An acid-based DES as a novel catalyst for the synthesis of pyranopyrimidines

Deep eutectic solvents have countless advantages over normal solvents, and in addition to complying with the principles of green chemistry, depending on their nature, they can also act as catalysts. The use of deep eutectic solvents as acid catalysts has several advantages such as non-toxicity, a catalytic effect similar to or higher than the acid itself, and the possibility of recovery and reuse without significant loss of activity. In this project, A novel deep eutectic solvent (MTPPBr-PCAT-DES) was prepared from a one-to-one mole ratio of methyltriphenyl-phosphonium bromide (MTPPBr) and 3,4-dihydroxybenzoic acid (PCAT = protocatechuic acid) and characterized by various techniques such as FT-IR, TGA/DTA, densitometer, eutectic point, ¹H NMR, ¹³C NMR and ³¹P NMR. Then, it was used as a novel and capable catalyst for the synthesis of pyranopyrimidines from the multicomponent condensation reaction of barbituric acid, 4-hydroxycoumarin, and aromatic aldehydes in mild conditions, short reaction times, and high yields.