Tungstic acid functionalized mesoporous SBA-15: A novel heterogeneous catalyst for facile one-pot synthesis of 2-amino-4H-chromenes in aqueous medium

Abstract

A new highly ordered mesoporous tungstic acid functionalized SBA-15, TAFMC-1 has been synthesized via post-synthesis modification of mesoporous SBA-15 with (3-chloropropyl) triethoxysilane followed by substitution reaction of chlorine atom of the 3-chloropropyl group by tungstic acid group under refluxing conditions in n-hexane. The tungstic acid functionalized mesoporous silica material has been characterized by using small angle powder X-ray diffraction, N₂ sorption, HR-TEM, FE-SEM, FT-IR and solid state MAS NMR studies. TAFMC-1 catalyzes the facile one-pot catalytic three-component condensation reaction of resorcinol, aromatic aldehyde and malononitrile for the synthesis of a diverse range of 2-amino-4H-chromenes in aqueous medium. This heterogeneous catalyst can be recycled very efficiently for six consecutive reaction cycles without significant loss of catalytic activity.