Collective Total Synthesis of 4‐Azafluorenone Alkaloids

Abstract: 4‐Azafluorenones are typically obtained by acid‐mediated cyclization of 2‐arylnicotinates. However, this approach fails to give 5‐oxygenated 4‐azafluorenones due to lactonization of 2‐(2‐alkoxy) phenylnicotinate intermediates. Herein, we report two modifications of established approaches to 4‐azafluorenone synthesis that, either in combination or by themselves, enable the flexible preparation of 4‐azafluorenones with diverse oxygenation patterns in the benzenoid ring. Undesired lactonization was circumvented via tert‐butyl hydroperoxide (TBHP)‐mediated radical cyclization of 2‐aryl‐3‐(hydroxymethyl) pyridines. In the absence of suitable protecting groups for phenolic intermediates, bromide substituents were regioselectively introduced as latent hydroxy groups and later converted under palladium catalysis. We present the first total syntheses of five 4‐azafluorenone alkaloids muniranine, darienine, 5,8‐dimethoxy‐7‐hydroxyonychine, 5,6,7,8‐tetramethoxyonychine, and 6,8‐dihydroxy‐7‐methoxyonychine in addition to new total syntheses of six 4‐azafluorenone alkaloids and one related pyridocoumarin alkaloid.

Location
Deutsche Nationalbibliothek Frankfurt am Main
Extent
Online-Ressource
Language
Englisch

Bibliographic citation
Collective Total Synthesis of 4‐Azafluorenone Alkaloids ; day:15 ; month:06 ; year:2023 ; extent:10
European journal of organic chemistry ; (15.06.2023) (gesamt 10)

Creator
Jourjine, Ilya A. P.
Bracher, Franz

DOI
10.1002/ejoc.202300399
URN
urn:nbn:de:101:1-2023061615064451348039
Rights
Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
Last update
14.08.2025, 10:47 AM CEST

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