Diels–Alder reactions of N-tosylpirroles developed in protic ionic liquids. Theoretical studies using DFT methods

N-Tosyl-2-nitropirrole and N-tosyl-3-nitropirrole react with poorly and activated dienes using protic ionic liquids as reaction media. They exhibit a dienophile character producing the corresponding indoles through a Diels–Alder process. In all cases the presence of protic ionic liquids as reaction media improves the yields with respect to use of molecular solvent, while the temperature and the reaction time decrease. Part of this work is specifically concerned with theoretical studies using DFT methods. The global and local electrophilicity and nucleophilicity indices were calculated for the dienophiles and dienes used in this study in order to evaluate reactivity and regioselectivity.