Research Article

An Eco-Friendly Improved Protocol for the Synthesis of Bis(3-indolyl)methanes Using Poly(4-vinylpyridinium)hydrogen Sulfate as Efficient, Heterogeneous, and Recyclable Solid Acid Catalyst

Table 1

Optimizing the reaction conditionsa.

EntryaP(4-VPH)HSO4 (mg)Time (min)Yieldb (%)

160Trace
253051
3103076
4151294
5201294

Reaction conditions: indole (2 mmol) and benzaldehyde (1 mmol), grinding at RT.
Isolated yields of the product 3a.