The Tautomerism of 5‐Amino‐3‐oxo‐1,2,4‐thiadiazole: An Experimental and Theoretical Study

Abstract The 1,2,4‐thiadiazole system was the subject of our research as a consequence of the pharmacological activity of some derivatives as GSK3 inhibitors. Therefore, in order to explore the active form responsible for receptor interaction, a systematic study of the tautomerism in the 5‐amino‐3‐oxo‐1,2,4‐thiadiazole system was performed by using experimental and theoretical methods. Thus, the relative stability of the possible tautomers was studied in the gas phase by density functional theory and local density functional methods. The theoretical study in solution was carried out by using severalcontinuum solvation models. Finally, experimental studies were carried out to unambiguously establish the tautomeric form.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)