Prediction of the chemo-and regioselectivity of Diels-Alder reactions of o-benzoquinone derivatives with thiophenes by means of DFT-based reactivity indices

Global and local reactivity indices derived from density functional theory were used to elucidate the regio- and chemoselectivity of Diels-Alder reactions of masked o-benzoquinones with thiophenes acting as dienophiles. The polarity of the studied reactions is evaluated in terms of the difference of electrophilicity powers between the diene and dienophile partners. Preferential cyclisation modes of these cycloadditions are predicted using Domingo's polar model based on the local electrophilicity index, (k), of the electrophile and the local nucleophilicity index, Nu(k,) of the nucleophile. The theoretical calculations, carried out at the B3LYP/6-311G(d,p) level of theory, are in good agreement with experimental findings.