Directing Groups Induced Rhodium(?)-Catalyzed C(sp~2)-H Bond Functionalization

Based on the direct functionalization of the ubiquitous C-H bond in organic compounds,transition metal catalyzed C-H functionalization has been explosively developed and provided new synthetic strategies for pharmaceutical science and material chemistry.With the assistance of transition metals such as palladium,iron,cobalt,nickel,copper or manganese,C-H bond of one reaction components is able to be activated and then reacts with other functionalized fragment molecule to deliver the target product.Among these reactions,rhodium(?)-catalyzed reaction is particularly attractive due to its high efficiency and excellent chemical selectivity.The utilization of directing group not only achieves regioselective functionalization via the control of reaction site,but also stabilizes the in situ generated organometallic intermediates via coordination.Directing groups containing heteroatoms such as nitrogen and oxygen are widely-used.The main content of this thesis is the introduction of silicon and fluorine containing fragment by means of the directing-group-assisted Rh(III)-catalyzed C-H bond activation,including:1.Introduction:Rhodium-catalyzed C-H bond functionalization assisted with directing groups:We summary different types of directing groups for the catalytic reaction,focusing on nitrogen and oxygen containing directing groups.Moreover,some typical rhodium-catalyzed C-H bond functionalization reactions are also presented.2.Rhodium-catalyzed switchable alkylation and alkenylation-cyclization of olefins:In contrast to previous works which need to change catalytic system or directing groups,under the same rhodium catalytic condition,reactions between olefins and acryl silanes yield alkylation and alkenylation-annulation products,respectively.Besides,this method leads to high chemical selectivity and compatibility of a wide range of functional groups.3.Construction of 2-fluoro-1,3-conjugated dienes via rhodium-catalyzed fluoroalkenylation:Rhodium-catalyzed C-H bond activation of olefins,combined with defluorination functionalization of gem-difluoroalkenes,successively provides coupling product 2-fluoro-1,3-conjugated dienes,which supplements the previous a-fluoroalkenylation studies which mainly based on(hetero)aromatics.In addition,this strategy also provides a new idea for the synthesis of fluorine-containing conjugated dienes.4.Rhodium-catalyzed difluoroalkylation of C(sp~2)-H bond based on hydroarylation:By taking advantage of the rhodium-catalyzed hydroarylation of gem-difluoroalkenes,potential biologically active small organic molecules containing difluoromethyl group can be obtained expeditiously.The chelation and coordination of Lewis bases in the olefin substrate were used to suppress the?-F elimination which could not be avoided in conventional methods.And the subsequent protodemetalation generatered the C2 difluoroalkylated indoles.