Green synthesis and characterization of mixed-phase Fe 2 O 3 nanorods as a novel magnetically recoverable heterogeneous catalyst for Biginelli synthesis

For the first time, mixed-phase (Hematite and Maghemite) magnetic Fe2O3 nanorods were successfully biosynthesis by sol-gel auto-combustion method using the 1:1 mixture of Eucalyptus citriodora and Mur -raya koenigii leaf extract as a capping agent, and its catalytic effect on synthesis of 6-(chloromethyl)-1,2,3,4-tetrahydro-2-pyrimidinone (THPMs) derivatives were investigated. Further, the phase formation, surface topography, and crystallinity of biosynthesized Fe2O3 nanorods (NRs) were explored using powder XRD (X-Ray Diffraction), UVDRS (UV-Visible Reflectance Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), FESEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive X-Ray), and VSM (Vibrating Sample Magnetometry). Furthermore, the catalytic activity of biosynthesized Fe2O3 NRs (C1, C2, and C3) was examined for one-pot synthesis of ethyl 6-(chloromethyl)-1,2,3,4-tetrahydro-2-oxo-4-arylpyrimidine-5-carboxylate via Biginelli reaction. To achieve high yields (93-99 %) of 6-(chloromethyl)-1,2,3,4-tetrahydro-2-pyrimidinone derivatives, this heterogeneous catalytic method is used with a wide range of aromatic aldehydes within a minimum reaction time, simple reaction work-up, and easily recov-erable catalyst by an external magnet. The recovered catalyst is then employed for five successive cycles without non-noticeable loss of catalytic activity. We believe that this protocol presents a broad scope for Biginelli reaction through greenly produced and magnetically separable heterogeneous catalysts.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

For the first time, mixed-phase magnetic Fe2O3 nanorods were successfully synthesized by biosynthesis using a sol-gel auto-combustion method. The catalytic effect of these nanorods on the synthesis of 6-(chloromethyl)-1,2,3,4-tetrahydro-2-pyrimidinone derivatives was investigated. The phase formation, surface topography, and crystallinity of the nanorods were explored using various spectroscopy and microscopy techniques.