Thermal Cyclization of 2-Acyl-1-azido-3-phenalenones to Phenaleno[1,2-c]isoxazol-7-ones

1-Azido-3-phenalenones 5 with acyl substituents in position 2, obtained by acylation and azidation of 1-hydroxy-3-phenalenones 1 , cyclized by thermolysis to give phenaleno1,2-c]isoxazol-7-ones 9 . The thermolysis conditions were studied by differential scanning calorimetry.