Synthesis of Pyrroloquinolines as Indole Analogues of Flavonols

Abstract

7-Acetyl-4,6-dimethoxy-3-phenylindole 10 was converted into a range of 7-indolyl chalcones 13 by reaction with aryl aldehydes under basic conditions. Oxidation of the chalcones 13 with alkaline hydrogen peroxide gave the isolable epoxides 14, which were cyclized with further base treatment into the indole flavonols, or 5-hydroxy-6-oxopyrroloquinolines 15. The related compounds 25 and 26, examples of indole flavanones and flavones, respectively, were also synthesized. UV spectroscopic comparisons between flavonoids and indole flavonoids are discussed.

Gold‐Catalyzed CH Annulation of Anthranils with Alkynes: A Facile, Flexible, and Atom‐Economical Synthesis of Unprotected 7‐Acylindoles

“…[13,14] While numerous studies have focused on the reactions of indoles with electrophiles,w ef ocused our attention on nucleophilic transformations of 7-acylindoles.F or instance,reduction of 3g afforded the 7-alkylated product 3g' ',a nd the unprotected 7-alkynyl indole 3g' '' ' could be obtained easily in excellent yield through Seyferth-Gilbert homologation (Scheme 5).…”

“…They ield increased to 84 %u pon decreasing the reaction temperature to À20 8 8C( entry 8). Further improvement was achieved by screening different silver salts (entries 9a nd 10) and solvents (entries [11][12][13][14][15][16][17][18]. Finally,u pt o9 0% yield of 3a was gained by employing 5mol %I PrAuCl/AgNTf 2 as the catalyst in PhCF 3 at À20 8 8C(entry 12).…”

Goldkatalysierte C‐H‐Anellierung von Anthranilen mit Alkinen: flexible, atomökonomische Synthese ungeschützter 7‐Acylindole

“…Unter den angepassten Bedingungen waren sowohl Alkyl‐ als auch Arylalkine für den Aufbau von C2‐funktionalisierten und C2,C3‐diarylierten Produkten geeignet (Tabelle 3, 7 a – 7 i ). Das 7‐substituierte Indol 7 j , das ein Schlüsselintermediat für die Synthese von Pyrrolchinolonderivaten ist,13 konnte – trotz der konjugierten Doppelbindung – bequem hergestellt werden.…”

Augmented indoles

“…indoles containing additional rings as the result of their ambident nucleophilic properties (Scheme 1). [1][2][3][4][5] We now present further examples of this strategy, together with some examples employing the second substitution pattern.…”