- Trans-Aminoboration across Internal Alkynes Catalyzed by B(C6F5)3 for the Synthesis of Borylated Indoles
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We report here a facile B(C6F5)3 catalyzed trans-aminoboration of internal alkynes, furnishing 3-position borylated indoles at ambient temperature. This reaction proceeds with the breaking of a B-N bond and the formation of N-C and B-C bonds to produce indole and derivatives in one step. It works well for various boron reagents and alkynyl-anilines. The borylated indoles can be further derivatized to give column stable organoboron compounds that can be used for future functionalization.
- Yuan, Kang,Wang, Suning
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Read Online
- A cyclization-rearrangement cascade for the synthesis of structurally complex chiral gold(I)-aminocarbene complexes
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A facile synthesis of chiral cyclic alkyl aminocarbene-gold(I) complexes from gold-free 1,7-enyne substrates was developed. The novel cyclization-rearrangement reaction sequence is triggered by the addition of (Me2S)AuCl to different 1,7-enynes and leads to structurally unique carbene-gold(I) complexes in high yields. These novel complexes are catalytically active and inhibit the proliferation of different human cancer cell lines.
- Kolundzic, Filip,Murali, Annamalai,Perez-Galan, Patricia,Bauer, Jonathan O.,Strohmann, Carsten,Kumar, Kamal,Waldmann, Herbert
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- Structurally-defined direct C-magnesiation and C-zincation of N-heterocyclic aromatic compounds using alkali-metal-mediated metallation
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Demonstrating direct synergic "low polarity metallation", 1-methylindole is C-magnesiated by (TMEDA)2·Na 2MgBu4 and C-zincated by (TMEDA)·Na( tBu)(TMP)Zn(tBu), and 1-methylpyrrole is C-zincated by the same reagent, with all three metal products successfully crystallographically characterised. The Royal Society of Chemistry.
- Conway, Ben,Hevia, Eva,Kennedy, Alan R.,Mulvey, Robert E.
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- Reaction of Phenacyltriphenylarsonium Bromides with N-Methylaniline and N,N-Dimethylaniline
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Reaction of phenacyltriphenylarsonium bromide with N-methylaniline furnished 2-phenylindole predominantly together with 1-methyl-2-phenylindole.The corresponding reaction of the arsonium salt with N,N-dimethylaniline did not give any indole, instead a simple nucleophilic substituted product, α-4'-(dimethylamino)deoxybenzoin was obtained.But, the latter reaction on being carried out in presence of hydrobromic acid afforded 1-methyl-2-phenylindole by the demethylation of N,N-dimethylaniline.
- Bansal, Raj Kumar,Bhagchandani, Gope
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- PALLADIUM-PHOSPHINE COMPLEX CATALYZED CROSS-COUPLING REACTION OF 1-METHYL-2-PYRROLYL-MAGNESIUM BROMIDE AND -ZINC CHLORIDE WITH ORGANIC HALIDES
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1-Methyl-2-pyrrolyl-magnesium bromide and -zinc chloride, which were prepared from 1-methyl-2-pyrrolyllithium with MgBr2 and ZnCl2 respectively, reacted with aryl- and heteroaromatic halides to give the corresponding 2-substituted pyrroles in good to excellent yields in the presence of palladium-phosphine complexes as catalysts.
- Minato, Akio,Tamao, Kohei,Hayashi, Tamio,Suzuki, Keizo,Kumuda, Makoto
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- N-Hydroxyphthalimidyl diazoacetate (NHPI-DA): A modular methylene linchpin for the C-H alkylation of indoles
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Despite the extensive studies on the reactions between conventional diazocompounds and indoles, these are still limited by the independent synthesis of the carbene precursors, the specific catalysts, and the required multi-step manipulation of the products. In this work, we explore redox-Active carbenes in the expedited and divergent synthesis of functionalized indoles. NHPI-DA displays unusual efficiency and selectivity to yield insertion products that can be swiftly elaborated into boron and carbon substituents that are particularly problematic in carbene-mediated reactions.
- Chowdhury, Rajdip,Mendoza, Abraham
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supporting information
p. 4532 - 4535
(2021/05/17)
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- Discovery of New 4-Indolyl Quinazoline Derivatives as Highly Potent and Orally Bioavailable P-Glycoprotein Inhibitors
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The major drawbacks of P-glycoprotein (P-gp) inhibitors at the clinical stage make the development of new P-gp inhibitors challenging and desirable. In this study, we reported our structure-activity relationship studies of 4-indolyl quinazoline, which led to the discovery of a highly effective and orally active P-gp inhibitor, YS-370. YS-370 effectively reversed multidrug resistance (MDR) to paclitaxel and colchicine in SW620/AD300 and HEK293T-ABCB1 cells. YS-370 bound directly to P-gp, did not alter expression or subcellular localization of P-gp in SW620/AD300 cells, but increased the intracellular accumulation of paclitaxel. Furthermore, YS-370 stimulated the P-gp ATPase activity and had moderate inhibition against CYP3A4. Significantly, oral administration of YS-370 in combination with paclitaxel achieved much stronger antitumor activity in a xenograft model bearing SW620/Ad300 cells than either drug alone. Taken together, our data demonstrate that YS-370 is a promising P-gp inhibitor capable of overcoming MDR and represents a unique scaffold for the development of new P-gp inhibitors.
