1H-indazoles from phenylhydrazenes: A exploratory DFT study of a possible intramolecular evolutionary synthetic route

The intramolecular evolutionary pathways of three phenylhydrazine derivatives are investigated via Density Functional calculations, as a possible convenient synthetic route towards the preparation of 1H-Indazole derivatives. All reaction steps occur via concerted four membered transition states; stabilized by intramolecular sigma-pi interactions when more than one aromatic rings are present. Steric and polarization effects are critical where activation and forward reaction free energies are concerned. The calculated values for these parameters are achievable under laboratory conditions, however, the first step of this process might require a high boiling solvent but for the remaining steps, the forward reactions potentials are increasingly modest.