Halide-free synthesis of novel fluorinated ionic liquids

To date, the synthesis of fine chemicals is mostly performed using conventional volatile organic solvents; however this is always associated with the dangers of handling large volumes of volatile and combustible solvents, human risk and safety issues and poor environmental performance. Ionic Liquids (i.e. salts melting below 100 C) represent a class of solvents, as their tunable structure allows creating reaction media for a specific purposes. Ionic liquids are typically prepared in a time-consuming two-step process that suffers from the formation of by-products and hence low atom efficiency. The constantly growing demand of ionic liquids for calls for more efficient preparation strategies. Moreover, the specifications needed for many applications ranging from electrochemistry to catalysis or tribology require hydrophobic ionic liquids without trace contamination of inorganic salts. This research project focuses on the development of an entirely novel strategy for the efficient preparation of hydrophobic ionic liquids with novel anions. The modular synthetic route offers a pathway for the design of ionic liquids free from metal- or halide impurities, and eventually provides access to novel, and to date never synthesized ionic liquids with high purity and broad application range. Eventually, the implementation of microreactor technologies enable the continuous production of these ionic liquids in large scale and high efficiency that cannot be reached with the current state-of-the-art process.

Nowadays, the synthesis of fine chemicals is still mostly performed in conventional organic solvents. These might be toxic and/or volatile, therefore resulting in safety risk for human health and environment. Ionic liquids - salts with a melting point below 100 C - could provide a powerful approach for the synthesis of task-specific compounds with broad applicability including analytics, catalysis, extraction or lubrication technologies. Nevertheless, ionic liquids are most commonly prepared in a classical two-step process via alkylation and subsequent anion metathesis. This results not just a quite time-consuming process, but it also generates large amount of waste water. In light of the growing awareness for sustainable chemical transformations, finding fast and efficient alternatives for ionic liquid synthesis and circumventing the aforementioned problems would be highly desired. (1) The first sub-project focused on the synthesis of hydrophobic, fluorinated ionic liquids (ILs) in continuous flow. As such, a novel, metal- and halide-free methodology has been developed, which provided simple and fast access to various hydrophobic fluorinated ionic liquids. Apart from providing a fast and simple access to ILs with reduced waste water production, this methodology also led to negligible halide content, which might significantly broaden the application range of ILs especially for material science and lubrication technologies. (2) The second sub-project focused on the synthesis of novel fluorinated ionic liquids with asymmetrically substituted anions. In order to obtain ILs bearing asymmetrical anions, asymmetric precursors are required. A two-step process implements this upon the stepwise introduction of the functional groups. Although we successfully introduced the first moiety to the precursor, our attempts to introduce the second one failed. (3) The third sub-project part focused on the application of hydrophobic ionic liquids for continuous-flow allylations by means of a supported ionic liquid phase (SILP) approach. As such, this method gave access to cheap and air-tolerant catalyst frameworks. These could be then successfully used for the (asymmetric) allylic alkylation of amines; and provided high catalytic activities and short reaction times under mild reaction conditions.