Maleimide-modified phosphonium ionic liquids: a template towards (multi)task-specific ionic liquids

Chemistry. 2010 Aug 9;16(30):9068-75. doi: 10.1002/chem.200902610.

Abstract

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.