Quantum chemical calculations on the annular tautomerism of some indazole derivatives. 1. A gas phase study

Abstract

In this work, physicochemical properties of some indazole derivatives were computed by using semi-empirical methods in the gas phase and the obtained results were evaluated by searching a possible correlation with the previously obtained experimental properties. The relative stabilities, proton affinities and dipole moments for the tautomeric forms of some indazoles and their fixed forms (model compounds in which proton migration is eliminated by replacing the mobile hydrogen atom with a methyl group) were calculated with full geometry optimization using AM1, PM3 and MNDO methods. When the annular tautomerism is taken into account the results of semi-empirical AM1, PM3 and MNDO calculations indicate that 1H-form of the studied molecules are more stable than that of 2H-form as stated in the literature.