- Chen, Zhe-Sheng,Dai, Qing-Qing,Li, Guo-Bo,Liu, Hong-Min,Liu, Hui,Wang, Bo,Wang, Shaomeng,Yu, Bin,Yuan, Shuo,Zhang, Jing-Ya,Zhang, Xiao-Nan,Zuo, Jia-Hui
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p. 14895 - 14911
(2021/10/12)
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- Synthesis of 2-Substituted Benzothio(seleno)phenes and Indoles via Ag-Catalyzed Cyclization/Demethylation of 2-Alkynylthio(seleno)anisoles and 2-Alkynyldimethylanilines
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An Ag-catalyzed cyclization/demethylation of 2-alkynylthio(seleno)anisoles and 2-alkynyldimethylanilines is described and applied for the construction of valuable benzothio(seleno)phenes as well as indoles. Various 2-substituted benzothio(seleno)phenes and indoles were obtained in good to excellent yields under mild reaction conditions with low catalyst loading. An application of this new method is also exemplified with a concise synthesis of a bioactive molecule precursor. Furthermore, a conceivable reaction mechanism is proposed with supports from isotope-exchange experiments.
- Cai, Tao,Feng, Chengjie,Shen, Fangqi,Bian, Kejun,Wu, Chunlei,Shen, Runpu,Gao, Yuzhen
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supporting information
p. 653 - 656
(2020/12/23)
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- In Situ Preparation of Palladium Nanoparticles for C-2 Selective Arylation of Indoles in Agro-Waste Extract Based Mixed Solvents
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An efficient and practical method for the in situ generation of palladium nanoparticles was successfully established in a water extract of pomelo peel ash. The produced palladium nanoparticles were characterized by energy-dispersive X-ray spectroscopy elemental mapping, field emission scanning electron microscopy, high-resolution transmission electron microscope, X-ray powder diffraction, and showed high catalytic activity for selective C-2 arylation of indoles. A series of 2-arylindoles were smoothly installed in moderate to good yields through the direct palladium-catalyzed cross-coupling reactions of indoles and iodoarenes without external ligand, base, oxidant, and preinstallation directing group.
- Jin, Weiwei,Liu, Chenjiang,Liu, Tianxiang,Sun, Yajun,Wang, Bin,Wang, Rui,Xia, Yu,Zhang, Yonghong
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supporting information
p. 2470 - 2473
(2021/06/25)
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- B(C6F5)3-Catalyzed Electron Donor-Acceptor Complex-Mediated Aerobic Sulfenylation of Indoles under Visible-Light Conditions
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An efficient B(C6F5)3-catalyzed aerobic oxidative C-S cross-coupling reaction of thiophenol with indoles was developed, affording a wide range of diaryl sulfides in good yields. An electron donor-acceptor complex between B(C6F5)3 and indoles was formed, facilitating the photoinduced single-electron transfer (SET) from indole substrates to the B(C6F5)3 catalyst. This protocol demonstrates a new reaction model using B(C6F5)3 as a single-electron oxidant.
- Yuan, Wenkai,Huang, Jie,Xu, Xin,Wang, Long,Tang, Xiang-Ying
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supporting information
p. 7139 - 7143
(2021/09/14)
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- 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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p. 1096 - 1102
(2021/01/26)
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- Tris-NHC-propagated self-supported polymer-based Pd catalysts for heterogeneous C-H functionalization
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Three-dimensionally propagated imidazolium-containing mesoporous coordination polymer and organic polymer-based platforms were successfully exploited to develop single-site heterogenized Pd-NHC catalysts for oxidative arene/heteroarene C-H functionalization reactions. The catalysts were efficient in directed arene halogenation, and nondirected arene and heteroarene arylation reactions. High catalytic activity, excellent heterogeneity and recyclability were offered by these systems making them promising candidates in the area of heterogeneous C-H functionalization, where efficient catalysts are still scarce.
- Choudhury, Joyanta,Dutta, Tapas Kumar,Mandal, Tanmoy,Mohanty, Sunit
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supporting information
p. 10182 - 10185
(2021/10/12)
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- Regioselective Direct C2 Arylation of Indole, Benzothiophene and Benzofuran: Utilization of Reusable Pd NPs and NHC-Pd@MNPs Catalyst for C–H Activation Reaction
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Abstract: A regioselective C2 arylation of indoles, benzothiophene and benzofuran without directing group has been accomplished using economically cheap Pd NPs and NHC-Pd@MNPs catalyst. The reusable catalyst is efficiently employed to access C2 arylated heterocycles in good to excellent yield. The reusability of the catalyst is studied up to five cycles and a gram-scale synthesis has been achieved. The reaction mechanism is well supported by control experiments and literature precedents. Grapic Abstract: [Figure not available: see fulltext.]
- Hegde, Rajeev V.,Ong, Tiow-Gan,Ambre, Ram,Jadhav, Arvind H.,Patil, Siddappa A.,Dateer, Ramesh B.
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p. 1397 - 1405
(2020/10/02)
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- Direct C-H bond activation: Palladium-on-carbon as a reusable heterogeneous catalyst for C-2 arylation of indoles with arylboronic acids
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Direct C(sp2)-H bond functionalization of indoles with arylboronic acids is achieved using palladium supported on carbon as a reusable heterogeneous catalyst in the presence of an oxidant under mild conditions. The current protocol formed exclusive C-2 selective products without the aid of any ligand or directing group. The catalyst is reusable for up to four catalytic cycles with the retention of catalytic efficiency.
- Bhattacharjee, Prantika,Bora, Utpal,Boruah, Purna K.,Das, Manash R.
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p. 7675 - 7682
(2020/06/09)
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- Catalytic Aerobic Dehydrogenatin of N-Heterocycles by N-Hydoxyphthalimide
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Catalytic methods for the aerobic dehydrogenation of N-heterocycles are reported. In most cases, indoles are accessed efficiently from indolines using catalytic N-hydroxyphthalimide (NHPI) as the sole additive under air. Further studies revealed an improved catalytic system of NHPI and copper for the preparation of other heteroaromatics, for example quinolines. (Figure presented.).
