Cascade Reactions Containing C-H Functionalizations For The Synthesis Of Nitrogen-Containing Heterocycles

Recently,transition-metal-catalyzed direct C-H functionalization has been extensively used for the construction of C-C and C-heteroatom bonds.Because rhodium catalysts have the advantages of low catalyst loading,well stability,good selectivity and mild condition,rhodium catalyzed C-H functionalization draws much attention.On the other hand,cascade reactions have become a powerful tool to construct comples molecules due to atom and step economy.This dissertation is mainly focused on rhodium(?)-catalyzed cascade nitrogen-containing group directed C(sp2)-H functionalization/cyclization reaction and iron catalyzed C(sp3)-H functionalization/cyclization reaction of ethers for synthesis of nitrogen-containing heterocycles,which as follows:1.Four-Component Cascade C-H Functionalization/Cyclization/Nucleophilic Substitution Reactions To Construct a-Functionalized Tetrahydroquinolines by the Strategy of in situ Directing Group FormationWe have developed a four-component cascade C-H functionalization/cyclization/nucleophilic substitution reactions of anilines,carboxylic anhydrides,propenol or propenal,and alcohols,by the strategy of in situ directing group formation,affording an efficient and convenient synthesis of a-alkoxyl tetrahydroquinolines from basic starting materials.A plausible mechanism involving rhodium(?)catalytic C-H functionalization and double nucleophilic attacks is proposed.The nucleophilicity order of some alcohols is also obtained for the cascade reaction.2.Rh?-catalyzed cascade C-H Functionalization/Amidation Reaction for Synthesis of Azepinone Derivatives.We have developed a Rh?-catalyzed cascade C-H functionalization/amidation reaction of aminobiaryls with diazomalonates directed by amino groups without N-substituents,affording new azepinone derivatives in moderate to excellent yields,which was important structural motifs in many alkaloids,pharmaceuticals,and other bioactive molecules.A plausible mechanism using rhodium(?)to activate both C(sp2)-H bonds for functionalization and the carbonyl group in the ester moiety for amidation is also proposed.3.Rh?-catalyzed tandem C-H Functionalization/Amidation Reaction for Synthesis of Isoquinolinediones.We have developed a novel and efficient method for the synthesis of isoquinolinediones and their analogous utilizing benzamides and diao compounds as starting materials.The reactions proceeded via a tandem chelation-assisted C(sp2)-H metalation,which is followed by Rh(?)-carbene formation,migratory insertion of C(sp2)-Rh(?)bond,second Rh(III)-carbene formation,migratory insertion of C(sp3)-Rh(III)bond(stabilized by coordination of ortho ester groups),subsequent protonation and cyclization.Which was rarely been reported maybe the C(sp3)-Rh(?)species is tended to be easier to protondemetallation and ?-hlyride eliminate.4.Iron-Catalyzed Direct C-H Functionalization of Ethers:An Efficient Synthesis of 6-Alkyl PhenanthridinesWe have developed an iron-catalyzed direct C-H functionalization of ethers with 2-isocyanobiphenyls for an efficient synthesis of 6-alkyl phenanthridines.Not only a series of cyclic ethers but also acyclic ethers undergo the reactions smoothly to give various 6-alkyl phenanthridines in high yields.A plausible mechanism involving intramolecular aromatic substitution of imidoyl radical is also proposed.