Synthesis of 4H-pyrimido[2,1-b]benzimidazoles catalyzed by a Schiff base cobalt(ii) complex supported on cobalt ferrite magnetite nanoparticles

Abstract

Nano-[CoFe₂O₄@SiO₂/propyl-1-(o-vanillinaldimine)][CoCl₂] was designed and reported with the Schiff base cobalt(II) complex anchored onto cobalt ferrite magnetite nanoparticles. The resulting nanomagnetite Schiff base cobalt(II) complex was employed as a recoverable catalyst for the condensation reaction of aryl aldehyde, 2-aminobenzimidazole and ethyl acetoacetate at 90 °C to synthesize 4H-pyrimido[2,1-b]benzimidazoles under solvent-free condition. According to the proposed mechanism, the cobalt complex can accelerate the reaction via a structural rearrangement from a tetrahedral to a square planar geometry.