In recent years, the trend in synthetic organic chemistry has been to put special emphasis on harmonization with the environment and reaction efficiency. Much R&D is taking place to address these issues. Polymer-supported synthetic reagents and catalysts are drawing much attention due to the ease of recovery of the reagent after reaction. For this reason, many polymer-supported reagents and catalysts with excellent properties have been reported.
One of the most common hypervalent iodine compounds, diacetoxyiodobenzene, has been supported on polystyrene by Togo and co-workers, and they have reported the oxidation of various functional groups. For example, they have reported the oxidation of alcohols in the presence of this polymer-supported reagent and TEMPO.¹⁾ Ishikawa and co-workers have developed 1,3-dimethylimidazolidinone supported on polystyrene. The derived 2-chloro-1,3-dimethylimidazolidium, using oxalyl chloride, is used for the esterification as a polymer-supported dehydrating and condensation reagent.²⁾
On the other hand, active research for development of the polymer-supported catalysts has also been carried out. Yao has developed a polyethylene glycol-bound Grubbs catalyst analog for olefin metathesis reactions.³⁾ After the reaction, this catalyst was precipitated by the addition of diethyl ether as a poor solvent. It can be recovered and reused. Ishihara and his group have developed a polystyrene-bound 4-bis(triflyl)methyl-2,3,5,6-tetrafluorobenzene and demonstrated its applications as a solid super Brønsted acid catalyst.⁴⁾ This solid catalyst swells effectively in organic solvents, and shows excellent activity with various acid-catalyzed reactions. This catalyst has been used in esterification, Friedel-Crafts reaction, Michael addition, acetalization, Sakurai-Hosomi allylation and Mukaiyama aldol reaction. Its catalytic activity was superior even to that of Nafion, which is well known as a solid strong acid. After reaction, the solid catalyst was quantitatively recovered by simple filtration and reused. It was also packed in a syringe as a reaction column, and various acid-promoted reactions were performed to afford the desired products by passing a solution of reactants through the syringe.
Ikegami and co-workers have developed the Pd complex catalyst, one of the most utilized catalyst in the organic synthesis, to support the polymer, and reported its usefulness.⁵⁾ This catalyst is a solid-phase catalyst which consists of an amphiphilic copolymer ligands, chloride and palladium. It takes up substrates and reagents of both hydrophilic and hydrophobic nature in the vicinity of palladium to smoothly promote the reaction. It forms a networked supermolecular complex, which is insoluble in water and organic solvents, and is easily recovered from reaction system. Since palladium is firmly held by the phosphine group of copolymer ligand, it is not lost during the reaction or upon work up; therefore, the catalyst can be recovered and reused multiple times. Ikegami and co-workers have demonstrated the uses of this catalyst for a Suzuki-Miyaura coupling reaction in water, and a Heck reaction in organic solvent. This amphiphilic polymer-supported Pd complex catalyst possesses high catalytic efficiency, and can be used in either water or organic solvents. It is now attracting attention as it has fulfilled harmonization with the environment and reaction efficiency.

A2006	B2372	B2370
B2371	B2292	C2141
D3525	D2766	H1208
I0680	M1452	M1857
P1415	P1427	P1425
P1698	P1697	S0545