- Palladium-catalyzed dearomative allylation of indoles with cyclopropyl acetylenes: access to indolenine derivatives
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A palladium-catalyzed redox-neutral allylic alkylation of indoles with cyclopropyl acetylenes has been disclosed. Various 1,3-diene indolenine framework bearing a quaternary stereocenter at the C3 position were synthesized straightforwardly in good to excellent yields with high regio- and stereoselectivities. The reaction could be further expanded to the dearomatization of naphthols to synthesize functionalized cyclohexadienones with 1,3-diene motifs. The reaction exhibited high atom economy and good functional group tolerance.
- Lu, Chuan-Jun,Chen, Yu-Ting,Wang, Hong,Li, Yu-Jin
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p. 635 - 644
(2021/02/06)
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- Synthesis of indoles through acceptorless dehydrogenative coupling catalyzed by nickel on silica-alumina
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The high atom-economical formation of indoles from anilines and diols was described with affordable and easy to handle Ni/SiO2-Al2O3. After optimization, 2,3-dimethylindole was isolated with an excellent 98% yield in neat conditions. The scope of the reaction was studied and 13 indoles were isolated in 16–80% yields.
- Charvieux, Aubin,Hammoud, Abdul Aziz,Duclos, Marie-Christine,Duguet, Nicolas,Métay, Estelle
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supporting information
(2021/07/25)
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- Fe-Catalyzed Sequential C(sp3)-H/N-H Annulation of 2-Methylindoles with Ethyl Trifluoropyruvate at Room Temperature: Construction of Pyrrolo[1,2-α]indoles
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An efficient and benign iron-catalyzed room-temperature method was developed for direct sequential C(sp3)-H/N-H annulation to construct pyrroloindole scaffolds. This strategy features cheap and readily available raw materials and mild room-temperature reaction conditions and provides a green and practical method for the one-pot rapid synthesis of a wide range of diversely functionalized pyrrolo[1,2-α]indoles.
- Wang, Le,Wang, Le,Zhou, Jia,Chen, Han-Qia,Li, Dong-Li,Lin, Jun-Bing,Lin, Jun-Bing,Li, Ke,Ding, Tong-Mei,Zhang, Shu-Yu,Zhang, Shu-Yu
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supporting information
p. 4716 - 4720
(2020/06/29)
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- Palladium-Catalyzed Dearomative Allylic Alkylation of Indoles with Alkynes to Synthesize Indolenines with C3-Quarternary Centers
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A palladium-catalyzed dearomative allylic alkylation of indoles with alkynes to construct indolenines with C3-quarternary centers was reported. The in situ formed arylallene intermediate omitted the need to install leaving groups on the allylic compounds and employ extra oxidants to oxidize the allylic C-H bonds. The reaction exhibited good functional group tolerance and high atom economy. Moreover, the reaction was further expanded to synthesize pyrroloindolines and furanoindolines.
- Gao, Shang,Wu, Zijun,Fang, Xinxin,Lin, Aijun,Yao, Hequan
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supporting information
p. 3906 - 3909
(2016/08/16)
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- Stereoselective synthesis of 2,3-disubstituted indoline diastereoisomers by chemoenzymatic processes
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Racemic indolines including a variety of structural motifs such as C-2 and C-3 substitutions (alkyl or aryl), cis/trans relative stereochemistry and functionalization of the aromatic ring (fluoro, methyl or methoxy groups) have been efficiently prepared through Fischer indolization and subsequent diastereoselective reduction of the unprotected indoles. Combination of Candida antarctica lipase type A and allyl 3-methoxyphenyl carbonate has been identified as the best tandem for their kinetic resolutions, observing excellent stereodiscriminations for most of the tested indolines.
- Lopez-Iglesias, Maria,Busto, Eduardo,Gotor, Vicente,Gotor-Fernandez, Vicente
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p. 8049 - 8055,7
(2020/10/15)
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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 and straightforward synthesis of tetrahydrocarbazoles and 2,3-dimethyl indoles catalyzed by CAN
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A simple protocol was established to synthesize 2,3-dialkyl indoles and various tetrahydrocarbazoles via Fischer indole synthesis. This method uses ceric ammonium nitrate as a catalyst for the Fischer indole synthesis with substituted phenyl hydrazine hydrochlorides and 2-butanone, phenyl propanal, and cyclohexanone. This process is a practical synthetic method for the preparation of various 2,3-disubstituted alkyl indoles and tetrahydrocarbazoles. Copyright Taylor & Francis Group, LLC.
- Varma, P. Prabhakara,Sherigara, Bailure S.,Mahadevan, Kittapa M.,Hulikal, Vijaykumar
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experimental part
p. 158 - 165
(2009/04/07)
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- Antimony (III) sulfate catalyzed one-pot synthesis of 2,3- disubstitutedindoles
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A novel one-pot Fischer indole synthesis approach has been developed by using antimony (III) sulfate as the catalyst. Good yields were obtained after reacting phenylhydrazines hydrochlorides and ketones in refluxing methanol. The exclusive formation of 2,3- disubstituted indoles was observed in the reaction of ethyl methyl ketone with phenylhydrazines. One-pot synthesis of indole-3-propanol using dihydropyran has also been described. The use of reusable antimony (III) sulfate as a catalyst makes this method both economically and environmentally friendly.
