Sulphonic Acid Functionalized Ionic Liquids as an Efficient Catalyst for the Synthesis of Digeranyl Ethers and Geranyl Phenols

Abstract

An alternate synthetic approach was developed for the synthesis of the digeranyl ether and naturally occurring biologically active geranyl phenols using −SO3H functionalized ionic liquids within 0.5–1.5 h with better yields. This approach was further explored for different naturally occurring activated phenols with geraniol yielding geranyl phenols via alkylation at ambient temperature using ionic liquids as catalyst. The synthesized ionic liquids were characterized using Py‐IR studies to establish the Brønsted acidity and the Hammett acidity characteristics of all the four ionic liquids. Amongst these ionic liquids IL‐1 exhibited beneficial catalytic activity towards the synthesis of digeranyl ether and geranyl phenols with excellent yields. Reusability studies indicated that IL‐1 was recycled for seven times without losing the catalytic activity which was further corroborated with pre‐ and post‐characterization of IL‐1. This work also highlights the alternate route for the synthesis of the cannabinoid compounds and their analogues.