The Study Of Transition Metal Catalyzed C-H Bon Activation To Form C-O And C-S Bonds

The study of transition metal catalyzed C-H bond activation to form C-C or C-heteroatomic bonds have become a topic in research of organic and biological sciences because of their widely exist in nature; and making full develop of it has been widely used to medicine, materials, spices, and other fields. Usually, the approaches for the formation of C-C or C-heteroatomic bonds rely on prefunctionalized starting materials, and then convert the bonds to target chemical groups. So direct convert C-H bond to C-C or C-heteroatomic bonds can not only improve the atom economy of reactions, but also increase the total efficiency of multi-step synthesis. This paper includes two parts: the first part is transition metals copper salt catalytic aldehyde C-H bond activation/C-O bond formation with alcohol in synthesis of ester; The second part explore supported palladium nanoparticles catalyzed ortho-directed sulfonylation reaction between 2-phenylpyridine and aiylsulfonyl chlorides and their mechanism research. The results are followed:Exploring a cheaper metal Cu+/Cu2+ salts catalyzed direct oxidative esterification of aldehydes with alcohols was explored for the synthesis of versatile esters. By using CuCl as a catalyst and tert-hydroperoxide as an oxidant, the reaction temperature is 80?, and reaction time is 24 h, then the methyl 4-methoxybenzoate was obtained in 90.0%. The results showed that the electronic effect of different substituted groups in aromatic aldehydes have no significant effect with same alcohol on the reaction, but the more sterically hindered alcohols was associated with the lower yield, when different alcohols react with 4-methoxy benzaldehyde.The catalyst of the Pd/?-Al2O3 , which were prepared by a modified impregnation-reduction method, catalyzed an ortho-directed sulfonylation reaction between 2-phenylpyridine and arylsulfonyl chlorides. By using ethylbenzene as an solvent, K2CO3 as the base to neutralize HCl with the reaction, and the reaction temperature is 120?, and time is 24h. The conversion rate of 2-phenylpyridine is 83.0%, and the yield of target product is 73.0%. The Pd/?-Al2O3 could be recycled and reused 3 times, and the catalytic performance of the Pd/?-Al2O3 declined apparently after every once recycle until the yield is 44.0% of product after the third time. In order to explain the reasons for the low recovery rate and the reaction mechanism of the system, the characteristics of palladium in catalysts were investigated by atomic absorption spectroscopy, X-ray photoelectron spectroscopy,transmission electron microscopy. At the same time, the solutions were detected by the hot filtration experiment and ICP-MS. The test results were showed by AAS and TEM that the possible cause of the target product declined apparently is loss of Pd. And through hot filtration experiment also prove this phenomenon. By XPS analysis shows that there does not exist a redox cycle between Pd0 and Pd?. So the results suggest that the supported PdNPs catalyzed ortho-directed sulfonylation would proceed in a homogeneous manner.