1,3-(4,4′-bipyridinium disulfonic acid) propane-dihydrogen sulfate as highly effectual bi-functional catalysts for the rapid preparing chromeno[4,3-b]chromenes and pyrido[2,3-d:6,5-d′]dipyrimidines

In this research, a novel Brønsted-acidic ionic liquid 1,3-(4,4′-bipyridinium disulfonic acid)-propane-dihydrogen sulfate (BPDSPDH) was synthesized as a bi-functional catalyst. BPDSPDH was characterized using various analytical techniques such as FTIR, TGA, ¹³CNMR, ¹HNMR, and mass spectrometry. Afterward, the catalytic ability of BPDSPDH was explored in the synthesis of chromeno[4,3-b]chromene and pyrido[2,3-d:6,5-d′]dipyrimidine derivatives. BPDSPDH is an ionic liquid catalyst with advantages such as having a high catalytic activity due to its acidic and basic sites, the use of affordable and easily accessible starting materials for catalyst production, recyclability of the catalyst up to 4 times without significant loss in catalytic activity, short reaction time, high yields and moderate reaction conditions. Graphical abstract: [Figure not available: see fulltext.]