1,3-Disulfonic acid imidazolium hydrogen sulfate {[Dsim]HSO4} as a highly efficient, recyclable and green catalyst for the preparation of α,α´-bis(arylidene)cycloalkanones

A highly efficient and simple method for the preparation of ?,?´-bis(arylidene)cycloalkanones under solvent-free conditions has been developed. The crossed-aldol condensation of cycloalkanones (Eq. 1) with arylaldehydes (Eq. 2) in the presence of 2.5 mol% of ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate {[Dsim]HSO4} afforded the title compounds in high yields and short reaction times. The catalyst has dual-functions and it is so because of possessing three acidic functional groups with different Br?nsted acidic and basic sites. High catalytic activity and low loading of the catalyst can be attributed to its dual-functions.