Sulfuric Acid

Mohammadi M et al. fabricated a magnetic solid acid by growing a hercynite FeAl₂O₄ core through alkaline co-precipitation of Fe(II) and Al(III) salts at 80 ℃, then grafting –SO₃H groups onto the nanoparticle surface with chlorosulfuric acid in dry n-hexane at room temperature. The resulting 30 nm hercynite@sulfuric acid was verified by FT-IR, XRD, SEM-EDX and VSM, confirming uniform sulfur coverage and super-paramagnetic behavior. They applied this catalyst to two acid-driven multicomponent reactions: (1) solvent-free Hantzsch condensation of aldehydes, dimedone, ethyl acetoacetate and NH₄OAc at 100 ℃; (2) cyclocondensation of aldehydes with anthranilamide in refluxing ethanol. Both protocols delivered the corresponding polyhydroquinolines and 2,3-dihydroquinazolin-4(1H)-ones in 86–98 % isolated yields within minutes, tolerated diverse substituents, and produced only water as a by-product.

Fig. 1 The synthesis of hercynite@sulfuric acid nanoparticles. (Mohammadi M.; et al. 2022)