green synthesis of bis(indolyl)methanes in water using sulfonic acid functionalized silica (sio2-pr-so3h)

bis(indolyl)methanes are important group of bioactive metabolites of terrestrial and marine regions. they were synthesized by different methods. herein, a clean, one-pot synthesis of bis(indolyl)methane derivatives by cyclo-condensation reaction of indole and various aldehydes using sulfonic acid functionalized silica (sio2-pr-so3h) in aqueous media is reported. the advantages of this new method were simple operation, good yields, short reaction times and easy work-up. sulfonic acid functionalized silica as an efficient heterogeneous solid acid catalyst could be prepared by simple operation from commercially available cheap starting materials such as silica. it catalyzes various organic reactions and could be easily removed, recovered and reused without significant loss of activity.