Synthesis of 3,4-Dihydropyrimidinone Derivatives by Using Mag@TOS as a Strong and Magnetically Recoverable Nanocatalyst

Abstract

In this study, a novel magnetic titanium-containing organosilica (Mag@TOS) nanocomposite with core-shell structure is synthesized via alkaline hydrolysis and co-condensation of tetramethoxysilane (TMOS), tetrabutyl orthotitanate (TBOT) and 1,2-bis(triethoxysilyl)ethane (BTEE) around Mag@SiO₂ in the presence of cetyltrimethylammonium bromide (CTAB) surfactant. The Mag@TOS composite was characterized by using FTIR, SEM, PXRD, EDX, ICP and VSM techniques. The inverse cubic spinel phase of Fe₃O₄ and no formation of TiO₂ phases in the synthesis path of Mag@TOS were confirmed by the wide-angle PXRD technique. Also, the formation of the mesoporous shell and the superparamagnetic behavior of Mag@TOS were confirmed by low-angle PXRD and VSM analyses, respectively. Mag@TOS was successfully used as a strong catalyst in the Biginelli reaction and gave the desired 3,4-dihydropyrimidinone products in high yields. In addition, this catalyst was recovered and reused at least 5 times with keeping its efficiency. Some other advantages of the present study are high stability and no-leaching of active catalytic species during reaction conditions, high reaction rate and also easy recoverability and reusability of the catalyst.