- NaI/PPh3-Mediated Photochemical Reduction and Amination of Nitroarenes
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A mild transition-metal- and photosensitizer-free photoredox system based on the combination of NaI and PPh3 was found to enable highly selective reduction of nitroarenes. This protocol tolerates a broad range of reducible functional groups such as halogen (Cl, Br, and even I), aldehyde, ketone, carboxyl, and cyano. Moreover, the photoredox catalysis with NaI and stoichiometric PPh3 provides also an alternative entry to Cadogan-type reductive amination when o-nitrobiarenes were used.
- Qu, Zhonghua,Chen, Xing,Zhong, Shuai,Deng, Guo-Jun,Huang, Huawen
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supporting information
p. 5349 - 5353
(2021/07/21)
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- Visible-light-driven Cadogan reaction
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Visible-light-driven photochemical Cadogan-type cyclization has been discovered. The organic D-A type photosensitizer 4CzIPN found to be an efficient mediator to transfer energy from photons to the transient intermediate that breaks the barriers of deoxygenation in Cadogan reaction and enables a mild metal-free access to carbazoles and related heterocycles. DFT calculation results indicate mildly endergonic formation of the intermediate complex of nitrobiarenes and PPh3, which corresponds with experimental findings regarding reaction temperature. The robust synthetic capacity of the photoredox Cadogan reaction systems has been demonstrated by the viable productivity of a broad range of carbazoles and related N-heterocycles with good tolerance of various functionalities.
- Qu, Zhonghua,Wang, Pu,Chen, Xing,Deng, Guo-Jun,Huang, Huawen
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supporting information
p. 2582 - 2586
(2021/03/09)
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- The synthesis of a series of fluorescent emitters and their application for dye lasing and cation sensing
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The following paper reported four carbazole-modified fluorescent emitters. Their molecular structure and electronic transition were analyzed via their single crystal and theoretical calculation. Their photophysical parameters, including absorption, emission and quantum yield, were determined and discussed. It was found that the emission performance of benzo-thiazole-based dyes was better than that of benzo-imidazole-based dyes, owing to the electron-donating effect from the S atom. Upon the presence of metal cations, these photophysical parameters were re-measured. Benzo-thiazole-based dyes were found insensitive towards most metal cations, while benzo-imidazole-based dyes showed obvious photophysical variation upon these metal cations, including absorption red shift and emission quenching. Detailed sensing performance of a representative dye was discussed. A linear working curve with good selectivity was finally observed. Its sensing mechanism was confirmed as the coordination between metal cation and deprotonated benzo-imidazole group. Benzo-thiazole-based dyes showed amplified spontaneous emission (ASE) behavior, with threshold energy of ~220 μJ. Given the optimal condition, a highest ASE efficiency of ~2% was observed, with FWHM value of 6 nm and emission peak of 435 nm. The major novelty and advancement of these fluorescent dyes shall be the stable ASE output (dye 4) under UV excitation and the linear sensing curve with good selectivity (dye 3), which was a hard task for emission turn off sensing probes. We attributed its causation to the valent-recognizing sensing mechanism.
- Cang, Sheng,Liu, Liang,Tian, Yaqiang,Yang, Zixuan,Zhang, Leiyu
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- Visible-light-promoted intramolecular C-H amination in aqueous solution: Synthesis of carbazoles
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An effective and operationally simple protocol is reported for the synthesis of versatile carbazoles. With water as a co-solvent, visible-light rather than various metals is used to facilitate the conversion of readily available 2-azidobiphenyls under mild conditions. Various functionalized bioactive natural alkaloids, such as glycoborine, clausine C, clausine L, clausine H and clauszoline K, were synthesized efficiently with nitrogen as a sole byproduct. The reaction could be performed in water, acidic or alkaline buffer solutions, showing its potential for applications in biochemistry.
- Yang, Lizheng,Zhang, Yipin,Zou, Xiaodong,Lu, Hongjian,Li, Guigen
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supporting information
p. 1362 - 1366
(2018/03/26)
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- Novel carbazole sulfonamide derivatives of antitumor agent: Synthesis, antiproliferative activity and aqueous solubility
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The current optimization of IG-105 (3) on the carbazole-ring provided a series of new carbazole sulfonamides derivatives 13a–13m. All of the compounds have been evaluated against HepG2 cells (hepatoma cancer) for antiproliferative activity. Compounds that showed activity better or comparable to that of 3 versus HepG2 were evaluated against MCF-7 (breast cancer), MIA PaCa-2 (pancreatic cancer), and Bel-7402 (hepatoma/liver cancer) for antiproliferative activity. Of the seven compounds selected for further study five (13b, 13g, 13j, 13k and 13l) were found to give IC50values against the four cell lines comparable to those for 3. Two compounds (13f and 13i) were more active than 3 and their activity against HepG2 and MCF-7 (IC50:0.01–0.07?μM) approached that of the positive controls podophyllotoxin (podo) and CA-4. Most of compounds showed aqueous solubility (0.11–19.60?μg/mL at pH 7.4 and 2.0) better than 3. These promising results warrant further development of new compounds 13f and 13i as potential potent antitumor drug candidates.
