Quaternization of Heteroaromatic Compounds: Quantitative Aspects

Abstract

This chapter focuses on important developments dealing with quaternization of annular nitrogen atoms of heterocyclic compounds. The chapter is essentially divided into two main parts. The first part describes the main electronic and steric factors of heteroaromatic nucleophilic reactants that influence their reactivity. The second part provides references to recent important developments. The chapter considers six-membered heteroaromatic rings before five-membered ones as the six-membered rings are studied in greater detail and consequently their reactions are better understood. The chapter notes that quaternization of an annular nitrogen atom is carried out with a wide range of alkylating agents. Most quaternization reactions involving an annular nitrogen atom and an alkylating agent proceed by way of an SN2 reaction in which the inversion of configuration of a chiral reagent takes place. One novel method, which indicates that the transition state is early, involves the study of volume changes. Many approaches are made to obtain information about the nature of the transition state of quaternization reactions, including a study of kinetic isotope effects.