- Chen, Weidong,Tang, Hao,Wang, Weilin,Fu, Qiang,Luo, Junfei
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supporting information
p. 3905 - 3911
(2020/08/10)
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- Method for preparing indole compound through air oxidation catalyzed by N-hydroxyphthalimide
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The invention discloses a method for preparing an indole compound through non-transition metal catalyzed air oxidation. According to the method, the low-cost N-hydroxyphthalimide is used as a catalystand air is used as an oxidizing agent, wherein indoline compounds are oxidized in an organic solvent, and synthesis of the indoline compounds is achieved. The method has the advantages of simple reaction operation, low reaction cost, high yield, mild conditions, no heavy metal pollution and the like.
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Paragraph 0092-0094
(2020/11/23)
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- Well-defined (NHC)Pd(N–heterocyclic carboxylate)(OAc) complexes-catalyzed direct C2-arylation of free (NH)-indoles with arylsulfonyl hydrazides
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A series of well-defined (NHC)Pd(N–heterocyclic carboxylate)(OAc) complexes (N–heterocyclic carboxylate = pyridine-2-carboxylate, quinoline-2-carboxylate and isoquinoline-1-carboxylate) were synthesized and fully characterized by NMR spectra, HR-MS and X-ray single crystal diffraction. The obtained complexes were then used for direct C2-arylation of free (NH)-indoles with arylsulfonyl hydrazides. With low catalyst loading, all complexes exhibited high catalytic activities for the arylation reactions.
- Yang, Jin,Zong, Ling-Li,Zhu, Xiao-Ting,Zhu, Xin-Ying,Zhao, Jian-Yi
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- Transition-Metal-Free Synthesis of Heterobiaryls through 1,2-Migration of Boronate Complex
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The synthesis of a diverse range of heterobiaryls has been achieved by a transition-metal-free sp2–sp2 cross-coupling strategy using lithiated heterocycle, aryl or heteroaryl boronic ester and an electrophilic halogen source. The construction of heterobiaryls was carried out through electrophilic activation of the aryl–heteroaryl boronate complex, which triggered 1,2-migration from boron to the carbon atom. Subsequent oxidation of the intermediate boronic ester afforded heterobiaryls in good yield. A comprehensive 11B NMR study has been conducted to support the mechanism. The cross coupling between two nucleophilic cross coupling partners without transition metals reveals a reliable manifold to procure heterobiaryls in good yields. Various heterocycles like furan, thiophene, benzofuran, benzothiophene, and indole are well tolerated. Finally, we have successfully demonstrated the gram scale synthesis of the intermediates for an anticancer drug and OLED material using our methodology.
- Paul, Swagata,Das, Kanak Kanti,Manna, Samir,Panda, Santanu
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p. 1922 - 1927
(2020/02/04)
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- Palladium complexes with an annellated mesoionic carbene (MIC) ligand: Catalytic sequential Sonogashira coupling/cyclization reaction for one-pot synthesis of benzofuran, indole, isocoumarin and isoquinolone derivatives
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Two Pd(ii) complexes (1 and 2) featuring a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based mesoionic carbene ligand have been synthesized and structurally characterized. Both complexes effectively catalyze the one-pot synthesis of benzofuran starting from phenylacetylene and 2-iodophenol under mild conditions. Complex 1 is found to be an excellent catalyst for the straightforward access to a library of benzofuran, indole, isocoumarin and isoquinolone derivatives by the reaction of terminal alkynes with 2-iodo derivates of phenol, N-methyl aniline, benzoic acid and N-methyl benzamide, respectively. The general utility of the catalytic method is demonstrated using a variety of diversely substituted terminal alkynes and the corresponding desired products are obtained in good to excellent yields. On the basis of control experiments, a two-cycle mechanism is proposed which involves the Sonogashira coupling of 2-iodo derivatives with alkynes and the subsequent cyclization of the corresponding 2-alkynyl compounds.
- Bera, Jitendra K.,Daw, Prosenjit,Reshi, Noor U Din,Tyagi, Akshi
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supporting information
p. 15238 - 15248
(2020/11/18)
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- C2–H Arylation of Indoles Catalyzed by Palladium-Containing Metal-Organic-Framework in γ-Valerolactone
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An efficient and selective procedure was developed for the direct C2–H arylation of indoles using a Pd-loaded metal–organic framework (MOF) as a heterogeneous catalyst and the nontoxic biomass-derived solvent γ-valerolactone (GVL) as a reaction medium. The developed method allows for excellent yields and C-2 selectivity to be achieved and tolerates various substituents on the indole scaffold. The established conditions ensure the stability of the catalyst as well as recoverability, reusability, and low metal leaching into the solution.
- Anastasiou, Ioannis,Van Velthoven, Niels,Tomarelli, Elena,Lombi, Aurora,Lanari, Daniela,Liu, Pei,Bals, Sara,De Vos, Dirk E.,Vaccaro, Luigi
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p. 2786 - 2791
(2020/03/24)
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- Room-temperature Pd/Ag direct arylation enabled by a radical pathway
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Direct arylation is an appealing method for preparing π-conjugated materials, avoiding the prefunctionalization required for traditional cross-coupling methods. A major effort in organic electronic materials development is improving the environmental and economic impact of production; direct arylation polymerization (DArP) is an effective method to achieve these goals. Room-temperature polymerization would further improve the cost and energy efficiencies required to prepare these materials. Reported herein is new mechanistic work studying the underlying mechanism of room temperature direct arylation between iodobenzene and indole. Results indicate that room-temperature, Pd/Ag-catalyzed direct arylation systems are radical-mediated. This is in contrast to the commonly proposed two-electron mechanisms for direct arylation and appears to extend to other substrates such as benzo[b]thiophene and pentafluorobenzene.
