Ionic liquid-supported iodoarenes

Kawano and Togo introduced an ionic liquid group into iodoarenes, to form ionic liquid-supported iodoarenes, and used them for the promotion of the synthesis of oxazoles [24]. The results of the reactions of acetonitrile, m-chloroperbenzoic acid (mCPBA), trifluoromethanesulfonic acid (TfOH), and acetophenone are shown in Table 12.1, using various IL-supported iodoarenes (IL-supported Phis). The reactivities of IL-supported iodoarenes (Phis) 17-25 are shown in entries 1-9, and IL-supported Phi 20 showed the best reactivity. Instead of acetonitrile as solvent, room temperature ILs, such as [emim][OTs], [bmim][PFg], and [bmpyjlNTf ], were used in the presence of IL-supported Phi 20 (entries 10-12). However, [emim][OTs] did not promote the oxazole formation at all, while [bmimJPF and [bmpy][NTfJ provided the oxazole in moderate to low yields. Thus, use of acetonitrile as solvent yielded the best reactivity as compared with these ILs. 

Likewise, efficient recyclable bifunctional catalysts 112 and 113 (Eigure 4.3) bearing ionic liquid-supported TEMPO and iodoarene moieties have been developed and used for the environmentally benign catalytic oxidation of alcohols [92]. Compounds 112 and 113 have been tested as catalysts for the oxidation of alcohols to the corresponding carbonyl compounds using peracetic acid as a green and practical oxidant. Ion-supported catalysts 112 and 113 can be conveniently recovered from the reaction mixture and reused without any loss of catalytic activity (Section 5.5). 

Although the iodoarene can often be recovered and used in the synthesis of At2IX [53], this process could be facilitated by the use of solid supported diaryliodonium salts. Polymer-bound reagents have, however, met with limited success in applications, possibly because of chemoselectivity problems resulting in the nucleophiles being transferred to the polymer backbone [42,54], Ionic liquid-supported Ar2lX were recently synthesized and applied in chemoselective O-arylations without the need for chromatography [55]. 

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