Wednesday, 16 May 2018: 09:40
Room 616 (Washington State Convention Center)
The development of site-selective catalytic methods for the conversion of carbon−hydrogen (C−H) bonds to carbon−carbon(C−C) and carbon−oxygen (C−O) bonds remains a significant challenge in synthetic chemistry. During the past decade, transition-metal-catalyzed site-selective C−H functionalization has emerged as a promising tool to construct carbon−carbon (C−C) and carbon−heteroatom (C−Y) bonds. Pd(II)-catalyzed C−H oxygenation reactions, in particular, have received significant attention. Previous studies have revealed that C−O reductive elimination, which is typically sluggish from Pd(II) centers, takes place under comparatively mild conditions from Pd(III) or Pd(IV) centers. While these transformations hold great promise in offering new disconnections in retrosynthetic analysis, the need for an external chemical oxidant constitutes a practical disadvantage in these systems. The most typical oxidants in Pd-catalyzed C−H oxygenation include PhI(OAc)2, t-BuOOAc, and K2S2O8. These oxidants have drawbacks in that they produce undesired byproducts, have poor atom economy, or are expensive. Electrochemical oxidation has a rich history in synthetic chemistry and has become a promising alternative to traditional chemical oxidants because it obviates the use of dangerous and toxic reagents. We have demonstrated the first example of Pd(II)-catalyzed C(sp3)−H oxygenation via anodic oxidation. This process offers an alternative to conventional methods that require harsh chemical oxidants and represents an environmentally benign tool for coupling various oxygen anions, including acetate, toslyate, and alkoxides, with C(sp3)−H bonds.