Dillenia indica (Elephant Apple) Fruit Decoction: A Green Catalyst for the Synthesis of Tetrahydrobenzo(b)pyran and Spirooxindole Derivatives

Abstract

In this research, we endeavour to demonstrate the potential of Aqueous Extract of Dillenia indica (AEDI) pseudosepals in catalyzing tetrahydrobenzo[b]pyran and spirooxindole derivatives, thereby paving the way for greener and more sustainable chemical synthetic strategies. The reactions proceed smoothly with AEDI as the catalyst in water at room temperature to afford high to near quantitative yields in a short duration of 15–45 minutes, making it a green and environmentally friendly alternative to existing protocols. This synthetic pathway satisfies several green chemistry principles such as avoiding the use of any toxic or hazardous metal catalyst and other external additives/promoters, the use of a biodegradable catalyst obtained from natural resources, auxiliary solvent conditions, and reusability of the catalyst. The protocol reported here offers remarkable attributes like wide substrate scope, high to near quantitative yields of products and the scale up viability along with ecological safety, straightforward work-up procedure and excellent values of green chemistry metrics as compared to other reported approaches.