- Luscombe, Christine K.,Mayhugh, Amy L.
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supporting information
p. 384 - 390
(2020/03/27)
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- Room-Temperature Palladium(II)-Catalyzed Direct 2-Arylation of Indoles with Tetraarylstannanes
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A palladium(II)-catalyzed direct 2-arylation of indoles by tetraarylstannanes with oxygen (balloon) as the oxidant at room temperature has been developed. Various tetraarylstannanes can be employed as aryl sources for 2-arylation of indoles in up to 89% yield, providing a practical and efficient catalytic protocol for accessing 2-arylindoles.
- Liu, Yuxia,Wang, Chao,Huang, Linjuan,Xue, Dong
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supporting information
p. 1613 - 1618
(2020/09/15)
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- Selective Methylation of Amides, N-Heterocycles, Thiols, and Alcohols with Tetramethylammonium Fluoride
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We herein disclose the use of tetramethylammonium fluoride (TMAF) as a direct and selective methylating agent of a variety of amides, indoles, pyrroles, imidazoles, alcohols, and thiols. The method is characterized by operational simplicity, wide scope, and ease of purification. Our computational studies suggest a concerted methylation-deprotonation as the preferred reaction pathway.
- Cheng, Hong-Gang,Pu, Maoping,Kundu, Gourab,Schoenebeck, Franziska
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supporting information
p. 331 - 334
(2019/12/30)
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- A Three-Component Strategy for Benzoselenophene Synthesis under Metal-Free Conditions Using Selenium Powder
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An efficient three-component benzoselenophenes formation has been developed from substituted indoles, acetophenones, and selenium powder under metal-free conditions. 2-Aryl indoles played an important role to promote benzoselenophene formation from acetophenone derivatives and selenium powder. One C-C and two C-Se bonds were selectively formed to provide 40 new benzoselenophenes in good yields.
- Ni, Penghui,Tan, Jing,Zhao, Wenqi,Huang, Huawen,Xiao, Fuhong,Deng, Guo-Jun
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supporting information
p. 3518 - 3522
(2019/05/24)
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- Metal-Free Double Csp2-H Bond Functionalization: Strategy for Synthesizing Benzo[a]carbazoles from 2-Arylindoles and Acetophenones/Alkynes
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A metal-free strategy for the synthesis of benzocarbazoles from 2-arylindoles and aryl ketones is developed. Various 2-aryl-3-vinyl-indoles were generated in situ through dehydrative condensation of aryl ketones and indoles. These key intermediates could be selectively converted into the corresponding benzo[a]carbazoles via a direct cyclization process between two Csp2-H bonds. Furthermore, terminal alkynes also could be used as the versatile C2 source to afford the corresponding products in good yields.
- Ni, Penghui,Tan, Jing,Zhao, Wenqi,Huang, Huawen,Xiao, Fuhong,Deng, Guo-Jun
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supporting information
p. 3687 - 3691
(2019/05/24)
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- Synthesis of 3-Formylindoles via Electrochemical Decarboxylation of Glyoxylic Acid with an Amine as a Dual Function Organocatalyst
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A new method for 3-formalytion of indoles has been developed through electrochemical decarboxylation of glyoxylic acid with the amine as a dual function organocatalyst. The amine facilitated both the electrochemical decarboxylation and the nucleophilic reaction efficiently, whose loading can be as low as 1 mol %. This protocol has a broad range of functional group tolerance under ambient conditions. The gram-scale experiment has shown great potential in the synthetic application of this strategy.
- Lin, Dian-Zhao,Huang, Jing-Mei
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supporting information
p. 5862 - 5866
(2019/08/26)
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- Electrochemically Enabled C3-Formylation and -Acylation of Indoles with Aldehydes
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Reported herein is an effective strategy for oxidative cross-coupling of indoles with various aldehydes. The strategy is based on a two-step transformation via a well-known Mannich-type reaction and a C-N bond cleavage for carbonyl introduction. The key step - the C-N bond cleavage of the Mannich product - was enabled by electrochemistry. This strategy (with over 40 examples) ensures excellent functional-group tolerance as well as late-stage functionalization of pharmaceutical molecules.
- Yang, Liquan,Liu, Zhaoran,Li, Yujun,Lei, Ning,Shen, Yanling,Zheng, Ke
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supporting information
p. 7702 - 7707
(2019/10/19)
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- Photocatalytic Oxidative C-H Thiolation: Synthesis of Benzothiazoles and Sulfenylated Indoles
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We report studies on the photocatalytic formation of C-S bonds to form benzothiazoles via an intramolecular cyclization and sulfenylated indoles via an intermolecular reaction. Cyclic voltammetry (CV) and density functional theory studies suggest that benzothiazole formation proceeds via a mechanism that involves an electrophilic sulfur radical, while the indole sulfenylation likely proceeds via a nucleophilic sulfur radical adding into a radical cationic indole. These conditions were successfully extended to several thiobenzamides and indole substrates.
- Aceves, Ernesto Millan,Albright, Samuel T.,Cedano, Mario R.,Dinh, Andrew N.,Gustafson, Jeffrey L.,Nguyen, Ashley D.,Smith, Diane K.
