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Substituent Effects, Reactant Preorganization, and Ligand Exchange Control the Reactivity in RhI-Catalyzed (5+2) Cycloadditions between Vinylcyclopropanes and Alkynes


  • We are grateful to the National Science Foundation for financial support of this research (CHE-0548209, CHE-0450638, and CHE-0131944). Calculations were performed on the National Science Foundation Terascale Computing System at the NCSA and on the UCLA ATS Cluster. P.H.-Y.C. is grateful for discussions with the new-reactions subgroup of the Wender labs.


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Heteroatom and bulky alkyl substituents dramatically increase the rate of RhI-catalyzed (5+2) cycloadditions of 1. This fact could be attributed to steric effects which ease the reactant preorganization, and to the stabilization of the allyl intermediate by (hyper)conjugation with the substituents. The methoxy- and isopropyl-substituted 1 have an activation energy 5 and 7 kcal mol−1, respectively, lower than the unsubstituted vinylcyclopropane.