Intramolecular nucleophilic aromatic substitution iodine

Nucleophilic aromatic substitutions involving loss of hydrogen are known. The reaction usually occurs with oxidation of the intermediate either intramolecularly or by an added oxidizing agent such as air or iodine. A noteworthy example is the formation of 6-methoxy-2-nitrobenzonitrile from reaction of 1,3-dinitrobenzene with a methanol solution of potassium cyanide. In this reaction it appears that the nitro compound itself functions as the oxidizing agent (10). 

An intramolecular aromatic nucleophilic substitution has been used for the preparation of 2-substituted benzothiazoles (388) in high yields from o-halothioanilides (387), the halogen atoms being iodine, bromide, or chlorine <82TL5093>. This reaction can also be carried out with naphtho-derivatives <89ijc(B)597>. Moreover, in the presence of sodium carbonate, the reaction can be extended to fluorine-substituted substrates (Equation (81)) <89JHC1039>. 

In principle, cyclohexadienones can be accessed through tautomerization of the corresponding phenol. However, the loss of aromatic stabilization makes this impractical in all but the most specialized of cases. In order to access an isolable cyclohexadienone, the aromaticity of the phenol must be destroyed. One way to do this is through C-alkylation, but this is mostly limited to intramolecular electrophiles. Oxidative dearomatization of the phenol is by far the most conunon method used to prepare both 2,4- and 2,5-cyclohexadienones. A variety of oxidants can be used for this transforma-tiOTi, but iodine(III)- and iodine(V)-based oxidants" have emerged as the reagents of choice in many cases. An attractive feature of these oxidants, especially those based on iodine(III), is that they can be used with a variety of different nucleophiles, thereby providing access to cyclohexadienones with different substitutents. 

The direct nucleophilic substitution of electron-rich phenol ethers using hypervalent iodine oxidants in the presence of Lewis acid or fluorinated alcohols and involving aromatic cation-radical intermediates was originally developed by Kita and coworkers in 1994 [362], Since then this procedure with some variations has been extensively applied by Kita and other researchers for various oxidative transformations. In the intermolecular mode, this reaction (Scheme 3.122) has been utilized for the preparation of the products 298 from N3, AcO , ArS, SCN , 3-dicarbony 1 compounds and other external nucleophiles [320]. The oxidative coupling reaction in the intramolecular mode provides a powerful synthetic tool for the preparation of various... 

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