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p. 1648 - 1655
(2019/08/26)
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- Tryptamine Synthesis by Iron Porphyrin Catalyzed C?H Functionalization of Indoles with Diazoacetonitrile
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The functionalization of C?H bonds with non-precious metal catalysts is an important research area for the development of efficient and sustainable processes. Herein, we describe the development of iron porphyrin catalyzed reactions of diazoacetonitrile with N-heterocycles yielding important precursors of tryptamines, along with experimental mechanistic studies and proof-of-concept studies of an enzymatic process with YfeX enzyme. By using readily available FeTPPCl, we achieved the highly efficient C?H functionalization of indole and indazole heterocycles. These transformations feature mild reaction conditions, excellent yields with broad functional group tolerance, can be conducted on gram scale, and thus provide a unique streamlined access to tryptamines.
- Hock, Katharina J.,Knorrscheidt, Anja,Hommelsheim, Renè,Ho, Junming,Weissenborn, Martin J.,Koenigs, Rene M.
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supporting information
p. 3630 - 3634
(2019/02/13)
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- Preparation method for indole compound
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The invention provides a preparation method for an indole compound, and belongs to the technical field of preparation of heterocyclic compounds. The preparation method comprises the following steps: with 1,2-dichloromethane as a solvent, silver oxide as a catalyst and 2-ethynylaniline and derivatives thereof as raw materials, subjecting the raw materials to a complete reaction at 10 to 60 DEG C inthe presence of p-toluenesulfonic acid monohydrate, carrying out spin-drying so as to obtain a crude product, and carrying out column chromatographic separation so as to obtain a fine product namelythe indole compound. The preparation method provided by the invention has the advantages of short preparation steps, mild reaction conditions, high product yield and low cost, and provides a universalnovel method for preparation of the indole compound.
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Paragraph 0035-0058
(2019/12/25)
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- Synthesis of 2-substituted indoles through cyclization and demethylation of 2-alkynyldimethylanilines by ethanol
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Herein, we demonstrated that 2-alkynyldimethylamines easily cyclize in EtOH according to a 5-endo-dig annulation into 2-substituted indoles without the aid of any additives or any metal catalysts to activate the triple bond. Thus, a variety of functionalized 2-styrylindoles, 2-arylindoles, 2-alkynylindoles, and 2-alkylindoles were prepared in high to excellent yields according to an environmentally friendly protocol. The mechanism has been explored to better understand this eco-friendly access to 2-substituted indoles and DFT calculations rationalized the role of the solvent in this N-annulation/dealkylation process.
- Zhao, Guangkuan,Roudaut, Christelle,Gandon, Vincent,Alami, Mouad,Provot, Olivier
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supporting information
p. 4204 - 4210
(2019/08/07)
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- Catalytic Tandem Friedel-Crafts Alkylation/C4-C3 Ring-Contraction Reaction: An Efficient Route for the Synthesis of Indolyl Cyclopropanecarbaldehydes and Ketones
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A general strategy for the synthesis of indolyl cyclopropanecarbaldehydes and ketones via a Br?nsted acid-catalyzed indole nucleophilic addition/ring-contraction reaction sequence has been exploited. The procedure leads to a wide panel of cyclopropyl carbonyl compounds in generally high yields with a broad substrate scope.
- Turnu, Francesca,Luridiana, Alberto,Cocco, Andrea,Porcu, Stefania,Frongia, Angelo,Sarais, Giorgia,Secci, Francesco
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supporting information
p. 7329 - 7332
(2019/10/02)
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- Nickel-Catalyzed Intramolecular Coupling of Sulfones via the Extrusion of Sulfur Dioxide
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We describe a method for intramolecular desulfonylative coupling using bis(cyclooctadiene)nickel as a catalyst. A broad range of aromatic, heteroaromatic and aliphatic sulfones can be utilized as substrates in this process. This method provides an atom-economical route to the synthesis of various biaryls and an efficient tool for the catalytic conversion of sulfonyl groups, representing a significant advancement in organic synthesis. (Figure presented.).
- Yu, Tian-Yang,Zheng, Zhao-Jing,Bai, Jing-Hua,Fang, Hong,Wei, Hao
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p. 2020 - 2024
(2019/03/26)
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- Mechanochemical Pd(II)-Catalyzed Direct and C-2-Selective Arylation of Indoles
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A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as the catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electron-rich and electron-deficient substituents both in indoles and iodoarenes. Arylation is possible in both unprotected indoles and N-protected indoles with the electron-donating group with the former substrate being relatively slower to react and little less yielding. Indoles with a deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in the gram scale. In general, the reactions were achieved in a shorter time than the conventional methods.
- Das, Dharmendra,Bhutia, Zigmee T.,Chatterjee, Amrita,Banerjee, Mainak
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p. 10764 - 10774
(2019/09/09)
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- Nickel-catalyzed reductive defunctionalization of esters in the absence of an external reductant: Activation of C-O bonds
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The nickel-catalyzed reductive cleavage of esters in the absence of an external reductant, which involves the cleavage of an inert acyl C-O bond in O-Alkyl esters is reported. Various groups, such as N-containing heterocycles, esters, amides, and even arene rings can function as a directing group.
- Iyori, Yasuaki,Takahashi, Kenjiro,Yamazaki, Ken,Ano, Yusuke,Chatani, Naoto
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supporting information
p. 13610 - 13613
(2019/11/14)
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- Transition-Metal-Free Synthesis of 1,2-Disubstituted Indoles
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Herein, we report a new transition-metal-free robust and cost-effective method for synthesis of 1,2-disubstituted indoles from easily available unactivated (i.e. without EWG, PPh3 or SiR3 groups) tertiary amides. Scope of synthetic applicability of the presented protocol was shown on 23 examples of 1,2-disubstituted indoles with different substitution patterns obtained in good to excellent yields. The reported method turned out to be especially effective for synthesis of N-arylated 2-CF3-indoles. Moreover, this approach can be performed in a one-pot two-step manner directly from commercially available secondary amines. Mechanistic studies showed that acyl transfer might be an important step in the course of the reaction. Viability of the presented approach for benzofurans and benzothiophenes synthesis was also discussed.
