Mechanistic Studies on the Nickel-Catalyzed Cyclopropanation with Lithiomethyltrimethylammonium Triflate

We report here our
mechanistic study of the previously published
nickel-catalyzed cyclopropanation reaction using lithiomethyltrimethylammonium
triflate as methylene donor. The cyclopropane yield is highly dependent
on the olefin substrate and correlates well with the binding affinity
of the olefin to Ni(0) as established elsewhere. On the basis of this
observation, we developed a simplified mechanistic model that can
explain several odd observations we found in our initial report. Most
importantly, a binding equilibrium between the olefin substrate and
phosphine ligand appears to govern the ratio between product formation
and unproductive ylide decomposition in a side reaction.