- 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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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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- Metal-free deoxygenation and reductive disilylation of nitroarenes by organosilicon reducing reagents
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A metal-free deoxygenation and reductive disilylation of nitroarenes was achieved using N,N’-bis(trime-thylsilyl)-4,4’-bipyridinylidene (1) under mild and neutral reaction conditions, and a broad functional group tolerance was possible in this reaction. Mono-deoxygenation, giving a synthetically valuable N,O-bis(trimethylsilyl)phe-nylhydroxylamine (7a) as a readily available and safe phenylnitrene source from nitrobenzene, and double-deoxy-genation, giving N,N-bis(trimethylsilyl)anilines 8, were easily controlled by varying the amounts of 1 and reaction temperature as well as adding dibenzothiophene (DBTP). Reaction of 2-arylnitrobenzenes with 1 resulted in the formation of the corresponding carbazoles 14 via in situ-gen-erated phenylnitrene species derived by thermolysis of N,O-bis(trimethylsilyl)phenylhydroxylamines 7, followed by their subsequent intramolecular C H insertion. In addition, the intramolecular N N coupling reaction proceeded in the reduction of 2,2’-dinitrobiphenyl derivatives by 1, giving the corresponding benzo[c]cinnolines.
- Bhattacharjee, Argha,Hosoya, Hiromu,Ikeda, Hideaki,Nishi, Kohei,Tsurugi, Hayato,Mashima, Kazushi
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p. 11278 - 11282
(2018/10/20)
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- Photochemical intramolecular amination for the synthesis of heterocycles
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Polycyclic heterocycles can be formed in good to excellent yields via photochemical conversion of the corresponding substituted aryl azides under irradiation with purple LEDs in a continuous flow reactor. The experimental set-up is tolerant to UV-sensitive functional groups while affording diverse carbazoles, as well as an indole and pyrrole framework, in short reaction times. The photochemical method is presumed to progress through a mechanism differing from the other methods of azide activation involving transition metal catalysis.
- Parisien-Collette, Shawn,Cruché, Corentin,Abel-Snape, Xavier,Collins, Shawn K.
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p. 4798 - 4803
(2017/10/23)
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- Design, synthesis, and evaluation of potent Wnt signaling inhibitors featuring a fused 3-ring system
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The Wnt signaling pathway is a critical developmental pathway which operates through control of cellular functions such as proliferation and differentiation. Aberrant Wnt signaling has been linked to the formation and metastasis of tumors. Porcupine, a member of the membrane-bound O-acyltransferase family of proteins, is an important component of the Wnt pathway. Porcupine catalyzes the palmitoylation of Wnt proteins, a process needed for their secretion and activity. Here we report a novel series of compounds obtained by a scaffold hybridization strategy from a known porcupine inhibitor class. The leading compound 59 demonstrated subnanomolar inhibition of Wnt signaling in a paracrine cellular assay. Compound 59 also showed excellent chemical, plasma and liver microsomal stabilities. Furthermore, compound 59 exhibited good pharmacokinetic profiles with 30% oral bioavailability in rat. Collectively, these results strongly support further optimization of this novel scaffold to develop better Wnt pathway inhibitors.
- Xu, Zhixiang,Li, Jiajun,Wu, Yiyuan,Sun, Zhijian,Luo, Lusong,Hu, Zhilin,He, Sudan,Zheng, Jiyue,Zhang, Hongjian,Zhang, Xiaohu
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p. 154 - 165
(2015/12/04)
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- Rh(I)-catalyzed decarbonylation synthesis of carbazoles via C-N cleavage
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A one-pot Rh(I)-catalyzed synthesis of 9-H carbazoles via C-N bond cleavage by activation of aldehyde C-H bonds is reported. This protocol offers good yields and tolerates a broad range of functional groups. Based on the extensive control experiments, we propose a plausible decarbonylation mechanism.
- Fan, Weizheng,Jiang, Shan,Feng, Bainian
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p. 4035 - 4038
(2015/06/02)
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- Direct synthesis of N -H carbazoles via iridium(III)-catalyzed intramolecular C-H amination
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The iridium-catalyzed dehydrogenative cyclization of 2-aminobiphenyls proceeds smoothly in the presence of a copper cocatalyst under air as a terminal oxidant through intramolecular direct C-H amination to produce N-H carbazoles. A similar iridium/copper system can also catalyze the unprecedented dimerization reaction of 2-aminobiphenyl involving 2-fold C-H/N-H couplings.
- Suzuki, Chiharu,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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p. 1597 - 1600
(2015/03/30)
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- One-pot synthesis of carbazoles via tandem C-C cross-coupling and reductive amination
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We have developed a highly efficient synthetic route to carbazoles that employs sequential C-C/C-N bond formation via Suzuki cross-coupling and Cadogan cyclization using commercially available or easily preparable starting materials. The developed method is compatible with electron neutral, rich or deficient substrates. The synthetic utility of this method was demonstrated by the concise syntheses of four natural products (glycozoline, glycozolicine, glycozolidine and clausenalene).
