Magnetic GO@AlFe2O4@SO3H nanocatalyst: a sustainable approach for the synthesis of 5-phenyl-1,3,4-thiadiazol-2-amines

A novel magnetic nanocatalyst, denoted as GO@AlFe 2 O 4 @SO 3 H, has been successfully designed and applied as an efficient and sustainable heterogeneous catalyst for the synthesis of 5-phenyl-1,3,4-thiadiazol-2-amines. This one-pot methodology involves the direct cyclocondensation reaction of readily available benzoic acid derivatives with thiosemicarbazide, employing phosphorus oxychloride (POCl 3 ) as a cyclodehydrating agent. Remarkably, the reaction proceeds smoothly in water as a green solvent at a mild temperature of 50 °C, completing within 30 min. The protocol demonstrates excellent substrate generality, affording a diverse library of 19 target heterocyclic compounds in consistently high yields ranging from 87% to 96%. The robust GO@AlFe 2 O 4 @SO 3 H nanocomposite, which integrates the high surface area of functionalized graphene oxide (GO) with the superparamagnetic properties of aluminium-doped iron oxide (AlFe 2 O 4 ) and Brønsted-acidic sulfonic sites (-SO 3 H), facilitates straightforward magnetic separation from the reaction mixture. This feature underpins the catalyst’s exceptional reusability, as it could be recovered and successively reused for up to seven consecutive cycles without a significant loss in its catalytic performance. The presented work underscores a sustainable, rapid, and practical approach for accessing biologically relevant 1,3,4-thiadiazole frameworks, highlighting the advantages of magnetically recoverable nanocatalyst in promoting sustainable synthetic methodologies.