Abstract: 1-Azido-2-hydrazonoacyl-3-oxo-heterocycles 2 such as 4-azido-3-hydrazonoacyl-
2-quinolones, 4-azido-3-hydrazonoacyl-coumarins or 4-azido-3-hydrazonoacyl-
2-pyridones, which were obtained from the corresponding acyl derivatives 1,
cyclize upon thermolysis to give 2-arylamino-pyrazolo[4,3-c]fused compounds 3.
The cyclization conditione were studied by differential scanning calorimetry (DSC)
. Structure elucidation of 3 by 13C nmr excluded
the formation of triazino isomers.
Attempts to use a reversed reaction path by azidation of the tosylate 4 to 2
resulted always in the cyclization to the 1-aryl-pyrazolo[4,3-c]fused compounds 5.
The pyrazols 5 could be obtained also from the precursors of 1 or
4, the corresponding hydroxy-hydrazonoacyl compounds by thermal decomposition.
1-Aryl-pyrazolo[4,3-c]quinolin-2-ones 5 are of interest because of their
potential biological activity .
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