Bread waste in the form of CoFe2O4@TBW catalyst was used as a green biocatalyst to synthesize pyranopyrazole and tetraketone derivatives

Bread scraps with transition metal oxide spinels were utilized to synthesize core–shell magnetic nanocatalyst. The prepared heterogeneous catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). This magnetic nanocatalyst opens up a new avenue to introduce a very useful and efficient catalytic system for the one-pot synthesis of tetraketone derivatives via Knoevenagel-Micheal reaction of 1,3 cyclohexanedione and benzaldehyde in ethanol as a green solvent at 50 °C, and one-pot four-component reaction of benzaldehyde, dimedone, ethyl acetoacetate, and hydrazine hydrate via tandem Knoevenagel-Micheal reaction for the synthesis of dihydropyrano[2,3-c] pyrazole derivatives in ethanol. The pharmaceutical properties of dihydropyrano[2,3-c] pyrazole and tetraketones make them both essential compounds. Moreover, the recyclability of the new heterogeneous magnetic catalyst does not significantly deteriorate its catalytic activity, and it can be easily recovered by an external magnet and reused ten times without significant loss of activity, making it environmentally friendly and economically feasible to perform the desired transformations. NBO calculations were carried out at the level of B3LYP/6–311 + + G (d, p) to obtain the atoms' natural charge data to justify the reaction's mechanism.