Palladium - Catalyzed Derivatization Of Sp ~ 2 C - H Bonds

The C-H bond functionalisation using Pd-catalyzed methods has caused extenisve attentions in recent years. Due to the effect of directing groups, this kind of reaction can form the C-C bond, C-N bond, C-0bond and C-X bond (X=CI, Br, I) from directed C-H bond cleavages. Moreover, these tools can dramatically streamline multi-step chemical processes by rendering functional group interconversion steps unnecessary, and the related reseaeh has aroused great inierest. In this dissertation, a series of C-H bond functionalisations are able to be conducted via the effects of directing groups in the appearance of Pd" as catalyst, which include:1. Pdâ…¡-catalyzed aromatic C-H bond activation using cyano as a directing group was carried out in TFA medium. Biphenyl-2-carbonitrile derivatives were therefore synthesized from aryl nitriles and aryl halides in moderate to good yields. The reaction is the first example of transition-metal-catalyzed direct arylation of aryl nitrile via a directed C-H functionalization.2. A Pd(OAc)2-catalyzed ortho-alkoxylation of benzonitrile has been described. With the cyano as a directing group, the aromatic C-H bond can be funetionalized efficiently with Na2S2O8as the oxidant to generate ortho-alkoxylated derivatives. Inexpensive, safe, and environmentally benign Na2S2O8was found to be a particularly effective terminal oxidant in these transformations. The reaction is the first example of transition-metal-catalyzed direct alkoxylation of aryl nitrile via a directed C-H functionalisation.3. A Pd(OAc)2-catalyzed cross-coupling reaction between2-arylpyridine and aryltrimethoxysilane in the presence of AgF and BQ in1,4-dioxane was studied. After various reaction parameters (catalyst, oxidant, additive, solvent and reaction temperature) were examined, the optimal conditions for the reaction were identified. The synthesis is compatible to aryltrimethoxysilane with both electron-withdrawing and electrondonating groups on the aryl moiety with moderate yields. The kinetic isotope effect (kH/kD) for the C-H bond activation was provided. This method possesses advantages such as environmental benignity, low toxicity and safe handling.