- 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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p. 2582 - 2586
(2021/03/09)
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- 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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- Synthesis of Carbazoles and Related Heterocycles from Sulfilimines by Intramolecular C?H Aminations
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While direct nitrene insertions into C?H bonds have become an important tool for building C?N bonds in modern organic chemistry, the generation of nitrene intermediates always requires transition metals, high temperatures, ultraviolet or laser light. We report a mild synthesis of carbazoles and related building blocks through a visible light-induced intramolecular C?H amination reaction. A striking advantage of this new method is the use of more reactive aryl sulfilimines instead of the corresponding hazardous azides. Different catalysts and divergent light sources were tested. The reaction scope is broad and the product yield is generally high. An efficient gram-scale synthesis of Clausine C demonstrates the applicability and scalability of this new method.
- Hashmi, A. Stephen K.,Song, Lina,Tian, Xianhai
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supporting information
p. 12342 - 12346
(2020/05/19)
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- Nitrogen-Iodine Exchange of Diaryliodonium Salts: Access to Acridine and Carbazole
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A nitrogen-iodine exchange protocol of diaryliodonium salts with sodium azide salt is developed for general construction of significant functional acridines and carbazoles, in which introduction of nitrogen at a late stage was successfully established avoiding heteroatom incompatibility. Inorganic sodium azide served as the sole nitrogen atom source in this transformation. The diversiform functional acridines and carbazoles were comprehensively achieved through annulated diaryliodonium salts, respectively. Notably, Acridine orange (a fluorescent indicator for cell lysosomal dye) and Carprofen (a nonsteroidal anti-inflammatory drug) were efficiently established through this protocol.
- Wang, Ming,Fan, Qiaoling,Jiang, Xuefeng
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supporting information
p. 216 - 219
(2018/01/17)
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- Carbazole compound, and synthesis method and application of compound
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The invention discloses a carbazole compound represented by a formula (2) and a synthesis method of the compound. A high-iodine salt is taken as a reaction raw material, and under the action of an inorganic nitrogen reagent, an additive, a base and a metal catalyst, a reaction is carried out in a solvent under a condition of 80-150 DEG C to obtain various carbazole compounds. According to the method provided by the invention, nitrogen atoms are introduced in a later period, so that the non-compatibility of nitrogen heterocyclic rings to the reaction conditions such as the metal catalyst and the like in an early reaction period is avoided. In addition, two aryl groups in the high-iodine salt are fully utilized, so that the atomic economic efficiency of the method provided by the present invention is fully exhibited. The carbazole compound prepared by the method provided by the invention can be further applied to the synthesis of non-steroidal anti-inflammatory drug carprofen.
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Paragraph 0058-0061
(2018/06/15)
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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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- Preparation of 2 - substituted oxazole compounds
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The present invention belongs to the field of organic chemistry, and particularly relates to a preparation method for 2-substituted carbazole compounds. According to the preparation method provided by the present invention, the raw material source is wide, reaction operation and post-treatment are simple and convenient, the yield is high, the application range is wide, and the industrial production is facilitated.
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-
Paragraph 0027; 0028
(2018/02/28)
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- Synthetic method of carbazole and derivatives thereof
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The invention discloses a synthetic method of carbazole and derivatives thereof. The synthetic method is characterized in that the carbazole and derivatives thereof are obtained by N-substituted reaction, vinylation reaction, removal of R2 group and olefin closed-loop double decomposition reaction. According to the synthetic method of the carbazole and derivatives thereof, disclosed by the invention, various derivatives of the carbazole can be synthesized according to substituent groups on indole rings of raw materials; in addition, no substituent group is formed on N of the carbazole; the substituent group can be used as an intermediate as required for next-step synthesis. Meanwhile, according to the synthetic method disclosed by the invention, the carbazole and derivatives thereof are synthesized by using the raw materials with abundant sources, and further the huge demand of the carbazole and derivatives thereof is met. Besides, a synthetic route is simple, reaction conditions are easily controlled and realized, the yield of a product is high, and higher practicality is realized.
