Synthesis Of Indole Olefin Chiral Compounds Based On C-N Axis

Acyclic axially chiral styrenes have attracted substantial research interest in recent years.However,chiral axes of this type of molecules are mostly limited to the C_aryl-C_vinyl bond.The reports of the construction of acyclic axially chiral styrene skeletons bearing the C_vinyl-N_hetero axes remains rare.Axially chiral compounds bearing C-N axes are the core skeletons of a variety of highly efficient ligands and catalysts.Moreover,they are widely found in natural medicines and biologically active molecules,which attracted much interest from researchers.Herein,we report a highly efficient stereospecific isomerization as well as AASI for the synthesis of indole-based axially chiral styrenes.Experimental results shown that the indole-based axially chiral compounds could be obtained in high enantioselectivities exhibiting particularly excellent configurational stability.Studies have shown that the reaction system involves two processes:1)metal catalyzes asymmetric allylic substitution to generate central chirality;2)base mediates the stereospecific[1,3]-proton transfer to generate axially chiral compounds.Experimental studies have shown that the optimal conditions for the reaction are:1)[Ir（cod）Cl]₂（3 mol%）,chiral phosphoramidite ligand（Feringa）（6 mol%）,cinnamyl carbonate analogues（0.2 mmol）,2-benzenesulfonyl-1H-indole analogues（0.4 mmol）,1,5,7-triazabicyclo[4.4.0]dec-5-ene（15 mol%）,1,8-diazabicycloundec-7-ene（DBU）（0.4 mmol）,dimethoxyethane（2.0 m L）;2)enantioenrich allylic centrally chiral compounds（0.1 mmol）,potassium tert-butoxide（0.1 mmol）,toluene（1.0 m L）.The reaction has a broad substrate scope with good yield and high enantiomeric excess（ee）.Preliminary mechanistic studies have shown that the isomerization process involves both intramolecular and intermolecular pathways,and the intramolecularπ…πstacking interactions of the axially chiral styrenes are the main reason of their excellent configurational stability.