DBU hydrogen sulfate bonded to chloropropyl-functionalized bilayer silica-nano-Fe₃O₄: as an efficacious magnetic nanocatalyst for rapid synthesis of pyrido[2,3-d:6,5-d′]dipyrimidines

This manuscript describes the preparation and characterization of DBU hydrogen sulfate bonded to chloropropyl-functionalized bilayer silica-nano-Fe₃O₄ (DHCBSF), as well as its use as a highly effective, heterogeneous, and recyclable catalyst to facilitate a valuable chemical reaction. FTIR, SEM, TEM, TGA, XRD, BET, VSM, and EDS techniques were used to identify the nanomagnetic catalyst. The nanomagnetic catalyst (0.01 g) was successfully used in a multicomponent reaction including 2-thiobarbituric acid (2 mmol), aryl aldehydes (1 mmol), and ammonium acetate (1.4 mmol) at 25 °C in H₂O (2 mL), so that it presented ten samples of pyrido[2,3-d:6,5-d']dipyrimidines with yields of 92–98% in 5–10 min. DHCBSF is a heterogeneous catalyst with advantages such as a high specific surface area, low environmental and economic impact, and ease of purification and separation from the reaction mixture. Furthermore, the nano-catalyst was recycled ten times without significantly altering its catalytic properties. Graphical Abstract: [Figure not available: see fulltext.]