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 α,α´bis(arylidene)cycloalkanones under solventfree conditions has been developed. The crossedaldol condensation of cycloalkanones (1 eq.) with arylaldehydes (2 eq.) 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 dualfunctions and it is so because of possessing three acidic functional groups with different Brønsted acidic and basic sites. High catalytic activity and low loading of the catalyst can be attributed to its dualfunctions. The promising points for the presented protocol are simple and clean reaction profile, efficiency, generality, low catalyst loading, high yields, performing the reaction in solventfree media without side reactions, nontoxicity as well as low cost of the catalyst, and good compliance with the green chemistry protocols, which makes it an attractive procedure for the synthesis of α,α´bis(arylidene)cycloalkanones as an important class of organic compounds.