DFT Study on the Mechanisms of Iron-Catalyzed Ortho C–H Homoallylation of Aromatic Ketones with Methylenecyclopropanes

Abstract

The mechanisms of iron-catalyzed ortho C–H homoallylation of aromatic ketones with methylenecyclopropanes are calculated using density functional theory calculations with B3LYP-D3BJ functionals and solvation model density (cyclohexane) model. Our results show that the catalytic cycle includes C–H bond oxidative addition, insertion of C–C double bond, ring-opening reaction, reductive elimination, ligand exchange, and the catalyst regeneration. Two possible catalytic cycles are calculated, where Path A is where the iron active catalyst first combined with 2,2-dimethyl-1-[4-(trifluoromethyl) phenyl]-propan-1-one and Path B is where the iron active catalyst initially attacked 2-phenyl-1-methylenecyclopropane. Our calculated results show that the rate-determining step in the whole catalytic cycle for the favored Path A is the C–H bond oxidation addition step, where Gibbs free energy in solvent cyclohexane, ΔGsol, is 10.8 kcal/mol.