1,2-Dimethyl-N-butanesulfonic acid imidazolium hydrogen sulfate as efficient ionic liquid catalyst in the synthesis of indeno fused pyrido[2,3-d]pyrimidines

Indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidin-4,6-(5H,11H)dione derivatives were synthesized regioselectively in high yields by a three-component reaction of 1,3-indanedione, aromatic aldehydes and 2,6-diaminopyrimidin-4(3H)-one in the presence of 1,2-dimethyl-N-butanesulfonic acid imidazolium hydrogen sulfate ([DMBSI]HSO4) ionic liquid as green and reusable catalyst. This protocol produced the desired products in high yields (87-95%) and short reaction times (3-6 min).