- Synthesis and characterization of carbazolide-based iridium PNP pincer complexes. Mechanistic and computational investigation of alkene hydrogenation: Evidence for an Ir(III)/Ir(V)/Ir(III) catalytic cycle
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New carbazolide-based iridium pincer complexes (carbPNP) Ir(C2H4), 3a, and (carbPNP)Ir(H)2, 3b, have been prepared and characterized. The dihydride, 3b, reacts with ethylene to yield the cis-dihydride ethylene complex cis-(carbPNP) Ir(C2H4)(H)2. Under ethylene this complex reacts slowly at 70 C to yield ethane and the ethylene complex, 3a. Kinetic analysis establishes that the reaction rate is dependent on ethylene concentration and labeling studies show reversible migratory insertion to form an ethyl hydride complex prior to formation of 3a. Exposure of cis-( carbPNP)Ir(C2H4)(H)2 to hydrogen results in very rapid formation of ethane and dihydride, 3b. DFT analysis suggests that ethane elimination from the ethyl hydride complex is assisted by ethylene through formation of (carbPNP)Ir(H)(Et)(C2H 4) and by H2 through formation of (carbPNP) Ir(H)(Et)(H2). Elimination of ethane from Ir(III) complex ( carbPNP)Ir(H)(Et)(H2) is calculated to proceed through an Ir(V) complex (carbPNP)Ir(H)3(Et) which reductively eliminates ethane with a very low barrier to return to the Ir(III) dihydride, 3b. Under catalytic hydrogenation conditions (C2H4/H 2), cis-(carbPNP)Ir(C2H4)(H) 2 is the catalyst resting state, and the catalysis proceeds via an Ir(III)/Ir(V)/Ir(III) cycle. This is in sharp contrast to isoelectronic (PCP)Ir systems in which hydrogenation proceeds through an Ir(III)/Ir(I)/Ir(III) cycle. The basis for this remarkable difference is discussed.
- Cheng, Chen,Kim, Bong Gon,Guironnet, Damien,Brookhart, Maurice,Guan, Changjian,Wang, David Y.,Krogh-Jespersen, Karsten,Goldman, Alan S.
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- Effect ofortho-biphenyl substitution on the excited state dynamics of a multi-carbazole TADF molecule
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We report a new thermally activated delayed fluorescence (TADF) molecule developed by theortho-biphenyl substitution of a multi-carbazole TADF molecule. The new TADF molecule,4mCzBN-BP, is composed of four dimethylcarbazole donors, a benzonitrile acceptor core and anortho-biphenyl triplet scaffold.4mCzBN-BPexhibits a bluish-green emission with a peak wavelength at 491 nm and a very high photoluminescence quantum yield (PLQY) of 95% in an mCBP host. To investigate the effect of theortho-biphenyl substitution on the excited-state dynamics and photophysical properties of the TADF molecule, we performed time dependent density functional theory (TD-DFT) calculations of4mCzBN-BPand two multi-carbazole TADF molecules with similar molecular structures. A local excited triplet state (3LE) with an energy (2.81 eV) close to the lowest singlet charge-transfer state (1CT) can be formed at the biphenyl of4mCzBN-BP. However, due to the planarization of the biphenyl at the triplet state and a large steric hindrance caused by adjacent carbazole donors,3LE at the biphenyl can only be formed by a subset of possible conformations of4mCzBN-BPmolecules in the solid mCBP host, leading to a multiexponential decay of the delayed fluorescence. Color coordinates of (0.196, 0.452), a high external quantum efficiency of 23.7% and a long operational lifetime (LT50) of 750 hours were achieved with the organic light emitting diodes based on4mCzBN-BP.
- Ha, Yeon-Hee,Kim, Jang-Joo,Kim, Yun-Hi,Woo, Seung-Je
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- Synthesis of novel aromatic nitroxides as potential DNA intercalators. An EPR spectroscopical and DFT computational study
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The synthesis and electron paramagnetic resonance (EPR) spectroscopic properties of three novel aromatic nitroxides and potential DNA intercalators, the carbazole-based 3,6-dimethylcarbazole-9-oxyl, as well as the acridane-based 9-acridanylidenemalonitril
- Beyer, Mario,Fritscher, Joerg,Feresin, Emiliano,Schiemann, Olav
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- Site-Specific Synthesis of Carbazole Derivatives through Aryl Homocoupling and Amination
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We synthesized various carbazoles from anilines through a three-step process with good overall yields (up to 48percent). This process comprises N -acetylation, copper(0)-mediated Ullmann homocoupling, and acid-mediated intramolecular amination. It permits various functional groups on the substrate. Scale-up of the developed three-step synthetic route to carbazoles was also demonstrated.
