Abstract
Under thermal conditions perezone, a sesquiterpene quinone, forms an equimolar amount of (- and β-pipitzol through an intermolecular cycloaddition reaction. Computational calculations at M06-2x/6-311++G(2d,2p) level of theory of the transition states and the associated reaction paths allow justifying the experimental observations. Only exo adducts are observed experimentally, which is in line with the calculated energy difference of 6.5 kcal/mol between the transition states associated with the endo and exo adducts. Activation free energy was accurately predicted, those the uncatalyzed thermal process of cycloaddition requires 37.0 kcal/mol. The study of the potential energy surface allows to establish the existence of folded conformers of perezone in the potential energy surface.