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Recent synthetic strategies for the construction of functionalized carbazoles and their heterocyclic motifs enabled by Lewis acids. RSC Adv 2023; 13:32596-32626. [PMID: 37936643 PMCID: PMC10626344 DOI: 10.1039/d3ra06396h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 10/25/2023] [Indexed: 11/09/2023] Open
Abstract
This article demonstrates recent innovative cascade annulation methods for preparing functionalized carbazoles and their related polyaromatic heterocyclic compounds enabled by Lewis acid catalysts. Highly substituted carbazole scaffolds were synthesized via Lewis acid mediated Friedel-Crafts arylation, electrocyclization, intramolecular cyclization, cycloaddition, C-N bond-formations, aromatization and cascade domino reactions, metal-catalyzed, iodine catalyzed reactions and multi-component reactions. This review article mainly focuses on Lewis acid-mediated recent synthetic methods to access a variety of electron-rich and electron-poor functional groups substituted carbazole frameworks in one-pot reactions. Polyaromatic carbazole and their related nitrogen-based heterocyclic compounds were found in several synthetic applications in pharma industries, energy devices, and materials sciences. Moreover, the review paper briefly summarised new synthetic strategies of carbazole preparation approaches will assist academic and pharma industries in identifying innovative protocols for producing poly-functionalized carbazoles and related highly complex heterocyclic compounds and discovering active pharmaceutical drugs or carbazole-based alkaloids and natural products.
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2
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Brønsted Acid-Catalyzed Reaction of N-arylnaphthalen-2-amines with Quinone Esters for the Construction of Carbazole and C-N Axially Chiral Carbazole Derivatives. J Org Chem 2023. [PMID: 36812409 DOI: 10.1021/acs.joc.2c02518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
We demonstrated here an efficient synthetic method of carbazole derivatives from readily available N-arylnaphthalen-2-amines and quinone esters catalyzed by Brønsted acid. With this strategy, a series of carbazole derivatives were obtained in good to excellent yields (76 to >99) under mild conditions. Large scale reaction illustrated the synthetic utility of this protocol. Meanwhile, a series of C-N axially chiral carbazole derivatives were also constructed in moderate to good yields (36-89% yield) with moderate to excellent atroposelectivities (44-94% ee) by using chiral phosphoric acid as a catalyst, which provides a novel strategy for the atroposelective construction of C-N axially chiral compounds and a new member of the C-N atropisomers.
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TPP‐NBS Induced [3+3] Cascade Annulation of Propargylic Alcohols and 1,3‐Bis Nucleophiles: Access to Chromenopyridines, 1,2‐Dihydropyridines**. ChemistrySelect 2023. [DOI: 10.1002/slct.202204964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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4
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A review towards synthesis of heterocycles using propargyl alcohols and propargyl amines. MONATSHEFTE FUR CHEMIE 2022. [DOI: 10.1007/s00706-022-02927-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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5
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Lewis Acid Zn(OTf)
2
Catalyzed Synthesis ofImidazo[1,2‐
a
]pyridines by [3+2] Annulation of 2‐Amino Pyridines and Propargylic Alcohols. ChemistrySelect 2022. [DOI: 10.1002/slct.202200063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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6
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Research Progress in the Cyclization Reactions with Propargyl Alcohols. CHINESE J ORG CHEM 2022. [DOI: 10.6023/cjoc202203037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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Synthesis of pyrano[3,2- c]quinolones and furo[3,2- c]quinolones via acid-catalyzed tandem reaction of 4-hydroxy-1-methylquinolin-2(1 H)-one and propargylic alcohols. RSC Adv 2022; 12:21066-21078. [PMID: 35919834 PMCID: PMC9302472 DOI: 10.1039/d2ra03416f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 07/17/2022] [Indexed: 11/28/2022] Open
Abstract
Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described. Depending mainly on the propargylic alcohol used, these tandem reactions proceed via either a Friedel–Crafts-type allenylation followed by 6-endo-dig cyclization sequence to form pyrano[3,2-c]quinolones or a Friedel–Crafts-type alkylation and 5-exo-dig ring closure sequence to afford furo[3,2-c]quinolones in moderate-to-high yields. The pyrano[3,2-c]quinolones products could be further transformed to tetracyclic 4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one derivatives. Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described.![]()
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8
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Reaction of Indole‐2‐Carboxylates/Carboxylic Acids with Propargylic Alcohols: Dearomative Ring Expansion/Spirocyclization vs Fused Pentacyclics. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202101038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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9
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Acid‐Promoted Cascade Reaction of 4
H
‐Chromenes: Access to Hexahydronapthalenes via Decarboxylative Intramolecular Cyclization. ChemistrySelect 2021. [DOI: 10.1002/slct.202004076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Benzannulation strategies for the synthesis of carbazoles, indolocarbazoles, benzocarbazoles, and carbolines. Org Chem Front 2021. [DOI: 10.1039/d1qo00092f] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review presents a critical and authoritative analysis of several exciting benzannulation approaches developed in the past decade for the construction of carbazoles, indolocarbazoles, benzocarbazoles, and carbolines.
