Palladium-Mediated C(sp3)-H Bond Activation of N-Methyl- N-(pyridin-2-yl)benzamide: Direct Arylation/Alkylation and Mechanistic Investigation

J Org Chem. 2023 Jul 7;88(13):8441-8453. doi: 10.1021/acs.joc.3c00429. Epub 2023 Jun 5.

Abstract

Herein, we present a facile synthetic methodology to produce a range of N-(CH2-aryl/alkyl)-substituted N-(pyridin-2-yl)benzamides via palladium-mediated C(sp3)-H bond activation. The N-methyl-N-(pyridin-2-yl)benzamide precursor was first reacted with palladium(II) acetate in a stoichiometric manner to obtain the key dinuclear palladacycle intermediates, whose structures were elucidated by mass spectrometric, NMR spectroscopic, and X-ray crystallographic studies in detail. The subsequent C(sp3)-H bond functionalizations on the N-methyl group of the starting substrate show facile productions of the corresponding N-(CH2-aryl/alkyl)-substituted N-(pyridin-2-yl)benzamides with good functional group tolerance. A plausible mechanism was proposed based on density functional theory calculations in conjunction with kinetic isotope effect experiments. Finally, the synthetic transformation from the prepared N-(CH2-aryl)-N-(pyridin-2-yl)benzamides through debenzoylation to N-(CH2-aryl)-2-aminopyridine was successfully demonstrated.

MeSH terms

  • Alkylation
  • Benzamides*
  • Catalysis
  • Palladium* / chemistry

Substances

  • Palladium
  • benzamide
  • Benzamides