Syntheses and Fluorescent Properties of 6-Methoxy-2-oxoquinoline-3,4-dicarbonitriles and 6,7-Dimethoxy-2-oxoquinoline-3,4-dicarbonitriles

4‐Chlorocarbostyrils 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 lithium p‐toluenesulfinate gave pure 4‐toluenesulfonylquinolone 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 methoxyaniline 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 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.