Palladium-Catalyzed Oxidative Acetoxyla-Tion Of C(sp~3)-H Bond Using Bidentate Auxiliary

Transition-metal-catalyzed C-H activation reactions provide a powerful tool for most efficient and straightforward methods for the construction of C-C bonds and C-X bonds in organic syntheses research field. Traditional methods for the construction of C-C bonds and C-X bonds embody Kumada, Stille, Heck, Suzuki-Miyaura, Sonogashira reactions. However, one main disadvantage of these methods is the need of prefunctionalization, such as halogenations or metallization. Therefore, transition metal-catalyzed C-H activation reactions is the most powerful and straightforward strategy without prefunctionalization of the substrates. At present, transition-metal-catalyzed C-H activation reactions are still an important research topic in organic methodology.Compared with the study of C(sp2)-H activation, the C(sp3)-H activation remains a big challenge due to the higher pKa and low acidity. In addition, traditional monodentate directing groups have difficult in coordination with the C(sp3)-H bonds and cyclometalation. In this dissertation, we mainly investigate transition-metal catalyzed functionalization of C(sp3)-H by using bidentate directing groups.In this work, a palladium-catalyzed oxidative acetoxylation of benzylic C-H Bond using bidentate auxiliaryis is described. The reaction employs picolinamides (PA)-protected toluidines derivatives as substrates and PhI(OAc)2as an oxidant and the acetate. The reaction is carried out in AcOH/Ac2O in toluene as the cosolvent at130℃under air for12h, leading to the corresponding products in moderate yield with broad substrate scope. Both electron-donating and electron-withdrawing groups present good compatibility with the optimal reaction conditions. The strong electron-withdrawing groups, such as SO2CH3and NO2, generate the corresponding products in low yields.According to the references and the knowledge we get, the mechanismis generally rationalized by a PdⅡ/PdⅣ catalyst system. Lastly, the further transformation of the acetoxylation products to2-aminobenzyl alcohol can be obtained in high yields, which show the potential synthetic application of the methodology.