Theoretical explanation of the regioselectivity of polar cycloaddition reactions between furan derivatives and Danishefsky's diene

The regioselectivity for a series of experimentally studied Diels-Alder reactions between furan derivatives and Danishefsky's diene has been rationalized within the framework of local DFT-based descriptors (i.e. electrophilicity and nucleophilicity indexes). The importance of the solvent in the calculations has been studied. It has been shown that the relative trend of an atomic center to behave as an electrophile is affected by the medium (gas phase or benzene solution) and the basis set used in the calculation of the reactivity descriptors. The local electrophilicity (ωk) and nucleophilicity (Nk) indexes properly account for the observed regioselectivity only when B3LYP/LANL2DZ and HF/LANL2DZ levels of theory have been used.