Oxidation of 7‐amino‐8‐hydroxyquinoline‐5‐sulfonic acid with silver oxide in dimethylformamide and in the presence of arylamines provided a series of 7‐amino‐5‐arylimino‐8(5H)‐quinolones (VIIIb). Reaction of 8‐dialkylamino‐5,6‐quinolinediones with triethyloxonium tetrafluoborate gave a series of unstable but synthetically useful enol ethers. These reacted with amines to give 6‐amino‐8‐imino‐5(8H)‐quinolones, isolated and characterized as tetrafluoborate salts (XIa). Proton magnetic resonance studies showed these to be vinylogous amidinium salts, analogous to those previously obtained with 2‐amino‐1,4‐naphthoquinone imines. 4,6‐Dihydroxy‐5,8‐quinolinedione underwent free radical alkylation to give a 7‐alkyl‐4,6‐dihydroxy‐5,8‐quinolinedione. Evaluation of the new compounds against various Plasmodium species in rodents, birds and mosquitoes revealed no significant antimalarial activity.
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