Studies on the tautomerism of benzoylcyclohexane-1,3-dione and its derivatives by ab initio calculation

Geometry optimizations were performed at different levels for the most stable triketone tautomer and cis-endocyclic double bond enol tautomers of benzoylcyclohexanedione. The effect of the calculation method and the size of the basis set on the relative stability of the tautomers were investigated therein. We calculated the equilibrium constants and the energy barrier of the benzoylcyclohexane-1,3-dione to study the tautomerization. The solvent effect was taken into account when calculating the equilibrium constants and the results were analyzed by comparing with the experimental results. Finally, the calculations were performed on several typical 2-substituting benzoylcyclohexane-1,3-dione derivatives. It appears that the tautomerism free energy and their HPPD inhibitive activity are correlated to some extent.