Synthesis Of Ruthenium Olefin Metathesis Complexes And Palladium-catalyzed Acylation Of Arylpyridine

1. Olefin metathesis is a unique carbon skeleton rearrangement in which unsaturated carbon-carbon bonds are rearranged in the presence of metal carbene complexes. Recently, Ru-based olefin metathesis catalysts have been widely used in organic synthesis because of their high catalytic activities, good thermal stabilities, and broad compatibilities with substrate functional groups.Based on the mechanism of olefin metathesis reported by Chauvin and Grubbs, three types of new olefin metathesis catalysts were designed and synthesized to better understand the impact of electronic effects and the spatial effects in olefin metathesis reactions.First, a series of phosphine ligands containing ferrocene were synthesized, and then used to replace the ligands in ?rst- and second-generation Grubbs catalysts, following a series of ruthenium carbene catalysts containing different phosphine ligands were developed. Catalytic studies showed that the activity of these ruthenium carbene catalysts containing ferrocene phosphine ligands were effective for RCM(ring-closing metathesis) reactions.The second type of catalyst involved replacing the phosphine ligand in ?rst-generation Grubbs catalyst with cyclopentadiene, cycloheptatriene, indenyl and 1,2,3,4,5-pentamethyl-cyclopenta-1,3-diene, to give four kinds of novel olefin metathesis catalysts. Activity tests showed that the electron-rich ligand were effective for increasing the catalyst activity.The third type of catalyst was a ruthenium carbene catalyst containing carbonyl group which was developed according to the special steric effects of the carbonyl group. This ruthenium carbene catalyst containing carbonyl group was effective for RCM reactions, but inferior to the second-generation Grubbs catalyst.2. Aromatic ketones are important materials in the manufacture of fine chemicals, pharmaceuticals, dyes, fragrances and agrochemicals. Friedel-Crafts acylation is one of the common methods used for these syntheses. However, these acylation reactions violate many of the principles of green chemistry because the traditional methods usually use large quantities of hazardous Lewis acids such as Al Cl3, TiCl4, or FeCl3. These have to be treated and generate large volumes of waste in the course of the work-up. Therefore, the development of catalytic alternatives is highly desired. An ef?cient approach for the direct acylation of the aromatic sp2 C-H bond using Pd has been developed. This resulted in the introduction of carbonyl functional groups to 2-arylpyridine. This new approach is not only a more environmentally friendly way to synthesizrs aromatic ketones, but it is also an alternative to the traditional Friedel-Crafts acylation reaction.