Polymer-supported hypervalent iodine as green oxidant in organic synthesis

Abstract

Jang et al. used macroporous polystyrene-supported IBX (MPSIBX) amides to convert a range of alcohols into corresponding carbonyl compounds in various solvents. Polymer supported IBX was prepared in two simple steps, and the polymeric reagent was then evaluated for its efficiency. The results indicated that the MPSIBX amides were compatible with a variety of solvents. Kumar et al. reported polystyrene-supported hypervalent iodine as new recyclable and reusable heterogeneous catalyst for diversityoriented synthesis of benzimidazole and benzoxa/(thia)zole libraries. A useful and novel application of polymer-supported IBX for the chemoselective and regioselective oxidation of phenolic compounds has been described. Hydroxytyrosol and carboxymethylated hydroxytyrosol have been prepared in good conversions and yields under green-chemistry conditions in the presence of dimethyl carbonate as solvent. The polymer-supported reagent has been recovered by simple filtration, regenerated, and reused for more cycles of oxidation reactions without loss of efficiency. Polystyrene-supported (dichloroiodo)benzene (loading of ICl2 up to 1.35 mmol/g) from polystyrene, iodine and bleach has been developed. This recyclable reagent is useful for efficient chlorination of organic substrates and selective oxidation of various alcohols to the carbonyl compounds in high yields under mild conditions. The ion-supported hypervalent iodine reagent has been used as a recoverable and reusable oxidant for the oxidation of primary alcohols to carbonyl compounds. The aldehydes do not undergo further oxidation to carboxylic acids even at longer reaction times. The reagent can be recovered and reused after oxidation with peracetic Reactions of commercial fluorous alkyl iodides RfnI (1-Rfn; Rfn = CF 3(CF2)n1; n = 7, 8, 10, 12) with 80% H2O 2 and trifluoroacetic anhydride give RfnI(OCOCF3)2 (2-Rfn; 8997% yield). These efficiently oxidize aliphatic and benzylic secondary alcohols into the corresponding ketones (5792% yield) in the presence of aqueous KBr and in the absence of organic or fluorous solvents. After the final cycle, 5759% of the original charge of the fluorous iodide species has been recovered. © Georg Thieme Verlag Stuttgart - New York.