A caffeine-based ionic liquid as a novel and eco-friendly catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes under solvent-free conditions

摘要

A new Bronsted acidic ionic liquid has been synthesized using caffeine and p-toluenesulfonic acid as precursors. The IL was fully characterized by FT-IR, H-1 NMR, C-13 NMR, MS, elemental analysis, as well as Hammett acidity function. The prepared reagent is efficiently able to catalyze the synthesis of 1,8-dioxo-octahydroxanthenes under solvent-free conditions. Various advantages associated with this method include novelty and easy preparation of catalyst, simple work-up procedure and purification, short reaction times, high product yields, and easy recovery and reusability of the catalyst.