45 research outputs found

    Branched-Selective Intermolecular Ketone α‑Alkylation with Unactivated Alkenes via an Enamide Directing Strategy

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    We describe a strategy for intermolecular branched-selective α-alkylation of ketones using simple alkenes as the alkylating agents. Enamides derived from isoindolin-1-one provide an excellent directing template for catalytic activation of ketone α-positions. High branched selectivity is obtained for both aliphatic and aromatic alkenes using a cationic iridium catalyst. Preliminary mechanistic study favors an Ir–C migratory insertion pathway

    <i>Ortho vs Ipso</i>: Site-Selective Pd and Norbornene-Catalyzed Arene C–H Amination Using Aryl Halides

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    A Pd and norbornene-catalyzed <i>ortho</i>-arene amination via Catellani-type C–H functionalization is reported. Aryl halides are used as substrates; <i>N</i>-benzoyloxyamines and isopropanol are employed as the amine source (oxidant) and reductant respectively. Examples are provided in 50–99% yields with high functional group tolerance. This method gives complementary site selectivity at the <i>ortho</i>- instead of <i>ipso</i>-position of aryl halides

    Catalytic Direct β‑Arylation of Simple Ketones with Aryl Iodides

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    Herein we report a direct β-arylation of simple ketones with widely available aryl iodides, combining palladium-catalyzed ketone oxidation, aryl-halide activation, and conjugate addition through a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance

    Direct Observation of C–H Cyclopalladation at Tertiary Positions Enabled by an Exo-Directing Group

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    Here we describe the first preparation of tertiary alkyl palladium complexes via C–H activation. Enabled by an exo-type oxime directing group, cyclopalladation occurred smoothly at the bridgehead position. Treatment of the resulting complex with iodine led to C–H iodination at the methine carbon. This study provides important mechanistic information for palladium-catalyzed functionalization of methine C–H bonds

    Direct β‑Alkylation of Ketones and Aldehydes via Pd-Catalyzed Redox Cascade

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    We report a direct β-alkylation of ketones and aldehydes with simple alkyl bromides through a Pd-catalyzed redox-cascade strategy. The use of a Cu cocatalyst is important for improved efficiency. The reaction is redox-neutral, without the need for strong acids or bases. Both cyclic and acyclic ketones, as well as α-branched aldehydes, are suitable substrates for coupling with secondary and tertiary alkyl bromides. Concise formal synthesis of Zanapezil is achieved using this β-alkylation method

    Rh-Catalyzed Decarbonylative Coupling with Alkynes via C–C Activation of Isatins

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    Herein we report a [5 + 2 – 1] transformation though catalytic decarbonylative coupling between isatins and alkynes, which provides a unique way to synthesize 2-quinolinone derivatives. A broad range of alkynes can be coupled efficiently with high regioselectivity. This reaction is proposed to go through C–C activation of isatins, followed by decarbonylation and alkyne insertion. Directing group (DG) plays a critical role in this transformation. Assisted by the DG, the C–C cleavage of isatins occurs at room temperature

    Catalytic Direct β‑Arylation of Simple Ketones with Aryl Iodides

    No full text
    Herein we report a direct β-arylation of simple ketones with widely available aryl iodides, combining palladium-catalyzed ketone oxidation, aryl-halide activation, and conjugate addition through a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance

    (4+1) vs (4+2): Catalytic Intramolecular Coupling between Cyclobutanones and Trisubstituted Allenes via C–C Activation

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    Herein we describe a rhodium-catalyzed (4+1) cyclization between cyclobutanones and allenes, which provides a distinct [4.2.1]-bicyclic skeleton containing two quaternary carbon centers. The reaction involves C–C activation of cyclobutanones and employs allenes as a one-carbon unit. A variety of functional groups can be tolerated, and a diverse range of polycyclic scaffolds can be accessed. Excellent enantioselectivity can be obtained, which is enabled by a TADDOL-derived phosphoramidite ligand. The bridged bicyclic products can be further functionalized or derivatized though simple transformations

    Controlled Rh-Catalyzed Mono- and Double-decarbonylation of Alkynyl α‑Diones To Form Conjugated Ynones and Disubstituted Alkynes

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    A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono- and double-decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of unstrained C–C bonds under nonoxidative conditions is presented

    Controlled Rh-Catalyzed Mono- and Double-decarbonylation of Alkynyl α‑Diones To Form Conjugated Ynones and Disubstituted Alkynes

    No full text
    A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono- and double-decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of unstrained C–C bonds under nonoxidative conditions is presented
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