[TMBSPD][OMs]2: An Efficient Recyclable Ionic Liquid for the Synthesis of Bis(indolyl)methanes from Aldehydes or Ketones and Indoles at Ambient Temperature

An efficient synthesis of bis(indolyl)methanes by the reaction of aldehydes and ketones with indoles catalyzed by N,N,N′,N′-tetramethyl-N,N′-bis(sulfo)biphenyl-4,4′-diaminium bis(methanesulfonate) ([TMBSPD][OMs]₂) has been developed. The reaction proceeds in ethanol at room temperature to provide the desired products in good to excellent yields. The proposed methodology is characterized by a broad substrate scope, environmental friendliness, and cost efficiency.