Synthesis of a Novel Pyrazolone-Based N-Heterocyclic Compound via Diazocoupling and In Situ Nitrogen Insertion

Abstract An interesting heterocyclic compound has been synthesised through diazocoupling of antipyrine with diazonium salt of 4-aminoantipyrine. The dinitrogen produced in situ in the reaction medium by the decomposition of some diazonium ions gets directly inserted into the antipyrine moiety within the reaction medium, forming a new five-membered N-heterocycle. The starting materials, 4-aminoantipyrine and antipyrine, are pyrazolones. New compounds formed also contain these moieties, and a new five-membered pyrazole ring is also formed due to this nitrogen insertion. As a result, the new molecule contains three pyrazole rings. This new compound is highly stable and is characterised by means of physicochemical and spectral analysis. Azo and new pyrazole ring formation are confirmed from single-crystal X-ray diffraction study.