Ring Closure and Rearrangement Reactions of 4-Azido-2-oxoquinoline-3-carboxylates and 4-Azidocoumarin-3-carboxylates [1]

Article abstract of DOI:10.1002/jhet.5570350322

4-Azido-2-oxoquinoline-3-carboxylates and 4-azidocoumarin-3-carboxylates 6, which were obtained from the corresponding 4-hydroxy derivatives 1 via 4-tosylates 2 or 4-chloro compounds 4, cyclized upon thermolysis to 3-alkoxyisoxazolo[4,3-c]quinolin-4(5H)-ones or the corresponding coumarins 8, whereas at slightly higher temperatures a 3-O, 4-O-rearrangement took place to give the 4-alkoxy-isoxazolo[4,3-c]-quinolin-3-ones and the corresponding coumarins 9. The necessary reaction conditions could be obtained easily with the help of differential scanning calorimetry.