- Chemoselective deprotection of allylic amines catalyzed by Grubbs' carbene
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A commercially available ruthenium complex (first generation Grubbs' carbene) was used for the catalytic deprotection of allylic amines (secondary as well as tertiary), by using for the first time reagents different from palladium catalysts. Interestingly, the catalytic system directs the reaction toward the selective deprotection of allylamines in the presence of allylic ethers.
- Alcaide, Benito,Almendros, Pedro,Alonso, Jose M.,Luna, Amparo
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- Ga(DS)3-catalysed double hydroarylation of acetylenic esters with indoles for the synthesis of bisindolyl propanoates
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Abstract An efficient synthetic method for bisindolyl propanoates has been developed. Ga(DS)3-catalysed double hydroarylation of acetylenic esters with indoles in water afforded regioselective products with up to 99% yield.
- An, Li-Tao,Cai, Jing-Jing,Pan, Xiang-Qiang,Chen, Tang-Ming,Zou, Jian-Ping,Zhang, Wei
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- CO2-Catalyzed Efficient Dehydrogenation of Amines with Detailed Mechanistic and Kinetic Studies
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CO2-catalyzed dehydrogenation of amines has been achieved under photocatalytic conditions. With this concept, various amines have been selectively dehydrogenated to the corresponding imines in the presence of different functional groups such as nitrile, nitro, ester, halogen, ether, thioether, and carbonyl or carboxylic acid moieties. At the end, the CO2-catalyzed synthesis of pharmaceutical drugs has been achieved. The CO2 radical has been detected by EPR spectroscopy using DMPO, and the mechanism of this reaction is proposed on the basis of DFT calculations and experimental evidence.
- Riemer, Daniel,Schilling, Waldemar,Goetz, Anne,Zhang, Yu,Gehrke, Sascha,Tkach, Igor,Hollóczki, Oldamur,Das, Shoubhik
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- Novel Arylindigoids by Late-Stage Derivatization of Biocatalytically Synthesized Dibromoindigo
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Indigoids represent natural product-based compounds applicable as organic semiconductors and photoresponsive materials. Yet modified indigo derivatives are difficult to access by chemical synthesis. A biocatalytic approach applying several consecutive selective C?H functionalizations was developed that selectively provides access to various indigoids: Enzymatic halogenation of l-tryptophan followed by indole generation with tryptophanase yields 5-, 6- and 7-bromoindoles. Subsequent hydroxylation using a flavin monooxygenase furnishes dibromoindigo that is derivatized by acylation. This four-step one-pot cascade gives dibromoindigo in good isolated yields. Moreover, the halogen substituent allows for late-stage diversification by cross-coupling directly performed in the crude mixture, thus enabling synthesis of a small set of 6,6’-diarylindigo derivatives. This chemoenzymatic approach provides a modular platform towards novel indigoids with attractive spectral properties.
- Schnepel, Christian,Dodero, Veronica I.,Sewald, Norbert
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- Hydrophobic Metal Halide Perovskites for Visible-Light Photoredox C?C Bond Cleavage and Dehydrogenation Catalysis
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Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Owing to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline-2-carboxylic acids. (HDA)2PbI4 or (HDA)2SnI4 were investigated as photoredox catalysts for these reactions, and quantitative conversion and high yields were observed with the former.
- Hong, Zonghan,Chong, Wee Kiang,Ng, Andrew Yun Ru,Li, Mingjie,Ganguly, Rakesh,Sum, Tze Chien,Soo, Han Sen
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- DMSO/t-BuONa/O2-Mediated Aerobic Dehydrogenation of Saturated N-Heterocycles
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Aromatic N-heterocycles such as quinolines, isoquinolines, and indolines are synthesized via sodium tert-butoxide-promoted oxidative dehydrogenation of the saturated heterocycles in DMSO solution. This reaction proceeds under mild reaction conditions and has a good functional group tolerance. Mechanistic studies suggest a radical pathway involving hydrogen abstraction of dimsyl radicals from the N-H bond or α-C-H of the substrates and subsequent oxidation of the nitrogen or α-aminoalkyl radicals.
- Cai, Hu,Tan, Wei,Xie, Yongfa,Yang, Ruchun,Yue, Shusheng
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- A new and efficient one-pot synthesis of indoles
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The synthesis of indoles is accomplished in high yields from phenylhydrazines and pyruvic acid using microwave irradiation.