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Paragraph 0070; 0071; 0072; 0073; 0074; 0075; 0106-0111
(2017/07/18)
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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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- Synthesis of the Carbazole Scaffold Directly from 2-Aminobiphenyl by Means of Tandem C–H Activation and C–N Bond Formation
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An efficient method for the synthesis of the carbazole scaffold was designed and investigated. The method was developed to produce substituted carbazoles by an intramolecular combination of a free amine group and an arene. The steps of the method involved tandem Pd-catalyzed C–H activation and intramolecular C–N bond formation. The method showed good functional group tolerance, and substituent(s) could be on either of the two rings or on both of the two rings of the 2-aminobiphenyl substrate. After ring closure, the reduced Pd catalyst was oxidized to PdIIby hydrogen peroxide. The novel method was also demonstrated to operate excellently with the corresponding 2-N-acetylaminobiphenyls.
- Bj?rsvik, Hans-René,Elumalai, Vijayaragavan
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supporting information
p. 5474 - 5479
(2016/11/25)
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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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- 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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- 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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- 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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- Recyclable copper catalyzed nitrogenation of biphenyl halides: A direct approach to carbazoles
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A novel A21-CuI catalyzed direct nitrogenation of biphenyl halides for the direct synthesis of carbazoles via a direct C-H amination process has been developed. A recyclable and inexpensive Cu-catalyst was successfully employed in N-heterocyclic compound synthesis via tandem azidation and C-H amination, which makes this protocol very practical and easy to handle.
- Ou, Yang,Jiao, Ning
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supporting information
p. 3473 - 3475
(2013/05/22)
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- CARBAZOLE COMPOUND AND USE THEREOF
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A carbazole compound represented by the following formula: wherein, when m=1, n=0, Ar1, Ar2, Ar3 and X2 are C6-50 aryl or C4-50 heteroaryl, provided that Ar1 and Ar2, or Ar3 and X2 may form together a ring; X1═C6-50 arylene; R1, R2, R4, R5 and R7 are H, halogen, amino, C1-18 alkyl, C1-18 alkoxy, C6-50 aryl or C4-50 heteroaryl, R3 and R6 are H, halogen, C1-18 alkyl, C1-18 alkoxy, C6-50 aryl or C4-50 heteroaryl; when m=0, n=1-3, Ar3, Ar4 and Ar5 are C6-50 aryl or C4-50 heteroaryl, Ar4 and Ar5 may form together a ring; X1═C1-18 alkyl, C6-50 aryl or C4-50 heteroaryl; X2═C6-50 arylene; R1-R7 are H, halogen, C1-18 alkyl, C1-18 alkoxy, C6-50 aryl or C4-50 heteroaryl; when m=0, n=0, X1═C1-18 alkyl, C6-50 aryl or C4-50 heteroaryl; Ar3 and X2 are C6-50 aryl or C4-50 heteroaryl; R2═H, halogen, C1-18 alkyl, C1-18 alkoxy; R1 and R3-R7 are H, halogen, C1-18 alkyl, C1-18 alkoxy, C6-50 aryl or C4-50 heteroaryl. The carbazole compound is suitable for an organic EL device.
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- One-pot synthesis of carbazoles from cyclohexanones and arylhydrazine hydrochlorides under metal-free conditions
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One-pot synthesis of carbazoles from cyclohexanones and arylhydrazine hydrochlorides is disclosed. Various substituted carbazoles were obtained in moderate to good yields via a sequence of condensation, cyclization and dehydrogenation under metal free conditions using molecular oxygen as an oxidant.
- Xiao, Fuhong,Liao, Yunfeng,Wu, Mingyue,Deng, Guo-Jun
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supporting information
p. 3277 - 3280
(2013/01/16)
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- An improved palladium-catalyzed conversion of aryl and vinyl triflates to bromides and chlorides
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A facile Pd-catalyzed conversion of aryl and vinyl triflates to aryl and vinyl halides (bromides and chlorides) is described. This method allows convenient access to a variety of aryl, heteroaryl, and vinyl halides in good to excellent yields and with greatly simplified conditions relative to our previous report.
- Pan, Jun,Wang, Xinyan,Zhang, Yong,Buchwald, Stephen L.