- Sun, Lianqi,Wu, Yanbin,Liu, Yonghua,Chen, Xiaofang,Hu, Laixing
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p. 261 - 265
(2016/12/27)
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- Palladium-Catalyzed Intramolecular C–H Amination in Water
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Palladium(II) catalysis was found to be effective for intramolecular C–H amination in water. With 2-azidobiphenyls as substrates, the reaction efficiently provided various carbazoles with N2as the sole byproduct. The reaction showed high functional-group tolerance and could be used in the synthesis of several natural carbazole alkaloids. The catalytic process was promoted by water, and the reaction was inefficient in the organic solvents that were investigated.
- Yang, Lizheng,Li, Hao,Zhang, Haifei,Lu, Hongjian
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supporting information
p. 5611 - 5615
(2016/12/14)
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- Substituted Carbazoles-A New Class of Anthelmintic Agent
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A series of novel carbazoles were synthesized based on structural modifications to lead carbazole 1 (EC100≤2.5M against Haemonchus contortus in vitro), which was revealed in a small molecule screening program as a potentially promising platform for the development of new anthelmintic drugs. Subsequently, analogues 19, 21, 41, 42 (EC100≤ 1.25M, all), and 39 (EC100≤0.625M) were demonstrated to exhibit enhanced in vitro anthelmintic activity over the lead structure, with compound 39 also being shown to be active in vivo against Heligmosomoides polygyrus.
- Rennison, David,Gueret, Stephanie M.,Laita, Olivia,Bland, Ross J.,Sutherland, Ian A.,Boddy, Ian K.,Brimble, Margaret A.
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p. 1268 - 1276
(2016/11/25)
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- Carbazole inhibitors of histamine receptors for the treatment of disease
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The present invention relates to carbazole compounds, pharmaceutical compositions comprising them, and methods which may be useful as inhibitors of H1R and/or H4R for the treatment or prevention of inflammatory, autoimmune, allergic, and ocular diseases.
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- First Suzuki-Miyaura type cross-coupling of ortho-azidobromobenzene with arylboronic acids and its application to the synthesis of fused aromatic indole-heterocycles
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A short synthesis of some fused indole-heterocycles has been achieved via Pd-catalyzed cross-coupling reactions between azido-2-bromobenzene and arylboronic acids and subsequent thermally induced nitrene insertion. Additionally, 4-amino-α-carboline, a versatile intermediate toward grossularine analogs has also been prepared by Suzuki-Miyaura cross-coupling of 4-pivaloylaminopyridine-3-boronic acid with 2-bromoaniline, followed by simple functional group transformations.
- Pudlo, Marc,Csányi, Dorottya,Moreau, Fabien,Hajós, Gy?rgy,Riedl, Zsuzsanna,Sapi, Janos
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p. 10320 - 10329
(2008/02/13)
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- Dioxomolybdenum(VI)-catalyzed reductive cyclization of nitroaromatics. Synthesis of carbazoles and indoles
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Reductive cyclization of nitrobiphenyls and nitrostyrenes to carbazoles and indoles, respectively, is carried out by triphenylphosphine under mild conditions catalyzed by a dichlorodioxomolybdenum(VI) complex. A one-pot procedure for the synthesis of regioselectively functionalized indoles has been developed from commercially available onitrobenzaldehydes and phosphoranes.
- Sanz, Roberto,Escribano, Jaime,Pedrosa, Maria R.,Aguado, Rafael,Arnaiz, Francisco J.
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p. 713 - 718
(2008/02/09)
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- Triphenylphosphine-mediated reductive cyclization of 2-nitrobiphenyls: A practical and convenient synthesis of carbazoles
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The synthesis of a series of substituted carbazoles from the corresponding 2-nitrobiphenyl derivatives using a novel modification of the Cadogan reaction is described. Cyclization of the 2-nitrobiphenyls was achieved via reductive deoxygenation of the nitro groups using a slight excess of triphenylphosphine in a suitable solvent. We have observed a temperature dependence on the extent of conversion under these conditions, with higher boiling solvents affording higher yields across a range of substrates. The new reaction conditions are very straightforward and convenient to execute, tolerate a broad range of functional groups, and yield carbazole products in the absence of unwanted side products.
- Freeman, Adam W.,Urvoy, Marie,Criswell, Megan E.
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p. 5014 - 5019
(2007/10/03)
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- FUSED CARBAZOLES BY TANDEM AZA WITTIG/ELECTROCYCLIC RING CLOSURE. PREPARATION OF 6H-PYRIDOCARBAZOLE, 11H-PYRIDOCARBAZOLE AND 11H-PYRIDOCARBAZOLE DERIVATIVES
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Aza Wittig type reaction of iminophosphoranes 3, 12 and 16, prepared from the appropriate formylcarbazole by sequential treatment with ethyl azidoacetate and triphenylphosphine, with isocyanates leads to the linear 6H-pyridocarbazole 5, the angular
- Molina, Pedro,Fresneda, Pilar M.,Almendros, Pedro
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p. 1223 - 1236
(2007/10/02)
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