Regiospecific, one-pot, and pseudo-five-component synthesis of 6,6′-(arylmethylene)bis(2-(<i>tert</i>-butyl)4-methylphenol) antioxidants using highly sulfonated multi-walled carbon nanotubes under solvent-free conditions

Abstract

This is the first report of an innovative, one-pot, pseudo-five-component, and solvent-free synthesis of 6,6′-(arylmethylene)bis(2-(tert-butyl)4-methylphenol) antioxidants from p-cresol, methyl tert-butyl ether, and aldehydes in the presence of sulfonated multi-walled carbon nanotubes (MWCNTs-SO 3 H) as heterogeneous, robust, and reusable catalysts under solvent-free conditions. MWCNTs-SO 3 H was prepared and characterized by some microscopic and spectroscopic techniques including scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, dispersibility in different solvent, and thermogravimetric analysis (one functionality every approximately five carbon atoms). The acidity of the catalyst was measured by acid–base titration (1.80 mmol g −1 ). This reaction proceeds smoothly to give the products in good yields. The catalyst was reused several times without efficient loss of its activity for the preparation of 6,6′-(arylmethylene)bis(2-(tert-butyl)4-methylphenol) antioxidants. In addition, high yields of the products and solvent-free and nontoxicity of the catalyst are other worthwhile advantages of the present method.