Abstract: Oxazolochinolone have been investigated in the last years because of their pharmakological
and herbicidal activities. Oxazolo[4,5-c]quinolones 2 can be obtained by thermolysis
of 4-azidoquinolines 1 in the presence of carboxylic acids and PPA.
The reaction proceeds via an intermediate aziridine, followed by a rearrangement
to give not the expected oxazolo[5,4-c]quinolone, but 2. Structural assignment
could be achieved by an independent synthesis via 3-amino-4-hydroxyquinolones 3.
Isoxazolo[4,3-c]quinolines 5 can be obtained from 3-acyl-4-azidoquinolones 4 by
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