The aza-Michael addition reactions of amines with a,b-unsaturated carbonyl compounds were efficiently carried out at room temperature under solvent-free condition employing sulfated zirconia as a reusable heterogeneous catalyst. The desired products were formed in short reaction times and in high yields. The bulk and surface properties of the synthesized catalyst was examined by X-ray powder diffraction, BET surface area, temperature programmed desorption of ammonia, scanning electron microscopy and thermogravimetric techniques. Characterization results reveal the super acidic nature of the catalyst.

An ecofriendly WO x -ZrO 2 solid acid catalyst has been employed for the synthesis of b-amino ketones by a three-component Mannich reaction in the liquid phase under solvent-free conditions at ambient temperature. To make the WO x -ZrO 2 catalyst, WO x from ammonium metatungstate was incorporated into the hydrous zirconia and calcined at 923 K. The incorporated promoter showed a strong influence on the surface and bulk properties of the zirconia. Surface and bulk properties of the catalyst were investigated by means of X-ray powder diffraction, temperature programmed desorption of ammonia, Raman spectroscopy, scanning electron microscopy, and BET surface area methods. Characterization studies reveal that the WO x -ZrO 2 catalyst exhibits strong solid acidity. The catalytic activity results suggest that the methodology adopted offers significant improvements for the synthesis of b-amino ketones with regard to yield of products, simplicity in the operation, and green aspects by avoiding toxic conventional catalysts and solvents.

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