Green synthesis and characterization of mixed-phase Fe2O3 nanorods as a novel magnetically recoverable heterogeneous catalyst for Biginelli synthesis

•First time report on the synthesis of Fe2O3 nanorods (NRs) by a green process via a mixture of Eucalyptus citriodora and Murraya koenigii leaf extracts.•XRD, FESEM, EDX, FTIR, UV-DRS, BET, and VSM analysis confirmed the biosynthesis of Fe2O3 NRs.•Fe2O3 NRs exhibited excellent catalytic performance for the Biginelli reaction.•The synthesized catalyst exhibited high stability, reusability, an excellent yield of Biginelli products, and easy workup. 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 Murraya 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 recoverable 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. [Display omitted]