PdH-Catalyzed Asymmetric Reduction Of Ketones And NiH-Catalyzed Remote Hydroalkylation Of Olefins

Transition metal hydride complexes play important roles in organometallic chemistry especially related to homogeneous catalysis.They often function as key intermediates for transferring hydrogen between molecules.There have been many reports on the study of transition metal hydrides.In recent years,the research focuses mainly on the structure and bonding of these complexes,especially their catalytic action in some reduction and reductive coupling reactions.Optically active secondary alcohols are extremely useful precursors for obtaining bioactive molecules,as well as valuable synthetic intermediates.One of the most fundamental methods for the synthesis of these compounds is the enantioselective reduction of ketones.The asymmetric hydroboration of ketones is an efficient strategy to achieve optically active alcohols.Pinacolborane is a useful borane reagent,and could tolerate a variety of different functional groups.Compared to the catalytic reduction of hydrogen gas as a hydrogen source and transition metal,palladium hydride formed by pinacolborane and palladium is more safe to reduce the ketone to alcohol.Furthermore,the conditions of the reaction,which are carried out synergistically with palladium hydride and a commercially available chiral bisphosphine ligand,are mild.In addition,the reaction needs no base and the efficiency is high.In the transition-metal-catalyzed reductive coupling reaction,due to the?-hydride elimination,cross-coupling is often accompanied by ?-hydride elimination by-products.To suppress P-hydride elimination has long been a problem when designing reactions.In recent years,by taking advatage of this undesirable reaction,a serials of organometallic species along the hydrocarbon chain could be obtained through chainwalking,one of which could be functionalized with a suitable ligand.Through this method,different isomerized olefin mixtures in the petrochemical feedstock can be reacted with the same electrophile to obtain pure other useful chemical products.The originally low-reactivity alkene substrate can also be converted into a more active olefin through the migration of a carbon-carbon double bond to react with another coupling reagent to realize the construction of different chemical bonds.Transition metals such as palladium,zirconium,rhodium,cobalt,etc.can also cause olefins isomerization.However,researches on nickel-hydride catalyzed olefin isomerization-functionalization have shown an upward trend in recent years.C(sp~3)-C(sp~3)bonds are the structural basis of aliphatic organic compounds,and their formation is a basic operation in the synthesis of pharmaceuticals and natural products.The cross-coupling of alkyl fragments using nickel catalysis has been investigated intensively.However,from the standpoint of step and atom economy,the requirement for pre-generated organometallic reagents is still less than ideal.The use of nickel hydride for iterative migration of the stable and widespread available olefins can generate organometallic species in situ,activate the otherwise inert carbon-hydrogen bonds in the aliphatic chain,and achieve functionalization at these sites.In this paper,we mainly introduce the PdH-catalyzed asymmetric reduction of ketones and NiH-catalyzed remote hydroalkylation of olefins.This thesis includes the following several parts:A.PdH-catalyzed asymmetric reduction of ketones.The chapter 1 summarized the background of the metal hydride catalyzed asymmetric reduction of ketones and the application and research progress of secondary chiral alcohols.The chapter 2 introduced PdH species formed by the pinacolborane and palladium acetate,are together with the commercially available chiral diphosphine ligand(S,S)-Ph-BPE to asymmetrically reduce ketone to alcohol with low catalyst loading,no base,and high reactivity,conversion and enantioselectivity.B.NiH-catalyzed remote hydroalkylation of olefins.The chapter 1 summarized the background of transition-metal-catalyzed carbon chain migration and the application and research progress of sp3-sp3 carbon-carbon bond formation.The chapter 2 introduced a combination of NiBr2,a simple pyrox ligand,an excess of silane and KF can allow for the hydroalkylation of alkenes at the terminal position.