Benzene, tris aromatic nucleophilic substitution

Kita and Tohma found that exposure of p-substituted phenol ethers to [bis(tri-fluoroacetoxy)iodo]benzene 12 in the presence of some nucleophiles in polar, less nucleophilic solvents results in direct nucleophilic aromatic substitution [Eq. (84)] [156]. Involvement of a single-electron transfer (SET) from phenol ethers to A3-iodane 12 generating arene cation radicals was suggested by the detailed UV-vis and ESR studies. SET was involved in the oxidative biaryl coupling of phenol ethers by 12 in the presence of BF3-Et20 [157]. 

The Friedel—Crafts alkjiation reaction is an electrophilic aromatic substitution that attaches an alkyl group to the aromatic ring. It is named for Charles Friedel (1832-1899) and James M. Crafts (1839—1917), who discovered it by acddent when they tried to synthesize pentyl chloride from pentyl iodide through reaction with aluminum chloride in an aromatic solvent. Instead of the hoped-for chloride, substituted aromatic hydrocarbons appeared. The Friedel-Crafts reaction is closely related to bromination and chlorination of benzene. If we treat benzene with isopropyl bromide in the hope that a nucleophilic attack of benzene on isopropyl bromide will produce isopropylbenzene (cumene), we are sure to be disappointed (Fig. 14.34). Benzene is by no means a strong nucleophile and isopropyl bromide can scarcely be described as a powerful electrophile. The proposed reaction is utterly hopeless, and ftuls to give product. 

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