Triethylammonium Hydrogen Sulfate Ionic Liquid-Assisted Highly Efficient Synthesis of Bis(indoyl)methanes

A highly efficient eco-benign pathway was developed for the synthesis of a library of 34 bis(indoyl)methane derivatives using triethylammonium hydrogen sulfate ionic liquid as a green catalyst in high to excellent yields (82-98%) at room temperature. The reaction was easy to execute by simply mixing two equivalents of indole with one equivalent of different aldehydes (including aromatic, heterocyclic, and aliphatic) using ionic liquid as a catalyst and water as a solvent under stirring at mild reaction environment. The current methodology has several benefits such as operational simplicity, short time period (25-60 min), cost-efficient, environment-friendly, easily recoverable catalyst, and highly reusable up to five cycles.