- Synthesis and characterization of indolocarbazole-quinoxalines with flat rigid structure for sensing fluoride and acetate anions
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A new series of indolocarbazole-quinoxalines (ICQ, receptors 6 and 7) are prepared and characterized for effective fluoride and acetate anion sensing. The new indole-based system has a highly flat rigid structure with a large π system, and exhibits high binding affinity and sensitivity for acetate and fluoride anions. Receptors 6 and 7 give abundant and unique spectral features in dimethyl sulfoxide (DMSO). Both fluoride and acetate anions cause a bathochromic shift of the absorption peaks of receptor 7 in DMSO, whereas only fluoride anion results in a remarkable shift of the absorption peak of receptor 6 in DMSO. Receptors 6 and 7 can also operate as efficient colorimetric sensors for naked-eye detection of fluoride and acetate anions, and their combined use also offers a simple way for distinguishing these two anions by the naked-eye. The analysis of a Job's plot for the binding of receptor 7 and F-, single crystal structures of 7?TBACl and 7?TBACH3COO confirm 1: 1 binding stoichiometry. Notably, the ICQ system offers novel and excellent receptors for acetate anion both in solution and in crystalline solid through the formation of two hydrogen bonds. The Royal Society of Chemistry.
- Wang, Ting,Bai, Yu,Ma, Liang,Yan, Xiu-Ping
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- Synthesis and structure of 5-indolyl-6-thienyl-1,2,4-triazines
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Acylation of indole and 2,5-dimethylthiophene with 2-(3-indolyl)-2- oxoacetyl chloride afforded the corresponding diketones. 1-(2,5-Dimethyl-3- thienyl)-2-(3-indolyl)ethanedione reacted with thiosemicarbazide under atmosperic and elevated pressure to give 6-(2,5-dimethyl-3-thienyl)-5-(3- indolyl)-2,3-dihydro-1,2,4-triazine-3-thione whose structure was studied in detail by the X-ray diffraction method. Reactions of 6-(2,5-dimethyl-3-thienyl)- 5-(3-indolyl)-2,3-dihydro-1,2,4-triazine-3-thione with amines and hydrazine resulted in formation of fused triazolo- and tetrazolotriazines.
- Krayushkin,Yarovenko,Sedishev,Zavarzin,Vorontsova,Starikova
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- Rationally designed tri-armed imidazole–indole hybrids as naked eye receptors for fluoride ion sensing
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The present communication describes the design, synthesis, and characterization of unique tri-armed imidazole–indole hybrids RA-RE for naked eye detection of fluoride ion in 9:1 DMSO–water at concentration level of 1.5 ppm, which is recommended permissible limit of fluoride ion. Molecular structures of the receptors are so fabricated that both heterocyclic units, namely, indole and imidazole have been rationally used as chromophore and binding unit, respectively. Strategical introduction of nitro group(s) at the fifth position of indole ring remarkably enhances the binding ability of receptor RD making it highly selective toward fluoride ion (tetrabutylammonium salt) over other typical anionic species. The sensing event can be visualized by naked eyes swiftly with color change. This observation is well corroborated by a redshift of 80 nm in UV–visible spectroscopic studies. A peak at 16.1 ppm due to HF2- in 1H NMR titration validates the deprotonation of imidazolium N?H by fluoride ion.
- Jain, Anshu,Gupta, Ragini,Agarwal, Madhu
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supporting information
p. 1307 - 1318
(2017/07/12)
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- Copper-catalyzed synthesis of indolyl diketones: Via C-H oxidation/diacylation of indoles with arylglyoxal hydrates
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An expedient protocol for Cu-catalyzed C-H oxidation/diacylation of indoles with arylglyoxal hydrates to construct indolyl diketones is developed. This methodology exhibits the synthetic utility of the synthesis of an indole-alkaloid 1,2-di(1H-indol-3-yl)ethane-1,2-dione and offers a straightforward means to produce different indolyl nitrogen-containing heterocycles such as indolyl quinoxaline, indolyl hydantoin and indolyl imidazole in high yields. Preliminary mechanistic studies indicate that two proposed pathways are involved in this process.
- Wang, Cuiping,Zhang, Zhiqiang,Liu, Kui,Yan, Jingbo,Zhang, Tiexin,Lu, Gonghao,Meng, Qingtao,Chi, Haijun,Duan, Chunying
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supporting information
p. 6185 - 6193
(2017/08/02)
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- Design, synthesis and characterization of indole based anion sensing receptors
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The design and synthesis of six new receptors (R1-R6) and their anion sensing properties through multiple channels are reported. These receptors are constructed in such a way that they possess indole groups as the binding sites and different acceptors units of varying electron acceptor strengths. Receptors R1, R3 and R5 could recognize fluoride ions visually and spectroscopically with high selectivity over other anions in DMF, which was demonstrated by a visual detection experiment and UV-Vis, fluorescence and 1H NMR spectral studies. The remaining three receptors (R2, R4 and R6) exhibited colour changes with both fluoride and cyanide ions. The binding constants for fluoride binding by these receptors were determined to be in the order of 104 to 106 M-1 and found to depend on the electron accepting property of the acceptor unit in the intra molecular charge transfer (ICT) transition existing with the indole donor units. 1H NMR titration experiments not only provide evidence for the existence of H-bonding interactions between the indolic N-H groups of these receptors and F-, but also offer key insight into the strengths of the receptor-anion complexes of stoichiometry 1:2. The higher fluoride binding ability of the receptor containing the naphthoquinone signalling unit has been interpreted in terms of the greater electron deficiency of the acceptor unit (quinone) and enhanced H-bond donating character of the indole N-H group. The results of the electrochemical and DFT computation studies corroborate well with the spectroscopic studies.
- Manivannan, Ramalingam,Satheshkumar, Angupillai,El-Mossalamy, El-Sayed H.,Al-Harbi, Laila M.,Kosa, Samia A.,Elango, Kuppanagounder P.
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p. 3936 - 3947
(2015/05/20)
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- Palladium-catalyzed heteroannulation approach to 1,2-bis(3-indolyl)ethanes
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Palladium-catalyzed heteroannulation between indole-3-butanal and various o-iodoanilines provides a straightforward synthesis of 1,2-bis(3-indolyl) ethanes, which are useful precursors to valued indolo[2,3a]carbazoles. 1,2-Bis(3-indolyl)ethanes bearing a
- Blair, Lachlan M.,Sperry, Jonathan
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p. 1931 - 1936
(2013/09/24)
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- Acylation of the zinc salt of indole
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The indole Grignard reagent was transmetallated with ZnCl2 and the resulting zinc salt of indole was acylated with a number of acid chlorides and gave 3-acylindoles in yields superior to those obtained with the indole Grignard reagent.
- Bergman, Jan,Venemalm, Lennart
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p. 6061 - 6066
(2007/10/02)
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