Synthesis Of Novel Porous Organic Polymers And Their Application In Heck?Suzuki?Hydrosilylation Of Alkynes

In this thesis,a series of novel porous organic polymers(POPs)have been designed and synthesized.The resulant POPs could play the roles as both ligands and supports simultaneously to prepare the efficient heterogeneous catalysts for organic reactions.It is proposed for the first time that the beneficial confinement effect of the pore structure in organic porous polymers can obviously promote the selectivity of organic reactions.Four chapters are included.Chapter 1:In this chapter there are two aspects:introduction and classification of porous organic polymers,application of porous organic polymers in heterogeneous catalysis.Chapter 2:In this chapter,the synthesis of conjugated microporous polymers based on o-alkynylpyridine and their application in selective oxidation of Heck reaction are briefly introduced.The Heck reaction is one of the most powerful transformations for the construction of C-C bonds.A key issue in the Heck reactions remains to be solved is to control regio-and stereoselectivities.For electronically biased olefins such as vinyl ethers,acrylatesa nd styrene,high selectivity can be achieved easily.Typically,electron-poor olefins favor coupling at the terminal site to give the linear products,while electron-rich olefins favor coupling at the internal site to deliver the branched products.However,the development of selective Heck reactions with electronically unbiased alkenes,in a catalytic manner is still a formidable challenge.In the past few years,some groups have focused on catalyst-controlled highly selective Heck reaction of simple olefins.However,to our knowledge,there have been no reports of heterogeneous ligands which are capable of promoting selective Heck reactions of simple olefins.A series of pyridine-type ligands containing acetylene bond were synthesized for selective oxidative Heck reactions of simple olefins.We utilized these ligands as functional units and integrated into the skeleton of conjugated microporous polymers.The resultant CMP material was used as a heterogeneous catalytic ligand for the high linear-selective oxidative Heck reaction of simple olefins(Scheme 1).Owing to the beneficial confinement effect of the porous structure in CMP ligands and the bifunctional ligand feature(consists of acetylene bonds and pyridine-N sites with proper coordination geometric angle),this CMP ligand displayed high regioselectivity toward a series of electronically unbiased alkenes.The linear selectivity of CMP ligand is about 30 times higher than that of its monomer in oxidative Heck reaction of simple olefins.In addition,DFT calculations shows the formation of linear regioisomer is much more preferable than that of branched isomer both thermodynamically and kinetically.This work opens a new front of using CMP materials as an promising platform for developing efficient heterogeneous catalysts in controlling the selectivity in organic reactions.Chapter 3:In this chapter,the synthesis of organic porous polymer based on triphenylphosphine and its application in suzuki coupling reaction of aryl chlorides are briefly introduced.The Suzuki-Miyaura cross-coupling reaction is one of the most powerful transformations for the construction of C-C bonds.Over the past several decades,great efforts have been devoted to develop homogeneous palladium catalysts for Suzuki-Miyaura cross-coupling reactions.However,application of these homogeneous catalysts in industry is still limited because of their high cost and the difficulty in recycling them from the mixtures.Transition-metal catalysts can be bound to ligand-containing polymers to form metal-polymer complexes.These complexes can be used as heterogeneous catalysts to solve some of the drawbacks of homogeneous catalysts.From an industrial point of view,the use of aryl chlorides is more attractive than aryl bromides and iodides because they aryl chlorides readily available and relatively cheap.In this regard,polystyrene-supported phosphines(PS-Ph3P),including single-pointed PS-Ph3P and two-fold cross-linked PS-Ph3P have been used both as ligands and supports for heterogeneous catalysts.However,these heterogeneous catalysts derived from PS-PIh3P and palladium still suffered from low catalytic activities and bad repeatability.In this work,we have synthesized a three-fold crosslinked polymer-bound phosphine with a high content of P.This resulting polymer forms a monodentate-P-ligated palladium complex,which displays outstanding reactivity in Suzuki-Miyaura coupling reaction of aryl chlorides(Scheme 2).More importantly,the hetrogeneous catalyst is highly stable as demonstrated by the negligible metal leaching and excellent reusability.These excellent properties of Pd/POL-Ph3P can be attributed to its high content of P atoms,which can prevent agglomeration of Pd nanoparticles.Chapter 4:This chapter briefly introduces the synthesis of organic porous polymers based Xantphos and its application in selective hydrosilation of alkynes(Scheme 3).Hydrosilylation of alkynes has been of high interest,as a straightforward and atom-economic method for vinylsilanes that are versatile intermediates in organic synthesis.A key issue need to be solved in the alkynes hydrosilylation is the control of regio-and stereoselectivities.In general,at least three isomers such as(E)-?-,(Z)-?-,and ?-vinylsilanes can be obtained in this transformation.Over the past several decades,a series of noble metals,such as Rh,Pt,Ru,Pd,Au and Th have been used almost as catalysts for selective hydrosilylation of alkynes.Recently,several groups have focused on the development of inexpensive metal-catalyzed highly selective hydrosilylation of alkynes,in the presence of well-designed homogeneous ligands.Ni complexes have been also proved effective to promote hydrosilylation of alkynes,but poor selectivity was usually observed.However,despite their widespread applications,limitations such as high costs and difficulty recycling have persisted,which restrict their industrial application.Therefore,the development of polymeric ligands supported non-noble metals as recyclable catalysts capable of promoting highly selective Si-H additions to alkynes,remained to be greatly challenging and significant.Herein,we have developed nikel-catalyzed hydrosilylation of alkynes with high anti-Markovnikov selectivity,by employing POPs as both ligand and support for the first time.Owing to the beneficial confinement effect of the porous structure in POPs,this polymeric ligand displayed excellent selectivity and activity toward a broad range of terminal and internal alkynes.Moreover,heterogeneous POL-Xantphos outperformed the monomeric Xantphos ligands in controlling the selectivity.By performing reactions in a flow reactor system,separation and regeneration of Ni/POL-Xantphos catalyst is easily achieved without any loss in selectivity or activity,which indicates its good prospect for industrial application.This work highlights the potential of using POPs as a excellent platform for developing highly efficient heterogeneous catalysts in controlling the regioselectivity.