Ringschlüsse an Chinonylmethanfarbstoffen und analogen Merocyaninen. 3. Mitteilung. Chinoide Derivate des anellierten Tetrahydro-isochinolino-chinoxalins. Ringschluss nach 1,7-Verschiebung von Wasserstoff?

Cyclization Reactions of Quinonylmethane Dyes and Analogous Merocyanines. 3. Communication. Quinoid Derivatives of the Anellated Tetrahydro-quinoxalino-quinoxaline. Cyclization Following 1,7-Hydrogene-Shift? The title compounds were obtained by proton catalyzed cyclization of the corresponding 2-(1-alkyl-3-methyl-1,2-dihydroquinoxalin-2-ylidenmethyl)-1,4-naphtho- and 1,4-anthraquinones. The visible and ¹H-NMR.- and some mass spectra of the dyes are given. Mechanistic aspects of the new-type cyclization reaction are discussed.