Magnetic resorcinol-formaldehyde supported Schiff-base/Cu as a robust and recoverable nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans.

In this study, the design and synthesis of a magnetic resorcinol-formaldehyde (RF) functionalized with Schiff-base/Cu (Mag@RF/SB-Cu) nanocomposite are reported. The Mag@RF/SB nanomaterial was synthesized through the functionalization of the Mag@RF composite with (3-aminopropyl)trimethoxysilane, followed by the formation of a Schiff base via condensation with 2-hydroxybenzaldehyde. The resulting nanomaterial was subsequently treated with Cu(NO3)2·3H2O to afford the Mag@RF/SB-Cu nanocomposite. The results obtained from FT-IR, EDX, PXRD, VSM and SEM analyses clearly confirmed the successful functionalization of the magnetite surface with the RF/SB-Cu complex, while retaining its crystalline structure. The Mag@RF/SB-Cu nanocomposite was used as a robust and efficient nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans in water at 25 °C. Using 0.005 g of the catalyst, the reactions gave the desired products in high yields (83-97%) within short times (15-35 min). Moreover, due to its good magnetic properties (24 emu per g), the catalyst exhibited remarkable reusability, retaining its catalytic performance over at least eight consecutive reaction cycles. The leaching test confirmed the heterogeneous nature of the Mag@RF/SB-Cu catalyst.