Silica-Supported Antimony(III) Chloride as Highly Effective and Reusable Heterogeneous Catalyst for the Synthesis of Quinoxalines

Abstract

Lewis acid site on silica-supported antimony(III) chloride (SbCl3/SiO2) acts as a highly efficient catalyst, even for low activity substrates, in the preparation of quinoxaline derivatives. The results of TG-DTA and BET indicated that dispersed SbCl3 coordinates with surface hydroxyl groups leading to formation-O–Sb–Cl as stable Lewis acid sites under the reaction condition. This user-friendly catalyst was found to be reusable without any loss of activity. The fact that SbCl3 did not leach makes SbCl3/SiO2 as alternative heterogeneous acid catalyst to the conventional homogeneous acids at room temperature. The wide range of turnover frequency values (11–800 h−1) shows that reaction rate is highly dependent on the nature of the functional groups on the aromatic ring of substrates. Lewis acid site on silica-supported antimony(III) chloride (SbCl3/SiO2) acts as a highly efficient catalyst, even for low activity substrates, in the preparation of quinoxaline derivatives. The results of TG-DTA and BET indicated that dispersed SbCl3 coordinates with surface hydroxyl groups leading to formation-O–Sb–Cl as stable Lewis acid sites under the reaction condition. This user-friendly catalyst was found to be reusable without any loss of activity. The fact that SbCl3 did not leach makes SbCl3/SiO2 as alternative heterogeneous acid catalyst to the conventional homogeneous acids at room temperature. The wide range of turnover frequency values (11–800 h−1) shows that reaction rate is highly dependent on the nature of the functional groups on the aromatic ring of substrates.