Nucleophilic Heteroaromatic Substitution

Abstract

Publisher Summary The nucleophilic aromatic substitution refers to the reactions consisting of essentially two stages, bond-making and bond-breaking, at the same carbon atom , whatever their relative timing may be. Two classes of compounds are of special importance in the field of nucleophilic aromatic substitution. These include the nitrobenzene derivatives and N-heteroaromatic compounds. The most widely accepted mechanism for nucleophilic aromatic substitution involves a change from sp 2 to sp 3 hybridization of the attacked carbon atom. All the aromatic nucleophilic substitutions reactions, discussed in this chapter, are described with respect to their general kinetic features and mainly involve aza-activated six-membered ring systems. A distinctive structural feature of most heteroaromatic substrates, viz. the basicity of the aza group, is responsible for the occurrence of acid catalysis in nucleophilic substitution. A theoretical explanation of the reactivity of nucleophilic reagents have centered on correlations with intrinsic electron-donor properties which are the fundamental basis of nucleophilicity. Such properties include basicity, polarizability, and the presence of unshared electron pairs on the atom adjacent to the nucleophilic atom of the reagent. The chapter concludes by discussing the inorganic heteroaromatic substitution reactions.