Direct Assembly of Benzo[<i>a</i>]carbazole‐5‐carboxylates via a Diels–Alder Reaction with Arynes and 3‐Alkenylindoles

Tao, Yuan; Zhang, Fei; Tang, Chunhui; Wu, Xin‐Yan; Sha, Feng

doi:10.1002/ajoc.201402152

Cited by 49 publications

(11 citation statements)

References 72 publications

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“…Due to their importance, a number of reliable methods for the preparation benzo[ a ]carbazole derivatives have been developed . Among them, a popular approach is to use diazo compounds as metal carbene precursors to form the required C−C bond(s) in constructing the benzo[ a ]carbazole scaffold ,,.…”

Section: Figurementioning

confidence: 99%

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

et al. 2018

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A highly chem-and regioselective synthesis of diversely substituted benzo[a]carbazoles and indolo[2,1-a]-isoquinolines through Rh(III)catalyzed cascade reactions of 2-arylindoles with sulfoxonium ylides is presented. To be specific, treatment of 2-arylindoles, 2-arylindole-3-carbaldehydes, 2-arylindole-3-carbonitriles or 2-aryl-3-methylindoles with sulfoxonium ylides under the catalysis of Rh(III) led to the selective formation of 6aryl/alkyl benzo[a]carbazoles, 5-acylbenzo[a]carbazoles, 6-amino-5-acylbenzo[a]carbazoles or 12methylindolo[2,1-a]isoquinolines, respectively. Mechanistically, the formation of the title compounds involves a cascade process including metalation of the inert C(sp 2 )ÀH bond, migratory insertion of ylide into the carbon-metal bond via an in situ carbenoid formation, protodemetalation, and condensation. To our knowledge, this is the first example in which b-carbonyl sulfoxonium ylides were used as stable carbene precursors and bifunctional C2 synthons to afford benzo[a]carbazoles and indolo[2,1-a]isoquinolines.

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Section: Figurementioning

confidence: 99%

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

et al. 2018

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“…In order to synthesize ethyl benzo[ a ]carbazole‐5‐carboxylates 4i–4k (Scheme ), the required starting materials 3i–3k were prepared according to the reported methods (see Appendix S1) 6h–j . The reaction of 3i under the standard reaction condition afforded ethyl benzo[ a ]carbazole‐5‐carboxylate 4i in good yield (73%) in short time (5 h). Similarly, the reaction of 3j ( syn / anti mixture) afforded 4j in good yield (82%).…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Benzo[a]carbazole Derivatives from β‐(2‐Arylindolyl)nitroalkanes via Mn(OAc)₃‐mediated Cyclization

Kim

Lim

Min

et al. 2016

Bulletin Korean Chem Soc

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Diversely substituted benzo [a]carbazoles and related derivatives are important because of their interesting biological activities such as neuroprotective property, antitumor activity, and kinase inhibitory activity. 1 Thus, various synthetic methods have been developed 2 including Lewis acidcatalyzed annulation of 2-arylindoles with propargylic alcohol derivatives, 2a,b double cascade cyclization of diynes catalyzed by gold, 2c-e iodine, 2f or palladium, 2g and coppercatalyzed synthesis via α-C-arylation of ketones. 2h Recently, we also reported the synthesis of benzo[a]carbazoles from 2-arylindoles via sequential propargylation, propargyl-allenyl isomerization, and 6π-electrocyclization approach, as shown in Scheme 1. 3 Various 5-benzyl-and 5-methylbenzo[a]carbazoles have been synthesized; however, 5-unsubstituted benzo[a]carbazoles could not be synthesized by the approach. 3 In order to develop a synthetic method of 5-unsubstituted benzo[a]carbazoles, we decided to examine the reaction of β-(2-phenylindolyl) nitroalkane 3a by Mn(OAc) 3 -mediated cyclization and subsequent elimination of nitrous acid, 4,5 as shown in Scheme 1. A similar synthesis of a naphthalene ring via Mn(OAc) 3mediated intramolecular oxidative coupling reaction between arene and nitroalkane moieties has already been reported in the previous studies. 5a The required starting materials 3a-3h were prepared from corresponding 2-arylindoles and β-nitrostyrenes according to the reported methods (see Appendix S1, Supporting information). 6a-g As reported in our previous paper, 5a the reaction of 3a was examined in EtOH (reflux, 24 h) in the presence of Mn(OAc) 3 (4.0 equiv). To our delight, 4a was obtained in a reasonable yield (56%) along with a low yield of 5-nitro derivative 5a (13%). The reactions in other solvents such as MeOH, n-propanol, n-butanol, and polyethylene glycol (PEG)-3400/ t BuOH were less effective when compared with EtOH. The reaction in AcOH showed the formation of many intractable side products. The use of CAN (cerium ammonium nitrate) in EtOH was completely ineffective. When we used lesser amount of Mn(OAc) 3 (3.0 equiv) in EtOH (reflux, 24 h), the yields of 4a (48%) and 5a (8%) decreased a little.The synthesis of various benzo[a]carbazoles was carried out under the typical reaction condition, and the results

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“…The syntheses of 3-alkenylindoles can generally be classified into the following three categories: (i) by Wittig or Doebner reaction of indoles bearing a 3-aldehyde group; (ii) by 1,4-or 1,2-addition of α,β-enones or carbonyl compounds, followed by oxidation or elimination, respectively; (iii) by Pd-catalysed oxidative coupling of indoles with activated alkenes. Several groups have used Wittig reactions for the synthesis of 3-alkenylindoles [13][14][15]. Another variant that uses the Doebner condensation was reported by Singh and co-worker, who condensed indole-3-carbaldehyde with phenylacetic acid in the presence of pyridine as the solvent/base and piperidine as the catalyst [16].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

Paul

Chatterjee

Banerjee³

et al. 2020

Beilstein J. Org. Chem.

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3-Alkenylindoles are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron-withdrawing and electron-donating groups on the indole moiety. Additionally, a “robustness screen” has also been employed to demonstrate the tolerance of several functional groups relevant to medicinal chemistry. With respect to the Ru nanocatalyst, it has been demonstrated that it is recoverable and recyclable up to four cycles. Also, the catalyst acts through a heterogeneous mechanism, which has been proven by various techniques, such as ICPMS and three-phase tests. The nature of the Ru nanocatalyst surface has also been thoroughly examined by various techniques, and it has been found that the oxides on the surface are responsible for the high catalytic efficiency of the Ru nanocatalyst.

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Direct Assembly of Benzo[a]carbazole‐5‐carboxylates via a Diels–Alder Reaction with Arynes and 3‐Alkenylindoles

Cited by 49 publications

References 72 publications

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

Synthesis of Benzo[a]carbazole Derivatives from β‐(2‐Arylindolyl)nitroalkanes via Mn(OAc)₃‐mediated Cyclization

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

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Direct Assembly of Benzo[a]carbazole‐5‐carboxylates via a Diels–Alder Reaction with Arynes and 3‐Alkenylindoles

Cited by 49 publications

References 72 publications

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

Selective Synthesis of Benzo[a]Carbazoles and Indolo[2,1‐a]‐Isoquinolines via Rh(III)‐Catalyzed C−H Functionalizations of 2‐Arylindoles with Sulfoxonium Ylides

Synthesis of Benzo[a]carbazole Derivatives from β‐(2‐Arylindolyl)nitroalkanes via Mn(OAc)3‐mediated Cyclization

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

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Synthesis of Benzo[a]carbazole Derivatives from β‐(2‐Arylindolyl)nitroalkanes via Mn(OAc)₃‐mediated Cyclization