Transition Metal Catalyzed Regioselective Hydroboration And Hydrosilylation Reaction Of Allene And 1,3-diyne

There are two main research aspects in this thesis.One is the transition metal catalyzed regiodivergent hydroboration of allenes and the regioselective hydrosilylation and hydroboration of 1,3-diynes.The second is the one-step synthesis of pyrazole compounds via a cascade Sonogashira coupling/cyclization from N-propargyl sulfonylhydrazones.The research content mainly includes the following four chapters:Chapter 1:This chapter is about the regiodivergent hydroboration of terminal allenes controlled by cheap metal nickel and cobalt.Organoboranes have good stability,low toxicity and easy operation.They are becoming multifunctional synthons in a series of synthetic transformations,such as palladium catalyzed Suzuki cross coup ling reaction and transition metal catalyzed 1,2-addition and 1,4-addition reactions.Among them,vinylboranes have special uses because they can provide olefin solid units with synthetic attraction in the organic skeleton.Theoretically,hydroboration of readily available allenes catalyzed by transition metals with pinacol borane may be one of the most effective and atom economical methods for the synthesis of such compounds.However,it is difficult to regulate the regioselectivity and stereoselectivity.For example,it is possible to generate six potential isomer products even for the mono-hydroboration of terminal allene and pinacolborane,and there may be products of side reactions such as multi-addition and hydrogenation in the reaction.In this chapter,boryl addition to internal or external carbon-carbon bond of the allene unit was achieved when nickel and cobalt bearing easily available phosphorus ligands were respectively employed.The regioselectivity of this catalytic hydroboration is mainly regulated by the use of different metal catalysts in the reaction.(Scheme 1)Chapter 2:This chapter focuses on regioselective hydrosilylation of 1,3-diyne regulated by metal nickel coordinated with porous organic polymers.In this chapter,we synthesized a kind of porous organic polymer(POL-Xantphos)and utilized it as a heterogeneous ligand for Ni-catalyzed highly regioselective and stereoselective hydrosilylation of 1,3-diynes.A series of symmetrical and unsymmetrical 1,3-diynes could smoothly react with secondary and primary silanes to give the corresponding product silyl-functionalized 1,3-enynes.Because of the confinement effect of microporous structure,POL-xantphos ligand improved the selectivity significantly than monomer xantphos ligand.The use of porous organic polymers as regioselective heterogeneous ligands in the 1,3-diyne hydrosilylation is first reported herein.The coordination of cheap and easily available metal catalysts with recyclable heterogeneous porous organic polymers as the catalytic system of reaction has a good application prospect in industrial development.(Scheme 2)Chapter 3:This chapter is about the regioselective hydro bo rat ion of 1,3-diyne catalyzed by NHC-silver[Ⅰ].In the past decades,the hydroboration of monoalkynes has been extensively studied and reported by organic chemists.A series of transition metals have been used to regulate the hydroboration of monoalkynes to selectively obtain the products of Markov or anti-Markov,cis-or trans-add it ion.Compared with the well-developed monoalkyne hydroboration,the current reports on 1,3-diyne hydroboration are still very limited,because even for mono hydroboration,there are still four possible addition reaction sites fo r 1,3-diyne,which makes the regulation of regioselectivity of the reaction challenging.In addition,there may be side reactions such as multi-addition or hydrogenation in the reaction.In the work of this chapter,we found that a common metal silver(Ⅰ)-NHC complex ligand plays a good regulatory role in the selective hydroboration reaction of 1,3-diyne,and can obtain the cis hydroboration addition products with high selectivity and excellent yield.(scheme 3)This is of great significance to improve the research of 1,3-diyne hydroboration reaction.Chapter 4:The content of this chapter is the one-step synthesis of pyrazole ring by Sonogashira coupling cyclization of N-propargyl sulfonylhydrazone catalyzed by Pd(Ⅱ)/Cu(Ⅰ).In this method,N-propargyl hydrazone with hydrogen atom at the end is used as the substrate,and the aryl iodide with electron absorbing group is first coup led under the joint catalysis of Pd/Cu,and then isomerized into an allene intermed iate under the promotion of basic triethylamine,and finally cyclized to obtain pyrazole compounds.In this study,we first reported the strategic application of Sonogashira reaction to construct pyrazole ring in a one-step operation,and the reaction can be carried out in series in one pot method.The reaction has the advantages of mild conditions and wide substrate range.In particular,it can synthesize some pyrazole compounds with trifluoromethyl,which is of great significance in medicinal chemistry.(Scheme 4)Scheme 4...