An Efficient and Ecofriendly WOx–ZrO2 Solid Acid Catalyst for Classical Mannich Reaction

Abstract

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.

Study on Solvent/Alkoxide Molar Ratios on Synthesis Zirconia Nanoparticles for Tungstated Zirconia Catalysts Over Esterification

“…It should be noted that the XRD peak at ca. 24.3°for all samples was assigned to the monoclinic zirconia (not WO x crystallites) [26][27][28]. The results were found to be in agreement with the work previously reported by our group, the catalysts did not show diffraction peaks at 2h = 23.2, 23.6 and 24.48 and did not show Raman bands at 720 and 807 cm -1 that [18,20,29].…”

A convenient synthesis of coumarins using reusable ionic liquid as catalyst

“…Over the years, numerous methods have been developed for the modifications of Pechmann reaction conditions using a variety of reagents (7Á9). Because of recent efforts toward green chemistry, attempts are being made to replace stoichiometric Brønsted and Lewis acids by non-stoichiometric solid acids, such as montmorillonite clay (10), cation-exchanged resin (11), and sulfated Ce x Zr 1Áx O 2 (12). Ionic liquids have been also employed for this purpose in the Pechmann condensation (13Á19).…”

Solvent effect on synthesis of zirconia support for tungstated zirconia catalysts

“…Some of the general conclusions are that the incorporation of tungsten into the zirconia favors the formation of the tetragonal phase, inhibits sintering of the support and enhances the acid strength of these solids by the slight reduction of the WO x species. Since then, many papers have been focused on the properties of catalysts prepared from zirconium oxyhydroxide [7,15,[18][19][20][21][22][23][24][25]. Systems based on the W deposited on crystallized zirconia were studied to a smaller extent [3,4,6,[26][27][28].…”