- Baek, Junghyun,Ban, Jaeyoung,Lim, Minkyung,Rhee, Hakjune,Shabbir, Saira
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p. 917 - 927
(2020/03/13)
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- Copper(II) catalyzed aromatization of tetrahydrocarbazole: An unprecedented protocol and its utility towards the synthesis of carbazole alkaloids
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An efficient protocol for the aromatization of tetrahydrocarbazole is described by using catalytic copper(II) chloride dihydrate in DMSO. This newly established methodology has utilized towards the synthesis of naturally occurring carbazole alkaloids, namely 3-methylcarbazole, 3-formyl carbazole, glycozoline, glycozolicine and clauszoline-K. In addition, the protocol is generalized for the aromatization of N-substituted tetrahydrocarbazole, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroisoquinoline and 1,2,3,4-tetrahydro β-carboline to give the corresponding heteroaromatic compounds from very good to excellent yield. Moreover, this method has been proven to be tolerant to a broad range of functional groups with excellent yields.
- Dalvi, Bhakti A.,Lokhande, Pradeep D.
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p. 2145 - 2149
(2018/05/08)
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- Ruthenium-catalyzed cross-dehydrogenative ortho-N-carbazolation of diarylamines: Versatile access to unsymmetrical diamines
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The dehydrogenative C-N cross-coupling of unprotected, secondary anilines through ortho-N-carbazolation has been achieved using a Ru catalytic system with O2 as the terminal oxidant. The reactions proceed in an intermolecular fashion, selectively in the ortho position. Implications for the field of organic synthesis are discussed. No-No-No: Amination of a non-acidic Ci£H bond, no pre-activation of the coupling partners, no chelate-assisting directing group. Dehydrogenative C-N cross-coupling through the ortho-N-carbazolation of unprotected, secondary anilines has been achieved using a Ru catalyst with O2 as the terminal oxidant. The reactions proceed in an intermolecular fashion, selectively in the ortho position.
- Louillat, Marie-Laure,Biafora, Agostino,Legros, Fabien,Patureau, Frederic W.
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supporting information
p. 3505 - 3509
(2014/04/03)
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- Carbocyclization versus oxycyclization on the metal-catalyzed reactions of oxyallenyl C3-linked indoles
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The preparation of previously unknown (indol-3-yl)-α-allenols and -allenones was accomplished from indole-3-carbaldehydes, through indium-mediated Barbier allenylation reaction taking advantage of the N-(2-pyridyl)sulfonyl group. Metal-catalyzed cyclizations of oxyallenyl C3-linked indoles proceeded in two ways depending on the presence or absence of the N-(2-pyridyl)sulfonyl group. For allenols, gold-catalyzed oxycyclization occurred in the presence of the protecting group; in the absence of the protecting group, palladium- and gold-catalyzed benzannulations operated. On the contrary, under gold catalysis furyl-indoles were obtained as exclusive products from NH-allenones, while 5-endo carbocyclization adducts were the major components starting from N-SO2py-protected allenones. These cyclization reactions have been developed experimentally, and their mechanisms have additionally been investigated by a computational study.
- Alcaide, Benito,Almendros, Pedro,Alonso, Jose M.,Fernandez, Israel
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p. 6688 - 6701
(2013/07/26)
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- A tandem reduction-oxidation protocol for the conversion of 1-keto-1,2,3,4-tetrahydrocarbazoles to carbazoles via tosylhydrazones through microwave assistance: Efficient synthesis of glycozoline, clausenalene, glycozolicine, and deoxycarbazomycin B and the total synthesis of murrayafoline A
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A novel and efficient methodology for the synthesis of carbazoles from 1-keto-1,2,3,4-tetrahydrocarbazoles via the corresponding tosylsulfonhydrazones by a one-pot tandem reduction-oxidation protocol using a combination of NaBH4 and Pd-C on MgSO4·7H2O, a solid support, under microwave is developed. The reaction is successfully extended toward the synthesis of several naturally occurring carbazole alkaloids, namely 3-methylcarbazole, glycozoline, clausenalene, glycozolicine, murrayafoline A, and deoxycarbazomycin B, a carbazole derivative that is known to have a promising antimicrobial activity.
