Computational Characterization of the Mechanism for the Oxidative Coupling of Benzoic Acid and Alkynes by Rhodium/Copper and Rhodium/Silver Systems

Abstract

DFT calculations were applied to study the oxidative coupling between benzoic acid and 1-phenyl-1-propyne catalyzed by [CpRhCl ] (Cp=cyclopentadienyl) by using either Cu(OAc) (H O) or Ag(OAc) as the terminal oxidant, a process that has been experimentally shown to have subtleties related to regioselectivity (placement of the phenyl substituent of the alkyne in the isocoumarin product) and chemoselectivity (isocoumarin or naphthalene derivatives). Calculations reproduced the experimental results and showed the involvement of the oxidant throughout the catalytic cycle. The regioselectivity was found to be decided in the alkyne insertion step, in particular by the relative arrangement of the two phenyl groups. The high chemoselectivity towards isocoumarin associated to Cu(OAc) (H O) could be explained by the fact that the copper moiety blocks the CO extrusion pathway, which would lead to naphthalene derivatives, something that does not happen if Ag(OAc) is used.

HFIP‐Assisted C−H Functionalization by Cp*CoIII: Access to Key Reactive Cobaltacycles and Implication in Catalysis

“…This result along with the catalytic experiments shown in Table 2s uggest that the increased polarity of the solvent mixture in the presence of HFIP may play acrucial beneficial effect on the formation of 4 pmi by enhancing the solubility of the required Cu/Ag salts. [25] In summary,wehave designed anew strategy for circumventing the reversible nature of the C À Hm etalation step when using Cp*Co complexes to access two of the most widely invoked cationic cobaltacyclic intermediates.O ur work reveals the boosting effect of HFIP as an additive,n ot only in the CÀHa ctivation step,b ut also on benchmark catalytic processes involving alkynes as coupling partners, presumably because of its capability as ap roton shuttle and polar nature. [26] Further investigations into the role of fluorinated alcohols in catalysis are currently underway.…”

Electroremovable Traceless Hydrazides for Cobalt-Catalyzed Electro-Oxidative C–H/N–H Activation with Internal Alkynes

“…117−125 Thus, the regiocontrol of the key migratory insertion was found to place the aryl group proximal to the heteroatom, thus reflecting the experimentally observed selectivities. Notably, the regioselectivity 126 was largely governed by secondary attractive dispersion π−π interactions between the (hetero)aryl motifs of the pyridine and the arylacetylene moieties (Figure 3).…”

Alkyne Linchpin Strategy for Drug:Pharmacophore Conjugation: Experimental and Computational Realization of a Meta-Selective Inverse Sonogashira Coupling

“…Therefore, both steric and electronic factors disfavour the reaction of substrate 1c in this alkynylation reaction. Experimentally, it is also possible that homocoupling of terminal alkynes occurs due to the presence of copper additives, [54][55][56][57][58][59] rendering this substrate incompetent. S12.…”