Polyvinylpolypyrrolidone-supported triflic acid (PVPP·OTf) as a new, efficient, and recyclable heterogeneous catalyst for the synthesis of bis-indolyl methane derivatives

A simple, inexpensive, environmentally friendly and efficient route for the synthesis of bis-indolyl methane derivatives by the reaction of indole or N-methyl indole with aldehydes using polyvinylpolypyrrolidone-supported triflic acid (PVPP·OTf) as a catalyst is described. PVPP·OTf catalyst is air-stable, heterogeneous, cost-effective, easy to handle, and easily removed from the reaction mixtures.