The Research Of Ligand Controlled Palldium-Catalyzed C-H Bond Activation

The Pd-catalyzed C-H bond activation is one of the most straightforward and powerful tools in synthetic chemistry.In particular,selective and direct activation of C-H bonds presents a fundamental challenge to chemists,as C-H bonds are ubiquitous in organic compounds with high bond energies.Many strategies are developed to solve these problems in recent research.First,directing group(DG)of the substrate can assist in activation of C-H bond with high selectivity.Second,increasing reactivity of the catalysts is also important to promote the reaction.In the transition metal catalyzed reaction,the ligands can control the catalytic activity through the adjustment of electron density and steric hindrance.Based on those effects,different kinds of ligands are developed to promote different types of C-H bond activation reactions.In this paper,the activity,regioselectivity,cis-trans selectivity and enantioselectivity of the reaction can be efficiently controlled through ligands optimization.Furthermore,the planar chiral ferrocenes are synthesized based on the chiral phosphine ligand.The P-stereogenic compounds and asymmetric double C-H bonds activation reaction proceeds successfully in the presence of the chiral phosphoric acid ligand.The cis-addition reaction of chloroaryl C-H bond with alkyne are achieved with 2-hydroxy-1,10-Phenanthroline ligand.This thesis includes six chapters to address the above research.The first chapter outlines different types of ligand-controlled Pd-catalyzed C-H bond activation reactions.The experimental research parts are as follows:1.The bisphosphine ligand controlled Pd-catalyzed asymmetric C-H bond arylation for the synthesis of planar chiral benzosiloloferrocenesPlanar chiral benzosiloloferrocenes which have optical activity,can only be synthesized through rhodium-catalyzed asymmetric catalysis in former literature.Herein,we developed a ligand-controlled palladium-catalyzed C-H bond activation reaction using the ferrocenyl-(2-bromophenyl)dimethylsilane as a substrate.Further screening of the ligands revealed that the JOSIPHOS ligand provide an effective control in the presence of palladium acetate.Under the optimized reaction conditions,a series of chiral ferrocenyl silanes(five-membered ring)were synthesized with ideal optical properties.(90%?98%ee)2.The monophosphine ligand controlled Pd-catalyzed asymmetric C-H bond arylation for the synthesis of planar chiral ferrocenyl silyl etherThe planar chiral ferrocenes are important units in catalysts and ligands for synthetic chemistry.The synthesis of ferrocenyl siloxane can only be achieved with rhodium catalysis in the literatures.We developed a palladium-catalyzed asymmetric C-H bond activation for the synthesis of the chiral ferrocenyl siloxane with chiral phosphine ligands.We find that palladium acetate and the TADDOL-derived phosphoramidite ligand with 3,5-tert-butyl-4-methoxyphenyl substituted provide an efficient control with excellent enantioselectivity Under the optimized reaction conditions,a series of chiral six-membered ferrocenyl siloxanes were obtained.(95%?99%ee)3.The chiral phosphoric acid promoted Pd-catalyzed asymmetric C-H bond arylation for the synthesis of P-stereogenic benzophospholesThe enantioselectivity of P-stereogenic phosphorus are well-controlled by the chiral phosphine or the amino acid ligand.For the palladium-catalyzed asymmetric cyclization of o-bromoarylphosphine oxide,the chiral phosphoric amide/acid is first applied in the reaction as the only chiral source to control stereoselectivity.By screening various chiral phosphoric acid ligands,the synergistic effect between chiral phosphoric acid ligand and the phosphoramide ligand provide the products with up to 90%ee.Further experiment indicated that the chiral phosphoric acid ligand is positively correlated to the selectivity of the product in a nonlinear relation.4.The chiral phosphoric acid promoted Pd-catalyzed cyclization via double asymmetric C-H bonds activation of the indolephosphine oxidesN-methylindole diarylphosphorus heterocycles have potential optical properties due to its multi-conjugated structure.Those compounds are typically synthesized by lithium salt with dibrominated aromatics.Herein,we employed a Pd(II)-catalyzed double C-H bonds activation for the synthesis of N-methylindole diarylphospholes.Adding a catalytic amount of 1-Adamantinecarboxylic acid can improve the overall yield.The reaction has a universal effect in a variety of aryl and indolyl substitution and is successfully applied in the synthesis of polyconjugated indole heterocyclic.Further asymmetric catalysis double C-H bonds activation was achieved with chiral ligand.The chiral BINOL-backbone phosphoric acid was found to be a chiral source for controlling enantioselectivity.Finally,the 2,4,6-triisopropylphenyl substituted of 3,3'-position chiral phosphoric acid ligand gave the product with 9:91 er.5.2-hydroxy-1,10-phenanthroline ligand accelerated Pd-catalyzed C-H alkenylation of arenes with alkynesSubstituted alkenes are widely present in natural compounds.Alkyne addition is one of the direct and efficient approaches for substituted alkene synthesis.We developed a synthetic sequence for the Pd-catalyzed hydroarylation ofp-dichlorobenzene C-H with alkyne using 2-hydroxy-1,10-phenanthroline as a ligand.The ligand reacts with palladium to generate the active catalyst that only one acetate anion on the palladium atom and a vacant coordination site can easily be generated for the incoming substrate.As a result,alkenyl chlorides can be obtained through 1,4-chlorine migration using dialkyl alkyne as a substrate and trisubstituted alkenes are produced with diaryl alkyne.Through the two-dimensional nuclear magnetic NOE experiment and the synthesis of standard products,the structure of the substituted alkenes was determined.These results indicated that the catalytic system could realize the cis-addition reaction of alkyne with arene in high selectivity.