Sulfonylbis(1,4-phenylene)bissulfamic acid (SPSA): Introduction of an efficient and reusable catalyst for the synthesis of bis(indolyl)methanes

A simple, efficient and convenient route is described for the synthesis of bis-indolyl methanes by using recyclable catalyst sulfonylbis(1,4phenylene)bissulfamic acid (SPSA). In this procedure, we synthesize a bis-indolyl methane derivative via the three component reactions of two equivalent indoles with one equivalent of various aromatic aldehydes in the presence of 10 mol% SBSA as a heterogeneous catalyst under solvent-free conditions at 110 °C for the convinced reaction times (30–60 min). The advantages of this protocol towards the synthesis of bis-indolyl methane derivatives are: I) use of solvent-free conditions, II) inexpensive catalyst, III) using commercially available precursors, d) reusability of SBSA up to several cycles without much loss in reactivity, IV) simple work-up, V) high yields of pure products, VI) short reaction times. The structure of all bis(indolyl)methane derivatives were confirmed by melting point, FT-IR, 1H NMR spectra and were compared with reliable references.