Study On The Preparation And Catalyst Properties Of Pd/Resin Composites

C-C cross-coupling reaction is an effective means to construct C-C bond,which is very important for modern organic synthesis.Its classical reactions include Sonogashira reaction,Suzuki reaction,Heck reaction,Kumade reaction and so on.In the past few decades,scientists have used this tool to synthesize a complex array of molecules,including drugs and natural products.At that time,conventional homogeneous palladium catalysts such as PdCl₂ and Pd?OAc?₂ were commonly used as common catalysts for Heck reaction.However,such catalysts have poor stability at high temperatures and are easily deactivated.In addition,it needs to add additional ligands,and the products are difficult to separate and the catalyst recovery is quite difficult after the reaction,so it is gradually eliminated.As the research progresses,researchers have found that supported heterogeneous catalysts can not only effectively improve the catalytic activity of the reaction,broaden the range of substrates,but also be easily recycled after the reaction,which has extremely high academic and industrial value.In this paper,we mainly focus on the development of resin-supported metal nanocatalysts.The classical Heck reaction and Suzuki reaction catalyzed by Pd@resin are our important research objectives.The specific research contents are as follows:I.Effect of different resins and adsorption conditions on the adsorption properties of Pd?II?In this paper,chelating resins Tulsion CH-95,D401,717,D201,D301 and D314 were selected as experimental objects.We adsorbed palladium ions under the same conditions by static adsorption method,and compared the adsorption capacity of each resin to Pd?II?.Finally,the most adsorbable resins of Pd?II?with D201,D301 and D314 were selected as the carrier of Pd-based heterogeneous catalyst.The effects of different adsorption conditions on the adsorption of Pd?II?on the resin were studied by controlling the adsorption time,reaction temperature,pH and stirring conditions.Among them,agitation was the most important factor.II.Pd@resin catalyzes the Heck reactionIn this paper,a resin-supported palladium-based heterogeneous catalyst was prepared by static adsorption method and one-step reduction of palladium.The optimal reaction conditions and the application range of Pd@resin for Heck reaction were investigated without any ligand.It was found that even if the palladium content in the reaction system was very low,the Heck reaction in which Pd@resin was involved still had a medium-to-high yield,and the substrate had a wide application range.III.Pd@resin catalyzes the Suzuki reactionThe catalytic effect of Pd@resin on the Suzuki reaction was also investigated.Under the optimal reaction conditions,Pd@resin also has a wide range of substrate applications for the Suzuki reaction.It was found that the catalytic stability of the three kinds of catalysts was excellent and could be stabilized for five times,and the yield was more than 85%.