A Recyclable Morpholine-Immobilized Silica Catalyst for One-Pot Multicomponent Construction of Furan–1,3,4-Thiadiazole Schiff Base Hybrids

A sustainable and operationally efficient multicomponent protocol has been developed for thesynthesis of structurally diverse furan–1,3,4-thiadiazole Schiff base hybrids. The methodinvolves a one-pot condensation of furfural, acetylacetone, and 2-amino-5-(substitutedphenyl)-1,3,4-thiadiazoles using morpholine-functionalized silica (Morpholin-SiO₂) as arecoverable heterogeneous base catalyst. Reactions carried out in refluxing methanol affordedthe desired azomethine products in excellent yields (89–96%) within short reaction times. Thecatalyst was readily separated by filtration and reused over five successive cycles withoutappreciable loss of activity. Structural elucidation of the synthesized compounds wasaccomplished using FT-IR, 1H NMR, and 13C NMR spectroscopy. The protocol combines highatom economy, mild conditions, and catalyst recyclability, making it an environmentallybenign alternative to conventional Schiff base synthesis.