Replacement of aromatic fluonne

The replacement of a substituent on an aromauc nng by a nucleophile is termed arylaUon. This chapter considers the replacement by nucleophihc oxygen, sulfur, nitrogen, and carbon of aromatic fluonne atoms, which are often activated by electron-withdrawing groups. 

An unactivated aryl fluorine may be activated by complexauon with chro-mium(VI). Replacement of the fluonne in the complexed system occurs readily, and the uncomplexetl aromatic product can be generated by treatment with iodine [84] (equation 46)... 

Perfluoropyridine gives the usual replacement of the 4-fluonne on reactions with either aromatic or aliphatic mercaptides [55, 36] The reaction of perfluoropyridine with cesium tnfluoromethyl mercaptide, generated from thiocarbonyl fluoride and cesium fluonde, shows temperature dependence of selectivity in fluonne displacement [55 36] (equation 24)... 

The replacement of reactive aromatic fluonne by nitrogen nucleophiles is a well-known process for the preparation of aromatic amines The aromatic fluonne IS activated by the presence of electron-withdrawing substituents on the aromatic ring, especially in ortho and para positions [57 38, 39] (equations 25-27)... 

The trtfluoromethyl group activates the fluorine in position 4 ofperfluorotolu ene toward reaction with carbon nucleophiles Examples on the use of perfluoro-toluene as an ary lation agent abound, and in all cases, the 4-fluonne atom is replaced predominantly or exclusively [86,87,88,89,90] (equation 48) Inperfluoromesity-lene, the aromatic fluorine atoms are activated toward SN Ar reaction, and a reaction with one equivalent of methylkthium causes smooth replacement of one fluorine atom [91] (equation 49)... 

Fluonne atoms in aromatic nitrogen heterocycles are readily replaced by oxygen nucleophiles [77] Bistnfluoromethyl hydroxylarmne anion is an interesting nucleophde for the introduction of oxygen into perfluoropyndine Rearrangement of the product occurs at 125 °C [18 (equation 12)... 

---