p-sulfonic acid calix[4]arene: An efficient reusable organocatalyst for the synthesis of bis(indolyl)methanes derivatives in water and under solvent-free conditions

In this work, a green, simple and highly efficient procedure for the synthesis of bis(indolyl)methanes is described. The condensation of indoles catalyzed by p-sulfonic acid calix[4]arene in water and under solvent-free conditions afford the title compounds in high yields and relatively short reaction times.

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