Mg(OTf)2 + ionic liquid - recyclable catalytic system in diels-alder reaction

Bożena Bittner,Ewa Janus,Eugeniusz Milchert

doi:10.2478/v10026-010-0023-0

Abstract

Mg(OTf)2 + ionic liquid - recyclable catalytic system in diels-alder reaction A comparative study of Diels-Alder reaction between cyclopentadiene and dimethyl maleate in catalytic system is reported. The catalytic system was formed from ionic liquid which was made of N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and magnesium trifluoromethanesulfonate. The yields, TONs, TOFs and endo:exo ratios were calculated. The optimal catalyst concentration was found in order to obtain the mixture of endo, exo isomers with the highest yields. Moreover recycling of the catalytic system consisting of Mg(OTf)2 (2 mol%) and ionic liquid was performed. The distillation was noticed to be a better product removal method than extraction by organic solvent, taking into consideration both the TON and TOF values.

Highlights

Diels-Alder reaction is a source of various cyclic and bicyclic compounds that are commonly used in pharmaceuticals, cosmetics, pesticides synthesis[1]
We investigated the catalytic activity of the system [hpy][NTf2] and Mg(OTf)[2]
We used the catalytic systems based on Mg(OTf)[2] and N-hexylpyridinium bis(trifluoromethylsulfonyl)imide in the reaction of cyclopentadiene with dimethyl maleate, which leads to a mixture of endo and

Summary

INTRODUCTION

Diels-Alder reaction is a source of various cyclic and bicyclic compounds that are commonly used in pharmaceuticals, cosmetics, pesticides synthesis[1]. Nowadays researchers are focused on finding an appropriate solvent for cycloaddition It should be nontoxic, enhancing reaction rate and selectivity, being recyclable and making the product separation easy. Ionic liquids have been successfully applied as alternative solvents in many reactions, in Diels-Alder cycloaddition. They are classified as green solvents because of specific properties such as negligible vapour pressure, being thermally stable and recyclable. Similar to our studies in cycloaddition between ethyl acrylate and cyclopentadiene, studies have been made with erbium triflate and pyridinium ionic liquids[15]. In those catalytic systems ionic liquids and metal salts consisted of the same triflate anion. In all the formed systems, the obtained yields and selectivities were higher than in the organic solvent based systems

EXPERIMENTAL PART

Results and discussion

CONCLUSIONS

LITERATURE CITED