3-Aminopyrazolo[4,3-<i>c</i>]pyridine-4,6-dione as a precursor for novel pyrazolo[4,5,1-ij][1,6]naphthyridines and pyrido[4’,3’:3,4]pyrazolo[1,5-<i>a</i>]pyrimidines

The versatile, 3-aminopyrazolo[4,3-c]pyridine-4,6-dione (<b>2</b>) was synthesized and allowed to react with aldehydes, aryldiazonium chlorides, chalcones and enaminones to afford regioselectively the novel pyrazolo[4,3-c]pyridine derivatives <b>4a-c</b>, pyrazolo[4,5,1-ij][1,6] naphthyridines <b>9a-d</b> and pyrido[4’,3':3,4]pyrazlo[1,5-a]pyrimidines <b>19a-i</b>. The structure of all the newly synthesized compounds was assigned from elemental analysis and spectral data. Also, the mechanistic aspects for the formation of the newly synthesized compounds is discussed.