The mechanism, and regioselectivity of Co-catalyzed alkenylation of 2-pyridone with terminal alkynes is probed and rationalized from density functional theory calculations. Four possible permutations of the ligand system (i.e. [AcOHCp], [AcOHCp*], [PivOHCp], and [PivOHCp*]) are examined. Results indicate that the bulkier group on the alkyne distal to the pyridone is more favorable for the overall catalytic cycle. The mechanism is found to involve three steps: C–H activation ortho to the pyridine directing group affording a six-membered cobaltacycle intermediate, insertion of the alkyne into the CoIII–aryl bond resulting in a seven-membered cobaltacycle intermediate, and a final proto-demetallation step, furnishing the product and regenerating the catalyst in situ. The influence of any possible dispersion effects between the acetate and cyclopentadienyl ligands is also investigated. The computed mechanism of the full catalytic cycle is consistent with the experimental data. Our detailed mechanistic survey provides important mechanistic insights for regioselective alkenylation reactions of 2-pyridones.

Mechanism and origins of regioselectivity of CoIII-catalyzed C-6 alkenylation of 2-pyridones with alkynes: A computational study

ACS Spring 2022

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