- Chakraborty, Suchandra,Chattopadhyay, Gautam,Saha, Chandan
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- Toward polynuclear Ru-Cu catalytic dehydrogenative C-N bond formation, on the reactivity of carbazoles
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The cooperative action of Ru and Cu catalysts enables direct polynuclear C-H and N-H activation for the dehydrogenative N-carbazolation of carbazoles, selectively at the C1 position. Initial mechanistic experiments are presented and discussed.
- Louillat, Marie-Laure,Patureau, Frederic W.
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p. 164 - 167
(2013/03/28)
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- A series of CBP-derivatives as host materials for blue phosphorescent organic light-emitting diodes
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We report a series of CBP-derivatives with superior thermal and electronic properties for the use as host materials for blue electrophosphorescent organic light emitting diodes. We applied a systematic variation of the substitution pattern in the 2- and 2′-position of the biphenyl unit and the 3- and 6-position of the carbazole moieties. In contrast to the crystalline parent compound CBP, all methyl and trifluoromethyl substituted derivatives show amorphous behaviour. Substitution in the 2- and 2′-position of the biphenyl causes a twisting of the phenyl rings. Hence, the degree of conjugation of the molecules is limited which leads to enlarged triplet energies of approximately 2.95 eV compared to 2.58 eV for CBP. The methyl substitution at the active 3- and 6-position of the pendant carbazole units yields materials with an electrochemically stable behaviour against oxidation. The Royal Society of Chemistry.
- Schroegel, Pamela,Tomkeviciene, Ausra,Strohriegl, Peter,Hoffmann, Sebastian T.,Koehler, Anna,Lennartz, Christian
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p. 2266 - 2273
(2011/10/12)
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- Preparation and study of 1,8-di(pyrid-2′-yl)carbazoles
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(Figure Presented) A series of three derivatives of 1,8-di(pyrid-2′- yl)carbazole were prepared by Stille-type coupling of 2-(tri-n-butylstannyl) pyridine with the appropriate 1,8-dibromocarbazole. The carbazoles were prepared by appropriate substitution methodologies on the parent carbazole or by palladium-catalyzed cyclization of di-(p-tolyl)amine to provide the carbazole ring system. An X-ray structure of the di-tert-butyl derivative confirmed that both pyridyl groups were oriented for favorable intramolecular H-bonding to the central N-H. Two orientations of the molecule were found in the unit cell and this observation was corroborated by two N-H stretching bands in the solid state IR. Substitution of N-H by N-D led to increased emission intensity through diminished intramolecular deactivation of the excited state. The di-tert-butyl derivative formed a tridentate complex with Pd(II), which showed a red-shifted band attributed to an intraligand charge transfer state.
- Mudadu, Maria S.,Singh, Ajay N.,Thummel, Randolph P.
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p. 6513 - 6520
(2008/12/22)
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- Microbial transformation of selected carbazole derivatives
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A strain of Pseudomonas aeruginosa and another of Aspergillus fumigatus are found to have the ability to degrade carbazole derivatives. These strains show different specificities for growth on 1- and 3-methylcarbazoles and accumulate forraylcarbazoles as end products in low yields. Pseudomonas species degrade 1- and 3-formylcarbazoles to the corresponding carboxylic acid derivatives which in turn are decarboxylated to carbazole in high yields. This strain also biotransforms the N-acetylcarbazoles (8, 9 and 10) and the respective deacetyl-derivatives (7,2 and 11) are obtained in good yields. This study provides an evidence in favour of the suggested biotransfonnation of 3-methylcarbazole to carbazole via 3-formylcarbazole and carbazole-3-carboxylic acid in the plants.
- Chakraborty,Chowdhury
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p. 617 - 620
(2007/10/03)
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- The Chemistry of Carbazoles. VII. Syntheses of Methylcarbazoles
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Thirty-six methylcarbazoles were prepared, and their synthetic methods were critically described.
- Kuroki, Masanate,Tsunashima, Yutaka
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p. 709 - 714
(2007/10/02)
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