Study On The Construction Of C-C/C-N Bond Based On C-H Bonds Activation

Recently,C-H bond activation has been the research topic for the demand of Green Chemistry and the development of organic synthesis. Using this method to construct new chemical bond directly from C-H bond, without any pre-functionalization, has been extensively employed in the synthesis of nature products and complicated molecules. Especially, our attention was focused on the construction of new chemical bond based on C-H bond activation.In this paper, synthesis of ferrocene derivatives with planar chirality and the construction of C-N bond via C-H bond activation under mild conditions are studied. The main results obtained are shown as belows: 1. Redox of ferrocene controlled asymmetric dehydrogenative Heck reaction via palladium-catalyzed dual C-H bond activationThe direct cross coupling of N,N-dimethylaminomethylferrocene with olefins controlled by redox process of ferrocene has been realized using palladium acetate as a catalyst, Boc-L-Phe-OH as a ligand, to achieve the corresponding planar-chiral 1,2-disubstituted ferrocene derivatives in high chemo- and enantio-selectivities under external oxidant free conditions(Scheme 1). The commercially available and cheap amino acid was emoloyed as a chiral ligand, and N,N-dimethylaminomethylferrocenium was used as a terminal oxidant, generated from N,N-dimethylaminomethylferrocene oxidized by air in situ. The synthetic strategy was designed from green, atom- and step-economic points of view and avoided using expensive chiral ligands, oxidants and lithium reagents. The reaction mechanism of this transformation was investigated by controlled experiments. 2. Synthesis of acylated ferrocene derivatives with planar chirality via palladium-catalyzed enantioselective C-H bond activation.A novel and convenient protocol to the 2-acyl-1-dimethylaminomethyl ferrocene with planar chirality in high chemo- and enantio-selectivities has been developed from a-diketone catalyzed by palladium acetate with commercially available and cheap amino acids as ligands(Scheme 2). The products obtained could be easily converted to various chiral ligands or bioactive compounds via diverse transformations. Starting from compounds obtained in the methodology, the planar-chiral N,O-ligands were prepared by treatment with lithium reagents in high yield, which could be applied in the catalytic asymmetric reaction. 3. Iridium-catalyzed direct C-H amidation of arylnitrones with sulfonyl azides at room temperature.An iridium-catalyzed direct amidation of arylnitrones has been developed employing sulfonyl azides as an amino source and internal oxidant(Scheme 3). A series of amidated nitrones were prepared in moderate to high yields. A variety of functional groups were well tolerated, allowing further synthesis of more complicated molecules. In this approach, external oxidants, acids or bases were not required and N2 as the sole byproduct, resulting in an environmentally benign amidation process.4. Direct regioselective nitriation of quinoline N-oxides with t-Butyl nitrite under metal and external oxidant free conditions.The directly cross coupling of quinoline-N-oxides with tert-butyl nitrite has been realized under metal-free and external oxidant-free conditions providing an environmentally benign nitration process for the corresponding 3-nitroquinoline-N-oxides(Scheme 4). The nitration selectively accured at the C-3 position of quinoline-N-oxides, affording the corresponding products in moderate to good yields.