10075-50-0Relevant articles and documents
Chemoselective deprotection of allylic amines catalyzed by Grubbs' carbene
Alcaide, Benito,Almendros, Pedro,Alonso, Jose M.,Luna, Amparo
, p. 668 - 672 (2005)
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.
CO2-Catalyzed Efficient Dehydrogenation of Amines with Detailed Mechanistic and Kinetic Studies
Riemer, Daniel,Schilling, Waldemar,Goetz, Anne,Zhang, Yu,Gehrke, Sascha,Tkach, Igor,Hollóczki, Oldamur,Das, Shoubhik
, p. 11679 - 11687 (2018)
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.
Novel Arylindigoids by Late-Stage Derivatization of Biocatalytically Synthesized Dibromoindigo
Schnepel, Christian,Dodero, Veronica I.,Sewald, Norbert
, p. 5404 - 5411 (2021)
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.
DMSO/t-BuONa/O2-Mediated Aerobic Dehydrogenation of Saturated N-Heterocycles
Cai, Hu,Tan, Wei,Xie, Yongfa,Yang, Ruchun,Yue, Shusheng
, p. 7501 - 7509 (2020)
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.
Aerobic oxidative dehydrogenation of N-heterocycles over OMS-2-based nanocomposite catalysts: Preparation, characterization and kinetic study
Bi, Xiuru,Tang, Tao,Meng, Xu,Gou, Mingxia,Liu, Xiang,Zhao, Peiqing
, p. 360 - 371 (2020)
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
Two-Dimensional Metal-Organic Layers for Electrochemical Acceptorless Dehydrogenation of N-Heterocycles
Yang, Ling,Ma, Fa-Xue,Xu, Fan,Li, Dong,Su, Liangmei,Xu, Hai-Chao,Wang, Cheng
, p. 3557 - 3560 (2019)
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.
Simple and selective removal of the t-butyloxycarbonyl (Boc) protecting group on indoles, pyrroles, indazoles, and carbolines
Ravinder,Reddy, A. Vijender,Mahesh, K. Chinni,Narasimhulu,Venkateswarlu
, p. 281 - 287 (2007)
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.
From Tryptophan to Toxin: Nature's Convergent Biosynthetic Strategy to Aetokthonotoxin
Adak, Sanjoy,Lukowski, April L.,Sch?fer, Rebecca J. B.,Moore, Bradley S.
supporting information, p. 2861 - 2866 (2022/02/23)
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.
Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis
Quan, Yangjian,Lan, Guangxu,Shi, Wenjie,Xu, Ziwan,Fan, Yingjie,You, Eric,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
supporting information, p. 3115 - 3120 (2020/12/09)
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.
Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
, p. 3498 - 3506 (2021/04/07)
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.