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56. Synthesis of oxazolo[4,5-c]quinolones by thermolytic degradation of 4-azido- 2(1H)-quinolones - (Organic azides in heterocyclic synthesis, 19)
Steinschifter W., Fiala W., Stadlbauer W., J. Heterocycl. Chem. 31 (1994), 1647-1652

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

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