Green and selective alkylation of barbituric acid and 1-phenyl-tetrazole-5-thione with α,β-unsaturated systems using Fe3O4@SiO2-(CH2)3-PHtt-Cu (II) magnetic catalyst

In this research, we immobilized the organic copper complex (1-phenyl-tetrazole-5-thione-Cu (II)) by (3-chloropropyltrimethoxysilane) on silica-coated magnetite (Fe 3 O 4 @SiO 2 ). The structure of Fe 3 O 4 @SiO 2 -(CH 2 ) 3 -PHtt-Cu(II) (FSTU) was confirmed using FT-IR, FE-SEM, BET, TGA, VSM, XRD, EDS-map, and AAS techniques. FSTU catalyst was used in the Michael reaction of barbituric acid with fumaric esters. The products were synthesized in good to excellent yields (74–97 %). For further investigation, we used the catalyst in the Michael reaction of 1-phenyl-tetrazole-5-thione (PHtt) with α,β -unsaturated systems and obtained interesting results. By controlling the temperature, we were able to change the selectivity. At room temperature (25 °C), the Michael reaction was carried out synthetically from the S position. As the temperature increased (thermodynamic conditions) the S-Csp 3 bond was broken during the rearrangement and the Michael reaction proceeded from the N 4 position. Product yields for both reactions were impressive, ranging from 90 to 100 % for the S -Michael product and 85–96 % for the N 4 -Michael product. FSTU catalyst demonstrated consistent activity and stability across all 3 reactions ( C -, N -, S -alkylation), resulting in product yields ranging from good to excellent. • Synthesis of Fe 3 O 4 @SiO 2 -(CH 2 ) 3 -PHtt-Cu(II) using a simple method. • Characterization of catalyst by FT-IR, XRD, FE-SEM, VSM, EDS-map, BET, TGA, and AAS techniques. • C -alkylation of barbituric acid in the presence of FSTU catalyst under green conditions. • Temperature-controlled S vs N Selective alkylation of PHtt in the presence of FSTU catalyst under green conditions. • High stability and activity of FSTU catalyst for PHtt and barbituric acid alkylation reactions after 6 recycling times.