- Srinivasa,Mahadevan,Varma, P. Prabhakara,Sudhakara
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experimental part
p. 1843 - 1853
(2010/02/28)
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- Bismuth nitrate promoted fischer indole synthesis: A simple and convenient approach for the synthesis of alkyl indoles
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A novel one-pot fisher indole synthesis approach has been developed by using bismuth nitrate as a catalyst. Yields around 90-95% were obtained after reaction in methanol at reflux temperature in 20-40 min. Apart from the mild reaction conditions of the process and its excellent results, the simplicity of product isolation and the possibility to recycle the bismuth nitrate offers a significant advantage.
- Sudhakara, Aralihalli,Jayadevappa, Honnali,Kumar, Hosanagara N.H.,Mahadevan, Kittappa M.
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scheme or table
p. 159 - 164
(2010/04/23)
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- Fischer indole synthesis in bronsted acidic ionic liquids: A green, mild, and regiospecific reaction system
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A novel one-pot Fischer indole synthesis approach has been developed by using Bronsted acidic ionic liquids as dual solvent-catalysts. Yields of 83-97 % were obtained after reaction in BMImHSO4 at 70-110°C in 0.5-6 h, and exclusive formation of 2,3-disubstituted indoles was observed in the reaction of alkyl methyl unsymmetrical ketones. The indoles produced could be conveniently separated from the reaction mixture without any volatile organic solvents, and the BMImHSO4 could be readily reused without efficiency loss after simple treatment involving only 1 equiv. of HCl for neutralization followed by filtration. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Xu, Dan-Qian,Yang, Wen-Long,Luo, Shu-Ping,Wang, Bing-Tao,Wu, Jian,Xu, Zhen-Yuan
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p. 1007 - 1012
(2008/03/12)
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- The regiospecific Fischer indole reaction in choline chloride· 2ZnCl2 with product isolation by direct sublimation from the ionic liquid
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The Fischer indole synthesis occurs in high yield with one equivalent of the ionic liquid choline chloride·2ZnCl2; exclusive formation of 2,3-disubstituted indoles is observed in the reaction of alkyl methyl ketones, and the products readily sublime directly from the ionic liquid.
- Morales, Raul Calderon,Tambyrajah, Vasuki,Jenkins, Paul R.,Davies, David L.,Abbott, Andrew P.
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p. 158 - 159
(2007/10/03)
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- A practical one-pot synthesis of 2,3-disubstituted indoles from unactivated anilines
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2-Substituted-3-methyl indoles are synthesized with good regioselectivity from readily available substrates and catalysts, i.e. the reaction of anilines with propargyl alcohols in the presence of 0.36-1 mol% Ru3(CO)12.
- Tokunaga, Makoto,Ota, Mitsuru,Haga, Masa-aki,Wakatsuki, Yasuo
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p. 3865 - 3868
(2007/10/03)
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- Synthesis of novel indole derivatives: Variations in the Bartoli reaction
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The synthesis of a range of novel substituted indoles and tricyclic indole derivatives is described using an extension of the Bartoli methodology.
- Dobbs, Adrian P.,Voyle, Martyn,Whittall, Neil
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p. 1594 - 1596
(2007/10/03)
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- Ruthenium Complex Catalyzed N-Heterocyclization. Syntheses of Quinolines and Indole Derivatives from Aminoarenes and 1,3-Propanediol of Glycols
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Aniline reacts with 1,3-propanediol under reflux in diglyme with spontaneous hydrogen evolution in the presence of a catalytic amount of ruth enium trichloride hydrate ( RuCl3*nH2O)-tributylphosphine (PBu3) to give quinoline in good yield.The yield of quinoline was markedly affected by the molar ratios of aniline to 1,3-propanediol and PBu3 to RuCl3*nH2O.The best yield (76percent) was achieved at the molar ratios of 2.5 of aniline / 1,3-propanediol and 2.0 of PBu3 / RuCl3*nH2O.Also, N-substituted anilines react with ethylene glycol in the presence of a catalytic amount of dichlor otris(triphenylphosphine)ruthenium (RuCl2(PPh3)3) to give N-substituted indole derivatives.The reactions were carried out at 180 deg C in dioxane with spontaneus hydrogen evolution.Aminoarenes also react with 2,3-butanediol and 1,2-cyclohexanediol ( mixture of cis and trans ) in the presence of RuCl2(PPh3)3 to give the corresponding 2,3-dimethylindoles and 1,2,3,4-tetrahydrocarbazoles in good to excellent yields.As the key intermediates of the reactions, N,N'-diarylpropylenediamine (5a) and N,N'-diarylethylenediamine (5b) and their dehydrogenated imine derivatives are postulated.
- Tsuji, Yasushi,Huh, Keun-Tae,Watanabe, Yoshihisa
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p. 1673 - 1680
(2007/10/02)
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