Hexamethylenetetramine-based ionic liquid/MIL-101(Cr) metal–organic framework composite: a novel and versatile tool for the preparation of pyrido[2,3-d:5,6-d′]dipyrimidines

In the current paper, a hexamethylenetetramine-based ionic liquid immobilized on the MIL-101(Cr) metal–organic framework was successfully synthesized as a novel, efficient, and recoverable catalyst for the synthesis of pyrido[2,3-d:5,6-d′]dipyrimidine derivatives via the reaction of barbituric acid derivatives, 6-aminouracil/6-amino-1,3-dimethyl uracil, and aromatic aldehydes under solvent-free conditions. Characterization of the catalyst was carried out using various methods such as field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectrophotometry (FT-IR), and Brunauer–Emmett–Teller (BET). Efficient transformation, short reaction times, excellent yields, easy product isolation, mild conditions, and the potential high recyclability of the organocatalyst are the main features of this protocol.