Synthesis and evaluation of aromaticity and tautomerization of pyrazolopyridazin(on)es

Aromaticity of pyrazolopyridazin(on)es was investigated using NICS(0), NICS(1), NICSzz(1), FIPC-NICS and HOMA aromaticity indexes and it was observed that aromaticity of pyridazin(on)es was amenable to aromaticity of pyrazole and vice versa. Some tautomeric forms of pyridazinone were analyzed and the localized orbital locator maps, electron density maps, Fuzzy, Laplacian, and Mayer bond order methods showed dominant form. Different substituents, amine, chlorine, phenyl, methyl, hydrogen, substituted-phenyl, etc. on both the rings were chosen to search out the substituent effect. Aromaticity of pyrazolopyridazin(on)es was searched out in detail for the first time. Graphical Abstract Synopsis: Aromaticity of Pyrazolopyridazine was calculated and the effect of bicyclic system on aromaticity was revealed. Furthermore, tautomerization of the same skeleton was investigated and the dominant tautomer was identified by means of aromaticity, bond order, and LOL map.