- Chesnokov, Gleb A.,Ageshina, Alexandra A.,Topchiy, Maxim A.,Nechaev, Mikhail S.,Asachenko, Andrey F.
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p. 4844 - 4854
(2019/08/01)
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- The controllable C2 arylation and C3 diazenylation of indoles with aryltriazenes under ambient conditions
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An efficient and regio-divergent method for both the C2 arylation and C3 diazenylation of C2,C3-unsubstituted indoles with aryltriazenes was developed. At room temperature, both reactions were carried out with HPF6/ionic liquids (ILs) as the promoter. The C2 arylation and C3 diazenylation activated by HPF6/ILs show remarkable reactivity, which results in corresponding products with yields of up to 99%. Notably, the practicality of the protocol was further demonstrated via gram-scale operations, late-stage modification and the reusability of the ILs.
- Liu, Yonghong,Ma, Xia,Wu, Gengxin,Liu, Ziran,Yang, Xiang,Wang, Bin,Liu, Chenjiang,Zhang, Yonghong,Huang, Yan
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supporting information
p. 9255 - 9259
(2019/06/17)
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- Pd-nanoparticles catalyzed denitrogenative coupling of aryl halides with arylhydrazines: Greener approach for biaryls synthesis under ligand-free condition
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The greener approach for the synthesis of biaryl using palladium nanoparticle (Pd–NPs) catalyzed denitrogenative coupling between aryl hydrazine and aryl halides under ligand-free condition has been described. The phytochemicals of the black pepper extract plays a dual role in reduction of PdII to Pd0 and acts as stabilizing agent for Pd–NPs. The electronically diver's arylhydrazines and commercially available aryl halides are used for the synthesis of symmetrical and unsymmetrical biaryls in good to excellent yield. The mechanism is well supported by control experiment and the recyclability, turnover number and turnover frequency of biogenically synthesized Pd–NPs is studied.
- Hegde, Rajeev V.,Ghosh, Arnab,Patil, Siddappa A.,Dateer, Ramesh B.
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supporting information
(2019/12/09)
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- Thioether-Directed Selective C4 C-H Alkenylation of Indoles under Rhodium Catalysis
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A thioether-directed Rh(III)-catalyzed C4 selective C-H alkenylation of indoles via the formation of 5-membered metallacycle intermediates is reported. This protocol allows a wide functional group compatibility and broad substrate scope. The directing group can be readily removed or transformed into other functional groups after the C-H functionalization event. The catalytic method is also applicable to related heterocyclic systems involving benzo[b]thiophene and benzo[b]furan scaffolds.
- Kona, Chandrababu Naidu,Nishii, Yuji,Miura, Masahiro
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supporting information
p. 4898 - 4901
(2018/08/24)
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- Abnormal NHC supported palladacycles: Regioselective arylation of heteroarenes via decarboxylation
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We report synthesis of two new palladium(II) complexes of abnormal N-heterocyclic carbene ligands. The catalytic activity of these palladium(II) complexes was examined for the decarboxylative arylation of N-methylindole-carboxylic acids. An exclusive regioselectivity and very good yields were obtained with a variety of aryl halide partners.
- Jose, Anex,Vijaykumar, Gonela,Vardhanapu, Pavan K.,Mandal, Swadhin K.
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- Mechanistic Study of Direct Arylation of Indole Using Differential Selectivity Measurements: Shedding Light on the Active Species and Revealing the Key Role of Electrophilic Substitution in the Catalytic Cycle
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Differential selectivity of the direct arylation of indole with aryl halides under competing and noncompeting conditions with a varying set of reaction parameters was determined using phase trajectories. The results described herein allow for conclusions to be drawn regarding the character of active complexes (cationic, neutral, or anionic) as well as realization of the indole electrophilic substitution in the catalytic cycle using the ligand-free catalytic system.
- Kurokhtina, Anna A.,Larina, Elizaveta V.,Yarosh, Elena V.,Lagoda, Nadezhda A.,Schmidt, Alexander F.
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supporting information
p. 2054 - 2063
(2018/07/25)
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- Arylation synthesis method for novel five-membered aromatic heterocycle and aromatic-ring five-membered aromatic heterocycle
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The invention belongs to the technical field of organic synthesis and in particular relates to an arylation synthesis method for a five-membered aromatic heterocycle or an aromatic-ring five-memberedaromatic heterocycle under the participation of an arylhydrazine derivative serving as a novel arylation reagent. The method comprises the steps: adding a raw material and aroyl hydrazine into a reactor, and carrying out a reaction at 60-100 DEG C for 8-24h under the condition that an oxidant and a transition metal catalyst are added; after the reaction is ended, carrying out suction filtration, extracting a filtrate by using ethyl acetate, carrying out drying to obtain a crude product of a target compound, and carrying out column chromatography on silica gel to obtain a pure product of the target compound. The arylation synthesis method for the five-membered aromatic heterocycle or the aromatic-ring five-membered aromatic heterocycle is scientific and reasonable and has the advantages such as simplicity and convenience in operation, relatively high yield and simplicity in amplification and purification.
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Paragraph 0112-0115; 0224-0227
(2018/07/07)
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- Exploration of Biaryl Carboxylic Acids as Proton Shuttles for the Selective Functionalization of Indole C-H Bonds
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A survey of diversely substituted 2-arylbenzoic acids were synthesized and tested for use as proton shuttle in the direct arylation of indoles with bromobenzenes. It was found that 3-ethoxy-2-phenylbenzoic acid gives superior yield and selectivity for this class of substrates.
