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123. Syntheses and Fluorescent Properties of 6-Methoxy- And 6,7-Dimethoxy-2-oxoquinoline-3,4-dicarbonitriles
Enoua G. C., Lahm, G., Uray G., Stadlbauer W.,
in J. Heterocyclic Chem. 51 (S1) (2014) E263-E275; online published May 2014

Abstract:
4-Chloro-carbostyrils 3, 12, 17, 24, 26 with methoxy substituents in 6, 7, or 6,7-position react with potassium cyanide in a p-toluenesulfinate mediated reaction either to the highly fluorescent and stable 2-oxoquinoline-3,4-dicarbonitriles 6, 27, 29, 30 or at slightly lower temperatures to 4-monocarbonitriles 5, 13, 18. 4-Chlorocarbostyril 3 and p-toluenesulfinate gave pure 4-tolylsulfonylquinolone 4, which reacted with potassium cyanide either to monocarbonitrile 5 or dicarbonitrile 6, depending on the reaction conditions. 4-Trifluoromethylquinolones 9 and 19 were prepared for fluorescence comparison from the appropriate methoxyanilines and 4,4,4-trifluoroacetoacetate. The fluorescence properties such as emission wavelengths and quantum yields of 6-methoxyderivatives 4, 5, 6, 9, 13 were studied and compared with the those of 7-methoxy derivatives 18, 19 and 6,7-dimethoxyderivatives 27, 28, 29, 30. 6,7-Dimethoxy derivatives show best results, showing long-waved fluorescence spectra up to 520 nm and acceptable quantum yields up to 0.46 for 3,4 dicyano derivative 27 excited at 440 nm in acetonitrile.


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