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 4

Reusability of P(4-VPH)HSO₄ for the synthesis of bis(3-indolyl)phenylmethane^a.

Run	Cycle	Yield^b (%)
1	0	94
2	1	93
3	2	92
4	3	92
5	4	90
6	5	88

aReaction conditions: indole (2 mmol), benzaldehyde (1 mmol), and P(4-VPH)HSO₄ (15 mg), grinding at RT for 12 min.
bIsolated yields.