Synthesis of oxazolo[4,5‐<i>c</i>]quinolones by thermolytic degradation of 4‐azido‐2(1<i>H</i>)‐quinolones

Abstract

Abstract 4‐Azido‐2(1 H )‐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.