N-tosyl-nitropyrroles as Dienophiles in Polar Cycloaddition Reactions Developed in Protic Ionic Liquids

N-tosyl-2-nitropirrole and N-tosyl-3-nitropirrole reacts with poorly and activated dienes using protic ionic liquids as reaction media. They exhibit a dienophilic character producing the corresponding indoles through a Diels-Alder process. In all cases the presence of protic ionic liquids as reaction media improve the yields respect to the use of molecular solvent, while the temperature and the reaction time decrease. A similar behavior was observed in disubstituted N-tosyl-pyrroles.