- Pi, Jing-Jing,Lu, Xiao-Yu,Liu, Jing-Hui,Lu, Xi,Xiao, Bin,Fu, Yao,Guimond, Nicolas
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p. 5791 - 5800
(2018/05/14)
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- Denitrogenative palladium-catalyzed coupling of aryl halides with arylhydrazines under mild conditions
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The development of a method for the Pd(ii)-catalyzed denitrogenative coupling of arylhydrazines to give functionalized biaryls in good yield, using aryl bromides or aryl iodides as convenient and inexpensive aryl sources, is reported. High functional group tolerance is demonstrated for electronically distinct arylhydrazines as well as aryl halides. The desired products were isolated in good to excellent yields for 58 examples. Control experiments and mechanism studies revealed that the transformation undergoes a base-promoted Pd-catalyzed process.
- Chang, Sheng,Dong, Lin Lin,Song, Hai Qing,Feng, Bo
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supporting information
p. 3282 - 3288
(2018/05/15)
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- Atom Efficient Magnesiation of N-Substituted Alkyl Indoles with a Mixed Sodium-Magnesium Base
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This study presents the alkali metal mediated magnesiation (AMMMg) of three N-alkylated indoles with the mixed Na/Mg base [(TMEDA)Na(TMP)2Mg(CH2SiMe3)] 1 (TMEDA = N,N,N′,N′-tetramethylethylenediamine, TMP = 2,2,6,6-tetramethylpiperidine). All three magnesiated indoles have been successfully characterised by single-crystal X-ray diffraction and solution state NMR studies, whereas iodolysis and Pd-catalysed cross coupling have been investigated. The steric nature of the N-alkyl group changes the reactivity and efficiency of 1 to give either atom efficient disodium tetraindol-2-ylmagnesiates [(Na-TMEDA)2Mg(α-C9H8N)4] 2 and [(Na-TMEDA)2Mg(α-C10H11N)4] 3, or [(TMEDA)Na(TMP)(α-C11H12N)Mg(TMP)] 4, whereby only one indole molecule is selectively deprotonated.
- Stevens, Michael A.,Blair, Victoria L.
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- Isocyanide-Induced Activation of Copper Sulfate: Direct Access to Functionalized Heteroarene Sulfonic Esters
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A novel and direct approach to alkyl/aryl heteroarene sulfonic esters using copper sulfate as the environmentally benign inorganic sulfonation reagent was first realized with the aid of isocyanide. A variety of heterocycles reacted to afford the corresponding sulfonic esters through C?H functionalization. In this transformation, the otherwise inert copper sulfate was unusually activated by an isocyanide and employed as the source of the sulfonic substituents in an unprecedented fashion. The findings suggest that an appropriate activator may liberate the chemical activities of some relatively inert inorganic salts for organic synthesis.
- Hong, Xiaohu,Tan, Qitao,Liu, Bingxin,Xu, Bin
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supporting information
p. 3961 - 3965
(2017/03/27)
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- Copper-mediated trifluoroacetylation of indoles with ethyl trifluoropyruvate
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Direct trifluoroacetylation of indoles with ethyl trifluoropyruvate as a trifluoroacetylating reagent has been developed. This novel protocol provides an attractive route for the preparation of 3-trifluoroacetylindole derivatives, due to its operational simplicity and practicability as well as mild reaction conditions.
- Yan, Guobing,Cao, Xihan,Zheng, Wanbin,Ke, Qiumin,Zhang, Jieyu,Huang, Dayun
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supporting information
p. 5904 - 5907
(2017/07/25)
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- Mild and selective base-free C-H arylation of heteroarenes: experiment and computation
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A mild and selective C-H arylation strategy for indoles, benzofurans and benzothiophenes is described. The arylation method engages aryldiazonium salts as arylating reagents in equimolar amounts. The protocol is operationally simple, base free, moisture tolerant and air tolerant. It utilizes low palladium loadings (0.5 to 2.0 mol% Pd), short reaction times, green solvents (EtOAc/2-MeTHF or MeOH) and is carried out at room temperature, providing a broad substrate scope (47 examples) and excellent selectivity (C-2 arylation for indoles and benzofurans, C-3 arylation for benzothiophenes). Mechanistic experiments and DFT calculations support a Heck-Matsuda type coupling mechanism.
- Gemoets, Hannes P. L.,Kalvet, Indrek,Nyuchev, Alexander V.,Erdmann, Nico,Hessel, Volker,Schoenebeck, Franziska,No?l, Timothy
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p. 1046 - 1055
(2017/02/10)
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- A Novel and Chemoselective Process of N -Alkylation of Aromatic Nitrogen Compounds Using Quaternary Ammonium Salts as Starting Material
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The process of N-alkylation of several pyrroles, indoles, and derivative heterocycles is herein described, using quaternary ammonium salts as the source of an alkylating agent. These reactions were carried out on several heterocyclic rings with triethylbenzylammonium chloride or tetradecyltrimethylammonium bromide and an NaOH solution at 50%, leading to a chemoselective N-alkylated product and an average yield of 73%. This is an alternative process to the traditional benzylation and methylation of N-heterocycles with direct handling of alkyl halides.
