Promoted Zirconia Solid Acid Catalysts for Organic Synthesis

Abstract

This review deals with the catalytic performance of sulfate, molybdate and tungstate ion promoted zirconia solid acid catalysts for various acid-catalyzed organic synthesis and transformation reactions in the liquid phase. These promoted zirconia catalysts exhibit superacidity which mainly depends on the preparation conditions. In particular, the sulfated zirconia catalyst exhibits very strong solid acidity and excellent catalytic activity not only for simple acylation, condensation and esterification reactions but also for other important reactions such as synthesis of aromatic gem-dihalides, stereocontrolled glycosidation, regioselective ring opening of aziridines, production of diaryl sulfoxides and so on. Molybdate and tungstate promoted zirconia catalysts that also exhibit good catalytic activity for various organic reactions of practical importance.

An Efficient Protocol for Aza-Michael Addition Reactions Under Solvent-Free Condition Employing Sulfated Zirconia Catalyst

“…Also in recent times, inorganic solid acid catalyzed organic reactions are gaining much attention due to the proven advantage of heterogeneous catalysts such as simplified product isolation, mild reaction conditions, high selectivity, ease in recovery and reuse of the catalysts, and reduction in the generation of wasteful products [29][30][31]. Sulfated zirconia has been reported to be an excellent catalyst for various organic synthesis and transformation reactions [28,[32][33][34][35][36][37] of industrial significance [26]. Herein, we report the azaMichael addition reaction of amines with a,b-unsaturated carbonyl compounds to produce the corresponding b-amino ketones in high yields (Scheme 1) employing sulfated zirconia (SO 4 2-/ZrO 2 ) catalyst under solvent-free conditions and at ambient temperature.…”

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

“…Among various solid acid catalysts that were reported, sulfated zirconia (SZ) gained much attention due to its high activity and efficiency to catalyze many reactions even at low temperatures [10][11][12][13][14][15][16]. However, the SZ catalyst gets deactivated rapidly at high temperatures and in reducing atmosphere by forming SO x and H 2 S, respectively.…”

Facile Oxidative Desulfurisation of Benzothiophene Using Polyoxometalate H4[α-SiW12O40]/Zr Catalyst

“…In order to improve the catalytic activity in heterogeneous system and stability of the Keggin type polyoxometalatev H4[α-SiW12O40] which has indicated from specific surface area and porosity, we support H4[α-SiW12O40] with zirconium by wet impregnation, thus these material is applied for oxidative desulfurization of benzothiophene as sulfur compound model under mild conditions. Zirconium was selected as the support due to its acid properties and unique physico-chemical properties for organic reactions and transformations [8]. Furthermore, this article presented the gradual characterization of H4[α-SiW12O40]/Zr catalyst, application of H4[α-SiW12O40]/Zr as desulfurization catalyst of benzothiophene.…”