| The Suzuki coupling reaction is a powerful and versatile method for the generation of unsymmetrical biaryls from arylboronates and aryl halides in a single step. The advantages of the Suzuki reaction include the tolerance of functional group on the substrates and mild reaction conditions. As an intriguingly flexible reaction, it offers considerable potential in the synthesis of natural products, herbicides, pharmaceuticals, and conducting polymers. In recent years, the development of new environmentally benign catalysts with enhanced reactivity has aroused much attention in the studies of Suzuki reaction, and significant advances have been made in the studies of Suzuki reaction in the aqueous phase. This dissertation mainly focused on the Suzuki coupling reaction in aqueous systems, which include:1.Pd(OAc)2-H2O-acetone system for the Suzuki coupling reaction of aryl monohalideSuzuki coupling reaction of aryl monohalides were studied in Pd(OAc)2-H2O-acetone system. It was found that this system could successfully catalyze the coupling reaction of aryl bromide and aryl iodide. Pd(OAc)2-H2O-acetone could tolerate a broad range of functional groups, such as NO2,COCH3,CN,OCH3 and OH. Compared to the catalytic system reported, the methodology utilized simple palladium salt as catalyst without any ligands. The reaction could be conducted under mild reaction condition in short time with high yields without the protection of inert gas. It could be easily handled, and after the reaction, the product could be easily separated by ether extraction. Notably, the TON up to 3300000 has been achieved for Pd(OAc)2-H2O-acetone system and the methodology showed potential to industrial application.2.Pd(OAc)2-H2O-DMF system for the Suzuki coupling reaction of aryl multihalide The methodology to construct polyaryls by multi-Suzuki coupling reaction of aryl multihalides was developed in Pd(OAc)2-H2O-DMF system with high selectivity. For each di- or trihalobenzene substrate examined, regardless of the halide substituent location and type, the major products resulted from the multiple coupling under the reaction conditions. The electron-rich, electron-poor, and electron-neutral arylboronic acids presented essentially the same reactivity and selectivity patterns. The reaction could be conducted under mild reaction conditions, and high yields were obtained after 12 h. The products could be easily separated from the reaction system by ether extraction. The protection of inert gas is unnecessary during the course of the reaction. Excessive arylboronic acid was needed for higher yield of polycyclic aromatic rings.3. Pd(OAc)2-H2O-PEG[Poly(ethylene glycol)] system for the Suzuki coupling reaction of aryl halidePoly(ethylene glycol) was first used in the Suzuki coupling reaction with water as the reaction medium. The ratio of PEG and water was pivotal to the Suzuki coupling reaction. It was found that aryl bromide and aryl iodide could readily couple with arylboronic acids in Pd(OAc)2-H2O-PEG system. Pd(OAc)2-H2O-PEG system could tolerate a broad range of functional groups, such as NO2,COCH3,CN,OCH3 and NH2. The reaction could be conducted under mild reaction conditions, and high yields were obtained within short reaction time. The protection of inert gas was unnecessary during the course of the reaction. The products could be easily separated form the reaction system by ether extraction, while metal catalyst was remained in PEG and water. So the catalytic system could be recycled for three times. The self-coupling reaction of arylboronic acid was not founded in Pd(OAc)2-H2O-PEG system. During our investigation of the substrates scope, we found that activated aryl chloride could couple with arylboronic acids under enhanced reaction conditions. According to the report, PEG could reduce Pd(â…¡) to Pd(0), and stabilize the existence of palladium nanoparticle. At the same time, PEG, as a phase transfer catalyst, could extensively increase the solubility of substrates. Pd(OAc)2-H2O-PEG system was an useful and efficient system for the Suzuki coupling reaction.4. Copper-catalyzed reaction of arynesAlkyne has been widely used as a substrate in the transition-metal-mediated C-C bond formation processes. However, the high reactivity and harsh preparing conditions of aryne often make it difficult as a component of catalytic reactions. Recently, a mild method for the preparation of arynes in situ at moderate temperatures from commercially available o-trimethylsilyl aryltriflates promoted the exploration of the reactions using arynes as the substrates and the transition metal-catalyzed reaction sequences are indeed occurred with arynes in high efficiency. Copper is one of the most efficient catalysts for the construction of carbon-carbon and carbon-heteroatom bonds, however, to the best of our knowledge, there is no report based upon copper-catalyzed strategy of arynes. We studied the copper-catalyzed two-component coupling reaction of alkynes with arynes and the co-tricyclization of arynes, which provides the novel methods for the preparation of internal alkynes and fused aromatics.
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