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Henri Doucet - One of the best experts on this subject based on the ideXlab platform.
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Metal-Catalyzed C-H Bond Activation of 5-Membered Carbocyclic Rings: A Powerful Access to Azulene, Acenaphthylene and Fulvene Derivatives
Chemistry - An Asian Journal, 2018Co-Authors: Xinzhe Shi, Jean-françois Soulé, Arpan Sasmal, Henri DoucetAbstract:Azulene, acenaphthylene and fulvene derivatives exhibit important physical properties useful in materials chemistry as well as valuable biological properties. Since about two decades ago, the metal-catalyzed functionalization of such compounds, via C-H Bond Activation of their 5-membered carbocyclic ring, proved to be a very convenient method for the synthesis of a wide variety of azulene, acenaphthylene and fulvene derivatives. For such reactions, there is no need to prefunctionalize the 5-membered carbocyclic rings. In this review, the progress in the synthesis of azulene, acenaphthylene and fulvene derivatives via metal-catalyzed C-H Bond Activation of their 5-membered carbocyclic ring are summarized.
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palladium catalyzed c3 or c4 direct arylation of heteroaromatic compounds with aryl halides by c h Bond Activation
Chemcatchem, 2010Co-Authors: Julien Roger, Aditya L Gottumukkala, Henri DoucetAbstract:In recent years, palladium-catalyzed direct C2 or C5 arylation of heteroaromatic compounds with aryl halides by C-H Bond Activation has become a popular method for generating carbon-carbon Bonds. For this reaction, a wide variety of heteroaromatics, such as furans, thiophenes, pyrroles, thiazoles, oxazoles, imidazoles, pyrazoles, indoles, triazoles, or even pyridines, can be employed. C3 and C4 arylations of heteroaromatics by C-H Bond Activation have also been described. Such reactions initially attracted much less attention than the C2 or C5 arylations due to the lower reactivity of the C3 and C4 positions. However, in more recent years, several results from using modified and improved catalysts and reaction conditions have been reported, which permit C3 and C4 arylations in synthetically useful yields. Several intramolecular cyclizations of 2-substituted heterocycles have been described, with formation of a C—C Bond on C3 resulting in the formation of five- to nine-membered rings incorporating pyrroles, indoles, thiophenes, furans, isoxazoles, or pyridines. Intermolecular C3 or C4 direct arylations are still quite rare for some heteroaromatics and are in several cases not highly regioselective. For such reactions, the best results have been obtained using pyrroles, thiophenes, or furans. For selected substrates, regioselective arylation at C3 or C4 of the heteroaromatic compounds took place under appropriate reaction conditions. Only a few examples of intermolecular couplings using oxazoles, thiazoles, imidazoles, isoxazoles, pyrazoles, triazoles, or pyridines have been reported. For most of these reactions, aryl iodides or bromides have been used as coupling partners, although a few examples with aryl chlorides are also known. This method allows the synthesis of complex molecules in only a few steps, and will provide access to a very wide variety of new heteroaryl derivatives in the next years.
Frank Glorius - One of the best experts on this subject based on the ideXlab platform.
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cooperative lewis acid cp co iii catalyzed c h Bond Activation for the synthesis of isoquinolin 3 ones
Angewandte Chemie, 2016Co-Authors: Ju Hyun Kim, Steffen Gresies, Frank GloriusAbstract:A facile route toward the synthesis of isoquinolin-3-ones through a cooperative B(C6 F5 )3 - and Cp*Co(III) -catalyzed C-H Bond Activation of imines with diazo compounds is presented. The inclusion of a catalytic amount of B(C6 F5 )3 results in a highly efficient reaction, thus enabling unstable NH imines to serve as substrates.
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c h Bond Activation enables the rapid construction and late stage diversification of functional molecules
Nature Chemistry, 2013Co-Authors: Joanna Wenceldelord, Frank GloriusAbstract:Over the past decade, C–H Bond Activation has progressively become a well-established synthetic tool. An increased scope and understanding of this transformation has seen it being used in a wide range of contexts, not only in traditional organic synthesis, but also in late-stage diversification strategies for organic materials and biologically active molecules.
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c h Bond Activation enables the rapid construction and late stage diversification of functional molecules
Nature Chemistry, 2013Co-Authors: Joanna Wenceldelord, Frank GloriusAbstract:The beginning of the twenty-first century has witnessed significant advances in the field of C-H Bond Activation, and this transformation is now an established piece in the synthetic chemists' toolbox. This methodology has the potential to be used in many different areas of chemistry, for example it provides a perfect opportunity for the late-stage diversification of various kinds of organic scaffolds, ranging from relatively small molecules like drug candidates, to complex polydisperse organic compounds such as polymers. In this way, C-H Activation approaches enable relatively straightforward access to a plethora of analogues or can help to streamline the lead-optimization phase. Furthermore, synthetic pathways for the construction of complex organic materials can now be designed that are more atom- and step-economical than previous methods and, in some cases, can be based on synthetic disconnections that are just not possible without C-H Activation. This Perspective highlights the potential of metal-catalysed C-H Bond Activation reactions, which now extend beyond the field of traditional synthetic organic chemistry.
