARYLETHYL) BENZYLAMINES AS ANTAGONISTS OF THE 5-HT6 RECEPTOR
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The present invention relates to the use compounds of formula I which are antagonists of the 5-HT 6 receptor, for treating a cognitive disorder selected from the group consisting of age-related cognitive decline, mild cognitive impairment and dementia
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Paragraph 0192
(2016/01/25)
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- Cesium carbonate-promoted hydroamidation of alkynes: Enamides, indoles and the effect of iron(III) chloride
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A series of enamide derivatives was prepared by a simple procedure for the hydroamidation of alkynes with amides and sulfonamides. The use of such a mild base as cesium carbonate promotes the latter transformation, and the addition of catalytic amounts of iron(III) chloride has a beneficial effect in the outcome of some of the presented hydroamidation reactions. A range of indoles was also synthesized from ortho-alkynylanilides by both complementary procedures, which proved to be useful for the construction of the indolo[1,2-c]quinazoline tetracyclic system from an ortho-(2-aminophenylalkynyl)anilide. Copyright
- Herrero, Maria Teresa,De Sarralde, Jokin Diaz,Sanmartin, Raul,Bravo, Laura,Dominguez, Esther
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p. 3054 - 3064
(2013/01/15)
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- Electrochemical-mediated cyclization of 2-alkynylanilines: A clean and safe synthesis of indole derivatives
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The electrochemical-mediated annulation of 2-alkynylanilines to the corresponding indole derivatives proceeds in good yields and under conditions that avoid the use of metal catalysts or classical organic acids and bases. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Arcadi, Antonio,Bianchi, Gabriele,Inesi, Achille,Marinelli, Fabio,Rossi, Leucio
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experimental part
p. 783 - 787
(2009/04/11)
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- Gold(III)-catalyzed annulation of 2-alkynylanilines: A mild and efficient synthesis of indoles and 3-haloindoles
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Gold(III)-catalyzed annulation of 2-alkynylanilines in EtOH or EtOH-water mixtures at room temperature gives indoles derivatives in good yields. One-flask protocol for the gold-catalyzed conversion of 2-alkynylanilines to 3-bromo and 3-iodoindoles is also reported.
- Arcadi, Antonio,Bianchi, Gabriele,Marinelli, Fabio
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p. 610 - 618
(2007/10/03)
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- A simple two-step synthesis of indoles
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A two-step synthesis of indoles that is suitable for use on a large scale is described. The general applicability of this methodology has also been briefly explored.
- Walkington, Andrew,Gray, Matthew,Hossner, Frank,Kitteringham, John,Voyle, Martyn
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p. 2229 - 2233
(2007/10/03)
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- Synthesis of N-aminoindole ureas from ethyl 1-amino-6-(trifluoromethyl)-1H-indole-3-carboxylate
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Two routes to the synthesis of ethyl 6-(trifluoromethyl)-1H-indole-3-carboxylate are described. N-Amination of this key intermediate with O-(diphenylphosphinyl)hydroxylamine and subsequent reactions with aryl isocyanates, using pyridine as solvent, gave t
- Belley,Scheigetz,Dubé,Dolman
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p. 222 - 225
(2007/10/03)
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- 6-SUBSTITUTED INDOLES FROM o-HALONITROBENZENES
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o-Chloro- and o-bromonitrobenzenes are efficiently converted to 6-substituted indoles in a four step synthesis, proceeding through o-trimethylsilylethynylnitrobenzenes, o-nitrophenylacetaldehyde dimethylacetals and o-aminophenylacetaldehyde dimethylacetal
- Tischler, Allan N.,Lanza, Thomas J.
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p. 1653 - 1656
(2007/10/02)
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- Synthesis of Substituted Indoles via Meerwein Arylation
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A new method for the synthesis of substituted indoles is detailed.Meerwein arylation of 4- and 6-substituted 2-nitrobenzenediazonium chlorides with vinyl acetate or vinyl bromide and subsequent reductive cyclization of the resulting adducts affords the corresponding 6- and 4-substituted (CH3, OCH3, Cl, Br, CF3) indoles.The diazonium bisulfates of weakly basic 2-nitroanilines (4-Cl, 6-Br, 4-CF3) gave higher yields of Meerwein arylation adducts than the corresponding diazonium chlorides.Coupling of 2-nitrobenzenediazonium chloride with 2-acetoxy-1-alkenes followed byreductive cyclization affords 2-alkylindoles.
- Raucher, Stanley,Koolpe, Gary A.
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p. 2066 - 2069
(2007/10/02)
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