Rh(III)-catalyzed Asymmetric CH Activation To Construct Axial Chirality And Multi-center Chiralit

Transition-metal catalyzed C-H bond activation has allowed development of various synthetic methods to access value-added organics.In this field,direct C-H bond conversion is one of the most effective and environmentally friendly processes to construct new C-C or C-X bonds.Rh(Ⅲ)-catalyzed C-H activation has aroused extensive research interest of domestic and foreign researchers due to the catalyst system features easily-prepared,high reactivity,controllable site selectivity,broad functional group compatibility.Despite the tremendous progress,enantioselective C-H activation remains largely underdeveloped.It remains necessary to development novel asymmetric systems to increase competitiveness of Rh(Ⅲ)catalysis in synthesis of chiral functional molecules.This article mainly focuses on the construction of axial chirality and central chirality by chiral Rh(Ⅲ)-catalyzed asymmetric C-H activation.The achieved results are as following:1.Rhodium-catalyzed enantioselective oxidative [3+2] annulation of arenes and azabicyclic olefins via twofold C-H activation.By employing a flexible chelating group and strong oxidant,we have realized Rh(Ⅲ)-catalyzed oxidative [3+2] annulation of arenes and azabenzonorbornadienes for enantioselective synthesis of cis-fused dihydrocarbazoles via rare enantioselective twofold C-H activation.Two distinct classes of arenes have been established as viable substrates on the basis of rational design and extensive screening.Mechanistic studies have been performed,and a chiral rhodacycle has been isolated as an active intermediate.2.Rhodium-catalyzed regio-,diastereo-,and enantioselective three-component carboamination of dienes via C-H activation.We have realized enantioselective three-component carboamination between arene,diene,and dioxazolone by rhodium catalysis.The reaction proceeds via a C-H activation pathway en route to thermodynamically stable as well as kinetically reactive π-ally intermediates.The reaction features mild reaction conditions,excellent 1,2-regioselectivity,and high enantioselectivity and represents a rare case of three-component enantioselective C-H activation.The regioselectivity also complements that of a related racemic three-component reactions recently reported.The mechanism of this reaction has been explored and the regioselectivity has been rationalized.3.Rhodium-catalyzed atroposelective access to axially chiral olefins via C-H bond activation and directing group migration.Axially chiral open-chain olefins represent an underexplored class of chiral platform.In this report,two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C-H activation of(hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes.The coupling of indoles bearing an N-aminocarbonyl directing group afforded C-N axially chiral acrylamides with assistance of a racemic zinc carboxylate additive.DFT studies suggest aβ-nitrogen elimination-reinsertion pathway for the directing group migration.Meanwhile,the employment of N-phenoxycarboxamide delivered C-C axially chiral enamides via migration of the oxidizing directing group.Experimental studies suggest that in both cases the(hetero)arene substrate adopts a well-defined orientation during the C-H activation,which in turn determines the disposition of alkyne in migratory insertion.Synthetic applications of representative chiral olefins have been demonstrated.Meanwhile,applications of chiral carboxamides as an additve to control the enantioselectivity of C-H activation were also explored.