Cycloaddition of Alkynes: Atom-Economic Protocols for Constructing Six-Membered Cycles

Recent advances on the synthesis of six-membered carbo- and heterocyclic compounds including functionalized benzenes, 1,3- cyclohexadienes, pyridines, pyridones, pyranones, coumarins and isocoumarins via the cycloaddition reaction of alkynes are reviewed. Special attention is paid to atom-economic controllable chemo- and regioselective reactions, which are currently extremely attractive methodologies in organic synthesis.