Synthesis of Biscoumarin Derivatives Catalysed by Cyclohexane-1,4-diyl bis(hydrogen sulfate) under Solvent-free Conditions

Coumarins play an important role in both natural and synthetic organic chemistry because of their potential applications in fragrance, pharmaceutical and agrochemical industries [1]. Biscoumarins are generally synthesized by combination of two equivalents of 4- hydroxycoumarin and different aldehydes. In the recent few years several methods have been reported for this synthesis which includes the use of different catalysts [2]. Sulfonated materials were usually synthesized through the oxidation of carbon materials by sulfur acid or oleum to produce sulfonic acid groups on the surface.It was before reported in the literature that sulfonic acid derivative is good catalyst for the synthesis of biological compounds[3].Cyclohexane-1,4-diyl bis(hydrogen sulfate) [CBDH]was prepared by reaction between cyclohexane-1,4-diol and chlorosulfonic acid (figure 1) Herein we report a mild, efficient, and environmentally benign procedure for the synthesis of bis-coumarins from reaction of aromaticaldehydes and 4-hydroxycoumarin in the presence of [CBDH] under solvent-free conditions as an efficient catalyst (figure 2)..