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DFT calculations have been carried out to investigate the reaction mechanism for PdII-mediated enantioselective C-H iodination. Iodination of the aryl ortho C-H bond of benzylamines catalyzed by PdII diacetate complexes in the presence of the L-MPAA ligand experiences three main steps: first, C-H bond activation; second, oxidative addition of iodine on PdII and reductive elimination of iodobenzene; third, catalyst regeneration through ligand exchange. The C-H bond activation is found to be the rate-determining step of the overall iodination due to higher activation energy. The reaction barrier for the formation of iodinated (R)-benzylamine is lower than that of (S)-benzylamine, which confirms the R enantioselectivity in iodination at room temperature. The retainment of the coordination of one acetic acid on PdII and the chelating MPAA ligand during the catalyzed reaction are suggested to give space economy to facilitate the C-H bond activation. The NHTf functional group on the substrate is found to be very important for ortho C-H iodination at ambient condition. Our calculated results are consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

DFT calculations have been carried out to investigate the reaction mechanism for PdII-mediated enantioselective C-H iodination. Iodination of the aryl ortho C-H bond of benzylamines catalyzed by PdII diacetate complexes in the presence of the L-MPAA ligand experiences three main steps: first, C-H bond activation; second, oxidative addition of iodine on PdII and reductive elimination of iodobenzene; third, catalyst regeneration through ligand exchange. The C-H bond activation is found to be the rate-determining step of the overall iodination due to higher activation energy. The reaction barrier for the formation of iodinated (R)-benzylamine is lower than that of (S)-benzylamine, which confirms the R enantioselectivity in iodination at room temperature. The retainment of the coordination of one acetic acid on PdII and the chelating MPAA ligand during the catalyzed reaction are suggested to give space economy to facilitate the C-H bond activation. The NHTf functional group on the substrate is found to be very important for ortho C-H iodination at ambient condition. Our calculated results are consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

As the first cascade C-H activation directed by a transient group, reaction of alkynols and 7-oxabenzonorbornadienes has been achieved via synergistic rhodium and scandium catalysis to afford spirocyclic dihydrobenzo[a]fluorenefurans. This transformation proceeds by a transient hemiketal group directed C-H activation, dehydrative naphthylation, and intramolecular Prins-type cyclization. Mechanistic studies and density functional theory calculations indicate that the rate-determining step is C-H bond cleavage and both the transient hemiketal group and synergistic RhIII/ScIII catalysis play key roles. [ABSTRACT FROM AUTHOR]