- Bratulescu, George
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- Aerobic oxidative dehydrogenation of N-heterocycles over OMS-2-based nanocomposite catalysts: Preparation, characterization and kinetic study
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OMS-2-based nanocomposites doped with tungsten were prepared for the first time and their remarkably enhanced catalytic activity and recyclability in aerobic oxidative dehydrogenation of N-heterocycles were examined in detail. Many tetrahydroquinoline derivatives and a broad range of other N-heterocycles could be tolerated by the catalytic system using a biomass-derived solvent as a reaction medium. Newly generated mixed crystal phases, noticeably enhanced surface areas and labile lattice oxygen of the OMS-2-based nanocomposite catalysts might contribute to their excellent catalytic performance. Moreover, a kinetic study was extensively performed which concluded that the dehydrogenation of 1,2,3,4-tetrahydroquinoline is a first-order reaction, and the apparent activation energy is 29.66 kJ mol-1
- Bi, Xiuru,Tang, Tao,Meng, Xu,Gou, Mingxia,Liu, Xiang,Zhao, Peiqing
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- Dehydrogenation of indoline by cytochrome P450 enzymes: A novel "aromatase" process
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Indoline derivatives possess therapeutic potential within a variety of drug candidates. In this study, we found that indoline is aromatized by cytochrome P450 (P450) enzymes to produce indole through a novel dehydrogenation pathway. The indole products can potentially be bioactivated to toxic intermediates through an additional dehydrogenation step. For example, 3-substituted indoles like 3-methylindole and zafirlukast [4-(5-cyclopentyloxy-carbonylamino-1-methyl- indol-3-ylmethyl)-3-methoxy-N-o-tolylsulfonylbenzamide] are dehydrogenated to form 3-methyleneindolenine electrophiles, which react with protein and/or DNA nucleophilic residues to cause toxicities. Another potentially significant therapeutic consequence of indoline aromatization is that the product indoles might have dramatically different therapeutic potency than the parent indolines. In this study, indoline was indeed efficiently aromatized by human liver microsomes and by several P450s, but not by flavin-containing monooxygenase (FMO) 3. CYP3A4 had the highest aromatase activity. Four additional indoline metabolites [2,3,4,7-tetrahydro-4,5-epoxy-1H-indole (M1); N-hydroxyindole (M2), N-hydroxyindoline (M3), and M4 ([1,4,2,5]dioxadiazino[2,3-a:5,6-a′] diindole)] were characterized; none was a metabolite of indole. M1 was an arene oxide from P450 oxidation, and M2, M3, and M4 were produced by FMO3. Our data indicated that indoline was oxidized to M3 and then to an intermediate indoline nitrone, which tautomerized to form M2, and subsequently dimerized to a di-indoline. This dimer was immediately oxidized by FMO3 or atmospheric oxygen to the final product, M4. No evidence was found for the P450-mediated production of an aliphatic alcohol from indoline that might dehydrate to produce indole. Therefore, P450 enzymes catalyze the novel "aromatase" metabolism of indoline to produce indole. The aromatase mechanism does not seem to occur through N-oxidation or dehydration of an alcohol but rather through a formal dehydrogenation pathway. Copyright
- Sun, Hao,Ehlhardt, William J.,Kulanthaivel, Palaniappan,Lanza, Diane L.,Reilly, Christopher A.,Yost, Garold S.
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- Two-Dimensional Metal-Organic Layers for Electrochemical Acceptorless Dehydrogenation of N-Heterocycles
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The catalytic acceptorless dehydrogenation (CAD) is an attractive synthetic route to unsaturated compounds because of its high atomic efficiency. Here we report electrochemical acceptorless dehydrogenation of N-heterocycles to obtain quinoline or indole derivatives using metal-organic layer (MOL) catalyst. MOL is the two-dimensional version of metal-organic frameworks (MOF), and it can be constructed on conductive multi-walled carbon nanotubes via facile solvothermal synthesis to overcome the conductivity constraint for MOFs in electrocatalysis. TEMPO-OPO3 2? was incorporated into the system through a ligand exchange with capping formate on the MOL surface to serve as the active catalytic centers. The hybrid catalyst is efficient in the organic conversion and can be readily recycled and reused.
- Yang, Ling,Ma, Fa-Xue,Xu, Fan,Li, Dong,Su, Liangmei,Xu, Hai-Chao,Wang, Cheng
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- Synthesis of bromoindole alkaloids from Laurencia brongniartii
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A regioselective synthesis of N-carbomethoxy-2,3,5-tribromoindole (6) via a sequential one-pot bromination-aromatization-bromination of N-carbomethoxyindoline (2) is described. The process for the transformation of 2 into 6 permitted the isolation of stable reaction intermediates N-carbomethoxy-5-bromoindoline (3), N-carbomethoxy-5-bromoindole (4), and N-carbomethoxy-3,5-dibromoindole (5). Compound 6 was used to complete the total synthesis of the natural products 1b and 1c. In addition, bromination of N-carbomethoxyindole (11) afforded N-carbomethoxy-2,3,6-tribromoindole (13), from which the natural product 1a was synthesized.
- Suarez-Castillo, Oscar R.,Beiza-Granados, Lidia,Melendez-Rodriguez, Myriam,Alvarez-Hernandez, Alejandro,Morales-Rios, Martha S.,Joseph-Nathan, Pedro
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- Simple and selective removal of the t-butyloxycarbonyl (Boc) protecting group on indoles, pyrroles, indazoles, and carbolines
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A highly selective and efficient deprotection of the N-t-butoxy carbonyl (N-Boc) group on indoles, pyrroles, indazoles, and carbolines has been achieved in high yields using a catalytic amount of NaOMe as a base in dry MeOH, at ambient temperature. Copyright Taylor & Francis Group, LLC.
- Ravinder,Reddy, A. Vijender,Mahesh, K. Chinni,Narasimhulu,Venkateswarlu
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- Luminescent Platinum(II) Complexes with Bidentate Diacetylide Ligands: Structures, Photophysical Properties and Application Studies
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A series of platinum(II) complexes supported by terphenyl diacetylide as well as diimine or bis-N-heterocyclic carbene (NHC) ligands have been prepared. The diacetylide ligands adopt a cis coordination mode featuring non-planar terphenyl moieties as revealed by X-ray crystallographic analyses. The electrochemical, photophysical and photochemical properties of these platinum(II) complexes have been investigated. These platinum(II) diimine complexes show broad emission with peak maxima from 566 nm to 706 nm, with two of them having emission quantum yields >60% and lifetimes 2 μs in solutions at room temperature, whereas the platinum(II) diacetylide complexes having bis-N-heterocyclic carbene instead of diimine ligand display photoluminescence with quantum yields of up to 28% in solutions and excited state lifetimes of up to 62 μs at room temperature. Application studies revealed that one of the complexes can catalyze photoinduced aerobic dehydrogenation of alcohols and alkenes, and a relatively non-toxic water-soluble Pt(II) complex displays anti-angiogenic activity.
