HClO4–SiO2 as a novel and recyclable catalyst for the synthesis of bis-indolylmethanes and bis-indolylglycoconjugates

Treatment of indole with structurally diverse aldehydes and ketones in the presence of a catalytic amount of HClO4–SiO2 as a heterogeneous, reusable and efficient catalyst at room temperature gave the corresponding bis-indolylmethanes and bis-indolylglycoconjugates in excellent yields.