Synthesis of tetra-substituted phenanthroimidazole derivatives using SBA-Pr-SO3H

Abstract

A one pot four-component reaction of 9,10-phenanthraquinone, aromatic aldehyde, aniline, and ammonium acetate was designed for the preparation of tetrasubstituted imidazoles (phenanthro[9,10-d]imidazole) derivatives in the presence of SBA-Pr-SO3H as a mesoporous solid acid catalyst. Phenanthro[9,10-d]imidazole derivatives were produced by the use of this technique in short reaction times and good to high yields. SBA-15 (Santa Barbara Amorphous), as a hexagonal mesoporous silica with 6 nm pore diameter, was synthesized and then its internal surface was modified with (3-mercaptopropyl)trimethoxysilane following an oxidation process to gain SBA-Pr-SO3H. The latter was then characterized; SEM image showed uniform particles about 700-900 nm and TEM image demonstrated the presence of parallel channels, which resemble the pores configuration of SBA-15. Additionally, the weight reduction in TGA curve in the temperature range of 200-600 °C (about 20% mass loss) established that the anchored propyl sulfonic acid groups onto the SBA-15 pores is about 1.2 mmol/g. This data was also confirmed by back-titration of SBA-Pr-SO3H with standardized NaOH and HCl solutions.