| C-H bond has broadly existed in various kinds of organic molecular frameworks, but because of the inert nature of most carbon-hydrogen bonds, C-H bond is difficult to cleavage. Traditional approaches relay on prefunctionalized starting materials, then construct a species of active metal complex intermediate. Finally generate products and stoichiometric salts waste. Tediously reaction steps and cost much time and low degree of atom economy. While Transition-metal-catalyzed C-H bond directly functionalization greatly reduced reaction steps, shorten reaction time, satisfied atom economy and green chemistry requirement. This article is major in studying directing group assisted Palladium-catalyzed ort ho-acylation reactions standing in the point of C-H bond activation.The first section, we will discuss the directing group assisted transition-metal-catalyzed C-H bond activation that can construct C-C bond, C-O bond, C-X bond and C-N bond. Also summarized transition-metal-catalyzed acylation reactions, providing the source of the subject composition.The second section,ortho-acylation of azoxybenzenes with aldehyde derivatives has been studied. The initial model acylation of azoxybenzene with aldehyde, using Pd(TFA)2 as catalyst and TBHP as oxidant, ortho-acylation via N-assisted C-H bond activation in the system that containing two kinds of directing atoms N and O. And synthesis a series of aromatic ketone compounds. This method is efficient, high selectivity and easy to handle.The third section, ortho-acylation of azoxybenzenes with alcohols has been studied. Benzyl alcohols are lower toxic, more stabl, inexpensive and commercial available, in contrast to other acylation reagents such as a-oxocarboxylic acid and aldehyde. We optimize the model reaction, and discuss the scope of different kinds of substrates. Meanwhile, proposed a possible mechanism of the catalytic progress, and characterized the products. Expand the synthesis of asymmetric azoxybenzene compounds. |