- González-González, Carlos A.,Vega, Juan Javier Mejía,Monroy, Ricardo García,González-Calderón, Davir,Corona-Becerril, David,Fuentes-Benítes, Aydeé,Mascarúa, Joaquín Tamariz,González-Romero, Carlos
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- Structure-activity relationships and docking studies of synthetic 2-arylindole derivatives determined with aromatase and quinone reductase 1
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In our ongoing effort of discovering anticancer and chemopreventive agents, a series of 2-arylindole derivatives were synthesized and evaluated toward aromatase and quinone reductase 1 (QR1). Biological evaluation revealed that several compounds (e.g., 2d, IC50 = 1.61 μM; 21, IC50 = 3.05 μM; and 27, IC50 = 3.34 μM) showed aromatase inhibitory activity with half maximal inhibitory concentration (IC50) values in the low micromolar concentrations. With regard to the QR1 induction activity, 11 exhibited the highest QR1 induction ratio (IR) with a low concentration to double activity (CD) value (IR = 8.34, CD = 2.75 μM), while 7 showed the most potent CD value of 1.12 μM. A dual acting compound 24 showed aromatase inhibition (IC50 = 9.00 μM) as well as QR1 induction (CD = 5.76 μM) activities. Computational docking studies using CDOCKER (Discovery Studio 3.5) provided insight in regard to the potential binding modes of 2-arylindoles within the aromatase active site. Predominantly, the 2-arylindoles preferred binding with the 2-aryl group toward a small hydrophobic pocket within the active site. The C-5 electron withdrawing group on indole was predicted to have an important role and formed a hydrogen bond with Ser478 (OH). Alternatively, meta-pyridyl analogs may orient with the pyridyl 3′-nitrogen coordinating with the heme group.
- Prior, Allan M.,Yu, Xufen,Park, Eun-Jung,Kondratyuk, Tamara P.,Lin, Yan,Pezzuto, John M.,Sun, Dianqing
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p. 5393 - 5399
(2017/11/20)
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- Palladium-catalyzed tandem addition/cyclization in aqueous medium: Synthesis of 2-arylindoles
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An efficient protocol to construct 2-arylindoles was developed through palladium-catalyzed tandem addition/cyclization of potassium aryltrifluoroborates with aliphatic nitriles in aqueous medium. The use of water as the reaction medium makes the synthesis process environmentally benign. A plausible mechanism for the formation of 2-arylindoles involving sequential nucleophilic addition followed by an intramolecular cyclization is proposed. Moreover, the utility of this catalytic tandem transformation was also demonstrated in an efficient gram-scale synthesis. This method provides an alternative synthetic tool for accessing a more diverse array of 2-arylindoles.
- Yu, Shuling,Hu, Kun,Gong, Julin,Qi, Linjun,Zhu, Jianghe,Zhang, Yetong,Cheng, Tianxing,Chen, Jiuxi
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p. 4300 - 4307
(2017/07/10)
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- Catalytic Access to Indole-Fused Benzosiloles by 2-Fold Electrophilic C-H Silylation with Dihydrosilanes
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A protocol for the catalytic synthesis of indole-fused benzosiloles starting from 2-aryl-substituted indoles and dihydrosilanes is reported. Compared to known procedures, this method does not require prefunctionalized starting materials and, hence, allows for a rapid access to those siloles. The net reaction is a 2-fold electrophilic C-H silylation catalyzed by cationic Ru-S complexes. Both reaction steps were separately investigated, and these results eventually led to the development of a two-step procedure. By preparing new Ru-S complexes with different weakly coordinating anions (WCAs), it is also shown that the latter can have a dramatic influence on the outcome of these reactions. Furthermore, the substrate scope of the new method is discussed.
- Omann, Lukas,Oestreich, Martin
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p. 767 - 776
(2017/04/21)
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- Synthesis and preliminary evaluation of 3-thiocyanato-1H-indoles as potential anticancer agents
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A novel series of twenty 3-thiocyanato-1H-indoles, carrying diversification at positions N-1, C-2 and C-5 of the heterocyclic core, were synthesized; their antiproliferative activity against four human cancer cell lines (HL60, HEP-2, NCI-H292 and MCF-7) was evaluated, employing doxorubicin as positive control. Indole, N-methylindole and 2-(4-chlorophenyl)-N-methylindole demonstrated to be essentially inactive, whereas several of their congener 3-thiocyanato-1H-indoles displayed good to excellent levels of potency (IC50 ≤ 6 μM), while being non-hemolytic. N-Phenyl-3-thiocyanato-1H-indole and 1-methyl-2-(4-chlorophenyl)-3-thiocyanato-1H-indole showed good to high potency against all the cell lines. On the other side, the N-(4-chlorophenyl)-, 2-(4-chlorophenyl)- and 2-phenyl- 3-thiocyanato-1H-indole derivatives were slightly less active against the test cell lines. Overall, these results suggest that the indole-3-thiocyanate motif can be suitably decorated to afford highly cytotoxic compounds and that the substituted indole can be employed as a useful scaffold toward more potent compounds.
- Fortes, Margiani P.,Da Silva, Paulo B.N.,Da Silva, Teresinha G.,Kaufman, Teodoro S.,Milit?o, Gardenia C.G.,Silveira, Claudio C.
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supporting information
p. 21 - 26
(2016/05/10)
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- Electronic Nature of Ketone Directing Group as a Key to Control C-2 vs C-4 Alkenylation of Indoles
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A novel mode of achieving site selectivity between C-2 and C-4 positions in the indole framework by altering the property of the ketone directing group is disclosed. Methyl ketone, as directing group, furnishes exclusively C-2 alkenylated product, whereas trifluoromethyl ketone changes the selectivity to C-4, indicating that the electronic nature of the directing group controls the unusual choice between a 5-membered and a 6-membered metallacycle. The screening of other carbonyl-derived directing groups reveals that strong and weak directing groups exhibit opposite selectivity. Experimental controls and deuteration experiments lend support to the proposed mechanism.
- Lanke, Veeranjaneyulu,Bettadapur, Kiran R.,Prabhu, Kandikere Ramaiah
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supporting information
p. 5496 - 5499
(2016/11/17)
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