تحضير مشتقات البنزايميدازول باستخدام السيليكا متوسطة المسام كمحفز غير متجانس

Synthesis of Benzimidazole Derivatives Using the Mesoporous Silica as Heterogeneous Catalyst

Abstract
This study consists of two parts, in each part a new catalyst is synthetic via extracting silica from rice husk and product MCM-41 which is used in preparation of Brønsted acidic ionic liquid as heterogeneous catalysts where catalyst 1 is labeled ([MCM-41-(PSim)][SO4H]) and catalyst 2 is labeled ([MCM-41-(PSim)][PO4H2]). This method is inexpensive and easy to synthesis the catalysts by employing rice husks as a green source. The catalysts are characterized and analyzed by utilizing FTIR, XRD, N2 adsorption-desorption analysis, TGA/DTG Thermo gravimetric Analysis and FESEM-EDS Energy-dispersive and X-ray Spectroscopy-Scanning electron microscopy. In first part, several types of aldehydes and carboxylic acids were subjected to coupling with o-phenylenediamine. This process employs [MCM-41-(PSim)][SO4H] as a new catalyst, utilizing water as the environmentally friendly solvent, and yields reasonable results, as display in the following Scheme I :

Scheme I: Synthesis of bezimidazole derivatives by catalyst 1
The second part in this work was described reacting o-phenylenediamine with different aldehydes in the presence of catalyst 2 ([MCM-41-(PSim)][PO4H2]) as an effective catalyst with the water as an economical and environmentally friendly solvent. Reaction work up was simple and reasonable yield of products was observed. To determine the influence of ultrasound, we compared this reaction under ultrasound irradiation and reflux conditions was performed, as shown in the following Scheme II:
Scheme II: synthesis of bezimidazole derivatives by catalyst 2
All benzimidazole derivatives obtained in this study were identified using melting points, FTIR, 1H-NMR and mass spectra. Benzimidazole derivatives consider important compounds used in many organic, medical and industrial applications.
These strategies are economically attractive and very suitable for the synthesis of benzimidazole derivatives due to the simple preparation of the catalyst, short reaction time, mild conditions, and low cost makes. Additionally, the catalysts can be easily recovered for several times.