Caffeinium Hydrogen Sulfate: A Green Solid Acid Catalyst for Selective One‐Pot Domino Knoevenagel‐Michael Transformations

Abstract

Abstract A green, water soluble and efficient solid acid catalyst Caffeinium Hydrogen Sulfate (CHS) is prepared by sulfonation of caffeine and characterized by 1 H‐NMR, 13 C‐NMR, FTIR spectroscopy, elemental and thermal analysis. The catalytic application of the prepared catalyst for the selective one‐pot domino Knoevenagel‐Michael synthesis of bis‐cyclohexenones and 1,8‐dioxooctahydroxanthenes is investigated. This report demonstrate the selectivity of CHS to synthesise bis‐cyclohexenone and xanthenes at different temperature conditions. The proposed methodology put forward various advantages such as cost effectiveness, excellent yields of the targeted products, clean and mild reaction profile, negligible waste generation, eliminate the use of harmful organic solvents and corrosive reagents, reusability of the catalytic system and afford pure products without any extraction and purification steps.