ORGANIC AZIDES IN HETEROCYCLIC SYNTHESIS - 23 - RING-CLOSURE AND REARRANGEMENT REACTIONS OF 4-AZIDO-2-OXOQUINOLINE-3-CARBOXYLATES AND 4-AZIDOCOUMARIN-3-CARBOXYLATES

4-Azido-2-oxoquinoline-3-carboxylates and 4-azidocoumarin-3-carboxylat es 6, which were obtained from the corresponding 4-hydroxy derivatives 1 via 4-tosylates 2 or 4-chloro compounds 4, cyclized upon thermolysi s 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-rearra ngement took place to give the 4-alkoxy-isoxazolo[4,3-c]-quinolin-3-on es and the corresponding coumarins 9. The necessary reaction condition s could be obtained easily with the help of differential scanning calo rimetry.