Studies on transition metal-catalyzed [2+2] cycloadditions between alkenes and alkynes are one of the major foci of our research program. We have recently studied various aspects of Ru-catalyzed [2+2] cycloadditions, including: asymmetric cycloadditions (Angew. Chem. Int. Ed. 2004, 43, 610), reactivity studies (J. Org. Chem. 2004, 69, 8467; J. Org. Chem. 2006, 71, 5830), remote substituent effects (Org. Lett. 2000, 2, 3031), studies of alkynyl halides (Org. Lett. 2004, 6, 4543) and ynamides (Org. Lett. 2005, 7, 3681) as the alkyne component in the cycloaddition, theoretical studies (J. Org. Chem. 2006, 71, 3793; Tetrahedron 2007, 63, 7659) and others. In 2004, we reported the first examples of asymmetric induction studies in ruthenium-catalyzed [2+2] cycloadditions between alkenes and alkynes (Angew. Chem. Int. Ed. 2004, 43, 610). The cycloadditions were found to be highly stereo- and regioselective, and excellent levels of asymmetric induction (up to 99% ee) in the cycloadditions were achieved. This chemistry is currently being expanded and applied to the asymmetric synthesis of 5-membered and 7-membered rings.