- Modular counter-Fischer?indole synthesis through radical-enolate coupling
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A single-electron transfer mediated modular indole formation reaction from a 2-iodoaniline derivative and a ketone has been developed. This transition-metal-free reaction shows a broad substrate scope and unconventional regioselectivity trends. Moreover, important functional groups for further transformation are tolerated under the reaction conditions. Density functional theory studies reveal that the reaction proceeds by metal coordination, which converts a disfavored 5-endo-trig cyclization to an accessible 7-endo-trig process.
- Chung, Hyunho,Kim, Jeongyun,Gonzalez-Montiel, Gisela A.,Cheong, Paul Ha-Yeon,Lee, Hong Geun
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supporting information
p. 1096 - 1102
(2021/01/26)
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- Nickel-catalyzed heteroannulation of o-haloanilines with alkynes
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A nickel-catalyzed heteroannulation has been developed where o-haloanilines react with alkynes to afford 2,3-disubstituted indoles. IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) was found to be an effective ligand for the reaction.
- Yoshida, Yuji,Kurahashi, Takuya,Matsubara, Seijiro
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supporting information; experimental part
p. 1067 - 1068
(2011/11/06)
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- Iridium- and ruthenium-catalysed synthesis of 2,3-disubstituted indoles from anilines and vicinal diols
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A straightforward and atom-economical method is described for the synthesis of 2,3-disubstituted indoles. Anilines and 1,2-diols are condensed under neat conditions with catalytic amounts of either [Cp*IrCl2] 2/MsOH or RuCl3·xH2O/phosphine (phosphine = PPh3 or xantphos). The reaction does not require any stoichiometric additives and only produces water and dihydrogen as byproducts. Anilines containing methyl, methoxy, chloro and fluoro substituents can participate in the cyclocondensation. Meta-substituted anilines give good regioselectivity for 6-substituted indoles, while unsymmetrical diols afford excellent regioselectivity for the indole isomer with an aryl or large alkyl group in the 2-position. The mechanism for the cyclocondensation presumably involves initial formation of the α-hydroxyketone from the diol. The ketone subsequently reacts with aniline to generate the α-hydroxyimine which rearranges to the corresponding α-aminoketone. Acid- or metal-catalysed electrophilic ring-closure with the release of water then furnishes the indole product.
- Tursky, Matyas,Lorentz-Petersen, Linda L. R.,Olsen, Lasse B.,Madsen, Robert
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experimental part
p. 5576 - 5582
(2011/02/18)
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- Efficient synthesis of 2-mono and 2,3-disubstituted indoles via palladium-catalyzed oxidation of aminoalcohols
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Efficient synthesis of 2-mono- and 2,3-disubstituted indoles has been accomplished via palladium-catalyzed oxidation of aminoalcohols.
- Aoyagi, Yutaka,Shishikura, Masahiro,Mizusaki, Toshihiko,Komine, Takashi,Yoshinaga, Tokuji,Inaba, Haruko,Ohta, Akihiro,Takeya, Koichi
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p. 1055 - 1059
(2008/12/20)
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- Zn(OTf)2-catalyzed cyclization of proparyl alcohols with anilines, phenols, and amides for synthesis of indoles, benzofurans, and oxazoles through different annulation mechanisms
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Zn(OTf)2 (10 mol %) catalyzed the cyclization of propargyl alcohols with PhXH (X = O, NH) in hot toluene (100 °C) without additive and gave indole and benzofuran products with different structures. In such transformations, α-carbonyl intermedia
- Kumar, Manyam Praveen,Liu, Rai-Shung
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p. 4951 - 4955
(2007/10/03)
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- Synthesis of 2,3-disubstituted indoles via palladium-catalyzed annulation of internal alkynes
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The palladium-catalyzed coupling of 2-iodoaniline and the corresponding N-methyl, -acetyl, and -tosyl derivatives with a wide variety of internal alkynes provides 2,3-disubstituted indoles in good-to-excellent yields. The best results are obtained by empl
- Larock,Yum,Refvik
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p. 7652 - 7662
(2007/10/03)
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- Rate acceleration of Fischer-indole cyclization by microwave irradiation
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Rate acceleration in Fischer-indole synthesis has been observed in a microwave oven and the reaction goes to completion within 28 sec in good yield in one-pot.
- Sridar, V.
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- Rate acceleration of Fischer-indole cyclization by microwave irradiation
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Rate acceleration in Fischer-indole synthesis has been observed in a microwave oven and the reaction goes to completion within 28 sec furnishing good yield in one-pot.
- Sridar
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p. 737 - 738
(2007/10/03)
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- Electrophylic Substitution in Indoles. Part 12. Kinetic Studies of the Rearrangement of 3,3-Disubstituted Indolenines to 2,3-Disubstituted Indoles
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The rearrangements of 3-alkyl-3-methylindolenine salts to the corresponding 2-alkyl-3-methylindoles have been studied over a range of temperatures by u.v. methods in isopropyl alcohol containing hydrochloric acid.The relativ migratory aptitudes of the various alkyl groups were as follows: Me, 1; Et, 14; Pri, 120; allyl, 400; p-nitrobenzyl, 188; benzyl, 1520.Attempts to prepare the analogous p-methylbenzyl and p-methoxybenzyl-3-methylindolenines by alkylation of the 3-methylindole Grignard reagent gave only the 2-benzylindoles owing to the much higher migratory aptitude of the methylbenzyl and p-methoxybenzyl groups.Spiro hydrochloride rearranged to tetrahydrocarbazole at ca. 7400 times the rate of rearrangement of 3,3-dimethylindolenine hydrochloride to 3,3-dimethylindole.Thermodynamic parameters for the various reactions were determined in view of their relevance to the mechanism of electrophylic substitution in 3-substituted indoles.
- Jackson, Anthony H.,Lynch, Patrick P.
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p. 1215 - 1220
(2007/10/02)
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- ORGANOMETALLIC REAGENTS IN SYNTHESIS A NEW PROTOCOL FOR CONSTRUCTION OF THE INDOLE NUCLEUS
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Organodilithium reagents derived from 2-alkyl-N-trimethylsilyl anilines undergo condensation with esters of carboxylic acids to afford substituted indoles.A total of 16 examples are reported; yields in general were good.In conjuction with this program, a convenient, large-scale procedure for preparation of monosilylated anilines was also developed.To demonstrate the utility of the new indole protocol in natural products synthesis, efficient syntheses of (+)-cinchonamine and (+)-epi-cinchonamine as well as a tetracyclic model system for the architecturally complex penitrem mycotoxins were completed in regio- and stereoselective fashion.
- Smith, III, Amos B.,Visnick, Melean,Haseltine, John N.,Sprengeler, Paul A.
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p. 2957 - 2970
(2007/10/02)
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- AN EXPEDIENT SYNTHESIS OF SUBSTITUTED INDOLES
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Condensation of carboxylic acid esters with organo-dilithium reagents derived from N-trimethylsilyl-o-toluidine or N-trimethylsilyl-o-ethyl aniline affords substituted indoles.
- Smith, Amos B.,Visnick, Melean
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p. 3757 - 3760
(2007/10/02)
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