- Traceless directing strategy: Efficient synthesis of N-alkyl indoles via redox-neutral C-H activation
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A general protocol for the synthesis of N-alkyl indoles has been developed via a redox neutral C-H activation strategy using a traceless nitroso directing group. A broad scope of substituted N-alkyl indoles has been prepared in good to excellent yields using a very simple Rh catalyst system in the absence of an external oxidant or any other additive. Good to excellent regioselectivity has been achieved for asymmetrically disubstituted acetylenes.
- Wang, Chengming,Huang, Yong
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- One-Pot Tandem ortho-Naphthoquinone-Catalyzed Aerobic Nitrosation of N-Alkylanilines and Rh(III)-Catalyzed C-H Functionalization Sequence to Indole and Aniline Derivatives
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The nitroso group served as a traceless directing group for the C-H functionalization of N-alkylanilines, ultimately removed after functioning either as an internal oxidant or under subsequent reducing conditions. The unique ability of o-NQ catalysts to aerobically oxidize the N-alkylanilines without using solvents and stoichiometric amounts of oxidants has rendered the new opportunity to develop the telescoped catalyst systems without a need for directly handling the hazardous N-nitroso compounds.
- Si, Tengda,Kim, Hun Young,Oh, Kyungsoo
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p. 1152 - 1163
(2021/01/14)
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- Assembly of Indole Cores through a Palladium-Catalyzed Metathesis of Ar-X σ-Bonds
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We describe the development of a new method for construction of highly substituted indole scaffolds through the strategic utilizing of the metathesis of Ar-X σ-bonds based on the dynamic nature of palladium-based oxidative addition/reductive elimination. A suitable and simple catalytic system has provided an appropriate platform for a productive ligand exchange and consecutive carbopalladation/C-H activation/amination of phosphine ligands with alkynes and aromatic/aliphatic amines for construction of structurally diverse indoles.
- Ferrier, Robert C.,Ghasemi, Mehran,Habibi, Azizollah,Jafarpour, Farnaz,Navid, Hamed,Rajai-Daryasarei, Saideh,Safaie, Niloofar
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supporting information
p. 9556 - 9561
(2020/12/21)
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- A Fast Track to Indoles and Annulated Indoles through ortho- vs ipso-Amination of Aryl Halides
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A complementary site selective ortho- vs ipso-amination of aryl halides using non-electrophilic amine sources for construction of indole scaffolds is reported. A palladium-catalyzed alkyne insertion/C-H activation/palladacycle amination via merger of three easily diversified components including iodoarenes, alkynes, and amines delivers indoles with different substitution patterns even in gram scales. By employing ortho-bromoanilines, a consecutive annulative π-extension of indoles proceeds to construct indolo[1,2-f]phenanthridine scaffolds via four C-C and C-N bond formations in one pot.
- Jafarpour, Farnaz,Ghasemi, Mehran,Mohaghegh, Farid,Asgari, Sara,Habibi, Azizollah
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supporting information
p. 10143 - 10148
(2019/12/24)
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- Predicting the Outcome of Photocyclisation Reactions: A Joint Experimental and Computational Investigation
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Photochemical oxidative cyclodehydrogenation reactions are a versatile class of aromatic ring-forming reactions. They are tolerant to functional group substitution and heteroatom inclusion, so can be used to form a diverse range of extended polyaromatic systems by fusing existing ring substituents. However, despite their undoubted synthetic utility, there are no existing models—computational or heuristic—that predict the outcome of photocyclisation reactions across all possible classes of reactants. This can be traced back to the fact that “negative” results are rarely published in the synthetic literature and the lack of a general conceptual framework for understanding how photoexcitation affects reactivity. In this work, we address both of these issues. We present experimental data for a series of aromatically substituted pyrroles and indoles, and show that quantifying induced atomic forces upon photoexcitation provides a powerful predictive model for determining whether a given reactant will photoplanarise and hence proceed to photocyclised product under appropriate reaction conditions. The propensity of a molecule to photoplanarise is related to localised changes in charge distribution around the putative forming ring upon photoexcitation. This is promoted by asymmetry in molecular structures and/or charge distributions, inclusion of heteroatoms and ethylene bridging and well-separated or isolated photocyclisation sites.
- Wonanke, A. D. Dinga,Ferguson, Jayne L.,Fitchett, Christopher M.,Crittenden, Deborah L.
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p. 1293 - 1303
(2019/02/25)
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- Rhodium(iii)-catalyzed indole synthesis at room temperature using the transient oxidizing directing group strategy
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Rh-catalyzed reactions of N-alkyl anilines with internal alkynes at room temperature have been developed using an in situ generated N-nitroso group as a transient oxidizing directing group. Due to mild reaction conditions, this method enabled synthesis of a broad range of N-alkyl indoles, including even two indole-based medicinal compounds. Our work disclosed the feasibility of the transient oxidizing directing group strategy in C-H functionalization reactions, which possesses the potential to enhance overall step-economy and impart new reactivity patterns to substrates.
- Shang, Yaping,Jonnada, Krishna,Yedage, Subhash Laxman,Tu, Hua,Zhang, Xiaofeng,Lou, Xin,Huang, Shijun,Su, Weiping
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supporting information
p. 9547 - 9550
(2019/08/15)
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- Rhodium-catalyzed annulation of tertiary aniline N-oxides to N-alkylindoles: Regioselective C-H activation, oxygen-atom transfer, and N-dealkylative cyclization
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[Cp?RhIII]-catalyzed annulation of tertiary aniline N-oxides with alkynes was reported to achieve the challenging ortho C-H functionalization of tertiary anilines via N-O bond acting as a traceless directing group. More significantly, this system represents the first example which integrates C-H activation, oxygen-atom transfer, and N-dealkylative cyclization in one reaction. This unprecedented coupling reaction has allowed the construction of N-alkylindole derivatives in high efficiency with broad substrate scope and good functional group tolerance.
