Ruthenium-catalyzed [2+2] cycloadditions between bicyclic alkenes and substituted alkynes are among the most efficient ways to form cyclobutene derivatives. A theoretical study was carried out to learn the origins of stereoselectivity and reactivity of this reaction.
Density functional theory was used to explore the properties of reactants, transition states, intermediates, and products with various substituents. Insights of the reaction mechanism were gained, especially at the following aspects:

Identification of the rate-determining steps
Remote substituent effects
Electron transfer and orbital interactions
Various types of intramolecular hydrogen bond
Preferred substituent group conformations
Electronic effects of substituents on CC triple bond activation
Steric effects of substituents on the reactivity of alkynes

1. Liu, P.; Jordan, R. W.; Goddard, J. D.; Tam, W., "Remote Substituent Effects in Ruthenium-Catalyzed [2+2] Cycloadditions: An Experimental and Theoretical Study." (In preparation)
2. Liu, P.; Tam, W.; Goddard, J. D., "Ruthenium-Catalyzed [2+2] Cycloadditions between Norbornadiene and Substituted Alkynes." (In preparation)

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