Versatile access to nitrogen-rich π-extended indolocarbazoles<i>via</i>a Pictet–Spengler approach

Heckershoff, Robin; Eberle, Lukas; Richert, Nick; Delavier, Christian; Bruckschlegel, Michael; Schäfer, Moritz R.; Krämer, Petra; Röminger, Frank; Rudolph, Matthias; Hashmi, A. Stephen K.

doi:10.1039/d2qo01459a

“…Inspired by Rossi et al [22a] . who reported a one‐pot gold‐catalyzed tandem reaction using 2‐(1 H ‐indol‐2‐yl) anilines as intermediates, followed by a subsequent Pictet–Spengler reaction (PSR) with aldehydes and our extension of this methodology, towards nitrogen‐rich π‐extended indolocarbazoles, [22b] we were curious if we could use the method herein for a related approach as well. In our case a completely different approach delivered the key aniline derivative 4‐fluoro‐2‐(1 H ‐indol‐2‐yl) aniline ( 3 p ), which then could be transformed to 2‐fluoro‐6‐phenyl‐11 H ‐indolo [3,2‐c] quinoline ( 10 ) via PSR in good overall efficiency (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

Cascade Reactions of Aryl‐Substituted Terminal Alkynes Involving in Situ‐Generated α‐Imino Gold Carbenes

Sun,

Hüßler,

Kahle

et al. 2023

Angew Chem Int Ed

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An efficient, highly selective and divergent synthetic method to construct 2‐substituted indoles and aryl‐annulated carbazoles via the intermolecular generation of α‐imino gold carbenes from terminal alkynes or diynes in combination with sulfilimines is disclosed. Importantly, the tandem reaction is proposed to proceed through an intermolecular gold carbene generation/ C‐H annulation followed by the activation of a second alkyne leading to 6‐endo‐dig cyclization, which is significantly different from previous dual activation or 1,6‐carbene shift approaches for diyne systems. In the case of ortho‐alkynylaniline as starting material, an unexpected regioselective formation of the indole moiety via the intermolecular path, instead of intramolecular hydroamination was discovered. This reactivity paved the way for a one‐pot synthesis of the 11H‐indolo [3,2‐c] quinoline scaffold by exploiting the formed amino indole for a subsequent Pictet‐Spengler reaction with aldehydes. The photophysical properties of the carbazoles indicated good violet‐blue emission with quantum yields up to 40%.

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“…Inspiriert von Rossi et al., [22a] die über eine goldkatalysierte Eintopftandemreaktion unter Verwendung von 2‐(1 H ‐Indol‐2‐yl)‐Anilinen als Zwischenprodukte und einer anschließenden Pictet–Spengler‐Reaktion (PSR) mit Aldehyden berichteten, und unserer Erweiterung dieser Methodik auf stickstoffreiche π‐erweiterte Indolocarbazole, [22b] waren wir neugierig, ob wir die hier beschriebene Methode auch für einen ähnlichen Ansatz verwenden könnten. In unserem Fall lieferte ein völlig anderer Ansatz das Schlüsselanilinderivat 4‐Fluor‐2‐(1 H ‐indol‐2‐yl)‐anilin ( 3 p ), das dann über PSR mit guter Gesamteffizienz in 2‐Fluor‐6‐phenyl‐11 H ‐indolo [3,2‐c] chinolin ( 10 ) umgewandelt werden konnte (Schema 3).…”

Section: Ergebnisse Und Diskussionunclassified

Kaskadenreaktionen von aryl‐substituierten terminalen Alkinen unter Beteiligung von in situ erzeugten α‐Imino‐Goldcarbenen

Sun,

Hüßler,

Kahle

et al. 2023

Angewandte Chemie

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An efficient, highly selective and divergent synthetic method to construct 2‐substituted indoles and aryl‐annulated carbazoles via the intermolecular generation of α‐imino gold carbenes from terminal alkynes or diynes in combination with sulfilimines is disclosed. Importantly, the tandem reaction is proposed to proceed through an intermolecular gold carbene generation/ C‐H annulation followed by the activation of a second alkyne leading to 6‐endo‐dig cyclization, which is significantly different from previous dual activation or 1,6‐carbene shift approaches for diyne systems. In the case of ortho‐alkynylaniline as starting material, an unexpected regioselective formation of the indole moiety via the intermolecular path, instead of intramolecular hydroamination was discovered. This reactivity paved the way for a one‐pot synthesis of the 11H‐indolo [3,2‐c] quinoline scaffold by exploiting the formed amino indole for a subsequent Pictet‐Spengler reaction with aldehydes. The photophysical properties of the carbazoles indicated good violet‐blue emission with quantum yields up to 40%.

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Recent advances in developing highly atom-economic C–H annulation reactions in water

Chatterjee

¹

,

Pattanayak

²

,

Satyanarayana

³

et al. 2023

Current Opinion in Green and Sustainable Chemistry

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Versatile access to nitrogen-rich π-extended indolocarbazolesviaa Pictet–Spengler approach

Abstract: The Pictet-Spengler reaction was applied to synthesize benzobispyrrolo[3,2-c]quinolines as new scaffolds for organic electronics. The adressed compounds are nitrogen-enriched analogues of -extended indolocarbazoles formally accessed by the isosteric replacement of...

Cited by 3 publications

References 87 publications

Cascade Reactions of Aryl‐Substituted Terminal Alkynes Involving in Situ‐Generated α‐Imino Gold Carbenes

Cascade Reactions of Aryl‐Substituted Terminal Alkynes Involving in Situ‐Generated α‐Imino Gold Carbenes

Kaskadenreaktionen von aryl‐substituierten terminalen Alkinen unter Beteiligung von in situ erzeugten α‐Imino‐Goldcarbenen

Recent advances in developing highly atom-economic C–H annulation reactions in water

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