Metal Porphyrins And Their Complexes:The Application In Selective Addition Reaction Of Alkynes

Porphyrin,a conjugated macrocyclic structure,can be converted to various metalloporphyrins by changing the substituents on the ring and central metal ions,and has a very wide range of applications in the field of catalysis.However,when metalloporphyrins are used as catalysts,there are two main disadvantages:1)they are easy to dimerize and deactivate in most reaction systems;2)Most of them are used as homogeneous catalysts,and can not be recycled.In order to solve these problems,metalloporphyrins were introduced into the metal organic framework as ligands,which not only retained the catalytic activity of metal porphyrins,but also effectively inhibited their dimerization and improved their recyclability.Porphyrinic metal-organic framework(PMOFs)materials have the advantages of adjustable structure,great specific surface area and good photosensitivity.Therefore,they have been widely used in catalytic field.In this paper,we use metal porphyrins and PMOFs as catalysts to explore their application in the selective addition of alkynes,and develop a series of efficient,heterogeneous/homogeneous catalytic selective addition methods for alkynes.At the same time,through the combination of experiments and theoretical calculations,the structure-activity relationships are systematically studied.The thesis is divided into five parts,summarized as follows.Chapter One.First,the structure and application of metalloporphyrins and their complexes are described in detail.Then,the research progress of selective addition of alkynes and the existing problems are introduced.Finally,the topic selection and significance of the thesis are explained.Chapter two.First,we review the important applications of vinyl borides and the main chanllenges in synthetic process:how to improve the chemical selectivity,regioselectivity and stereoselectivity during the addition reaction.In summary,the PCN-222(Cu)shows superior performance for the hydroboration of alkynes to produce(E)-?-vinylboronates using B₂Pin₂ as boron reagents.The heterogeneous catalytic process is effective for aromatic,aliphatic,terminal and internal alkynes with high regio-and stereoselectivity.Furthermore,control experiments and DFT calculations show that the excellent catalytic activity of PCN-222(Cu)is derived from the synergistic effect of Cu(II)ions,N atoms of porphyrin rings and terminal-OH groups on Zr-nodes.A series of deuterium labeling experiments prove that H₂O molecule of solvent is the proton source of the syn-addition reaction.Importantly,we reveal that five-membered ring centring on“Cu-N-B-C-C”skeleton is the key specie of selective hydroboration process.Third chapter.Firstly,the application of?-ketosulfone compounds and synthetic challenges are introduced,such as harsh reaction conditions,long reaction time,complicated starting materials,etc.In this work,we used Xenon lamp as the light source,PCN-222(Cu)as the heterogeneous photocatalyst,air as the oxidant,and aromatic alkynes and sodium p-toluenesulfinate as starting materials to achieve the construction of a series of?-ketosulfones.This method has the following advantages:1)it makes full use of the photosensitivity of PMOFs,which can promote the generation of sulfonyl radicals under light condition;2)the central metal of the porphyrin can provide the characteristics of Lewis acid catalytic sites,which can active alkynes.At the same time,it is proved that 1)the reaction is a free radical process through controlled experiments;2)the"oxygen"of the carbonyl group in the product come from the water molecular of solvent and O₂ in the air.Chapter Four.Firstly,we introduce the research progress of the transfer hydrogenation of alkynes,and detail the chem-and stereoselectivity problems in the semi-hydrogenation of alkynes.In this work,we apply tetra-phenyl porphyrinic palladium(Pd-TPP)to the semi-hydrogenation of alkynes.Under mild conditions,we use pinacol borane(HBPin)as the hydrogen source to achieve efficient and selective conversion of alkynes to olefins.The reaction shows high chem-and stereoselectivity.Through the investigation of the mechanism,it is found that the hydrogen source of the hydrogenation come from the hydrogen atom of HBPin and the water molecular in the solvent.Chapter 5 is the summary of this paper and the prospect of the research.