Synthesis of isomeric (E)-[4-(dimethylamino)phenyl]-vinylquinoxalines – precursors for a new class of nonlinear optical chromophores

Abstract

© 2017, Springer Science+Business Media, LLC. [Figure not available: see fulltext.] Methods are presented for the preparation of isomeric (Е)-3-, (Е)-6-, (Е)-7-[4-(dimethylamino)phenylethenyl] quinoxalin-2-ones and 2-phenylquinoxalines – compounds of “donor–π-bridge” type, which serve as precursors for new nonlinear optical chromophores with potentially high first hyperpolarizability values. The introduction of dimethylanilinoethenyl moiety at position 3 of the quinoxaline system was achieved in good yields by fusion of 3-methyl derivatives with 4-(dimethylamino)benzaldehyde at 220°С in the presence of catalytic amounts of acetic anhydride and pyridine during the synthesis of 3-(dimethylaminophenylethenyl)quinoxalin-2-ones or as a result of condensation of these reactants by the action of 20 М sodium hydroxide solution in the presence of Aliquat 336 during the synthesis of 3-(dimethylaminophenylethenyl)-2-phenylquinoxalines. The introduction of dimethylanilinoethenyl moiety at positions 6 and 7 was achieved by Heck reaction of p-dimethylaminovinylbenzene with 6- or 7-bromoquinoxalines in the presence of palladium acetate. The structures of isomeric 6-bromo- and 7-bromo-3-methyl derivatives of quinoxalines were confirmed by X-ray diffraction analysis.