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, ΔG sol, is 10.8 kcal/mol.

Role of TMEDA in Iron-Catalyzed C(sp2)–C(sp3) Cross-Coupling Reactions: A Mechanistic Study Using DFT Calculations

“…Compared with the traditional transition-metal catalysts like palladium or nickel, which are still extensively utilized at the moment, iron catalysts have many merits, such as low price, low toxicity, and great abundance in the earth . Of particular interest are iron-catalyzed transformations, which can provide a huge potential for sustainable, low-cost methodologies for the selective formation of C–C, C–N, and other carbon–heteroatom bonds . More specifically, the iron-catalyzed alkylations of aromatic Grignard reagents have attracted broad research interests …”