Diversity of Heterocyclic Reactants in the Click Reaction

Variants of the Huisgen 3+ 2 cycloaddition with respect to heterocyclic substitution on both the acetylenic and azide reacting components are presented. This chapter details applications of the click reaction to classes of heterocyclic reactants which bear either the acetylenic or azide reactive groups en route to the target triazoles. While the reaction coverage involves transformations whereby at least one reactant, either an acetylene or an azide, bears a heterocycle, its general focus includes the function of the product triazoles and forms the basis of the chapter outline and content. The synthetic methods and macrocycles sections involve new reactions, strategies or constricts. Other than the synthetic methods and macrocycles sections, the products of the click reactions are divided into classes which are categorized according to the role they play in catalysis, ligands, biological function or as probes, sensors or materials. In the sections which involve medicinal chemistry or drug development many of the reaction entries are general with selected examples describing biological activity for brevity.