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.