The role of a Lewis acid in the Nenitzescu indole synthesis

Velezheva, V. S.; Sokolov, Andrey I.; Kornienko, A.G.; Nelyubina, Yulia V.; Godovikov, Ivan A.; Peregudov, Аlexander S.; Mironov, A. F.

doi:10.1016/j.tetlet.2008.09.087

Cited by 35 publications

(21 citation statements)

References 13 publications

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“…In particular, we tried a reaction of 2‐(2‐chloropyridin‐3‐yl)cyclohexa‐2,5‐diene‐1,4‐dione 11 with 1.2 equiv. of 12 a using 1 mol% zinc iodide in CH 2 Cl 2 at 40 °C for 2 h [55] . The yield did not improve for the reaction with the use of Lewis acid, even after increasing the reaction time.…”

Section: Resultsmentioning

confidence: 93%

Tandem Nenitzescu Reaction/Nucleophilic Aromatic Substitution to Form Novel Pyrido Fused Indole Frameworks

et al. 2021

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5‐Hydroxyindoles are privileged structures that form part of various bioactive compounds. The Nenitzescu reaction of quinones and enamines is one of the most powerful methods to obtain 5‐hydroxyindoles. In this work, we have applied the Nenitzescu reaction to 2‐(2‐chloropyrid‐3‐yl)benzoquinones. Mixtures of regioisomers were obtained that could be separated in the 4‐ and 6‐substituted analogues, and then cyclized separately in a metal‐free base‐catalyzed reaction, affording novel tetracyclic indole derivatives. These are indeed the first examples reported in the literature of the linear pyrido[3′,2′ : 4,5]furo[3,2‐b]indole and angular 1H‐pyrido[2′,3′ : 4,5]furo[2,3‐c]indole systems. The regioselectivity and the yield of the Nenitzescu reaction were found to be dependent on the N‐substituent at the enamine. Furthermore, we analyzed the UV‐Vis and PL spectra of the new systems, and this was supported by DFT calculations, allowing us to compare the properties of angular compared to linearly shaped compounds.

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Section: Resultsmentioning

confidence: 93%

Tandem Nenitzescu Reaction/Nucleophilic Aromatic Substitution to Form Novel Pyrido Fused Indole Frameworks

et al. 2021

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“…These dative bonds are longer than the Zn-O bonds for Zn1 in the NO chelate but are similar to other reported values. [19] Related to complexes 3 and 4 are the complexes [H 2 L·ZnCl 2 ] and [LFe·ZnCl 2 ], reported by Velezheva et al [20] and Floriani et al, [21] respectively. [H 2 L·ZnCl 2 ] was prepared from the direct reaction of H 2 L with anhydrous ZnCl 2 in dichloromethane and is a mononuclear zinc complex in which the zinc(II) chloride is coordinated to the ligand through two oxygen atoms in a similar fashion to Zn2 in 3 and 4.…”

Section: Resultsmentioning

confidence: 99%

Di‐, Tetra‐, Penta‐ and Polynuclear Zinc Complexes Supported by a Flexible Tetradentate Schiff Base Ligand

2012

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When treated with Et2Zn, the tetradentate Schiff base N,N′‐ethylenebis(4‐iminopentan‐2‐one) (H2L) led to the formation of dimers, [L2Zn2], a tetranuclear complex, [L4Zn4] (1) and a polymeric material [LZn(Et)]n (2), thus highlighting the coordinative versatility of the ligand. Halogenation of 1 with SO2Cl2 or Br2 afforded in moderate yield the dinuclear zinc complexes [LZn(thf)·ZnCl2] (3) and [LZn(thf)·ZnBr2] (4). [LZn·ZnI(μ‐OEt)]2 (5) was isolated from the reaction of an in situ generated mixture of 1 and 2 with iodine. This product likely results from adventitious oxygen in the reaction mixture. This was seemingly confirmed by the diffusion of air into a solution of 2 in toluene, thereby resulting in a pentanuclear zinc complex, [(LZn·ZnEt)2{Zn(μ‐OEt)4}] (6). Complex 6 features a central Zn(OEt)4 unit, in which the ethoxide groups bridge two dinuclear fragments. The identities of complexes 1–6 were conclusively identified by X‐ray crystallography, thereby revealing similar structural features that were confirmed by spectroscopic data and, for 1–5, supported by DFT calculations.

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“…Velezheva and coworkers described the Lewis acidcatalyzed Nenitzescu indolization using zinc iodide in dichloromethane (Scheme 9, equation 1 and 43-45) [23], later improved to the use of zinc chloride (equations 2, 3) [24]. These workers also propose a face-to-face sandwich electron-transfer complex that mediates the oxidation-reduction step (equation 1).…”

Section: Scheme 5 Allen and Weiss Applications Of The Nenitzescu Indomentioning

confidence: 99%

Nenitzescu 5‐Hydroxyindole Synthesis

Gribble

2016

Indole Ring Synthesis

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The role of a Lewis acid in the Nenitzescu indole synthesis

Cited by 35 publications

References 13 publications

Tandem Nenitzescu Reaction/Nucleophilic Aromatic Substitution to Form Novel Pyrido Fused Indole Frameworks

Tandem Nenitzescu Reaction/Nucleophilic Aromatic Substitution to Form Novel Pyrido Fused Indole Frameworks

Di‐, Tetra‐, Penta‐ and Polynuclear Zinc Complexes Supported by a Flexible Tetradentate Schiff Base Ligand

Nenitzescu 5‐Hydroxyindole Synthesis

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