DFT Mechanistic Study of Functionalizations of ω-Ene-Cyclopropanes and Alkylidenecyclopropanes via Allylic C–H and C–C Bond Cleavage Facilitated by a Zirconocene Complex

Abstract

A DFT mechanistic study has been performed to understand the [Zr]C4H8 (Zr = ZrCp2)-mediated transformations of ω-ene-cyclopropane (ω-ene-CP) and alkylidenecyclopropane (ACP) to acyclic compounds. The transformations proceed via allylic C–H bond activation, hydride transfer, C–C bond cleavage of the three-membered ring, and additions of electrophiles. The energetic results indicate that, among the possible pathways, the one leading to the experimental products is most energetically favorable, rationalizing the selectivity of the reactions. The Zr-walk takes place via allylic C–H bond activation followed by hydride transfer, completing a 1,3-hydrogen transfer. In comparison, the Pd-walk involved in the Pd-catalyzed Heck-type relay coupling reactions proceeds via migratory insertion followed by β-H elimination, resulting in a 1,2-hydrogen transfer. The difference is due to the fact that the [Zr] active species does not have a Zr–H or Zr–C bond for C═C bond migratory insertion, while the Pd–H or Pd–C bond in ...