- Luo, Zaoli,Liu, Yungen,Tong, Ka-Chung,Chang, Xiao-Yong,To, Wai-Pong,Che, Chi-Ming
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- From Tryptophan to Toxin: Nature's Convergent Biosynthetic Strategy to Aetokthonotoxin
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Aetokthonotoxin (AETX) is a cyanobacterial neurotoxin that causes vacuolar myelinopathy, a neurological disease that is particularly deadly to bald eagles in the United States. The recently characterized AETX is structurally unique among cyanotoxins and is composed of a pentabrominated biindole nitrile. Herein we report the discovery of an efficient, five-enzyme biosynthetic pathway that the freshwater cyanobacterium Aetokthonos hydrillicola uses to convert two molecules of tryptophan to AETX. We demonstrate that the biosynthetic pathway follows a convergent route in which two functionalized indole monomers are assembled and then reunited by biaryl coupling catalyzed by the cytochrome P450 AetB. Our results revealed enzymes with novel biochemical functions, including the single-component flavin-dependent tryptophan halogenase AetF and the iron-dependent nitrile synthase AetD.
- Adak, Sanjoy,Lukowski, April L.,Sch?fer, Rebecca J. B.,Moore, Bradley S.
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supporting information
p. 2861 - 2866
(2022/02/23)
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- Ruthenium-Catalyzed Vinylene Carbonate Annulation by C?H/N?H Functionalizations: Step-Economical Access to Indoles
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A convenient and effective method of ruthenium-catalyzed C?H/N?H annulations using vinylene carbonate as oxidizing acetylene surrogate has been disclosed. This method is scalable and compatible with a wide range of functional groups, providing a step-economical access to indole synthesis Preliminary mechanistic studies provided support for a reversible, acetate-assisted C?H ruthenation, along with a subsequent olefin insertion. (Figure presented.).
- Li, Bo,Li, Zheyu,Ma, Wenbo,Tan, Yuqiang,Wang, Yang,Yu, Yao,Zhang, Chunran,Zhao, Huan
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- Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis
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We report the design of a bifunctional metal–organic layer (MOL), Hf12-Ru-Co, composed of [Ru(DBB)(bpy)2]2+ [DBB-Ru, DBB=4,4′-di(4-benzoato)-2,2′-bipyridine; bpy=2,2′-bipyridine] connecting ligand as a photosensitizer and Co(dmgH)2(PPA)Cl (PPA-Co, dmgH=dimethylglyoxime; PPA=4-pyridinepropionic acid) on the Hf12 secondary building unit (SBU) as a hydrogen-transfer catalyst. Hf12-Ru-Co efficiently catalyzed acceptorless dehydrogenation of indolines and tetrahydroquinolines to afford indoles and quinolones. We extended this strategy to prepare Hf12-Ru-Co-OTf MOL with a [Ru(DBB)(bpy)2]2+ photosensitizer and Hf12 SBU capped with triflate as strong Lewis acids and PPA-Co as a hydrogen transfer catalyst. With three synergistic active sites, Hf12-Ru-Co-OTf competently catalyzed dehydrogenative tandem transformations of indolines with alkenes or aldehydes to afford 3-alkylindoles and bisindolylmethanes with turnover numbers of up to 500 and 460, respectively, illustrating the potential use of MOLs in constructing novel multifunctional heterogeneous catalysts.
- Quan, Yangjian,Lan, Guangxu,Shi, Wenjie,Xu, Ziwan,Fan, Yingjie,You, Eric,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
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supporting information
p. 3115 - 3120
(2020/12/09)
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- Visible light mediated selective oxidation of alcohols and oxidative dehydrogenation of N-heterocycles using scalable and reusable La-doped NiWO4nanoparticles
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Visible light-mediated selective and efficient oxidation of various primary/secondary benzyl alcohols to aldehydes/ketones and oxidative dehydrogenation (ODH) of partially saturated heterocycles using a scalable and reusable heterogeneous photoredox catalyst in aqueous medium are described. A systematic study led to a selective synthesis of aldehydes under an argon atmosphere while the ODH of partially saturated heterocycles under an oxygen atmosphere resulted in very good to excellent yields. The methodology is atom economical and exhibits excellent tolerance towards various functional groups, and broad substrate scope. Furthermore, a one-pot procedure was developed for the sequential oxidation of benzyl alcohols and heteroaryl carbinols followed by the Pictet-Spengler cyclization and then aromatization to obtain the β-carbolines in high isolated yields. This methodology was found to be suitable for scale up and reusability. To the best of our knowledge, this is the first report on the oxidation of structurally diverse aryl carbinols and ODH of partially saturated N-heterocycles using a recyclable and heterogeneous photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Balasubramaniam, K. K.,Baskar, B.,Divya, P.,Mani Rahulan, K.,Rahman, Abdul,Sridhar, R.,Srinath, S.
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p. 5990 - 6007
(2021/08/24)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of N-Heterocycles
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Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.
- Manna, Srimanta,Kong, Wei-Jun,B?ckvall, Jan-E.
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supporting information
p. 13725 - 13729
(2021/09/08)
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- Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.
- Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
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supporting information
p. 7290 - 7296
(2021/03/01)
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- Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
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An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
- Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1611 - 1615
(2021/03/03)
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- Method for catalytically synthesizing indole derivative by using ferrous complex
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The invention relates to a method for catalytically synthesizing an indole derivative by using a ferrous complex, which comprises the following step: by taking arylamine and acetaldehyde as raw materials and a ferrous complex containing a meta-carboboryl methylpyridine structure as a catalyst, conducting reacting at room temperature to prepare the indole derivative. Compared with the prior art, the method utilizes the ferrous complex to efficiently catalyze the reaction of arylamine and acetaldehyde at room temperature to prepare the indole derivative, the reaction condition is mild, the substrate range is wide, and the method has high catalytic activity and yield.
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Paragraph 0041-0044
(2021/07/31)
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- Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5240 - 5245
(2020/07/03)
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- Visible-Light-Promoted Efficient Aerobic Dehydrogenation of N-Heterocycles by a Tiny Organic Semiconductor Under Ambient Conditions
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An efficient reusable catalytic system has been developed based on perylene diimide (PDI) organic semiconductor for the aerobic dehydrogenation of N-heterocycles with visible light. This practical catalytic system without any additives proceeds under ambient conditions. The minute aggregates of PDI molecules on the surface of SiO2 nanospheres form tiny organic semiconductors, resulting in high-efficiency photo-oxidative activity. Notably, the robustness of this method is demonstrated by the synthesis of a wide range of N-heteroarenes, gram-scale experiments as well as reusability tests.
- Su, Chenliang,Yu, Kunyi,Zhang, Hanjie,Zhu, Yongfa
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supporting information
p. 1956 - 1960
(2020/04/10)
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- Reusable, homogeneous water soluble photoredox catalyzed oxidative dehydrogenation of N-heterocycles in a biphasic system: Application to the synthesis of biologically active natural products
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Herein, a simple and efficient method for the oxidative dehydrogenation (ODH) of tetrahydro-β-carbolines, indolines and tetrahydro-(iso)quinolines is described using a reusable, homogeneous cobalt-phthalocyanine photoredox catalyst in a biphasic medium. A biphasic system offers an advantage of easy separation of the product and an efficient reusability of the homogeneous photoredox catalyst. Also, the current system significantly helps to overcome the solubility issue of the substrate and catalyst at room temperature. Its potential applications to organic transformations are demonstrated by the synthesis of various biologically active N-heterocycles such as indoles, (iso)quinolines and β-carbolines and natural products such as eudistomin U, norharmane, and harmane and precursors to perlolyrine and flazin. Without isolation and purification, the catalyst solution can be reused up to 5 times with almost comparable reactivity. Furthermore, the efficiency of the reaction was demonstrated on a gram scale. To the best of our knowledge, this is the first report on ODH reactions using a non noble, reusable and homogeneous cobalt photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Baskar, B.,Mariappan, M.,Prasanth, Arun,Sridhar, R.,Srinath, S.
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p. 2575 - 2587
(2020/05/13)
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- Aerobic Dehydrogenation of N-Heterocycles with Grubbs Catalyst: Its Application to Assisted-Tandem Catalysis to Construct N-Containing Fused Heteroarenes
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An aerobic dehydrogenation of nitrogen-containing heterocycles catalyzed by Grubbs catalyst is developed. The reaction is applicable to various nitrogen-containing heterocycles. The exceptionally high functional group compatibility of this method was confirmed by the oxidation of an unprotected dihydroindolactam V to indolactam V. Furthermore, by taking advantage of the oxygen-mediated structural change of the Grubbs catalyst, we integrated ring-closing metathesis and subsequent aerobic dehydrogenation to develop the novel assisted-tandem catalysis using molecular oxygen as a chemical trigger. The utility of the assisted-tandem catalysis was demonstrated by the concise synthesis of N-containing fused heteroarenes including a natural antibiotic, pyocyanine.
- Kawauchi, Daichi,Noda, Kenta,Komatsu, Yoshiyuki,Yoshida, Kei,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 15793 - 15798
(2020/10/12)
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- Monoamine Oxidase (MAO-N) Biocatalyzed Synthesis of Indoles from Indolines Prepared via Photocatalytic Cyclization/Arylative Dearomatization
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The biocatalytic aromatization of indolines into indole derivatives exploiting monoamine oxidase (MAO-N) enzymes is presented. Indoline substrates were prepared via photocatalytic cyclization of arylaniline precursors or via arylative dearomatization of unsubstituted indoles and in turn chemoselectively aromatized by the MAO-N D11 whole cell biocatalyst. Computational docking studies of the indoline substrates in the MAO-N D11 catalytic site allowed for the rationalization of the biocatalytic mechanism and experimental results of the biotransformation. This methodology represents an efficient example of biocatalytic synthesis of indole derivatives and offers a facile approach to access these aromatic heterocycles under mild reaction conditions.
- Black, Gary W.,Brancale, Andrea,Castagnolo, Daniele,Colonna, Serena,Ferla, Salvatore,Masci, Domiziana,Turner, Nicholas J.,Varricchio, Carmine,Zhao, Fei
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p. 6414 - 6421
(2020/07/09)
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- Efficient synthesis process of medical intermediate 5-bromoindole
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The invention discloses an efficient synthesis process of a medical intermediate 5-bromoindole, comprising the following steps of: using an indole compound as a raw material, carrying out low-pressureliquid-phase hydrogenation to destroy five-membered ring conjugation of indole to obtain an indoline compound; enabling the indoline compound to react with an acylation reagent, and protecting nitrogen, so as to obtain an N-acyl indoline compound; carrying out bromination on the N-acyl indoline compound to obtain a 5-bromo-N-acyl indoline compound; carrying out deacylation protection on the 5-bromo-N-acyl indoline compound to obtain a 5-bromoindoline compound; and carrying out oxidative dehydrogenation on the 5-bromoindoline compound by using oxygen or air under the action of a cuprous catalyst and nitric oxide to obtain the target compound 5-bromoindole. The steps involved in the process are convenient to operate, the conditions are mild, and environmental pollution is reduced; finally,the prepared product is high in yield, high in purity and low in energy consumption.