- Goo, Deuk-Young,Woo, Sang Kook
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supporting information
p. 122 - 130
(2015/12/30)
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- Synthesis of carbazoles by copper-catalyzed intramolecular C-H/N-H coupling
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A Cu-catalyzed intramolecular C-H amination for the synthesis of carbazoles has been developed. The key to success is the installation of the picolinamide-based directing group, which is spontaneously removed after the coupling event. The Cu catalysis proceeded smoothly under Pd- and I(III)-free conditions, and its mild oxidation aptitude enables the rapid and concise construction of heteroatom-incorporated carbazole core π-systems.
- Takamatsu, Kazutaka,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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p. 2892 - 2895
(2014/06/23)
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- Rapid synthesis of fused N-heterocycles by transition-metal-free electrophilic amination of arene C-H bonds
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We disclose an efficient and operationally simple protocol for the preparation of fused N-heterocycles starting from readily available 2-nitrobiaryls and PhMgBr under mild conditions. More than two dozen N-heterocycles, including two bioactive natural products, have been synthesized using this method. A stepwise electrophilic aromatic cyclization mechanism was proposed by DFT calculations. Controlled fusion: A transition-metal-free, low-temperature, and regioselective intramolecular amination of aromatic C(sp2)-H bonds provides fused N-heterocycles. This reaction is operationally simple and scalable (1-10 mmol) and the scope of substrates is wide (see scheme). Density functional calculations indicate that a stepwise electrophilic aromatic cyclization mechanism may be operative.
- Gao, Hongyin,Xu, Qing-Long,Yousufuddin, Muhammed,Ess, Daniel H.,Kuerti, Laszlo
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p. 2701 - 2705
(2014/03/21)
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- The first general and selective palladium(II)-catalyzed alkoxycarbonylation of arylboronates: Interplay among benzoquinone-ligated palladium(0) complex, organoboron, and alcohol solvent
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Methoxycarbonylation of aryl- and alken-ylboron compounds was performed using the palladium (II) acetate/triphenylphosphine [PdACHTUNGTRENNUNG(OAc) 2/PPh3] catalyst with p-benzoquinone as a stoichiometric oxidant in methanol at ambient temperature to obtain the corresponding methyl esters in good yields. A wide variety of functional groups including various carbonyl functionalities, nitrile, nitro, sulfone, and unprotected pyrrole rings were tolerated in the methoxycarbonlation, while the use of higher alcohols except for tert-butanol afforded various pchlorobenzoates in moderate to high yields. The catalytic alkoxycarbonylation proceeded without any acid or base additive, and an oxidative transmetalation step is proposed to explain the exceptional efficacy of this protocol. DFT and MP2 calculations support the proposed mechanism.
- Yamamoto, Yoshihiko
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supporting information; experimental part
p. 478 - 492
(2010/07/03)
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- ACYLGUANIDINE DERIVATIVE
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An object of the present invention is to provide a novel and excellent agent for treating or preventing dementia, schizophrenia and the like, based on the 5-HT5A receptor modulating action. It was confirmed that a compound characterized by a st
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Page/Page column 16
(2009/12/05)
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- ACYLGUANIDINE DERIVATIVE OR SALT THEREOF
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[Problem] To provide a compound which can be used in the prevention and/or treatment of diseases in which S-HT2B receptor and 5-HT7 receptor are concerned, particularly in the treatment of irritable bowel syndrome (IBS) and/or preven
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Page/Page column 18
(2008/12/05)
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- Microwave-enhanced cadogan cyclization: An easy access to the 2-substituted carbazoles and other fused heterocyclic systems
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A microwave-enhanced Suzuki-Miyaura cross-coupling reaction in combination with a microwave-assisted Cadogan reductive cyclization is presented as an easy access to a variety of 2-substituted carbazoles and other fused heterocyclic systems. Microwave irradiation was found very useful in minimizing the proto-deboronation issues in the cross-coupling reaction, and enhances the rate of reductive cyclization in a dramatic manner.
- Appukkuttan, Prasad,Van Der Eycken, Erik,Dehaen, Wim
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p. 127 - 133
(2007/10/03)
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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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- Stille and suzuki cross coupling reactions of o-nitrophenyl triflates: A versatile route to a variety of heterocycles
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The cross coupling reactions of selected o-nitrophenyl triflates with arylstannane and arylboron substrates are reported. The resultant 2-nitrobiphenyls provide ready access to a variety of substituted heterocycles.
- Holzapfel, Cedric W.,Dwyer, Catherine
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p. 1513 - 1518
(2007/10/03)
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