Maleimide-Modified Phosphonium Ionic Liquids: A Template Towards (Multi)Task-Specific Ionic Liquids

The synthesis and characterization of several compounds representing a new class of multitask‐specific phosphonium ionic liquids that contain a maleimide functionality is reported. The maleimide moiety of the ionic liquid (IL) is shown to undergo Michael‐type additions with substrates containing either a thiol or amine moiety, thus, serving as a template to introduce wide structural diversity into the IL. Multitask‐specific ILs are accessible by reaction of the maleimide with Michael donors that are capable of serving some function. As a model example to illustrate this concept, a redox active ferrocenyl thiol was incorporated and examined by cyclic voltammetry. Because the maleimide moiety is highly reactive to additions, the task‐specific ionic liquids (TSILs) are prepared as the furan‐protected Diels–Alder maleimide. The maleimide moiety can then be liberated when required by simple heating. Multitasking: A class of multitask‐specific phosphonium ionic liquids (ILs) containing a functionality that is capable of further organic transformations is reported. Multitask‐specific ILs are accessible by reaction of maleimide with a Michael donor capable of serving some function. A ferrocenyl thiol is used to illustrate this concept (see scheme).