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Paragraph 0036-0037; 0042; 0043-0044; 0049; 0050-0051; 0056
(2020/08/06)
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- A NaH-promoted N-detosylation reaction of diverse p-toluenesulfonamides
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A NaH-mediated detosylation reaction of various Ts-protected indoles, azaheterocycles, anilines and dibenzylamine was reported. The method features cheap reagent, convenient operations, mild reaction conditions and broad substrate scope. Moreover, this study revealed that the loading of NaH in tosylation reactions of nitrogen-containing compounds with NaH as a base in DMA or DMF should be controlled due to the possibility of adverse detosylation.
- Sun, Wanwan,Chen, Xiaobei,Hu, Ying,Geng, Huihui,Jiang, Yuanrui,Zhou, Yuxin,Zhu, Wenjing,Hu, Min,Hu, Haohua,Wang, Xingyi,Wang, Xinli,Zhang, Shilei,Hu, Yanwei
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supporting information
(2020/10/05)
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- Decarboxylation of indole-3-carboxylic acids under metal-free conditions
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Two reaction systems have been developed for the decarboxylation of indole-3-carboxylic acids. The decarboxylation can be achieved smoothly under K2CO3-catalyzed or acetonitrile-promoted basic conditions. It provided an efficient and simple method for the transformation of indole-3-carboxylic acids and the corresponding indoles were isolated with good to excellent yields. From the experimental facts, we put forward the possible reaction mechanism.
- Chen, Xia,Zhou, Xiao-Yu
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supporting information
p. 805 - 812
(2020/02/20)
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- A Reusable Cobalt Catalyst for Reversible Acceptorless Dehydrogenation and Hydrogenation of N-Heterocycles
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The development of robust catalytic systems based on base-metals for reversible acceptorless dehydrogenation (ADH) and hydrogenation of feedstock chemicals is very important in the context of ‘hydrogen storage’. Herein, we report a highly efficient reusable cobalt-based heterogeneous catalyst for reversible dehydrogenation and hydrogenation of N-heterocycles. Both the ADH and the hydrogenation processes operate under mild, benign conditions.
- Jaiswal, Garima,Subaramanian, Murugan,Sahoo, Manoj K.,Balaraman, Ekambaram
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p. 2449 - 2457
(2019/05/10)
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- A 5 - cyano indole synthesis method (by machine translation)
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The invention relates to a 5 - cyano indole synthesis method, through to indole as the starting material, with sodium bisulfite reaction, and then sequentially by acetylation, brominated, protection, [...] and de-protected to obtain 5 - cyano indole. The present invention provides a method of synthesis of the price of raw materials is low cost and easily, thereby reducing the production cost. At the same time the invention synthetic route is short, high yield, high chemical purity of the obtained product, all the reactions are not need special production equipment, and the produced intermediate and final products are not needs the column chromatography and crystallization purification. So the invention not only reduces production cost, convenient for the industrial scale production; and can provide the market with high purity products, obtain the good economic benefits. (by machine translation)
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Paragraph 0048-0053
(2019/11/13)
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- Gold(0) catalyzed dehydrogenation of N-heterocycles
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Gold nanoclusters are good catalyst precursors for the catalytic dehydrogenation of indolines, tetrahydroquinazolines, and related N-heterocycles. The catalytically active species is presumably Au(0) nanoparticles.
- Kumaran, Elumalai,Leong, Weng Kee
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supporting information
p. 3958 - 3960
(2018/10/02)
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- Electrochemical Acceptorless Dehydrogenation of N-Heterocycles Utilizing TEMPO as Organo-Electrocatalyst
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Catalytic acceptorless dehydrogenation (CAD) has been a basically important organic transformation to ubiquitous unsaturated compounds without the usage of a sacrificial hydrogen acceptor. In this work, we successfully developed the first electrochemical acceptorless dehydrogenation (ECAD) of N-heterocycles using TEMPO as the organo-electrocatalyst. We have achieved the catalytic dehydrogenation of N-heterocycles in an anode and the release of H2 in a cathode using an undivided-cell system. A variety of six-membered and five-membered nitrogen-heteroarenes can be synthesized in good yields in this system. In addition, this protocol can also be used in the application of important molecular synthesis. Our electrochemical strategy provides a mild and metal-free route for (hetero)aromatic compounds synthesis via the CAD strategy.
- Wu, Yong,Yi, Hong,Lei, Aiwen
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p. 1192 - 1196
(2018/02/14)
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- Acceptorless Dehydrogenation of N-Heterocycles and Secondary Alcohols by Ru(II)-NNC Complexes Bearing a Pyrazoyl-indolyl-pyridine Ligand
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Ruthenium(II) hydride complexes bearing a pyrazolyl-(2-indol-1-yl)-pyridine ligand were synthesized and structurally characterized by NMR analysis and X-ray single crystal crystallographic determinations. These complexes efficiently catalyzed acceptorless dehydrogenation of N-heterocycles and secondary alcohols, respectively, exhibiting highly catalytic activity with a broad substrate scope. The present work has established a strategy to construct highly active transition metal complex catalysts and provides an atom-economical and environmentally benign protocol for the synthesis of aromatic N-heterocyclic compounds and ketones.
