A novel liquid-phase strategy for organic synthesis using organic ions as soluble supports

This critical review describes a new liquid-phase strategy for organic synthesis by using organic ions as soluble supports. Catalysts or reagents or substrates are immobilized onto organic ions. They are generally soluble in polar organic solvents (e.g. CH(3)CN) or ionic liquids but insoluble in non-polar solvents (e.g. ether or hexanes). Their reactions are carried out in homogeneous solution phase with a polar organic solvent or ionic liquid. After the reaction, the ion-supported species can be phase separated through precipitation from the polar organic solvent by the addition of a less polar organic solvent or extraction with organic solvents from ionic liquids. The ion-supported species can therefore be easily recovered and purified from the reaction mixture by simple washings with the less polar solvent. The ion-tagged species can function in the role of a catalyst, or as a reagent, or as the substrate in the synthesis of small molecules or bio-oligomers. Ion-supported catalysts and reagents can usually be recovered and reused with little diminution of activity. Important biooligomers such as peptides, oligosaccharides and oligonucleotides have been synthesized with this method (136 references).