Synthesis of a Variety of Activated Pyrrolo[3,2,1-ij]quinolines

Jumina, Jumina; Wenholz, Daniel S.; Kumar, Naresh; Black, David StC.

doi:10.1055/s-0037-1612280

Cited by 4 publications

(1 citation statement)

References 19 publications

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“…The pyrrolo[3,2,1-ij]quinoline framework can be synthesised by cyclisation of tetrahydroquinoline derivatives to complete the indole ring, 1,2 or by cyclisation of 1-or 7-substituted indoles to complete the tetrahydroquinoline ring. [3][4][5][6][7][8][9][10][11] Our methodology in this work has involved the specific activation at C7, as a consequence of placing the electron-donating methoxy groups at C4 and C6. In particular, 3-substituted-4,6dimethoxyindoles undergo smooth formylation at C7 and C2, with the major product being the 7carbaldehyde.…”

Section: Introductionmentioning

confidence: 99%

A new synthetic route to pyrroloquinolines and pyrroloindoles

Pchalek¹,

Condie²,

Kumar³

et al. 2021

Arkivoc

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4,6-Dimethoxy-3-substituted-indole-7-carbaldehydes and 4,6-dimethoxy-3-substituted-indole-2carbaldehydes undergo reaction with dimethyl acetylenedicarboxylate and triphenylphosphine to give the corresponding pyrroloquinolines and pyrroloindoles respectively. In the case of an indole-2,7-dicarbaldehyde, reaction at the 2-carbaldehyde is preferred, giving the related pyrroloindole. In the case of a 6-hydroxy-4methoxy-3-substituted-indole-7-carbaldehyde formation of a pyrroloquinoline is preferred to cyclisation on to the phenolic group to generate a pyranoindole. The pyrroloquinolines and pyrroloindoles are highly fluorescent.

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Section: Introductionmentioning

confidence: 99%

A new synthetic route to pyrroloquinolines and pyrroloindoles

Pchalek¹,

Condie²,

Kumar³

et al. 2021

Arkivoc

Self Cite

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Six-membered ring systems: pyridines and benzo derivatives

Badenock

2021

Progress in Heterocyclic Chemistry

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Hexafluoroisopropanol-Mediated Intramolecular Ring-Opening Cyclization of Indolyl-N-Tethered Epoxides: Tether-Length-Controlled Synthesis of 1,7- and 1,2-Fused Indoles

2021

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Despite having the capability to construct benzo-fused heterocycles in complete atom economy and high chemo-, regio-, enantio-, and diastereoselectivities, intramolecular Friedel–Crafts epoxide arene cyclization (IFCEAC) remains underutilized in organic synthesis. The wide adaptation of this powerful Csp2–Csp3 bond-forming reaction, therefore, requires a broad understanding of the substrate scope to better impact heterocycle synthesis. Along this line, we investigated the applicability of IFCEAC for the synthesis of 1,7- and 1,2-fused indoles. In this article, we report the results of our systematic investigation into the scope and limitations of the first examples of the hexafluoro-2-propanol (HFIP)-mediated IFCEAC of readily accessible indolyl-N-tethered epoxides. We observed that the nature and position of the indole and epoxide substituents and the tether length separating these two reacting moieties have strong effects on the cyclization. This mild and transition-metal-free protocol delivered pyrrolo[3,2,1-ij]quinolin-5-ols in moderate to good yields from substrates bearing both a methylene linker that connects the indole and epoxide moieties and an electron-rich indole carbocyclic ring. Notably, the reactions required the presence of a π-activating aryl substituent on the reacting epoxide carbon atom. Interestingly, replacing the methylene tether with an ethylene unit resulted in regioswitching, which delivered the corresponding tetrahydropyrido[1,2-a]indol-8-ols in good to high yields. We could also successfully extend this methodology to pyrrolyl-N-tethered epoxides for a very high-yielding synthesis of tetrahydroindolizin-7-ols.

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Synthesis of a Variety of Activated Pyrrolo[3,2,1-ij]quinolines

Cited by 4 publications

References 19 publications

A new synthetic route to pyrroloquinolines and pyrroloindoles

A new synthetic route to pyrroloquinolines and pyrroloindoles

Six-membered ring systems: pyridines and benzo derivatives

Hexafluoroisopropanol-Mediated Intramolecular Ring-Opening Cyclization of Indolyl-N-Tethered Epoxides: Tether-Length-Controlled Synthesis of 1,7- and 1,2-Fused Indoles

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