Aktivierte Chinone: Substitution von Azulenen, Benzofuran und Indolen durch 2‐Methoxycarbonyl‐1,4‐benzochinon. Regiospezifische Synthesen von Polymethoxy‐fluorenonen und eine neue Synthese des 2,6‐Dihydro‐naphtho[1,2,3‐cd]indol‐6‐on‐Systems

Abstract

Activated quinones : substitution reactions by methoxy-carbonyl-l,4-benzoquinone of azulenes, benzofuran and indoles; regiospecific syntheses of polymethoxy-fluorenones ; a new synthesis of the 2,6-dihydro-naphtho[l, 2,3-cdlindol-6-one system. SummaryWe present new electrophilic substitution reactions of azulenes and 5-membered heterocyclics by methoxy-carbonyl-l,4-benzoquinone. Hydroquinones 3a and 5 are prepared from azulene, and 3 b from guaiazulene (see Scheme I ) . Benzofuran undergoes a-and #I-substitution (hydroquinones 9 and 10) (see Scheme 2). Only 8-substitution is observed with indole (hydroquinone 20) (see Scheme 4). After methylation, saponification and intramolecular acylation of the substituted indoles 22c, 22 d, derivatives of 2,6-dihydro-naphtho[ 1,2,3-cd]indol-6-one have been obtained. Spectral data prove the presence of the methylidenequinone tautomer. By protonation or alkylation at the carbonyl group of 23, the violet, highly delocalized 16n-electron systems 25 are generated. Analogously, polymethoxy-fluorenones have been prepared from methoxylated diphenylquinones 15 (see Scheme 3). They also are transformed by protonation and alkylation to the highly coloured and delocalized 12 zelectron systems 18. By contrast, anthracene is not substituted by methoxycarbonyl-1,4-benzoquinone, but undergoes cycloaddition to the triptycene derivative 1 (see Scheme I ) . A summary is presented of previously described reactions of activated quinones.Benzo-1,4-und Naphtho-1 ,4-chinon-derivate, welche stark elektronenanziehende Substituenten (I-und M-Effekte) wie NO$), Cyano-, Acyl-und Alkoxycarbonylgruppen besitzen, sind gegenuber ihren nichtsubstituierten Analogen vie1 reaktions-1) Aus der Dissertation [l]. 2,Aus der Diplomarbeit [2]. 3)Mit Nitrochinonen sind noch kaum Untersuchungen ausgefuhrt worden.