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Reported herein is a palladium/norbornene‐catalyzed ortho‐arene acylation of aryl iodides by a Catellani‐type C H functionalization. This transformation is enabled by isopropyl carbonate anhydrides, which serve as both an acyl cation equivalent and a hydride source.  相似文献   

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Efficient couplings using equimolar quantities of each coupling partner and multiple C? H bond arylation reactions are achieved with an Ir‐based catalytic system for the C? H bond arylation of electron‐rich heteroarenes with iodoarenes to construct extended π‐systems. The dramatic ligand effect on reaction efficiency leads to the discovery that Crabtree's catalyst (see scheme) is the optimal catalyst precursor.

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The surface of hydrogen‐terminated diamond resembles a solid hydrocarbon substrate. Interestingly, the C? H bonds on the diamond surface are not as unreactive as that of saturated hydrocarbon molecules owing to its unique surface electronic properties. The invention of C? H bond activation and C? C coupling reactions on the diamond surface allows chemists to develop powerful chemical transistors, biosensors, and photovoltaic cells on the diamond platform.  相似文献   

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The double C? H bond activation of a series of linear and cyclic ethers by the iridium complex [Tptol′Ir(C6H5)(N2)] ( 2? N2), which features a cyclometalated hydrotris(3‐p‐tolylpyrazol‐1‐yl)borate ligand (Tptol′) coordinated in a κ4N,N′,N′′,C manner, has been studied. Two methyl ethers, namely, Me2O and MeOtBu, along with diethyl ether and the cyclic ethers tetrahydrofuran, tetrahydropyran (THP), and 1,4‐dioxane have been investigated with formation in every case of the corresponding hydride carbene complexes 3 – 8 , which are stabilized by κ4‐coordination of the ancillary Tptol′ ligand. Five of the compounds have been structurally authenticated by X‐ray crystallography. A remarkable feature of these rearrangements is the reversibility of the double C? H bond activation of Me2O, MeOtBu, Et2O, and THP. This has permitted catalytic deuterium incorporation into the methyl groups of the two methyl ethers, although in a rather inefficient manner (for synthetic purposes). Although possible in all cases, C? C coupling by migratory insertion of the carbene into the Ir? C σ bond of the metalated linkage has only been observed for complex 8 that contains a cyclic carbene that results from α,α‐C? H activation of 1,4‐dioxane. Computational studies on the formation of iridium carbenes are also reported, which show a role for metalated Tp ligands in the double C? H activation and account for the reversibility of the reaction in terms of the relative stability of the reagents and the products of the reaction.  相似文献   

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A trityl ion mediated C H functionalization of ethers with a wide range of nucleophiles at ambient temperature has been developed. The reaction displays high chemoselectivity and good functional group tolerance. The protocol also exhibits excellent regio‐ and diastereoselectivities for the unsymmetric ethers, thus stereoselectively generating highly functionalized disubstituted 2,5‐trans tetrahydrofurans (THF), 2,6‐trans tetrahydropyrans (THP), 2,6‐trans dihydropyrans (DHP), and 1,3‐trans isochromans, and highlighting the capacity of the protocol in complex molecule synthesis.  相似文献   

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The alkylation of complexes 2 and 7 with Grignard reagents containing β‐hydrogen atoms is a process of considerable relevance for the understanding of C–H activation as well as C–C bond formation mediated by low‐valent iron species. Specifically, reaction of 2 with EtMgBr under an ethylene atmosphere affords the bis‐ethylene complex 1 which is an active precatalyst for prototype [2+2+2] cycloaddition reactions and a valuable probe for mechanistic studies. This aspect is illustrated by its conversion into the bis‐alkyne complex 6 as an unprecedented representation of a cycloaddition catalyst loaded with two substrates molecules. On the other hand, alkylation of 2 with 1 equivalent of cyclohexylmagnesium bromide furnished the unique iron alkyl species 11 with a 14‐electron count, which has no less than four β‐H atoms but is nevertheless stable at low temperature against β‐hydride elimination. In contrast, the exhaustive alkylation of 1 with cyclohexylmagnesium bromide triggers two consecutive C–H activation reactions mediated by a single iron center. The resulting complex has a diene dihydride character in solution ( 15 ), whereas its structure in the solid state is more consistent with an η3‐allyl iron hydride rendition featuring an additional agostic interaction ( 14 ). Finally, the preparation of the cyclopentadienyl iron complex 25 illustrates how an iron‐mediated C–H activation cascade can be coaxed to induce a stereoselective C C bond formation. The structures of all relevant new iron complexes in the solid state are presented.  相似文献   

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Direct arylation of the ortho‐C? H bond of an aryl pyridine or an aryl imine with an aryl Grignard reagent has been achieved by using an iron‐diamine catalyst and a dichloroalkane as an oxidant in a short reaction time (e.g., 5 min) under mild conditions (0 °C). The use of an aromatic co‐solvent, such as chlorobenzene and benzene, and slow addition of the Grignard reagent are essential for the high efficiency of the reaction. The present arylation reaction has distinct merits over the previously developed reaction that used an arylzinc reagent, such as its reaction rate and atom economy. Selective C? H bond activation occurs in the presence of a leaving group, such as a tosyloxy, chloro, and bromo group. Studies on a stoichiometric reaction and kinetic isotope effects shed light on the reaction intermediate and the C? H bond‐activation step.  相似文献   

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A mild and catalytic method to form difluoromethylated arenes through the activation of benzylic C H bonds has been developed. Utilizing AgNO3 as the catalyst, various arenes with diverse functional groups undergo activation/fluorination of benzylic C H bonds with commercially available Selectfluor reagent as a source of fluorine in aqueous solution. The reaction is operationally simple and amenable to gram‐scale synthesis.  相似文献   

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A palladium‐catalyzed intermolecular cross‐coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency.  相似文献   

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