Vicarious nucleophilic substitution arenes

The synthetic application of vicarious nucleophilic substitution, whereby hydrogen of an electrophilic arene is replaced by an a-functionalized alkyl substituent, has been reviewed 177 the sequence usually involves attack on a nitroalkene by a carbanion containing a leaving group X at the carbanionic centre, /i-elimination of HX from the er-adduct, and rearomatization on subsequent protonation. 

In a so-called vicarious nucleophilic substitution of hydrogen, the carbanion of an arene halomethyl sulfone adds to the electron-deficient ring position of nitroarenes or azaaromatic systems such as quinoxalines and naphthyridines, followed by base-induced /(-elimination of the corresponding hydrogen halide.73... 

The chapter Nucleophilic Substitution of Hydrogen in Arenes and Heteroarenes by Mieczyslaw M kosza and Krzysztof Wojciechowski (Institute of Organic Chemistry, The Polish Academy of Sciences, Warsaw, Poland) provides us with the comprehensive review on both oxidative and eliminative versions of the Sn reactions, including the so-called vicarious nucleophilic substitution, which appears to be a very essential part of the Sn methodology. Indeed, the presence of a vicarious (auxiliary) group facilitates elimination of hydrogen with pair of electrons from the intermediate c -adducts. 

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