Spinel ferrites as efficient magnetically reusable nanocatalysts in the solvent-free synthesis of substituted trisphenols

A series of copper and cobalt substituted nanospinel ferrites have been synthesized by the hydrothermal method. These compounds were characterized by FT-IR, XRD, EDX, SEM and VSM techniques. All of the synthesized nanospinel ferrites were found to be highly efficient and magnetically recoverable in the solvent-free synthesis of substituted 2,6-(2-hydroxybenzyl)-phenols (trisphenols). A wide range of trisphenols were successfully synthesized from the reaction of 2,6-bis (methylol) phenols (BMPs) and different substituted phenols in the presence of Cu0.5Co0.5Fe2O4 nanocatalyst. The best results were obtained in the presence of Cu0.5Co0.5Fe2O4 and molar ratios of phenol: BMP: catalyst, 3: 1: 0.1 under solvent-free conditions at 90°C. The catalyst could be easily separated using an external magnet. Comparison of the efficiency of Cu0.5Co0.5Fe2O4 with other reported catalytic systems showed that this catalyst has a higher activity for the synthesis of trisphenols. All the products were obtained in short reaction times and high yields. This could be related to the synergistic catalytic effect of copper and cobalt in the nanospinel on the activation of hydroxyl groups of BMPs.