Construction Of Carbon-Heteroatom And Carbon-Carbon Bonds Catalyzed By Platinum And Palladium With Buchwald Ligands In PEG

In recent years,the great development of green organic synthesis has been made in both industrial and academic researches.Toxic and volatile organic solvents are continuously replaced by green solvents such as solvent-free,water,polyethylene glycol?PEG?or ionic liquids.As a polyether compound,polyethylene glycol?PEG?has good solubility in water and is compatible with many organic compounds and organometallic complexes.Therefore,polyethylene glycol is often used as a surrogate for general organic solvents and a catalyst carrier,which can realize efficient recycling of the catalytic system in organic reactions.Buchwald ligands are widely used in transition-metal-catalyzed organic reactions,but due to their high cost and quite complicated procedures for the preparation of them,the recycling of Buchwald ligands remains a challenge in industry and academia.Thus,it is of great significance to find an efficient and practical method that enables the recycling of both metals and ligands.The use of PEG as a green reaction medium in organic reactions has been considered as the main means for achieving effective separation of catalyst and reaction product and recycling of the catalytic system.In this dissertation,we investigated the construction of carbon-heteroatom and carbon-carbon bonds catalyzed by platinum and palladium with Buchwald ligands in PEG and the recycling of the catalytic systems.The research work mainly includes the following three parts:In the first part,we investigated the hydrosilylation of terminal acetylenes with hydrosilanes catalyzed by K₂PtCl₄/XPhos-SO₃Na in a mixed solvent of polyethylene glycol?PEG-400?and water.The results indicated that under mild conditions,a wide range of aromatic or aliphatic terminal acetylenes underwent the hydrosilylation with various hydrosilanes highly regio-and stereoselectively,producing a variety of functionalized?-?E?-vinylsilanes in good to excellent yields with 100%?-?E?-selectivity.In addition,the expensive K₂PtCl₄ catalyst and XPhos-SO₃Na ligand in PEG-400/H₂O?V/V=2:1?could be recycled up to eight times without any loss of catalytic activity.The present work provides a convenient and practical route to a variety of functionalized?-?E?-vinylsilanes.In the second part,we studied the borylation reaction of aryl chloride with bis?pinacolato?diboron catalyzed by Pd₂?dba?₃ and XPhos ligand in PEG-2000 and explored the recycling performance of the catalytic system.The results indicated that the Pd₂?dba?₃/XPhos can efficiently catalyze the borylation of a wide of electron-deficient and electron-rich aryl chlorides with bis?pinacolato?diboron in PEG-2000,yielding a variety of pinacol arylboronates in good to excellent yields.This catalytic system has a broad scope of substrates and can be recycled for many times without significant loss of activity.In the third part,we investigated cyanation reaction of aryl chlorides with K₄[Fe?CN?₆]catalyzed by Pd?OAc?₂/XPhos-SO₃Na in a mixture of PEG-400 and water to prepare a variety of substituted benzonitriles.The results indicated that the cyanation reaction of a wide of electron-deficient and electron-rich aryl chlorides with K₄[Fe?CN?₆]proceeded smoothly under catalysis of Pd?OAc?₂/XPhos-SO₃Na in a mixture of PEG-400/H₂O?V/V=1:1?,yielding a variety of substituted benzonitriles in moderate to excellent yields.In addition,the Pd?OAc?₂/XPhos-SO₃Na/PEG-400/H₂O system could be recycled for several times without loss of catalytic activity.