- Li, Bin,Xu, Hong,Wang, Huanan,Wang, Baiquan
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p. 3856 - 3862
(2016/07/06)
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- Br?nsted acid cocatalysis in photocatalytic intramolecular coupling of tertiary amines: Efficient synthesis of 2-arylindols
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We report herein a highly efficient intramolecular coupling reaction of tertiary amines and ketones (α,β-unsaturated ketones) by using a Br?nsted acid as a cocatalyst, affording 2-arylindols in good to excellent yields (up to 92%) under visible light irra
- Yuan, Xiaoqian,Wu, Xinxin,Dong, Shupeng,Wu, Guibing,Ye, Jinxing
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supporting information
p. 7447 - 7450
(2016/08/16)
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- Co(III)-Catalyzed, Internal and Terminal Alkyne-Compatible Synthesis of Indoles
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A Co(III)-catalyzed, internal and terminal alkyne-compatible indole synthesis protocol is reported herein. The N-amino (hydrazine) group imparts distinct, diverse reactivity patterns for directed C-H functionalization/cyclization reactions. Notable synthetic features include regioselectivity for a meta-substituted arylhydrazine, regioselectivity for a chain-branched terminal alkyne, formal incorporation of an acetylenic unit through C2-desilylation on a C2-silylated indole derivative, formal inversion of regioselectivity through consecutive C3-derivatization and C2-desilylation processes, and formal bond migration for a linear-chain terminal alkyne.
- Zhou, Shuguang,Wang, Jinhu,Wang, Lili,Chen, Kehao,Song, Chao,Zhu, Jin
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supporting information
p. 3806 - 3809
(2016/08/16)
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- Cationic Cobalt(III) Catalyzed Indole Synthesis: The Regioselective Intermolecular Cyclization of N-Nitrosoanilines and Alkynes
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The unique regioselectivity and reactivity of cobalt(III) in the direct cyclization of N-nitrosoanilines with alkynes for the expedient synthesis of N-substituted indoles is demonstrated. In the presence of a cobalt(III) catalyst, high regioselectivity was observed when using unsymmetrical meta-substituted N-nitrosoanilines. Moreover, internal alkynes bearing electron-deficient groups, which are almost unreactive in the [Cp?RhIII]-catalyzed system, display good reactivity in this transformation.
- Liang, Yujie,Jiao, Ning
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supporting information
p. 4035 - 4039
(2016/03/19)
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- Facile regiospecific synthesis of 2,3-disubstituted indoles from isatins
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A facile regiospecific synthesis of 2,3-disubstituted indoles from isatins has been developed. Nucleophilic addition of Grignard reagents to commercially available isatins, followed by reduction with borane, afforded an array of structurally diverse 2,3-disubstituted indoles in moderate to good yields. The method described herein represents a novel and very simple approach to synthesize various 2,3-disubstituted indoles, extremely important structural motifs in the pharmaceutical industry and medicinal chemistry. This journal is the Partner Organisations 2014.
- Dou, Xiaowei,Yao, Weijun,Wen, Shan,Lu, Yixin
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supporting information
p. 9469 - 9472
(2014/08/18)
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- Rhodium(III)-catalyzed synthesis of indoles from 1-alkylidene-2- arylhydrazines and alkynes via C-H and N-N bond cleavages
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1-Alkylidene-2-arylhydrazines undergo annulative coupling with internal alkynes in the presence of a rhodium(III) catalyst and a copper(II) salt. The reaction proceeds through cleavage of the C-H and N-N bonds of hydrazines to afford 1,2,3-trisubstituted indole derivatives.
- Matsuda, Takanori,Tomaru, Yuki
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supporting information
p. 3302 - 3304
(2014/06/09)
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- Diborane as reducing agent: Part VII - Novel reduction of indole-1-ketones to 1-alylindoles to 1-alkylindoles and mechanism of reduction of indole-1-aldehydes and ketones
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Borane/THF reduction of nine indole-1-ketones (1a-1i) forms 1-ethylindoles (6a-6h) and the 1-benzylindole (6i) in 50-80percent yields.The ketones 1h and 1i, each of which bears phenyl groups at positions 2 and 3, also undergo deacylation to furnish 2,3-diphenylindole (8) in ca. 40percent yield.The mechanism of formation of both 8 and 6a-6i have been rationalised.The rate of borane/THF reduction of 1 is apparently slower than that of indole-1-carboxaldehydes (9).An attempt has been made to throw some light on the cause of this difference.
- Biswas, K M,Dhara, R N,Mallik, Haimanti,Halder, Sumita,Sinha-Chaudhuri, Arunima,et al.
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p. 906 - 910
(2007/10/02)
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- Indolization by Phosphorus Trichloride of Functionalized Ketone Arylhydrazones: Synthesis of Pharmacological Interesting Indoles
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The synthesis of indoles starting from phosphorus trichloride and arylhydrazones either functionalized in the ketone entity or N-substituted is reported.The reaction, carried out at room temperature, allows several substituents on the ketone framework of the hydrazone (e.g. ether, alkoxycarbonyl, halogeno, dialkylamino, olefinic, and phosphonic).Under optimum conditions high product yields were obtained.Evidence for the proposed mechanism is also reported.
- Baccolini, Grazieno,Dalpozzo, Renato,Todesco, Paolo E.
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p. 971 - 974
(2007/10/02)
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