Caffeine hydrogen sulfate: a recyclable solid acid catalyst for mechanochemical synthesis of 2-arylbenzothiazoles

A highly efficient mechanochemical protocol for the synthesis of 2-arylbenzothiazole derivatives using substituted aromatic aldehydes and 2-aminothiophenol and caffeine hydrogen sulfate (CHS) as an eco-friendly catalyst was developed. The green protocol was performed efficiently at room temperature in solvent-free conditions using a grindstone method. The title compounds were obtained in high yields (85-93%) in less reaction time (2.5-5 min). The compounds were well characterized by spectral analysis. The present protocol has numerous advantages such as eco-friendly, excellent yield of products, solvent-free, reaction at room temperature, no tedious setup, high recyclability of catalyst, and easy workup. The CHS catalyst was reusable up to 5 times without appreciable loss of activity.

Automated summary

A highly efficient and eco-friendly mechanochemical protocol was developed for the synthesis of 2-arylbenzothiazole derivatives using CHS as a catalyst, resulting in high yields of products in a short reaction time. The protocol offers various advantages, including being environmentally friendly, high product yield, solvent-free conditions, and ease of operation.