Electrophilic arenes nucleophilic aromatic substitution

This reaction is a powerful tool and represents an alternative for the synthesis of substituted arenes difficult to prepare via classical electrophilic or nucleophilic aromatic substitution. Using bi- or polyfunctional arenes as starting materials, this reaction affords novel organoiron polymers [76] (Scheme 1.35). 

Reactions of Arenes Electrophilic and Nucleophilic Aromatic Substitution... 

By reorganizing certain related topics, the number of chapters in Organic Chemistry has been reduced from 29 in the 7th edition to 27 in the 8th. Thus, nucleophilic aromatic substitution has now joined electrophilic aromatic substitution in Chapter 12 Reactions of Arenes Electrophilic and Nucleophilic Aromatic Substitution while Chapter 20 Enols and Enolates combines the treatment of ester enolates with that of aldehyde and ketone enols and enolates. 

This chapter covers reactions in which coordination of a transition metal to the ir-system of an arene ring activates the ring toward addition of nucleophiles, to give V-cyclohexadienyl-metal complexes (1 Scheme 1). If an electronegative atom is present in the ipso position, elimination of that atom (X in 1) leads to nucleophilic aromatic substitution (path a). Reaction of the intermediate with an electrophile (E+) can give disubstituted 1,3-cyclohexadiene derivatives (path b). If a hydrogen occupies the ipso posi-... 

The facility of arene reductive elimination underpins numerous C-C, C-O and C-N bond-forming reactions, which may be catalysed by late transition metals, in particular palladium (Figure 4.10). Although there are many variants, the general reaction scheme involves introduction of the aryl in electrophilic form via oxidative addition of an aryl halide (or sulfonate), substitution of the palladium halide by a nucleophile (which may also be carbon based) followed by reductive elimination. It is noteworthy that nucleophilic aromatic substitution in the absence of such catalysts can be difficult. 

Within the year a wide range of photoreactions in which an aromatic residue undergoes change in substitution has been published. As previously, the diversity of the various processes makes any classification of the reactions unrealistic, and so their order of presentation here is somewhat arbitrary. Aromatic photosubstitution reactions have been reviewed by Parkanyi although the treatment is not extensive, the processes of free radical, electrophilic, and nucleophilic photoinduced substitutions of arenes are well covered.Arene photoreactions initiated by electron transfer with electron donors or acceptors are the subject of a review by Pac and Sakurai. The requirements for the efficient photogeneration of the ion radicals are considered and the synthetic utility of the photoreactions, which include reduction, cyanation, and amination, is discussed. 

In addition to electrophilic aromatic substitution reaction and copper salts-mediated or -catalyzed C-H bond functionalization, nucleophilic aromatic substitution reaction has also been explored to introduce the functional groups [60, 61]. One of successful examples is the amination reaction of dichloro-substituted azacalix[2]arene[2]triazine with various amines based on the reactivity of chlorotriazine moiety (Scheme 14.18) [60]. 

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