Poly styrene oxidative iodination

Tsarevsky has found that hypervalent iodine compounds can be used for the direct azidation of polystyrene and consecutive click-type functionalization [49]. In particular, polystyrene can be directly azidated in 1,2-dichloroethane or chlorobenzene using a combination of trimethylsilyl azide and (diacetoxyiodo)benzene. 2D NMR HMBC spectra indicate that the azido groups are attached to the polymer backbone and also possibly to the aryl pendant groups. Approximately one in every 11 styrene units can be modified by using a ratio of PhI(OAc)2 to trimethylsilyl azide to styrene units of 1 2.1 1 at 0 °C for 4 h followed by heating to 50 °C for 2 h in chlorobenzene. The azidated polymers have been further used as backbone precursors in the synthesis of polymeric brushes with hydrophilic side chains via a copper-catalyzed click reaction with poly(ethylene oxide) monomethyl ether 4-pentynoate [49],... 

Polymer-supported hypervalent iodine compounds in general are readily prepared and they have gained recently considerable popularity as reagents for clean oxidations. However, they are not newcomers since they have been known since 1961. A detailed procedure for the iodination of polystyrene and its conversion to poly[(diacetoxyiodo)styrene] appeared in 1972 [85]. However, this and other related methods were time consuming and despite encouraging results did not gain popularity. 

Poly(vinylbenzyl mercaptan) has been described by several authors. The synthesis always follows the same path chloromethylation of polystyrene followed by reaction with thiourea and hydrolysis of the isothiuronium salt 1,53,55,63-65). The redox properties of a polymer obtained from chloromethylated styrene-divinylbenzene copolymers have been evaluated (3). Redox capacities givrai for mercaptyl resins were determined to be 2. W>-5.27 milliequivalents of iodine reduced per gram of (dry) resin in aqueous potassium iodide. The oxidized form of the resin could be easily reduced with 10% aqueous bisulfite fmr a complete redox cycle. Recently polyvinylbenzyl mercaptan resins were prepared directly by treating chloromethylat polystyrene with KSH in dimethyl formamide (66). 

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