- Wang, Qingfu,Chai, Huining,Yu, Zhengkun
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p. 584 - 591
(2018/03/08)
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- A indole compound and its preparation method and application (by machine translation)
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The invention discloses a indole compound and its preparation method and application. The indole compounds of the structural formula such as formula (I) is shown. The indoles, rice galenical demonstrate the excellent inhibitory activity, the effect of most of the compound is obviously better than the positive control drug validamycin; especially compound I - 43, I - 44, I - 54, I - 73, II - 7 and II - 17, its galenical very good living body protection and treating effect, effect is better than the positive control; more specifically, compound I - 43 of the rice sheath blight bacteriostatic activity than validamycin activity is improved by nearly 300 times. The indole compounds in the prevention and/or treatment of rice sheath blight has great application prospects. In addition the compound of the invention is simple in construction, the preparation method is simple, and is suitable for large-scale industrial production. (I). (by machine translation)
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Paragraph 0131; 0152; 0153
(2018/10/02)
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- Synergistic Cooperative Effect of Sodium borohydride-Iodine Towards Cascade C?N and C?S/Se Bond Formation: One-pot Regioselective Synthesis of 3-Sulfenyl/selenyl Indoles and Mechanistic Insight
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In this work, a new strategy to synthesize 3-sulfenyl/selenyl indole is reported wherein LC?MS reveals a novel insight into synergistic cooperative effect of NaBH4-I2 which allows cascade C?N and C?S/C?Se bond formations via reduction-nucleophilic cyclization-chalcogenylation, three steps in one-pot, towards regioselective synthesis of diverse 3-chalcogenyl indoles including 5-bromo-3-[(3,4,5-trimethoxyphenyl)thio]-1H-indole, a known lead anticancer compound, directly from 2-amino-phenacylchlorides and thiophenols or disulfides/diselenides in aqueous dioxane under transition-metal-free condition. (Figure presented.).
- Lavekar, Aditya G.,Equbal, Danish,Saima,Sinha, Arun K.
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p. 180 - 185
(2018/01/12)
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- Tandem Wittig – Reductive annulation decarboxylation approach for the synthesis of indole and 2-substituted indoles
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A simple tandem Wittig reaction-reductive decarboxylation route is established for the synthesis of indoles from commercially available o-nitrobenzaldehydes and a stable phosphorane. The method allows access to indoles in a very fast manner without involving any metal or expensive reagents or inert atmosphere. Also 2-substituted indoles are obtained which forms an important core of many biological active compounds.
- Volvoikar, Prajesh S.,Tilve
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supporting information
p. 1851 - 1854
(2018/04/14)
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- Preparation method of 5-bromoindole
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The invention discloses a preparation method of 5-bromoindole. The preparation method comprises the following steps of dissolving prepared 2-sodium sulfonate-1-acetylindole in DMF (dimethyl formamide), adding NBS (N-bromosuccinimide), mixing and stirring, reacting for 2-3 hours at room temperature, adding a sodium hydroxide solution to regulate pH to be 9-10, heating to be 60-80 DEG C, carrying out reflux reaction for 8-12 hours, then regulating the pH to be neutral, carrying out reduced-pressure distillation, filtering, and carrying out ethanol recrystallization on solid substances to obtainthe 5-bromoindole. The preparation method disclosed by the invention has the advantages of simple operation, mild reaction condition, green and environment-friendly effects, fewer side products, highproduct purity and higher product yield.
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Paragraph 0025; 0034; 0039; 0043; 0052; 0061
(2018/04/28)
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- Dehydrogenation of Nitrogen Heterocycles Using Graphene Oxide as a Versatile Metal-Free Catalyst under Air
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Graphene oxide (GO) has been developed as an inexpensive, environmental friendly, metal-free carbocatalyst for the dehydrogenation of nitrogen heterocycles. Valuable compounds, such as quinoline, 3,4-dihydroisoquinoline, quinazoline, and indole derivatives, have been successfully used as substrates. The investigation of various oxygen-containing molecules with different conjugated systems indicated that both the oxygen-containing groups and large π-conjugated system in GO sheets are essential for this reaction. (Figure presented.).
- Zhang, Jingyu,Chen, Shiya,Chen, Fangfang,Xu, Wensheng,Deng, Guo-Jun,Gong, Hang
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supporting information
p. 2358 - 2363
(2017/07/22)
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- Acceptorless Dehydrogenation of N-Heterocycles by Merging Visible-Light Photoredox Catalysis and Cobalt Catalysis
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Herein, the first acceptorless dehydrogenation of tetrahydroquinolines (THQs), indolines, and other related N-heterocycles, by merging visible-light photoredox catalysis and cobalt catalysis at ambient temperature, is described. The potential applications to organic transformations and hydrogen-storage materials are demonstrated. Primary mechanistic investigations indicate that the catalytic cycle occurs predominantly by an oxidative quenching pathway.
