Ultrasound-promoted metal-free homogenous olefins epoxidation and direct conversion of alkenes to cyclic carbonates using catalytic TAIm[X] (X = WO42-, HSO5-) recyclable ionic liquid under mild conditions

Abstract

TAIm[WO4] and TAIm[HSO5] ionic liquids were prepared and used as efficient solvent and recyclable catalysts for the mild epoxidation of olefins and the domino preparation of cyclic carbonate from alkenes under ultrasound irradiation. H2O2 was used as an oxidant. The physical properties and structure of the ionic liquids were studied by various analytical methods including FTIR, EDX, viscosity, and density measurements. High to excellent yields were obtained for a wide variety of olefins whether aliphatic or aromatic types for the epoxides as well as the conversion of cyclic and terminal olefins to cyclic carbonates at low CO2(g) pressure (∼1 atm.). Moderate CO2(g) solubility in the ionic liquids was found. Also, excellent epoxide-selectivity was obtained for all olefins. Scalability of the method demonstrated a direct scalability for the promising gram scale epoxidation of olefins with at least efficiency loss. The TAIm[WO4] and TAIm[HSO5] ionic liquids could be recycled from the homogenous mixture by a simple solvent-solvent extraction, and reused for at least several times with insignificant activity loss.