Reactions Of New Directing Groups In Pd-Catalyzed C-H Functionalization

Pd-catalyzed direct C-H functionalization has been emerged as a novel strategy in the traditional retrosynthetic analysis of total synthesis. It has been a central problem of the methodology during the past decades. This thesis mainly focuses on the Reactions of new directing groups in Pd-catalyzed C-H functionalization. The main contents include:The first chapter simply reviews the Pd -catalyzed C-H bond functionaliztion history and the current status of the development. By comparing the examples of C-H bond activation reactions of Pd catalysts with the other metal catalysts, we finally concluded the unique characters and the frontier of the Pd chemistry.In chapter 2, we think the key point to apply direct C-H functionaliztion in organic synthesis is to diversify the directing groups. In order to solve the problem of poor coordination ability of Pd with O-directing group, we choose phenol esters as the substrate. With the promotion of catalytic amount of strong acid (HOTf), we first reported the phenol ester directed C-H/Aryl-Aryl coupling with diaryliodonium triflates reaction and characterized the key intermediates. This new protocol provides a new method to synthesize 2-arylphenols, inhibitors of EGF-stimulated cellular proliferation and 3,3'-bis-arylated-BINOLs.In chapter 3, we further choose aromatic ketones as substrate which shows similar low coordination abilities as phenol esters with much more electron-deficiency. We choose amides as the coupling partner considering that amides are lack of attentions in cross coupling reactions. We discovered HOTf also promoted the cyclopalladation, and successfully realized the C-N coupling of 4-chlorophenyl sulfonamide. Meanwhile, we indicated that the new reaction does not seem to proceed through a nitrene intermediate, but much more like through N- reductive elimination. The mechanism is a new aspect in Pd chemistry.In addition, we found that the direct C-H activation on o-arylphenol could only be achieved via the cross coupling strategy intermolecularly, while the intramolecular reductive elimination in activating of C-H bond on o-arylphenol has rarely been reported. In response to this phenomenon, we found phenol directed C-H activation was very easy to take place, but the difficulty of reductive elimination retarded the intramolecular cyclization. By tuning the Carboxylic acid anion and the ligand, we successfully realized the high yield of intramolecular C-O cross coupling. This method can provide a series of functionalized dibenzofuran derivatives.