The concept of homogeneous supported catalysts has emerged as a useful alternative to homogeneous as well as heterogeneous catalysis, possibly combining positive aspects of both. Designing catalysts with respect to not only their catalytic activity but also their physical-chemical properties, appears to be a possible way towards sustainable chemical synthesis. Such tailored catalytic systems would ideally have high catalytic activities and some property enabling their efficient recycling. We reviewed the field of specifically designed ionic catalysts used mostly in ionic liquids.

Proline-catalysed asymmetric direct aldol reaction of different aromatic aldehydes with acetone and several other ketones in the room temperature ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate achieved good yields of aldolisation products with reasonable enantioselectivities, even when just 1–5% of proline was used as the catalyst; immobilisation of the catalyst in an ionic liquid phase offers simple product isolation and reuse of the catalytical system in subsequent reactions.