Theoretical estimation of the annular tautomerism of indazoles

Theoretical calculations at semi-empirical AM1 and density functional B3LYP/6–31G* levels were carried out on 52 NH-indazoles. Although in most cases the 1H-tautomer is the most stable, we found several indazoles for which the 2H-tautomer is more stable than the 1H-tautomer. The differences in energy between the 1H- and 2H-tautomers were interpreted in terms of substituent effects with the use of a Free–Wilson (presence–absence) matrix. Copyright © 2005 John Wiley & Sons, Ltd.

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