The Reaction Of P(?)-Chelation-Assisted C-H Activation

With the advantages of no pre-modification of the substrate,high atom economy and is easy to operate,C-H bond activation has always been the research focus in the field of organic chemistry.Organic molecules usually contain various C-H bonds with different activities,so it is an important strategy to perform regioselective C-H activation by installing guiding group in molecules,which not only could shorten the reaction procedures,but also has good compatibility with the functional groups of the substrate.In terms of the selection of guiding atoms,it has been reported massively that N,O and S atoms can be used as the guiding atoms for C-H functional grouping,while other heteroatoms,especially phosphine atoms,are rarely reported.Our group is engaged in activation of various inert bonds(C-H bond,C-F bond,C-O bond,C-N bond and C-C bond)and has achieved some progress.Therefore,my doctoral thesis is focused mainly on the study of trivalent phosphine-guided C-H activation so as to make such chemical conversion have wider substrate universality,excellent chemical selectivity and good applicability.The research contents of this thesis include mainly:(1)Tertiary phosphine directed C-H silylation;(2)Construction of monophosphines ligand libraries by hydroarylation of alkenes/alkynes;(3)Indole C7-position selective silylation;(4)Ortho-C-H alkynylation of arylphosphines.Details are as follows:Part ?:Rhodium catalyzed,in situ modification is conducted on biaryl-type monophosphines through trivalent phosphine-orientation to construct quickly a series of monophosphines libraries containing silyl groups with different electronic properties and spatial sizes.The proposed method has many advantages:materials easy to acquire,not requiring additional ligand and oxidizing agent,universal substrate,high-efficiency and high regioselectivity.The synthesized new-type phosphorous ligand is applied in Pd-catalyzed asymmetric Suzuki coupling reactions with good results.Part ?:Many biphenyl monophosphines with alkyl/alkenyl substituents are widely used in chemical transformation,especially in metal-catalyzed carbon-carbon and carbon-hetero bond reactions.Since these ligands have good value in application,it has always been a research focus on how to improve the utility of commercialized monophosphines through late modification.In this study,a series of alkyl/alkenyl monophosphines with different steric hindrances and electronic properties are synthesized with high efficiency.Meanwhile,the key part of the phosphine-directed olefin/alkyne hydrogenation reaction mechanism is studied thoroughly through some control experiments.Part ?:Indole motifs containing carbon-silicon(C-Si)bonds is an essential intermediate for the synthesis of some natural products,medicines and organic materials.In the past,C-Si bond was constructed by conducting C-H activation on indole compound through non-metal/metal catalysis,which has been reported massively.However,these methods were usually limited to C3 or C2 position with higher activity in indole,so it is a challenge to conduct regioselective C-H functionalization on the benzene core of the indole.In this study,C7-selective C-H silylation of indoles is achieved by installing a N-P~tBu2 with powerful coordinating capacity to the nitrogen atom of indole as the directing group.At the same time,silicon substituent in the products is transformed to show its potential values in application.In addition,a series of the key mechanism of the reaction is also discussed through multiple control experiments and density functional theory(M06-2X)computation.Part ?:In 1968,it was first reported that four-membered ring metal complex can be synthesized by metal and triphenylphosphine through C-H activation of ortho position.This thesis studies rhodium-catalyzed alkynylation of the benzene ring ortho position of arylphosphine via a four-membered ring transition state.The proposed method has high reaction efficiency,good substrate universality and is easy to operate.In addition,through late transformation the alkynylation products can be used to synthesize various phosphine compounds with different luminescent properties.