Preparation and thermal stability of optically active 1,2,4-triazolium-based ionic liquids

Paweł Borowiecki,Jan Plenkiewicz,Jan Maurin,Monika Wielechowska,Marcin Poterała

doi:10.3998/ark.5550190.0013.823

Abstract

The synthesis of optically active ionic liquids, in a four-step reaction sequence, is described. In the first step an oxirane ring of cyclohexene oxide was opened with 1,2,4-triazole, yielding a racemic mixture of (1R,2R)- and (1S,2S)-2-(1H-1,2,4-triazol-1-yl)cyclohexanol. Kinetic resolution of the racemate by a lipase catalyzed transesterification with vinyl acetate followed by alkylation (quaternization) of the triazole ring resulted in the appropriate optically active salts formation. After the anion metathesis, thermally stable novel chiral ionic liquids were obtained.

Highlights

The growing interest in recent years in chiral ionic liquids inclined us[1] to prepare and investigate some properties of a few 1,2,4-triazolium-based salts
Ionic liquids (ILs) are salts consisting of big organic cations and inorganic or organic anions with melting points lower than 100 °C (373.15 K).[2]
The salts were prepared from enantiomerically enriched (1S,2S)-2-(1H-triazol-1-yl)cyclohexanol and (1R,2R)-2-(1H-triazol-1yl)cyclohexyl acetate obtained through lipase mediated kinetic resolution of the racemate

Summary

Introduction

The growing interest in recent years in chiral ionic liquids inclined us[1] to prepare and investigate some properties of a few 1,2,4-triazolium-based salts. We here report that (1S,2S)-2-(1H-1,2,4-triazol-1-yl)cyclohexanol can be selectively quaternized at the N-4 atom in the triazole ring by using a threefold molar excess of alkyl iodides or bromides yielding solid salts, which after anion exchange become liquids at room temperature.

Results

Conclusion