- He, Ke-Han,Tan, Fang-Fang,Zhou, Chao-Zheng,Zhou, Gui-Jiang,Yang, Xiao-Long,Li, Yang
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supporting information
p. 3080 - 3084
(2017/03/14)
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- Preparation method of drug intermediate 5-bromoindole
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The invention relates to a preparation method of a drug intermediate 5-bromoindole. The preparation method uses an N-acyl indoline compound 3 as a raw material, a 5-bro-N-acyl indoline compound 4 is obtained through bromization, then a 5-bromoindole compound 5 is obtained through diacylation protection, and a target compound 6, namely 5-bromoindole, is obtained through oxidative dehydrogenation. The preparation method is suitable for large-scale production, the production cost is relatively lower, colors can be thoroughly removed through pure recrystallization, and the preparation method has the positive significance on application of the 5-bromoindole and quality control of relevant drugs.
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Paragraph 0020; 0023; 0026
(2017/08/29)
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- Environment-friendly synthesis method for medicine intermediate 5-bromoindole
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The invention relates to an environment-friendly synthesis method for a medicine intermediate 5-bromoindole. The method comprises the following steps: (1) subjecting indole to low-temperature low-pressure liquid-phase hydrogenation in the presence of a metal catalyst, so as to obtain indoline; (2) subjecting indoline to an action with an acetylation reagent, so as to produce N-acetylindoline; (3) subjecting N-acetylindoline to a clean bromination reaction, so as to produce N-acetyl-5-bromoindoline; (4) subjecting N-acetyl-5-bromoindoline to deacetylation under acidic conditions, so as to obtain 5-bromoindoline; and (5) subjecting 5-bromoindoline to oxidative dehydrogenation, thereby preparing the key medicine intermediate 5-bromoindole. Compared with the prior art, the method has the beneficial effects that a new environment-friendly synthesis process is developed, compared with the original process, bromo isomers of the 5-bromoindole product are effectively controlled, and the safety of medicine products can be higher; compared with the original acetic anhydride and bromine bromination process, the reaction conditions are mild, the environmental pollution is light, and the cost is low; and the equipment investment is small, the process is simple, the operation is easy, the equipment corrosion is low, and the process is more applicable to industrial production.
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Paragraph 0114-0117; 0141-0144; 0168-0171
(2017/03/28)
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- Organo-Photoredox Catalyzed Oxidative Dehydrogenation of N-Heterocycles
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We report here for the first time the catalytic oxidative dehydrogenation of N-heterocycles by a visible-light organo-photoredox catalyst with low catalyst loading (0.1–1 mol %). The reaction proceeds efficiently under base- and additive-free conditions with ambient air at room temperature. The utility of this benign approach is demonstrated by the synthesis of various pharmaceutically relevant N-heteroarenes such as quinoline, quinoxaline, quinazoline, acridine, and indole.
- Sahoo, Manoj K.,Jaiswal, Garima,Rana, Jagannath,Balaraman, Ekambaram
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supporting information
p. 14167 - 14172
(2017/10/16)
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- Carbon-catalyzed Dehydrogenation of Indolines: Detection of Active Intermediate and Exploration of High-performance Catalyst
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Metal-free oxidation of indoline using molecular oxygen as an oxidant was investigated. Among various carbon-based catalysts, we found that reduced graphene oxide (rGO) was the most active. Superoxide radical was formed in the course of the reaction. Although graphene oxide (GO) did not function as a catalyst, rGO could be recycled at least 5 times without any structural change.
- Morimoto, Naoki,Takeuchi, Yasuo,Nishina, Yuta
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supporting information
p. 21 - 23
(2016/01/20)
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- MAGNETICALLY SEPARABLE IRON-BASED HETEROGENEOUS CATALYSTS FOR DEHYDROGENATION OF ALCOHOLS AND AMINES
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The present invention discloses an iron-based nitrogen doped graphene catalyst, process for preparation thereof and use of said catalyst in oxidant-free catalytic dehydrogenation of alcohols and amines to the corresponding carbonyl compounds, amines and N-heterocylic compounds with extraction of molecular hydrogen as the only by-product.
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Page/Page column 19; 20; 21
(2016/12/22)
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- Active and Recyclable Catalytic Synthesis of Indoles by Reductive Cyclization of 2-(2-Nitroaryl)acetonitriles in the Presence of Co-Rh Heterobimetallic Nanoparticles with Atmospheric Hydrogen under Mild Conditions
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A cobalt-rhodium heterobimetallic nanoparticle-catalyzed reductive cyclization of 2-(2-nitroaryl)acetonitriles to indoles has been achieved. The tandem reaction proceeds without any additives under the mild conditions (1 atm H2 and 25 °C). This procedure could be scaled up to the gram scale. The catalytic system is significantly stable under these reaction conditions and could be reused more than ten times without loss of catalytic activity.
- Choi, Isaac,Chung, Hyunho,Park, Jang Won,Chung, Young Keun
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p. 5508 - 5511
(2016/11/17)
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- Development of indole sulfonamides as cannabinoid receptor negative allosteric modulators
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Existing CB1 negative allosteric modulators (NAMs) fall into a limited range of structural classes. In spite of the theoretical potential of CB1 NAMs, published in vivo studies have generally not been able to demonstrate the expected therapeutically-relevant CB1-mediated effects. Thus, a greater range of molecular tools are required to allow definitive elucidation of the effects of CB1 allosteric modulation. In this study, we show a novel series of indole sulfonamides. Compounds 5e and 6c (ABD1075) had potencies of 4 and 3?nM respectively, and showed good oral exposure and CNS penetration, making them highly versatile tools for investigating the therapeutic potential of allosteric modulation of the cannabinoid system.
- Greig, Iain R.,Baillie, Gemma L.,Abdelrahman, Mostafa,Trembleau, Laurent,Ross, Ruth A.
