Palladium Schiff-base complex loaded SBA-15 as a novel nanocatalyst for the synthesis of 2,3-disubstituted quinoxalines and pyridopyrazine derivatives

Abstract

SBA-15-supported palladium catalyst containing N–O chelating Schiff-base ligand has been prepared by the reaction of SBA-15 and a Pd(II) Schiff-base complex. The Pd(II) Schiff-base complex was prepared by the reaction of salicylaldehyde and (3-aminopropyl)trimethoxysilane in methanol and subsequent complexation with Pd(OAc)2. Characterization of the nanocatalyst was carried out with powder X-ray diffraction (XRD), BET nitrogen adsorption–desorption method, transmission electron microscopy (TEM), atomic absorption and IR spectroscopy. XRD, TEM and BET analyses revealed the retention of the textural properties of SBA-15 during the grafting procedure. The entitled catalyst was applied successfully for the synthesis of quinoxaline, [1,2-b]pyrazine, pyrido[2,3-b]pyrazine, and pyrido[3,4-b]pyrazine heterocycles with good to excellent yields in water. A variety of 2,3-disubstituted quinoxalines and related heterocycles were synthesized under green conditions by cyclocondensation of various 1,2-diamines and 1,2-diketones using a catalytic amount of the nanocatalyst.