Studies Of Transition-Metal-Catalyzed Directed C-H Bond Activation

Transition-Metal-Catalyzed C-H activation has become the most powerful and straightforward tool in synthetic chemistry because its highly efficient and atom-economic organic transformations for the construction of complex molecules. In recent years, many efforts have been focused on the application of the C-H bond activation and a lot of natural products and pharmaceutical moleculars have been synthesized using this method. The study of the C-H bond activation could be devided into two issues:(1) the direct C-H bond activation which is aimed at more acidic C-H bond;(2) the directed C-H bond activation which need a directing group to coordinate with the metal. This dissertation mainly focused on the studies of the directed C-H bond activation, the contents are as following:1. Ester directed selective olefination of acrylates by rhodium-catalysisEster directed olefination of acrylates via rhodium(III)-catalyzed was developed. Various alkenes were reacted with acrylates to give desired products in high stereoselectivity. The X-ray spectra of the product conformed its structure. Mechanistic investigation revealed that ester directed C-H bond activation was the key-step to this reaction.2. Ester directed selective hydroarylation of alkynes and synthesis of aryl-substituted naphthols via rhodium-catalysisEster directed olefination and cyclization of phenol derivative was developed. Different products could be detected when the reaction condition was changed. Alkynes with electron-withdrawing and electon-donation group could react with phenol derivative to give the alkenyl products when acetic acid and acetic anhydride existed.3. N, N-dimethylaminomethyl group directed C-H ortho-arylation of arenes via palladium-catalysisA novel protocol for palladium-catalyzed arylation of C(sp2)-H bond directed by N,N-dimethylaminomethyl group in the presence of AgOAc and Cu(OAc)2?H2O is described. Various aryl iodides proved to be efficient coupling partners, furnishing the corresponding ortho monoarylated or diarylated arenes in moderate to good yields. Cu(OAc)2?H2O is found to be the important additive to improve the yields in this transformation. The sepctra of XRD revealed that Ag (I) may play the role of abstraction halide.4. Palladium-catalyzed bidentate-assisted sp3C-H functionalization:highly efficient to synthesize3-substituted prolineRegio-and diastereoselective arylation of prolines using Pd-catalyzed C(sp3)-H activation has been investigated. Prolines can be directly arylated in C3-position in moderate to high yields with a variety of (hetero)aryl iodides and bromides to give the optically pure proline derivatives, which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. The directing and protected group could be removed to give3-substituted prolines.