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p. 4403 - 4407
(2016/08/25)
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- Bronsted acid ionic liquid-catalyzed reductive Friedel-Crafts alkylation of indoles and cyclic ketones without using an external reductant
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In the absence of an external reductant, C3-cycloalkylated indole could be synthesized through reductive alkylation of indole with cyclic ketone using a sulfonyl-functionalized Bronsted acid ionic liquid as a catalyst. Water generated in the initial stage of the reaction played a key role in rendering the reductive coupling possible. The reaction proceeds most likely in a radical way.
- Taheri, Amir,Lai, Bingbing,Cheng, Cheng,Gu, Yanlong
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supporting information
p. 812 - 816
(2015/03/04)
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- Copper nanoparticles from copper aluminum hydrotalcite: An efficient catalyst for acceptor- and oxidant-free dehydrogenation of amines and alcohols
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An efficient and simple process for the preparation of stable nanocopper(0) on alumina [Cu(0)/Al2O3] from the inorganic composite precursor copper aluminum hydrotalcite (Cu-AlHT) by a chemical reduction method is described. Cu(0)/ Al2O3 was employed as an efficient catalyst in the acceptor- and oxidant-free dehydrogenation of various amines and alcohols to their corresponding dehydrogenated products in good to excellent yields. The stability of Cu(0)/Al2O3 was assessed by studying its recoverability and reusability in the dehydrogenation of amines and alcohols for up to five cycles.
- Damodara, Dandu,Arundhathi, Racha,Likhar, Pravin R.
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supporting information
p. 189 - 198
(2014/03/21)
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- Deformylation of indole and azaindole-3-carboxaldehydes using anthranilamide and solid acid heterogeneous catalyst via quinazolinone intermediate
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The deformylation of indole and azaindole-3-carboxaldehydes was achieved in the presence of anthranilamide and a solid acid heterogeneous catalyst under reflux conditions in 25-90% yield. The reaction proceeds via quinazolinone intermediate, which undergoes acid catalyzed cleavage to form deformylated product.
- Yadav, Rammohan R.,Battini, Narsaiah,Mudududdla, Ramesh,Bharate, Jaideep B.,Muparappu, Nagaraju,Bharate, Sandip B.,Vishwakarma, Ram A.
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experimental part
p. 2222 - 2225
(2012/05/20)
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- Integrated structure-based activity prediction model of benzothiadiazines on various genotypes of HCV NS5b polymerase (1a, 1b and 4) and its application in the discovery of new derivatives
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This work presents the first structure-based activity prediction model for benzothiadiazines against various genotypes of HCV NS5b polymerase (1a, 1b and 4).The model is a comprehensive workflow of structure-based field template followed by guided docking. The field template was used as a pre-filter and a tool to provide hits in good orientation and position. It was created based on detailed molecular interaction field analysis which includes Topomer CoMFA, grid independent analysis and Superstar. On the other hand, Guided docking was used as a refinement and assessment tool. It was actively directed by two scores: Moldock score as an interaction descriptor (r2 = 0.65) and a template similarity score as a measure for accurate binding-mode compliance. The docking template was based on energy-based pharmacophore analysis. The whole procedure was formulated and tweaked for both screening (ROC of AUC = 0.91) and activity prediction (r2 of 0.8) for the genotype 1a. In order to widen the model scope, linear interaction energy was used as a tool for predicting activities of other genotypes based on the docked ligand poses while mutation binding energy was used to investigate the effect of each amino acid mutation in genotype 4. The model was applied for structure-based fragment hopping by screening a library designed by reaction enumeration. A top scoring hit was used to generate a focused library such that it has lower TPSA than the original class ligands and thus better pharmacokinetic properties. After that, experimental validation was carried out by the synthesis of this library and its biological evaluation which yielded compounds that exhibit EC50 ranging from 1.86 to 23 μM.
- Ismail, Mohamed A.H.,Abou El Ella, Dalal A.,Abouzid, Khaled A.M.,Mahmoud, Amr H.
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supporting information; experimental part
p. 2455 - 2478
(2012/05/05)
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- A systematic study of two complementary protocols allowing the general, mild and efficient deprotection of N-pivaloylindoles
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Two mild and general protocols for the high-yielding deprotection of indoles and related fused heterocyclic systems are described, involving either hydride transfer from LDA or hydrolysis by the DBU-water system. Both methods were shown to tolerate a wide variety of substituents and functional groups, but the hydrolytic one proved to be particularly general, being compatible with 2-alkyl substituents, aldehydes, ketones, carboxylic acids, halogens, ethers, amides and esters. Yields were normally excellent in both cases, but were usually slightly higher for the reductive method. Taken together, these two protocols provide a general solution to the problem of pivaloyindole deprotection.
- Ruiz, Míriam,Sánchez, J. Domingo,López-Alvarado, Pilar,Menéndez, J. Carlos
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experimental part
p. 705 - 710
(2012/01/06)
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- Ruthenium-catalyzed transformation of aryl and alkenyl triflates to halides
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Aryl triflates were transformed to aryl bromides/iodides simply by treating them with LiBr/NaI and [Cp*Ru(MeCN)3]OTf. The ruthenium complex also catalyzed the transformation of alkenyl sulfonates and phosphates to alkenyl halides under mild conditions. Aryl and alkenyl triflates undergo oxidative addition to a ruthenium(II) complex to form η'1- arylruthenium and 1-ruthenacyclopropene intermediates, respectively, which are transformed to the corresponding halides.
- Imazaki, Yusuke,Shirakawa, Eiji,Ueno, Ryota,Hayashi, Tamio
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supporting information
p. 14760 - 14763
(2012/11/07)
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