Abstract: 1-Azido-2-hydrazonoacyl-3-oxo-heterocycles , which were obtained from the corresponding acyl derivatives , cyclize upon thermolysis to give 2-arylamino-pyrazolo[4,3-c]fused compounds. The cyclization conditione were studied by differential scanning calorimetry (DSC). Structure elucidation by ¹³C nmr excluded the formation of triazino isomers.
Attempts to use a reversed reaction path by azidation of the tosylates resulted always in the cyclization to the 1-aryl-pyrazolo[4,3-c]fused compounds. Theses pyrazols could be obtained also from other precursors, the corresponding hydroxy-hydrazonoacyl compounds by thermal decomposition. 1-Aryl-pyrazolo[4,3-c]quinolin-2-ones are of interest because of their potential biological activity

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