4‐Chloro‐3‐nitro‐2‐quinolones 3 obtained from the 4‐hydroxy quinolones 1 by nitration and chlorination, reacted with sodium azide to the 4‐azido derivatives 4 which cyclized on thermolysis to yield the furoxanes 5. Nucleophilic substitution reactions of 3 led to the 4‐amino‐, 4‐fluoro‐ and 4‐alkoxy‐3‐nitroquinolones 7, 8 and 9, respectively. With thiols either 4‐thio‐3‐nitro‐ 10 or 3,4‐dithioquinolones 11 were obtained depending on the basic catalyst.

4‐Azido‐2(1H)‐quinolones 1 are thermolyzed in the presence of carboxylic acids and polyphosphoric acid to yield oxazolo[4,5‐c]quinolones 3. Formation of other possible isomeric ring closure products such as oxazolo[5,4‐c]quinolones 2 or isoxazolo[4,3‐c]quinolones 4 could be excluded by independent syntheses.

Chlorination of 1‐substituted 3‐formyl‐4‐hydroxy‐2‐quinolones (1a, b) with phosphorylchloride leads to 4‐chloro‐3‐dichloromethylquinolones (2), which can be hydrolyzed to 4‐chloro‐3‐formyl‐quinolones (4). From the anilinomethylene quinolinediones (3), at low temperatures the formylquinolones 4 can be obtained directly, whereas at high temperatures cleavage of the tautomeric azomethine moiety followed by subsequent ring closure to the naphthyridines (7) takes place. With 1‐unsubstituted 3‐formyl‐4‐hydroxy‐2‐quinolones (1d) either the 3‐dichloromethylquinolone (2d) or the 2,4‐dichloro‐3‐dichloro‐methylquinoline (10) is obtained depending on the reaction conditions. Similar results are obtained with the 1‐unsubstituted anilinomethylene compounds (3). Attempts to obtain the 3‐formyl‐2,4‐dichloroquinoline (11) were unsuccessful because in all experiments the 2‐chloro‐group was converted to an oxygen function.

4‐Chloro‐3‐nitro‐2‐pyridines 3 and 10, obtained from 4‐hydroxy‐2‐pyridones 1 and 8 after nitration and chlorination, gave with sodium azide 4‐azido‐3‐nitropyridines 4 and 11, which cyclized on thermolysis to furoxans 6 and 12. Desoxygenation of the furoxan 6 with triphenylphosphane gave the furazan 7. Thermal decomposition conditions of the azide 4 and the desoxygenation reaction of 6 to 7 were studied by differ ential scanning calorimetry (DSC).

4‐Azido‐3‐acylquinolones 4 obtained from 4‐hydroxy derivatives 1 via tosylates 3 or chlorides 5, reacted with arylhydrazines 6 to generate 4‐azido‐3‐hydrazonoalkylquinolines 7. Thermolysis of 7 gave ring closure products which were assigned to 2‐arylaminopyrazolo[4,3‐c]quinolones 10. The thermal decomposition conditions of the azides 4 and 7 were studied by differential scanning calorimetry (DSC).