Directed C-H Bond Activation By Group ?B Transition Metal-catalyzed

Transition metal catalyzed C-H activation have developed as efficient and atom economy methods in organic and medicinal chemistry.In recent years,transition metals(such as rhodium,ruthenium,cobalt)received extensive attention.Based on the unique catalytic activity of rhodium,ruthenium,cobalt catalyst system,we carry forward series of research work of rhodium,ruthenium,cobalt catalysts in C-H bond functionalization reactions.The main contents of this paper include:1.Summary of recent research results of rhodium,ruthenium,cobalt catalyst system.A briefly introduce to the development of rhodium,ruthenium,cobalt catalyst systems.According to the aromatic group-directed,allylation of alkene,alkyne cyclization,amination,cyanide,etc,made a brief classification for transition metal catalyzed.2.Rh(?)C-H bonds in situ and ex situ cyclization.We report herein a versatile,traceless C-H activation-based approach for ex-situ and in-situ synthesis of diversified heterocycles.Rh(?)-catalyzed,N-amino-directed C-H alkenylation leads to the formation of either olefination products or indoles(in-situ annulation)in an atom-and step-economic manner at room temperature.The remarkable reactivity endowed by this directing group enables the scale-up of the reaction to 10 g scale at a very low catalyst loading(0.01 mol%/0.1 mol%).Ex-situ annulation of olefination product,via polarity relay or configuration inversion,allows its transformation into an array of heterocycles.The isolation of two catalysis-relevant rhodacycles and identification of a side product(with 15N NMR),in combination with competition and kinetic isotope experiments,suggest rate-limiting C-H activation and N-N bond cleavage/internal oxidation mechanism for the C-H alkenylation reaction.3.Ru(?)catalyzed C-H activation functionalization reactionsA hitherto elusive Ru(?)-catalyzed N-N bond-based traceless C-H functionalization strategy is reported in this chapter.An N-amino(hydrazine)group is used for directed C-H functionalization with either an alkyne or alkene,affording indole derivative or olefination product.The synthesis features a broad substrate scope,superior atom and step economy,and mild reaction condition.4.Co(?)-catalyzed traceless indole synthesisA hitherto elusive terminal alkyne-compatible traceless indole synthesis protocol is reported herein.N-amino(hydrazine)directing group imparts distinct,diverse reactivity patterns for Co(?)-catalyzed C-H functionalization/cyclization with both internal and terminal alkynes,which translates into unique substitution patterns and expanded structural space for the cyclic framework.Notable synthetic features achievable with our reaction system include:regioselectivity for a meta-substituted arylhydrazine,regioselectivity for a chain-branched terminal alkyne,formal incorporation of an acetylenic unit through C2-desilylation on a C2-silylated indole derivative,formal inversion of regioselectivity through consecutive C3-derivatization and C2-desilylation processes,formal bond migration for a linear chain terminal alkyne.5.Rh(?)-Catalyzed Synthesis of NaphthalenesWe report herein the use of enaminone as an effective synthon for directed C-H functionalizaiton.Proof-of-concept protocols have been developed for Rh(III)-catalyzed synthesis of naphthalenes,based on the coupling of enaminones with either alkynes or a-diazo-?-ketoesters.Two inherently reactive functionalities(hydroxyl and aldehyde)are streamlined into the newly formed cyclic framework and a broad range of substituents are tolerated,rendering target products readily available for further synthetic elaboration.6.Co(?)catalyzed oxidation of the C-H activation cyclizationWe report herein a traceless Cobalt-catalyzed bidentate C-H activation approach for in-situ synthesis of isoquinoline.Co(?)-catalyzed,2-hydrazino pyridine-directed C-H cyclization leads to the formation of isoquinoline(in-situ annulation)in an step-economic manner at mild conditions.The remarkable progress endowed by this directing group enables the traceless of bidentate C-H activation.The combination with competition and kinetic isotope experiments,suggest rate-limiting C-H activation and N-N bond cleavage/the driving force into the ring for the C-H activation cyclization.