Alkynes and azides: beyond click chemistry

The relatively weak π-bonds in alkynes and azides present a unique opportunity to more easily access high energy reactive intermediates. This opportunity has been harnessed through copper-catalyzed azide-alkyne cycloadditions (CuAAC), one of the well-known reactions associated with "click chemistry." This review covers the additional chemistry of alkynes and azides that is beyond the CuAAC realm. This includes cascades and interconversions of reactive intermediates that can be accessed through mild means, due to the combination of weak bonds in both reactants. The products of these reactions, often heterocycles, are core structures of molecules of interest and the processes to obtain the products are of mechanistic value. Thus, the chemistry of alkynes and azides included herein is a valuable addition to the arsenal of synthetic chemists.