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11
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Dearomatization-Rearomatization Strategy for Synthesizing Carbazoles with 2,2'-Biphenols and Ammonia by Dual C(Ar)-OH Bond Cleavages. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:13200-13205. [PMID: 32223264 DOI: 10.1021/acs.jafc.0c00644] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Carbazole is an essential building block in various pharmaceuticals, agrochemicals, natural products, and materials. For future sustainability, it is highly desirable to synthesize carbazole derivatives directly from renewable resources or cheap raw materials. Phenolic compounds are a class of degradation products of lignin. On the other hand, ammonia is a very cheap industrial inorganic chemical. Herein, an efficient dearomatization-rearomatization strategy has been developed to directly cross-couple 2,2'-biphenols with ammonia by dual C(Ar)-OH bond cleavages. This strategy provides a greener pathway to synthesize valuable carbazole derivatives from phenols.
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12
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13
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14
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Zn(OTf) 2-Catalyzed Formal [3 + 3] Cascade Annulation of Propargylic Alcohols with 2-Aminochromones: Accessing the Chromeno[2,3- b]pyridines. J Org Chem 2019; 84:13967-13974. [PMID: 31552742 DOI: 10.1021/acs.joc.9b02120] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A Zn(OTf)2-catalyzed formal [3 + 3] cascade annulation strategy for the synthesis of functionalized chromeno[2,3-b]pyridines has been developed using propargylic alcohols and 2-aminochromones as the substrates. The protocol provides a convenient and atom-economical method of accessing a broad range of chromeno[2,3-b]pyridine derivatives in excellent yields with good functional-group tolerance. The method is also effective on the gram scale, which highlights the inherent practicality of this synthetic transformation.
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15
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Brønsted acid−catalyzed synthesis of tetrasubstituted allenes and polysubstituted 2H-chromenes from tertiary propargylic alcohols. Tetrahedron 2019. [DOI: 10.1016/j.tet.2019.05.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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16
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17
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Gold catalysed transformation of 2-arylindoles to terphenyl amines via 3-dienyl indoles and Brønsted acid promoted formation of 2-carboxyindoles to 3-indenylindoles via 3-allenylindoles. Org Biomol Chem 2019; 17:3275-3284. [PMID: 30848275 DOI: 10.1039/c9ob00232d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gold-catalysed intramolecular reaction of unprotected/protected 3-dienyl indoles leads to the formation of functionalised terphenylamines with high efficiency; this reaction can also be accomplished in one pot by starting with 2-arylindole and propargylic alcohols. This reaction occurs via 3-dienyl indoles and proceeds likely by gold-catalysed cascade cyclisation, aromatisation and fragmentation of the indole heterocyclic moiety. We have also found that PTSA can work well giving comparable yields, but at least one mole equivalent of PTSA is required. On the other hand, 3-indenylindoles have been synthesised from indole-2-carboxylates (2-carboxyindoles) and propargylic alcohols through Brønsted acid mediation. Many of these indenylindoles exhibit isomerism (probably diastereomers) in the solution state (1H NMR). Two examples of indolo-indenyl acetates have been prepared by reacting the above terphenylanilines with PhI(OAc)2. Key products are characterised by X-ray crystallography.
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18
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Access to polyfunctionalized carbazoles through π-extension of 2-methyl-3-oxoacetate indoles. Org Chem Front 2019. [DOI: 10.1039/c9qo01093a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A structurally diverse set of polyfunctionalized carbazoles was efficiently synthesized in acceptable to excellent yields.
