THE SYNTHESIS OF SALICYLATE PROMPTED BY BR0NSTED ACIDIC IONIC LIQUIDS

Abstract

Bronsted acidic ionic liquids based on imidazolium cation were employed as a series of efficient and environmentally benign catalysts and solvents for the synthesis of salicylate, the yields could reach 76%-96%. The optimal reaction conditions were determined. The results showed that Bronsted acidic ionic liquids were efficient catalysts and solvents which could be recycled easily without obvious decline in catalytic activities. . Toluene-p-sulfonic acid, sodium acid sulfate and solid acid had been used as substitute catalysts for the synthesis of salicylate, but the recovery of them was difficult 1-3 . Bronsted acidic ionic liquids (ILs) 1-butyl-3-methyl-imidazolium hydrogen sulphate ((bmim)HSO4), 1-butyl-3-methyl-imidazolium dihydogen phosphate ((bmim)H2PO4), 1-methyl-3-hydro-imidazolium tetrafluoroborate ((Hmim) BF4), 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulphate ((HSO3- pmim)HSO4), 1-methyl-3-(3-sulfopropyl)-imidazolium tetrafluoroborate ((HSO3-pmim)BF4) and 1-methyl-3-(3-sulfopropyl)-imidazolium 4-methylbenzenesulfonate ((HSO3-pmim)(pTSA)) had received vast research interests in recent years which had been used as satisfactory acidic catalysts and solvents for many organic reactions 4-6 , due to their particular properties, such as high thermal stability, reusability, miscibility with organic compounds and so on 7-9 . In this paper, an efficient and feasible procedure for the synthesis of salicylate was reported, using Bronsted acidic ILs (bmim)HSO4, (bmim) H2PO4, (Hmim)BF4, (HSO3-pmim)HSO4, (HSO3-pmim)BF4 and (HSO3-pmim) (pTSA) (Figure 1) as recyclable catalysts and solvents (Scheme 1). The optimal reaction conditions were determined and the results showed that Bronsted acidic ILs were efficient catalysts and solvents for the synthesis of salicylate. ILs used could be recycled easily without obvious decline in catalytic activities.