Rhodium(?)-Catalyzed Coupling Reactions Of Nitrogen-Containing Organics With Diazo Compounds

Nitrogen-containing organic molecules are widely found in biomass resources in plants,including indoles,amines and so on.These nitrogen-containing organic molecules are widely used in functional materials,drugs,pesticides and dyes.Therefore,the functionalization of nitrogen-containing organic molecules has attracted intensive attention.In recent decades,transition metals catalyzed C-H functionalization provide a more convenient,atom-economic,environmental and efficient way for the synthesis of complex organic molecules.Among them,trivalent rhodium complex has recieved intensive attention due to its unique catalytic activity.Diazo compounds are the precursor of carbene,which are easy to take off equivalent nitrogen to generated carbene under lighting,heating,or transition metal catalysis.Therefore,diazo compounds usually serve as a good coupling reagent.In order to realize deep processing of natural products,this paper explore the C-H functionalization of natural molecular,such as indole,with Rh(?)as a catalyst and diazo compounds as a coupling reagent.The obtained research outputs are described as follow:1.An intermolecular enantioselective C-H annulation of indoles with various diazo compounds catalyzed by a chiral half-sandwich Rhodium(?)complex was reported,affording a new family of chiral 1H-imidazo[1,5-a]indol-3(2H)-one derivatives.This method features short reaction time(short to 0.5 h),high yields(65-98%),excellent enantioselectivities(up to 98%e.r.).This paper illustrates the 25 examples,proved that the reaction system has wide compatibility of functional groups of both the indole substrates and diazo compouds.The function groups of indoles contain methyl and methoxy(electron donating group),ester base(electron withdrawing group),allyl(unsaturated group)and halogen groups on the C3-C6 positions.The groups of diazao compounds contain benzyl,p-methyl benzyl,p-chloride benzyl,phenethyl,methoxyl,ester,butyl,et.al.The higher steric resistance of the diazo compound at the ester position,the better enantioselectivity of the reaction system.The reaction system can also realize chiral functionalization of pyrrole compound at the C2 position.2.Whit the strategy of introduction of acyl as weak directing group at C3 position of indoles,this paper realized the thermodynamic control to synthesize C2 cyclized indoles and the dynamic control to synthesize C4 alkylated indoles.This catalytic system was operated with the trivalent rhodium complex as catalyst,diazo compounds as coupling reagents and no additional oxidant was added.This study expand the 43 examples to illustrate the good compatibility of functional groups of both indole substrates and diazo compounds.The functional groups contain methyl and isopropyl,n-butyl phenyl,benzyl,pyridine,halogen,ester of indoles at N 1 and C4-C7 positions and methyl,ethyl,isopropyl,benzyl,acetyl,allyl of diazo compounds.3.With the strategy of tandem catalysis using trivalent rhodium complex and lewis acid,the cinnolinium salts and isquinolizinium salts was synthesized in 53-99%yield with diazo compounds as the coupling reagent.This system follows a Lewis acid-assisted annulation pathway with the elimination of a hydroxy group under redox-neutral conditions.This reaction features low catalyst dosage,silver and oxidant free and wide range of substrates.The cinnolinium salts were synthesized from the coupling reactions of symmetric and asymmetric azo compound with diazo compounds;the isoquinolium salts were synthesized from the reactions of oxime ethers with diazo compounds.This paper showed 35 examples to illustrate the good compatibility of functional groups such as methyl,methoxy,trifluoromeoxy,tert-butyl groups,halogen,n-propyl,cyclohexyl and phenethyl et.al.The mechanism of reaction is explored in detail,and the possible intermediates were isolated,which provide evidence for the predicted reaction pathay.