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Nitromethane as a Carbanion Source for Domino Benzoannulation with Ynones: One‐Pot Synthesis of Polyfunctional Naphthalenes and a Total Synthesis of Macarpine. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201810652] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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20
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Nitromethane as a Carbanion Source for Domino Benzoannulation with Ynones: One‐Pot Synthesis of Polyfunctional Naphthalenes and a Total Synthesis of Macarpine. Angew Chem Int Ed Engl 2018; 57:16847-16851. [DOI: 10.1002/anie.201810652] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 10/07/2018] [Indexed: 11/10/2022]
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21
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Transition-Metal-Free, Brønsted Acid-Mediated Cascade Sequence in the Reaction of Propargyl Alcohols with Sulfonamido-indoles/-indolines: Highly Substituted δ- and α-Carbolines. J Org Chem 2018; 83:15043-15056. [DOI: 10.1021/acs.joc.8b02293] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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22
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Cu(I)-/Base-Mediated Domino [5 + 3 + 1] Annulation for Highly π-Extended Carbazole Frameworks and DFT Mechanistic Insights. Org Lett 2018; 20:5648-5652. [DOI: 10.1021/acs.orglett.8b02363] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Sequential σ-Bond Insertion/Benzannulation Involving Arynes: Selective Synthesis of Polysubstituted Naphthalenes. J Org Chem 2018; 83:9156-9165. [PMID: 29877082 DOI: 10.1021/acs.joc.8b01207] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
An interesting σ-bond insertion/benzannulation reaction for the synthesis of polysubstituted naphthalene derivatives has been developed from readily accessible ketones, arynes, and alkynoates. This practical and transition-metal-free method provides a novel route to diverse naphthalenes through a substrate-controlled rearrangement reaction with the cleavage of C-C bonds.
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24
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Catalyst-free and atom-economic synthesis of substituted 1-acetyl and 1-hydroxyl carbazoles. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.02.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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25
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Facile synthesis of substituted diaryl sulfones via a [3 + 3] benzannulation strategy. Org Biomol Chem 2018; 16:3560-3563. [DOI: 10.1039/c8ob00662h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A metal-free and efficient synthesis of highly substituted diaryl sulfones via a base-mediated [3 + 3] benzannulation strategy.
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26
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N-Bromosuccinimide (NBS)-Catalyzed C-H Bond Functionalization: An Annulation of Alkynes with Electron Withdrawing Group (EWG)-Substituted Acetyl Indoles for the Synthesis of Carbazoles. Org Lett 2017; 19:6140-6143. [PMID: 29094599 DOI: 10.1021/acs.orglett.7b03021] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An N-bromosuccinimide-catalyzed intermolecular annulation of acetyl indoles with alkynes was developed, allowing for regioselective formation of valuable carbazoles through direct C-H bond functionalization. The readily available catalyst, wide substrate scope, gram scale synthesis, and mild conditions make this method practical. Mechanistic investigations indicate that the bromination of acetyl indole takes place to generate a bromide intermediate, followed by coupling with an alkyne and intramolecular cycloaromatization to furnish carbazole products.
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27
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Synthesis of Organophosphorus Compounds through Copper-Catalyzed Annulation Involving C–O and C–P Bond Formations. J Org Chem 2017; 82:11636-11643. [DOI: 10.1021/acs.joc.7b01947] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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28
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Synthesis of spiroindenyl-2-oxindoles by montmorillonite K-10-catalyzed tandem Friedel-Crafts alkenylation/hydroarylation of propargylic alcohols with sterically hindered and electron-rich arenes. Tetrahedron Lett 2017. [DOI: 10.1016/j.tetlet.2017.09.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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29
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Lewis Acid‐Catalyzed [4+2] Annulation between Propargylic Alcohols with Benzo[
d
]isoxazoles. Adv Synth Catal 2017. [DOI: 10.1002/adsc.201700495] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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30
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One-Pot Synthesis of 3-(Benzo[e
]indol-2-yl)-2-oxindoles from Isatin-derived Propargylic Alcohols and N
-Acetyl-2-aminonaphthalenes. B KOREAN CHEM SOC 2017. [DOI: 10.1002/bkcs.11127] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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31
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Synthesis of Iodine-Substituted Quinolines, Quinolinium Salts, and Isoquinolinium Salts via a Three-Component Tandem Reaction of Aryl Azides, Propargylic Alcohols, and Iodine. ASIAN J ORG CHEM 2016. [DOI: 10.1002/ajoc.201600503] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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32
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33
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Regio- and Stereoselective Domino Synthesis of Oxazolo Fused Pyridoindoles and Benzofurooxazolo Pyridines from ortho-Alkynylarylaldehydes. J Org Chem 2016; 81:9356-9371. [DOI: 10.1021/acs.joc.6b02062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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34
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Synthetic Approach to Dictyodendrins: A Facile Synthesis of Pyrrolo[2,3-c]carbazole, Pyrrolodibenzothiophene, and Benzo[e]indole. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600674] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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35
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Enaminones as Synthons for a Directed C−H Functionalization: Rh
III
‐Catalyzed Synthesis of Naphthalenes. Angew Chem Int Ed Engl 2016; 55:9384-8. [DOI: 10.1002/anie.201603943] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 05/14/2016] [Indexed: 12/31/2022]
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36
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Ring-Opening/Expansion Rearrangement of Cycloprop[2,3]inden-1-ols Catalyzed byp-Toluenesulfonic Acid. Adv Synth Catal 2016. [DOI: 10.1002/adsc.201600246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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37
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Enaminones as Synthons for a Directed C−H Functionalization: Rh
III
‐Catalyzed Synthesis of Naphthalenes. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201603943] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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38
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Diastereoselective Synthesis of Substituted Tetrahydroisoquinolines and Isoindolinesviaa Silver(I) Triflate-Promoted Tandem Reaction. Adv Synth Catal 2016. [DOI: 10.1002/adsc.201500903] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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39
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One-Pot Sequential Propargylation/Cycloisomerization: A Facile [4+2]-Benzannulation Approach to Carbazoles. Chemistry 2016; 22:2501-6. [DOI: 10.1002/chem.201503496] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Indexed: 11/11/2022]
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40
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Silver catalyzed domino aza-annulation/Diels–Alder cyclization of 2-ene-yne anilines: a facile one-pot access to carbazole, dihydrocarbazole and tetrahydrocarbazole frameworks. Chem Commun (Camb) 2016; 52:4581-4. [DOI: 10.1039/c6cc00633g] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
AgSbF6-catalyzed domino aza-annulation/Diels–Alder/aromatization cascade for the construction of carbazoles, dihydrocarbazoles, tetrahydrocarbazoles and 3-indolyl-substituted tetrahydrocarbazoles was achieved.
