Metal-Free and Solvent-Free Oxidative Coupling of Amines to Imines with Mesoporous Carbon from Macrocyclic Compounds

Abstract

A new series of carbon-based heterogeneous catalysts aiming at the oxidative coupling of amines to imines is disclosed here, which are easily synthesized by pyrolysis of macrocyclic compounds, including phthalocyanine and porphyrin under different temperatures. Silica colloid or ordered mesoporous silica SBA-15 is employed as the hard template to fulfill the mesoporous structures. The most active catalyst fabricated from phthalocyanine and silica colloid shows remarkable catalytic activity, excellent selectivity, and robust stability toward the imine formation in the presence of molecular oxygen under neat conditions. Kinetic analysis demonstrates that the apparent activation for benzylamine oxidation is 47.6 kJ mol–1 and that cationic species are involved in the reaction. The unprecedented performance of mesoporous carbon catalysts can be attributed to their high surface area, profitable pore volume, as well as homogeneous distribution of defect sites.