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supporting information; experimental part
p. 4974 - 4976
(2011/11/06)
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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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- Carbamate caspase inhibitors and uses thereof
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This invention provides caspase inhibitors of formula I: wherein Z is oxygen or sulfur; R1 is hydrogen, —CHN2, R, CH2OR, CH2SR, or —CH2Y; Y is an electronegative leaving group; R2 is COsub
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- Synthesis of carbazoles from N-(N,N-diarylamino)phthalimides with aluminum chloride via diarylnitrenium ions
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Generation of diarylnitrenium ions from N-(N,N-diarylamino)phthalimides by treatment with AlCl3 in benzene or in 1,2-dichloroethane leads to formation of carbazoles by intramolecular C-C bond formation. The reaction proceeds in synthetically useful yields.
- Kikugawa,Aoki,Sakamoto
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p. 8612 - 8615
(2007/10/03)
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- Oxidation of diphenylamines by iodate - A kinetic study
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Oxidation of diphenylamines (DPA) by iodate in aqueous methanol (70percent, v/v) at 303 K is first order in and fractional order in and is acid-catalysed.There is a dipole-dipole interaction between the oxidant and DPA.The substituent effect on the rate of reaction shows that electron-relasing groups on the benzene ring enhance the rate and electron-withdrawing groups retard the rate compared to the unsubstituted DPA.The product identified is the corresponding carbazole.Thermodynamic parameters are calculated and a suitable mechanism is proposed.
- Brahmaiah, A.,Manikyamba, P.,Sundaram, E.V.
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p. 247 - 251
(2007/10/02)
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- The Pyrolysis of 2-Azidobenzoates. A New Synthesis of Carbazoles and Other N-Heterocycles
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The spray pyrolysis of aryl 2-azidobenzoates yields carbazoles, involving a rearrangement whereby the nitrogen of the product is attached to the aryl 1-carbon, a process involving a spiro 6-membered intermediate.When the aryl ortho-positions were both alkyl substituted the product was ab acridan instead.With an ortho-carboxylate, acridone formation competed with that of carbazole.When the CO-O group of the substrate was replaced by O-CO, CO-S, CO-NPh, or SO2-O the pyrolysis was ineffective.Benzyl 2-azidobenzoates, however, pyrolysed to yield 1-benzyl-2,1-benzisoxazolones by an unprecedented C-O insertion reaction of the intermediate nitrene.
- Clancy, Michael G.,Hesabi, Massoud M.,Meth-Cohn, Otto
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p. 429 - 434
(2007/10/02)
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- One-electron photooxidation of carbazole in the presence of carbon tetrachloride. Part II. Carbon tetrachloride as a reaction medium. Use of ammonia after irradiation and during irradiation
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In part I of this series of papers we proposed the mechanism of electron transfer as the primary photochemical reaction in the carbazole - carbon tetrachloride system along with a secondary photochemical reaction initiated by transformations of the radical cation of carbazole in the solvent cage resulting in intermediates: .In this paper we discuss the influence of ammonia, used after and during irradiation, on the mechanism of secondary transformation and the formation of thermodynamically stable products in the system studied.Such compounds as N-cyanocarbazole, 1-cyanocarbazole, and 3-cyanocarbazole have been formed as the main products during neutralization of the photolyte solution by ammonia gas.The mechanism of formation of these compounds has been explained by the chemical reaction of ammonia with cations α and γi.If ammonia is present in the solution of carbazole in CCl4 during irradiation, such products as N,N'-dicarbazyl and N-cyanocarbazole are mainly formed along with 3-(N-carbazyl)carbazole, 3,9-di-(N-carbazyl)carbazole, and N-cyano-3-(N-carbazyl)carbazole.In such a case, reactions of radicals β are the determining factors in the secondary photochemical transformations.Radicals β are formed by the reaction involving ammonia with radical cations of carbazole.All the results in this paper have been discussed taking under consideration the influence of the reaction media on the mechanism of photochemical transformation of carbazole.
- Zelent, Bogumil,Durocher, Gilles
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p. 2442 - 2450
(2007/10/02)
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