Chickpea leaf exudates: a green Brønsted acid type biosurfactant for bis(indole)methane and bis(pyrazolyl)methane synthesis

Abstract

A clean and highly efficient protocol for green synthesis of bis(indole)methanes and bis(pyrazolyl)methanes has been successfully achieved by using a naturally sourced bio-surfactant, chickpea leaf exudates (CLE), as a Brønsted acid-type catalyst. The reaction proceeds smoothly with CLE in alcoholic medium at 60 °C in a very short reaction time, and therefore it is a green, environmentally sound alternative to the existing protocols. In comparison to the reported conventional methods, this synthetic pathway complies with several key requirements of green chemistry principles such as avoiding the use of any toxic/hazardous catalyst and additives/promoters, the use of a biodegradable catalyst obtained from renewable resources, auxiliary solvent conditions, and reusability of the catalyst. Thus, the reported protocol offers an attractive option because of its ecological safety, straightforward work-up procedure and excellent values of green chemistry metrics as compared with other reported methods.