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Synthesis of polysubstituted 1,2-dihydroquinolines and indoles via cascade reactions of arylamines and propargylic alcohols catalyzed by FeCl3·6H2O. Org Biomol Chem 2016; 14:2515-21. [DOI: 10.1039/c5ob02658j] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Syntheses of 1,2-dihydroquinolines from arylamines and propargylic alcohols via cascade Friedel–Crafts-type reaction and 6-endo-trig hydroamination catalyzed by FeCl3·6H2O are described.
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Construction of highly functionalized carbazoles via condensation of an enolate to a nitro group. Chem Sci 2015; 6:7028-7033. [PMID: 29861941 PMCID: PMC5947529 DOI: 10.1039/c5sc02407b] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 09/02/2015] [Indexed: 12/20/2022] Open
Abstract
This paper describes a novel synthesis of highly functionalized and diverse carbazoles via transition-metal-free and mild base-promoted condensations of readily available 2-nitrocinnamaldehyde or 2-nitrochalcones with various β-ketoesters or 1,3-diaryl-2-propanones. The method selectively forms four bonds by the intramolecular conjugate addition of an enolate to the enal or chalcone bearing an o-nitro group. This group then undergoes in situ N-O bond cleavage under non-reductive conditions in a one-pot procedure. This protocol allows for the introduction of various functional groups at all positions of the newly formed aromatic ring of the carbazole moiety. The utility of this methodology is further illustrated by the concise synthesis of naturally occurring hyellazole and chlorohyellazole.
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Facile Synthesis of Trisubstituted Carbazoles by Acid‐Catalyzed Ring‐Opening Annulation of 2‐Amidodihydrofurans with Indoles. Chemistry 2015; 21:16383-6. [DOI: 10.1002/chem.201503260] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Indexed: 11/05/2022]
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44
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45
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Brønsted Acid Mediated Alkenylation and Copper-Catalyzed Aerobic Oxidative Ring Expansion/Intramolecular Electrophilic Substitution of Indoles with Propargyl Alcohols: A Novel One-Pot Approach to Cyclopenta[c]quinolines. Org Lett 2014; 16:6060-3. [DOI: 10.1021/ol502783j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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46
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Diversity oriented convergent access for collective total synthesis of bioactive multifunctional carbazole alkaloids: synthesis of carbazomycin A, carbazomycin B, hyellazole, chlorohyellazole, and clausenaline D. Org Lett 2014; 16:5470-3. [PMID: 25296703 DOI: 10.1021/ol502721r] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Facile syntheses of imperative carbazole alkaloids carbazomycin A, carbazomycin B, hyellazole, chlorohyellazole, and clausenaline D have been demonstrated starting from readily available Boc-protected 3-formylindole and dimethyl maleate. The suitably substituted aromatic rings have been designed comprising three/four significant C-C bond forming reactions. The competent Wittig reaction, selective monoalkylations, one-pot regioselective Weinreb amide formation and Boc-deprotection, well designed Grignard reactions, dehydrative intramolecular cyclizations, and Baeyer-Villiger rearrangement of aromatic aldehydes were the main features.
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47
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Regioselective π-extension of indoles with rhodium enalcarbenoids – synthesis of substituted carbazoles. Org Biomol Chem 2014; 12:8641-5. [DOI: 10.1039/c4ob01693a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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