Quinine based ionic liquids: A tonic for base instability

Abstract

Six basic ionic liquids were synthesised from the natural molecule quinine, including one room temperature ionic liquid. The thermal properties were studied and the basicity analysed by Hammett measurements. The properties are discussed in relation to the crystal structure of one of the salts, [C 4 Qn][NTf 2 ] (2c) and electron density models generated using Spartan. The ionic liquids were shown to catalyse the Knoevenagel condensation of Malononitrile and Benzaldehyde.

Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

“…S1-S13 in the ESI. † Selective N-methylation of the quinuclidine N (N1) is achieved by treating Qn with MeI at room temperature, 28 giving MeQn + , whereas a reaction temperature of 100 C leads to Me 2 Qn 2+ by N-methylation of both N1 and the quinoline N (N2). 29,30 This selectivity follows the known basicity trend of N1 and N2.…”

Basic ionic liquids for catalysis: the road to greater stability

“…McNeice et al prepared six quinine-derived ILs, including the first example of a room-temperature ionic liquid based on quinine ( Figure 7). 68 Spartan computational calculations showed the basicity of the ionic liquids to be similar to neutral quinine. These ionic liquids were applied to the Knoevenagel condensation between malononitrile and benzaldehyde ( Figure 4).…”

“…The general structure of quinine ionic liquids. 68 Strongly basic ionic liquids can be prepared using Brønsted basic anions, but these generally have low stability due to attack on the cation by the anion, as discussed in section 2.2. McNeice et al stabilized ionic liquids containing a strongly basic anion by preparing binary ionic liquids, combining a relatively base stable pyrrolidinium cation with iso-propoxide and the neutral anion Figure 8).…”

Naturally based ionic liquids with indole-3-acetate anions and cations derived from cinchona alkaloids

“…All products obtained were amorphous, glassy solids at 25 C. A similar state was observed for the majority of other quinine-based ILs. 33,35 This means that the cation based on cinchona alkaloid inuenced the physical state and the viscosity of the obtained products. These phenomena may be partly attributed to the presence of the hydroxyl moiety in the alkaloid-based cation, which is a donor of particularly strong hydrogen bonds 46 that are only partially disrupted by the introduction of an organic anion.…”

“…Two cinchona alkaloids, which are mutual pseudoenantiomers, quinine and quinidine, were chosen as sources of cations. Only a few groups of ILs with quininederived cations have been described thus far, [33][34][35] while there are no literature reports on the preparation of ILs with a quinidine-based cation. According to basic assumptions concerning 3rd generation ILs, the novel forms of IAA designed herein should be characterised by more favourable physicochemical properties compared to the acidic form of IAA.…”