HIGHLY EFFICIENT SYNTHESIS OF ARYLDIPYRROMETHANES IN PRESENCE OF BRONSTED ACIDIC IONIC LIQUIDS

Highly efficient and selective synthesis of aryldipyrromethanes in presence of Bronsted acidic ionic liquids in dichloromethane is reported by the condensations of aromatic aldehydes with pyrrole (2 equivalents) at room temperature. The aryldipyrromethanes can be isolated directly from the reaction mixture in an essentially pure state by simple recrystallization with ethyl acetate and hexane. Time control seems to be essential to avoid significant formation of the tripyrromethane analogue and the reaction time is strongly dependent on the nature of the aromatic aldehyde. In this reaction the products were obtained in short reaction time and easy operation under mild conditions without using any strong acid.