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

Abstract

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.

Keywords:

• Bis(indoyl)methane
• triethylammonium hydrogen sulfate
• Ionic liquid
• green synthesis
• bis-heterocyclic compounds

Author contributions

PT performed the experimental and wrote the main manuscript text. NS, AS, and JS helped in data interpretation and reviewed manuscript. SA contributed to writing, revising, and overall reviewing of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

Data (¹HNMR and ¹³C NMR spectra of all the synthesized compounds) associated with the article have been provided in the supporting information.

Additional information

Funding

P. Teli and N. Sahiba is very much grateful to the Council for Scientific and Industrial Research (CSIR) (file no. 09/172(0099)2019-EMR-I and 09/172(0088)2018-EMR-I) New Delhi for the award of Senior Research Fellowship as financial support. A. Sethiya is thankful to UGC-MANF for Senior Research Fellowship. S. Agarwal sincerely acknowledges Ministry of Education, Government of India and Ministry of Higher Education, Government of Rajasthan, India for providing NMR facility under RUSA 2.0, Research and Innovation project.