Electrophilicity and nucleophilic aromatic

Substituted 1,2,3-triazole 1-oxides 448 have been reported to undergo electrophilic and nucleophilic aromatic substitution and are subject to debromination, proton-metal exchange, and halogen-metal exchange followed by electrophilic addition. Transmetallation and cross-coupling have not been described. 3-Substituted 1,2,3-triazole 1-oxides 448 can be proton-ated or alkylated at the O-atom and they can be deoxygenated and deal-kylated. The individual reactions are described in Section 4.2.7.1-4.2.7.14. 

Understand the mechanisms of electrophilic and nucleophilic aromatic substitutions. Predict the products of these reactions and use them in syntheses. 

Electrophilic and nucleophilic aromatic substitution ch22-ch23... 

Note the differences between electrophilic and nucleophilic aromatic 1 substitutions Electrophilic substitutions are favored by electron-donofi g substituents, which stabilize the carbocation intermediate, while nucleophilic substitutions are favored by d ron-withdrawing substituents, which stabilize a carbanion intermediate. The electron-withdrawing groups that deactivate rings for electrophilic substitution (nitro, carbonyl, cyano, and so on) activate them for nucleophilic substitution. What s more, these groups are meta directors in electrophilic substitution, but are ortho-para directors in nucleophilic substitution. 

Using electrophilic and nucleophilic aromatic substitution in five- and six-membered heterocycles. Chemo- and regioselectivity The synthesis of pyridazines... 

There is, for example, no end-of-text chapter entitled Heterocyclic Compounds. Rather, heteroatoms are defined in Chapter 1 and nonaromatic heterocyclic compounds introduced in Chapter 3 heterocyclic aromatic compounds are included in Chapter 11, and their electrophilic and nucleophilic aromatic substitution reactions described in Chapters 12 and 23, respectively. Heterocyclic compounds appear in numerous ways throughout the text and the biological role of two classes of them—the purines and pyrimidines—features prominently in the discussion of nucleic acids in Chapter 27. 

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