- Convenient Synthesis of 6,7,12,13-Tetrahydro-5H-Cyclohepta[2,1-b:3,4-b’]diindole Derivatives Mediated by Hypervalent Iodine (III) Reagent
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Bisindolyl alkaloids represent a large family of natural and synthetic products that display various biological activities. Among the bisindole compounds, 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b’]diindoles have received little attention. Only two methods have been developed for the construction of the 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b’]diindole scaffold thus far, including the classical Fischer indole synthesis conducted by reacting indole-fused cycloheptanone and hydrazines, and the condensation reaction to build the seven-membered ring. Here, we report for the first time a new route to synthesize 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b’]diindoles through intramolecular oxidative coupling of 1,3-di(1H-indol-3-yl)propanes in the presence of PIFA, DDQ and TMSCl with moderate to excellent yields.
- Peng, Lei,Zhang, Xiaofei,Yang, Chunhao
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- Synthesis of indoles and tryptophan derivatives via photoinduced nitrene C-H insertion
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Functionalized indoles and tryptophans can be obtained from stannylated alkenes and o-iodoanilines via Stille coupling. Subsequent azidation and photochemical nitrene generation results in the formation of the heterocyclic ring systems via C-H insertion.
- Junk, Lukas,Kazmaier, Uli
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- Substitution of the Dimethylamino Group in Gramines and One-Pot Cyclization to Tetrahydro-β-carbolines Using a Triazine-Based Activating Agent
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A new method for the substitution of 3-[(dimethylamino)methyl]indoles (gramines) with malonate-based nucleophiles was developed using 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) as the activating agent for the dimethylamino group. The reaction was completed in 1.5-6 h at room temperature in the presence of a tert-amine base and lithium salt. CDMT afforded superior results to methyl iodide, a common activating agent for the dimethylamino group in Mannich bases, particularly in the reactions of 1-substituted gramines. The reactivity of the possible intermediates, bis(indol-3-ylmethyl)dimethylammonium salts, was examined to obtain mechanistic insights on the reaction. This substitution method with CDMT enabled the sequential transformation of gramines: substitution with (N-alkylidene)aminomalonates followed by the Pictet-Spengler reaction under acidic conditions afforded 1,2,3,4-tetrahydro-β-carboline derivatives in one pot.
- Fujita, Hikaru,Nishikawa, Riho,Sasamoto, Ozora,Kitamura, Masanori,Kunishima, Munetaka
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- 5-(Cyano)dibenzothiophenium Triflate: A Sulfur-Based Reagent for Electrophilic Cyanation and Cyanocyclizations
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The synthesis of 5-(cyano)dibenzothiophenium triflate 9, prepared by activation of dibenzo[b,d]thiophene-5-oxide with Tf2O and subsequent reaction with TMSCN is reported, and its reactivity as electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9, which includes amines, thiols, silyl enol ethers, alkenes, electron rich (hetero)arenes and polyaromatic hydrocarbons, illustrate the synthetic potential of this reagent. Importantly, Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions, which are not promoted by typical electrophilic cyanation reagents, demonstrating the superior ability of 9 to trigger challenging transformations.
- Li, Xiangdong,Golz, Christopher,Alcarazo, Manuel
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- Synthesis of 3,3-Spiroindolines via FeCl3-Mediated Cyclization of Aryl- or Alkene-Containing 3-Substituted N-Ac Indoles
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We report the cyclization of 3-substituted N-acetylindoles for the straightforward synthesis of 3,3-spiroindolines via the Friedel-Crafts reaction of an appended aryl group or the formal [2 + 2] cycloaddition of an appended alkene. Our strategy involves a
- Nandi, Raj Kumar,Guillot, Régis,Kouklovsky, Cyrille,Vincent, Guillaume
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supporting information
p. 1716 - 1719
(2016/05/19)
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- Convenient synthesis of spiroindole derivatives via palladium-catalyzed cyclization of propargyl chlorides
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Abstract Herein, we report the palladium-catalyzed cyclization reactions of indoles bearing a propargyl chloride side chain at their 3-position. In the presence of an external nucleophile, such as a sulfonamide or malonate, indoles bearing a propargyl gro
- Iwata, Akira,Inuki, Shinsuke,Oishi, Shinya,Fujii, Nobutaka,Ohno, Hiroaki
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supporting information
p. 6580 - 6585
(2015/08/18)
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- Dearomative indole [5+2] cycloaddition reactions: Stereoselective synthesis of highly functionalized cyclohepta[b]indoles
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The first dearomative indole [5+2] cycloaddition reaction with an oxidopyrylium ylide resulted in efficient and diastereoselective construction of some highly functionalized and synthetically challenging oxacyclohepta[b]indoles. The protocol proceeds unde
- Mei, Guangjian,Yuan, Hao,Gu, Yueqing,Chen, Wei,Chung, Lung Wa,Li, Chuang-Chuang
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p. 11051 - 11055
(2015/03/30)
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- Enantioselective gold-catalyzed allylic alkylation of indoles with ALcohols: An efficient route to functionalized tetrahydrocarbazoles
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[Chemical equation presented] Breaking the taboo: The direct use of allylic alcohols in catalytic and enantioselective Friedel-Crafts alkylation is described for the first time In the presence of chiral gold complexes. This intramolecular Friedel-Crafts reaction was used to prepare a broad range of functionalized tetrahydrocarbazoles (see scheme; X=Me, F, Br, Cl, OMe; R=Me, Et, tBu; R′=H, Me).
- Bandini, Marco,Eichholzer, Astrid
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supporting information; experimental part
p. 9533 - 9537
(2010/03/24)
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- Coupling of activated esters to gramines in the presence of ethyl propiolate under mild conditions
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The coupling of activated esters to gramine derivatives is described using ethyl propiolate. A series of substrates have been prepared using these mild conditions to provide a scope and limitations for this methodology.
- Jones, David T.,Artman III, Gerald D.,Williams, Robert M.
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p. 1291 - 1294
(2007/10/03)
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- Nucleophilic substitution reaction of 1-methoxy-6-nitro-indole
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Nucleophilic substitution reaction of 1-methoxy-6-nitroindole (1) was examined. In the reaction with sodium methoxide or sodium cyanide as a nucleophile, 2- and 3-methoxy-6-nitroindoles, and 7-cyano-6-nitroindole were obtained, respectively. A novel methylene homologation at the 3-position was found in the reaction of 1 with sodium methyl sulfide or potassium salt of diethyl malonate to give 3-methylthiomethytyl-6-nitroindole and its 2-methylthio derivative, and diethyl 2-(6-nitroindol-3-yl)methylmalonate, respectively. Possible reaction mechanism is discussed.
- Yamada, Koji,Kawasaki, Toshiya,Fujita, Tomomi,Somei, Masanori
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p. 1151 - 1159
(2007/10/03)
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- On the Origin of Nonexponential Fluorescence Decay in Tryptophan and Its Derivatives
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The nonexponential fluorescence decay of tryptophan and its derivatives is discussed in terms of a simple model based on conformers about the Cα-Cβ bond and the relative rates of charge transfer from indole to various electrophiles.Accurate predictions concerning the relative fluorescence lifetimes and the form of the fluorescence decay law are made for tryptophan and 17 of its derivatives, including three new derivatives synthesized specifically to test the model.
- Petrich, J. W.,Chang, M. C.,McDonald, D. B.,Fleming, G. R.
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p. 3824 - 3832
(2007/10/02)
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