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towards mild metal catalyzed c h Bond Activation
Chemical Society Reviews, 2011Co-Authors: Joanna Wenceldelord, Thomas Droge, Fan Liu, Frank GloriusAbstract:Functionalizing traditionally inert carbon–hydrogen Bonds represents a powerful transformation in organic synthesis, providing new entries to valuable structural motifs and improving the overall synthetic efficiency. C–H Bond Activation, however, often necessitates harsh reaction conditions that result in functional group incompatibilities and limited substrate scope. An understanding of the reaction mechanism and rational design of experimental conditions have led to significant improvement in both selectivity and applicability. This critical review summarizes and discusses endeavours towards the development of mild C–H Activation methods and wishes to trigger more research towards this goal. In addition, we examine select examples in complex natural product synthesis to demonstrate the synthetic utility of mild C–H functionalization (84 references).
Sukbok Chang - One of the best experts on this subject based on the ideXlab platform.
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recent advances in the transition metal catalyzed twofold oxidative c h Bond Activation strategy for c c and c n Bond formation
Chemical Society Reviews, 2011Co-Authors: Jaesung Kwak, Sukbok ChangAbstract:The direct functionalization of heterocyclic compounds has emerged as one of the most important topics in the field of metal-catalyzed C–H Bond Activation due to the fact that products are an important synthetic motif in organic synthesis, the pharmaceutical industry, and materials science. This critical review covers the recent progresses on the regioselective dehydrogenative direct coupling reaction of heteroarenes, including arylation, olefination, alkynylation, and amination/amidation mainly utilizing transition metal catalysts (113 references).
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pt catalyzed sp3 c h Bond Activation of o alkyl substituted aromatic carboxylic acid derivatives for the formation of aryl lactones
Tetrahedron Letters, 2006Co-Authors: Ji Min Lee, Sukbok ChangAbstract:Abstract Synthesis of aryl lactones from ortho-alkyl substituted aromatic carboxylic acids is described on the basis of sp3 C–H Bond Activation using either palladium or platinum catalysts. Kinetic isotope studies reveal that the reaction takes place presumably by the chelation assistance of metal catalyst to the carboxylic group followed by the C–H Bond Activation.
Pranjal Gogoi - One of the best experts on this subject based on the ideXlab platform.
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palladium ii catalyzed c h Bond Activation c c and c o Bond formation reaction cascade direct synthesis of coumestans
Journal of Organic Chemistry, 2016Co-Authors: Kashmiri Neog, Ashwini Borah, Pranjal GogoiAbstract:A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C–H Bond Activation/C–O and C–C Bond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology was applied to the synthesis of natural product flemichapparin C.
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Palladium(II)-Catalyzed C–H Bond Activation/C–C and C–O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans
2016Co-Authors: Kashmiri Neog, Ashwini Borah, Pranjal GogoiAbstract:A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C–H Bond Activation/C–O and C–C Bond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology was applied to the synthesis of natural product flemichapparin C
Jonathan A Ellman - One of the best experts on this subject based on the ideXlab platform.
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direct functionalization of nitrogen heterocycles via rh catalyzed c h Bond Activation
Accounts of Chemical Research, 2008Co-Authors: Jared C Lewis, Robert G Bergman, Jonathan A EllmanAbstract:Nitrogen heterocycles are present in many compounds of enormous practical importance, ranging from pharmaceutical agents and biological probes to electroactive materials. Direct functionalization of nitrogen heterocycles through C−H Bond Activation constitutes a powerful means of regioselectively introducing a variety of substituents with diverse functional groups onto the heterocycle scaffold. Working together, our two groups have developed a family of Rh-catalyzed heterocycle alkylation and arylation reactions that are notable for their high level of functional-group compatibility. This Account describes our work in this area, emphasizing the relevant mechanistic insights that enabled synthetic advances and distinguished the resulting transformations from other methods. We initially discovered an intramolecular Rh-catalyzed C-2 alkylation of azoles by alkenyl groups. That reaction provided access to a number of di-, tri-, and tetracyclic azole derivatives. We then developed conditions that exploited mic...
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total synthesis of lithospermic acid by asymmetric intramolecular alkylation via catalytic c h Bond Activation
Journal of the American Chemical Society, 2005Co-Authors: Steven J Omalley, Anja Watzke, Robert G Bergman, Jonathan A EllmanAbstract:The total synthesis of (+)-lithospermic acid is described. The efficient synthesis features an asymmetric alkylation via C−H Bond Activation to assemble the dihydrobenzofuran core of the natural product. This was accomplished via a chiral imine-directed C−H Bond functionalization and represents the first application of this C−H Activation method to natural product synthesis. Furthermore, a challenging deprotection of a late-stage permethylated lithospermic acid was achieved.
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highly efficient and enantioselective cyclization of aromatic imines via directed c h Bond Activation
Journal of the American Chemical Society, 2004Co-Authors: Reema K Thalji, Jonathan A Ellman, Robert G BergmanAbstract:The first highly enantioselective catalytic reaction involving aromatic C−H Bond Activation is communicated. Enantioselective cyclization of aromatic ketimines containing alkenyl groups tethered at the meta position of an imine directing group has been achieved using 5 mol % [RhCl(coe)2]2 and 15 mol % of an (S)-binol-derived phosphoramidite ligand. Selectivities of up to 96% ee and up to quantitative yields were obtained. Moreover, the identified catalyst system enables the intramolecular alkylation reaction to be performed at temperatures 75 °C lower than our previously reported achiral system. The reaction can even be performed at room temperature for one of the optimal substrates.