Functionalized ionic liquid-assisted chromatography-free synthesis of bis(indolyl)methanes.

A chromatography-free synthesis of bis(indolyl)methanes has been developed using sulfonic acid and sulfonyl hydrazine-functionalized ionic liquids as catalyst and scavenger, respectively. The employed excess aldehyde for completion of the reaction was scavenged by sulfonyl hydrazine-functionalized ionic liquid. Purification of products without column chromatography, ease of monitoring and shorter reaction time are the salient features of the developed protocol. The reuse and regeneration of the catalyst and scavenger have been achieved up to 5 and 2 times, respectively, without significant loss of activity.