Palladium-Metalated Porous Organic Ligand Polymers As Catalysts For Selective Decarbonylation Of Aldehydes,Oxidative Heck,and Hydrocarboxylation Of Olefins

Organic synthesis reactions involving transition metals are an important cornerstone of the development of modern organic chemistry.The precise synthesis of organic molecular intermediates catalyzed by transition metals is an organic synthesis problem that has not been properly solved so far,and it is related to many chemicals with high added value（such as:chemical fuel,luminescent materials,pesticides,drugs that have been prepared or have Large-scale and precise production of synthetic drug potential drug molecules,etc.）.In this type of synthesis method,most metal catalysts participate in organic reactions in a homogeneous catalysis manner,so most of them have the disadvantages of high cost and difficulty in recycling.The heterogeneous transformation of homogeneous metal/ligand catalytic system can solve this problem well.Porous organic polymer materials（POPs）,due to their stable physical and chemical properties,wide range of composition and electronic structure modulation,good swelling,and multi-stage pores,can not only integrate the variability of transition metal-catalyzed homogeneous reactions,but also It can inherit the reusability of heterogeneous materials,so it is a potential advantage carrier for heterogeneous catalysts.In this thesis,a variety of new porous organic ligand polymers have been synthesized.By controlling the loading of palladium metals with different particle sizes,they have been derivatized into porous organic polymer catalysts with local active centers of metal/ligand.In this way,the palladium/porous organic ligand polymers catalyzed chemoselective decarbonylation of aldehydes,regioselective oxidative Heck of electrons unbiased olefins,and regioselective hydrocarboxylation of electron-deficient olefins with formic acid as a carbon source were developed.The thesis is divided into three parts:Part 1:A porous organic ligand polymer with 4,5-bisdiphenylphos-phine-9,9-dimethylxanthracene（xantphos）ligand as a skeleton,which was reduced with palladium acetate to obtain a nanocatalyst Pd NPs/POL-xantphos.And successfully catalyzed the decarbonylation reaction of aldehydes,resulting in highly chemoselective decarbonylation products.Decarbonylation reactions are a class of reactions that have important applications in the conversion of important biomass such as 5-hydroxymethylfurfural into bioenergy such as furfuryl alcohol that can be incorporated into gasoline combustion.However,due to the highly reactive substrate aldehyde and relatively high temperature reaction conditions,such reactions often have competition for reactions such as reduction.Therefore,controlling the chemoselectivity of the decarbonylation reaction is a challenging subject.In this chapter,I designed and synthesized an organic porous ligand polymer with xantphos as the backbone and applied it to the decarbonylation reaction of aldehydes（Scheme 1）.Xantphos polymer is not only the ligand of the catalyst,but also the carrier of the heterogeneous catalyst.Through the core ligand structure of xantphos in the polymer backbone and the porous nature of the polymer,the reaction shows excellent selectivity and catalytic activity and recyclability,which has industrial development potential.Chapter 2:A series of mononuclear palladium metal catalysts Pd@POP-NHC were obtained by the coordination of porous organic polymers with a bidentate nitrogen heterocyclic carbene ligand as the core ligand framework.The Heck reaction of non-activated olefins was successfully catalyzed to produce highly regioselective linear-E-styrene products.The linear-E-type selective Heck reaction is an important method for the construction of trans internal olefins in drug synthesis.In the conventional synthesis methods,electron-rich olefins are easy to obtain branched products,and electron-deficient olefins are easily to linear products.The regioselective conversion of non-activated olefins that lack chelation and substituent effects has not yet been solved.Therefore,the highly regioselective Heck reaction of non-activated olefins is a very challenging subject.In this chapter,I realized the design and synthesis of a series of stable mononuclear palladium/bidentate-NHC catalysts through an original pre-coordination polymerization strategy.Among them,the strong electron-donating effect of the bidentate nitrogen heterocyclic carbene makes the palladium metal’s negative charge significantly higher.The steric hindrance effect of the polymer backbone kinetically limits the attack direction of palladium to olefins,which in turn leads to highly selective oxidation Implementation of heck reaction（Scheme 2）.Among the synthesized series of catalysts,Pd@POP-9 showed the best regioselectivity,and obtained the highest regioselectivity of the Heck reaction of electron-unbiased olefins to date.In addition,the catalyst has low synthesis cost and high catalytic efficiency,and the catalytic activity will not decrease after repeated application for 10 times,and it has industrial development potential.Chapter 3:A porous organic ligand polymer with a triarylphosphine ligand as a backbone was used to obtain a Pd₁@POL-PAr₃ metal polymer catalyst through a ligand exchange reaction.And successfully catalyzed the hydrocarboxylation reaction of olefins using formic acid as a hydrogen source and a carbon source to produce highly stereoselective linear carboxylic acid products.In this chapter,I designed and synthesized an organic porous ligand polymer with 2-substituted methoxy-substituted triphenylphosphine as the backbone,and applied it to high linear regioselectivity of electron-deficient terminal olefins using formic acid as a carbon source.Carboxylation（Scheme 3）.Among them,the phosphine ligand skeleton,isopropyl-like substituents from polymerization,and the methoxy group regulate the electron donor of the coordination phosphine atom,which plays a decisive role in the selectivity of the catalytic system.The enrichment of formic acid promotes the catalytic efficiency of the reaction,accelerates the reaction process,and further improves the reaction selectivity.The olefin hydrocarboxylation has been a fundamental reaction for industrial development,but flammable and explosive gases such as CO are the sources of carbon for reaction,and the problem of chemo-and regioselectivity of the reaction have always been the core issue of the response.The catalyst exhibits excellent selectivity,catalytic activity,and recyclability.It is an excellent alternative to the existing high-risk,low-selective hydrocarboxylation,and has industrial development potential.