Ruthenium-Catalyzed Oxidative Synthesis of 2-Pyridones through C–H/N–H Bond Functionalizations

With optimized reaction conditions in hand, we explored the scope of the ruthenium-catalyzed pyridone

Lutz Ackermann; Alexander V. Lygin; Nora Hofmann

2011

Scholarcy highlights

  • An inexpensive ruthenium catalyst enabled oxidative annulations of alkynes by acrylamides with ample scope, which allowed for the preparation of 2-pyridones employing various electron-rich and electron-deficient acrylamides as well asaryl- andalkyl-substituted alkynes
  • With optimized reaction conditions in hand, we explored the scope of the ruthenium-catalyzed pyridone
  • Acrylamides 1 bearing different substituents in the R- or β-position could be employed in the ruthenium-catalyzed oxidative annulation
  • Our new ruthenium-based annulation method allowed for the first use of R,β-disubstituted acrylamides in oxidative 2-pyridone syntheses, which provided direct access to products 3ma and 3na
  • Optimal reaction conditions involved the use of Cu(OAc)2H2O as the terminal oxidant in t-AmOH as the solvent. Other sacrificial oxidants, such as benzoquinone, air, or AgOAc, provided less satisfactory results
  • The inexpensive ruthenium catalyst was not limited to the oxidative annulation of tolane and enabled the efficient conversion of functionalized diaryl-substituted alkynes 2bÀ2g
  • These results clearly illustrate the beneficial features and remarkable potential of far underexplored ruthenium catalysts in oxidative annulative CÀH bond functionalization processes

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