Finely Dispersed Fe3O4 and Ag Nanoparticles Adhered by Starch Nano‐layers: an Efficient Catalyst for the Synthesis of Pyrano[2,3‐d]Pyrimidines.

Hot‐water‐soluble starch (HWSS) was employed as binder for fabrication of a composite from magnetite and Ag nanoparticles (NPs). Electron microscopy images showed a good dispersion of magnetite NPs in the matrix of HWSS. This observation indicates that HWSS tends to coat the maximum surface of magnetite by encapsulation of individual magnetite NPs, leading to disassembly of their aggregates. The HWSS‐coated magnetite NPs were employed as nano‐support for immobilization of fine Ag NPs generated in situ via reduction of Ag+ cations by glucose. Monitoring of the formation and growth of Ag NPs by UV–Vis spectroscopy made it possible to set up an optimal condition for fabrication of the nano‐composite and to verify the supremacy of HWSS‐coated magnetite NPs over bare magnetite NPs as support in this new protocol. Valuable insights into the texture of the nano‐composite were obtained by VSM, FT‐IR and XRD studies. The bio‐derived nano‐composite displayed an interesting magnetic property and an efficient catalytic activity in the three‐component synthesis of pyrano[2,3‐d]pyrimidines. It is a robust heterogeneous catalyst and can be simply retrieved from reaction mixtures by magnetic separation method. [ABSTRACT FROM AUTHOR]