Reactivity of 1,3-azoles

Electrophiles can add to N-3, the azomethine =N-of 1,3-azoles as they can to the pyridine nitrogen. N-Alkylation is complicated in the case of imidazole 

A-Acylation is mechanistically similar, and monoacylation can he accomplished by using two molar equivalents of imidazole to one of the acylating agent, the second mole serving to deprotonate the first-formed A-3-acylimidazolium salt. Note that in 

3-diazoles are much less susceptible to electrophilic substitution than pyrrole, furan, and 

Substitution occurs at C-5, but tautomerism then leads to tbe 4(5) mixture. The position of substitution may be predicted from a consideration of resonance structures attack at C-5 provides maximum delocalization 

In general, the 1,3-diazoles do not react by nucleophilic substitution, although imidazole can participate in the Chichibabin reaction with substitution at C-2 the position of substitution is eqmvalent to that noted with pyridine (see Section 11.4.1). Nucleophilic species that are strong bases, like 

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