We have developed microwave-mediated [2+2+2] cyclotrimerization reactions that enable the rapid construction of carbo- and heterocyclic molecules from simple alkyne and nitrile starting materials. These reactions are conducted in either an intermolecular or an intramolecular fashion depending on the architectural requirements and the desired chemo- and regioselectivity. We typically use cobalt, rhodium, ruthenium, and nickel catalysts to facilitate these cycloaddition reactions.