New chiral ionic liquids based on imidazolinium salts

The preparation and application of a new series of chiral ionic liquids are described. The salts are based on imidazolinium cations. Some of the cations also incorporated an axial chirality at the C(2) position next to the central chirality. These cations display a very high rotational barrier along the arene–imidazolinium axis. Furthermore, an analogue with a chiral anion was prepared. The salts have low melting points. Their potential as solvents and as chiral shift reagents was explored, resulting for the first time in an example of a chiral ionic liquid as a shift reagent for a neutral compound.

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(S)-4-Isopropyl-3-(methoxymethyl)-1-methyl-2-phenyl-4,5-dihydro-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)amideC17H23F6N3O5S2[α]D25=+20 (c 1.33, CHCl3)Ee = 100%Source of chirality: chiral poolAbsolute configuration: (S)

(S)-4-Isopropyl-3-((2-methoxyethoxy)methyl)-1-methyl-2-phenyl-4,5-dihydro-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)amideC19H27F6N3O6S2[α]D25=+18 (c 1.29, CHCl3)Ee = 100%Source of chirality: chiral poolAbsolute configuration: (S)

3-(((1R,2S,5R)-2-Isopropyl-5-methylcyclohexyloxy)-methyl)-1-methyl-2-phenyl-4,5-dihydro-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)amideC23H33F6N3O5S2[α]D25=-39.7 (c 1.02, CHCl3)Ee = 100%Source of chirality: chiral poolAbsolute configuration: (1R,2S,5R)

3-Butyl-1-methyl-2-phenyl-4,5-dihydro-1H-imidazol-3-ium ((1S,4S)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)methanesulfonateC24H36N2O4S[α]D25=-19 (c 1.43, CHCl3)Ee = 100%Source of chirality: chiral poolAbsolute configuration: (1S,4S)