Heteropolytungstostannate as a homo- and heterogeneous catalyst for Knoevenagel condensations, selective oxidation of sulfides and oxidative amination of aldehydes

Abstract

W 18 O 68 (HOSn IV OH) 3 ]$20H 2 O (1) is used as a homo-and heterogeneous catalyst for Knoevenagel condensations. New Fe 3 O 4 @SiO 2 @CH 2 (CH 2 ) 2 NH 3 + -[P 2 W 18 O 68 (HOSn IV OH) 3 ] 11À nanocatalyst was fabricated through electrostatic grafting of (1) on aminemodified silica-coated magnetic nanoparticles. The new magnetically recoverable nanocatalyst wascharacterized using infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffractometry (XRD), energy-dispersive X-ray analysis (EDX) and alternating gradient force magnetometry (AGFM). The results indicate that the particles are mostly spherical in shape and have an average size of approximately <30 nm. The catalytic activity of the catalyst was investigated in the selective oxidation of sulfides to sulfoxides and oxidative amination of aldehydes in an aqueous medium. The catalyst was reused at least five times without significant decrease in catalytic activities, and the structure of the catalyst remained unchanged after recycling.

Tris(2-Aminoethyl)Amine/Metal Oxides Hybrid Materials—Preparation, Characterization and Catalytic Application

“…The Knoevenagel condensation can be successfully performed with the use of different amines as catalysts in the homogeneous [ 1 , 2 ] and heterogeneous [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ] systems. The Knoevenagel reaction is the condensation which involves a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which water is eliminated.…”