Chemistry of Quinoline-5,8-diones

Room-temperature acid-catalyzed methanolysis of 7-formamido-, 7-acetamido-, or 7-isobutyramido-2-methylquinoline-5,8-diones (3, 4, 5) gives good to excellent yields of 7-amino-2-methylquinoline-5,8-dione (6). Simple methods for the synthesis of novel 7-amino-6-chloro-2-methylquinoline-5,8-dione (7), 7-alkoxy-2-methylquinoline-5,8-diones (9−11), and quinoline quinols (12, 13) are described, and the corresponding mechanisms are discussed. The replacement of an amino group on a quinone ring by alkoxy groups to produce 9−11 is reported for the first time and offers easy routes for the syntheses of these alkoxy derivatives. Also, the 1,2-addition of an ethyl group (rather than the expected 1,4-addition of a cyano group) of the reagent diethylaluminum cyanide to a quinolinedione is another novel reaction for the efficient preparation of quinoline quinols 12 and 13. An easy transformation of amino compound 6 to its acetamido derivative 4 is also described.