Silica Supported Sodium Hydrogen Sulfate and Amberlyst‐15: Two Efficient Heterogeneous Catalysts for Facile Synthesis of Bis‐ and Tris(1H‐indol‐3‐yl)methanes from Indoles and Carbonyl Compounds[1]

Bis‐ and tris(1H‐indol‐3‐yl)methanes are synthesized in high yields by an electrophilic substitution reaction of indoles with carbonyl compounds under mild reaction conditions using two efficient heterogeneous catalysts, silica supported sodium hydrogen sulfate (NaHSO4⋅SiO2) and amberlyst‐15. The second catalyst can be reused.