15 research outputs found

    Enantioselective Synthesis of Tetrahydroisoquinolines via Iridium-Catalyzed Intramolecular Friedel–Crafts-Type Allylic Alkylation of Phenols

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    An efficient iridium-catalyzed intramolecular Friedel–Crafts-type allylic alkylation reaction of phenols was developed, affording tetrahydroisoquinolines with moderate to excellent yields, enantioselectivity, and good regioselectivity

    Highly Enantioselective Synthesis of Tetrahydrocarbolines <i>via</i> Iridium-Catalyzed Intramolecular Friedel–Crafts Type Allylic Alkylation Reactions

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    A highly enantioselective synthesis of substituted tetrahydrocarbolines <i>via</i> Ir-catalyzed Friedel–Crafts type intramolecular asymmetric allylic alkylation of 2-indolyl allyl carbonates has been developed. This strategy features excellent chemoselectivity and enantioselectivity, mild reaction conditions, and an easily accessed chiral ligand

    Aerobic, Transition-Metal-Free, Direct, and Regiospecific Mono-α-arylation of Ketones: Synthesis and Mechanism by DFT Calculations

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    We disclose a facile, aerobic, transition-metal-free, direct, and regiospecific mono-α-arylation of ketones to yield aryl benzyl and (cyclo)­alkyl benzyl ketones with substitution patterns that are currently inaccessible or challenging to prepare using conventional methods. The transformation is operationally simple, scalable, and environmentally friendly. There is no need for pre-functionalization (i.e., α-halogenation or silyl enol ether formation) or the use of specialized arylating agents (i.e., diaryliodonium salts). DFT calculations suggest that the <i>in situ</i>-generated enolate undergoes direct C–C bond formation with the nitroarene followed by regioselective O<sub>2</sub>-mediated C–H oxidation

    Highly Enantioselective Synthesis of Tetrahydrocarbolines <i>via</i> Iridium-Catalyzed Intramolecular Friedel–Crafts Type Allylic Alkylation Reactions

    No full text
    A highly enantioselective synthesis of substituted tetrahydrocarbolines <i>via</i> Ir-catalyzed Friedel–Crafts type intramolecular asymmetric allylic alkylation of 2-indolyl allyl carbonates has been developed. This strategy features excellent chemoselectivity and enantioselectivity, mild reaction conditions, and an easily accessed chiral ligand

    Aerobic, Transition-Metal-Free, Direct, and Regiospecific Mono-α-arylation of Ketones: Synthesis and Mechanism by DFT Calculations

    No full text
    We disclose a facile, aerobic, transition-metal-free, direct, and regiospecific mono-α-arylation of ketones to yield aryl benzyl and (cyclo)­alkyl benzyl ketones with substitution patterns that are currently inaccessible or challenging to prepare using conventional methods. The transformation is operationally simple, scalable, and environmentally friendly. There is no need for pre-functionalization (i.e., α-halogenation or silyl enol ether formation) or the use of specialized arylating agents (i.e., diaryliodonium salts). DFT calculations suggest that the <i>in situ</i>-generated enolate undergoes direct C–C bond formation with the nitroarene followed by regioselective O<sub>2</sub>-mediated C–H oxidation

    C–H Bond Functionalization via [1,5]-Hydride Shift/Cyclization Sequence: Approach to Spiroindolenines

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    A concise synthesis of spiroindolenines from 2-substituted (Me, Et) indoles and 2-(pyrrolidin-1-yl)­benzaldehydes has been developed via a [1,5]-hydride shift/cyclization sequence. This method features a wide substrate scope and an operationally simple procedure, affording the spiroindolenines in good to excellent yields and moderate diastereoselectivity (3.5/1 dr). When the inseparable mixture of spiroindolenine isomers were washed with isopropyl ether after flash chromatography, the major isomers could be obtained in up to >20/1 dr

    Direct Intermolecular C–H Functionalization Triggered by 1,5-Hydride Shift: Access to <i>N</i>‑Arylprolinamides via Ugi-Type Reaction

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    A novel Ugi-type reaction triggered by 1,5-hydride shift has been established, giving access to <i>N</i>-arylprolinamides and related compounds in high atom economy and good yields. This is an example of a two starting material–three component reaction. The benzyl alcohol substrate <b>1</b> acts as a dual synthon, which upon treatment with a Brþnsted acid affords iminium ion and water. Nucleophilic attack at the iminium ion by the third component isocyanide, followed by hydrolysis with the endogenic water, gives the Ugi-type reaction products. The reaction proceeds under mild conditions and is tolerable to a broad scope of substrates

    Stereoselective Synthesis of Arylglycine Derivatives via Palladium-Catalyzed α‑Arylation of a Chiral Nickel(II) Glycinate

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    A practical and efficient stereoselective synthesis of arylglycine derivatives was realized via palladium-catalyzed α-arylation of a chiral nickel­(II) glycinate complex with aryl bromides. The structurally diverse arylglycine products were obtained in excellent isolated yields and with good diastereoselectivity. A simple acidic hydrolysis furnished optically pure arylglycines in high yield, and the chiral ligand (S)-BPB could be efficiently recovered and reused

    Construction of Oxadiazepines via Lewis Acid-Catalyzed Tandem 1,5-Hydride Shift/Cyclization

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    Expeditious access to oxadiazepines via 1,5-hydride shift/cyclization of pyrrolidine- or tetrahydroisoquinoline-containing nitrones has been developed. With 1,3-dipole nitrones serving as the hydride acceptors, this transformation was promoted by a Lewis acid, providing access to structurally diverse oxadiazepines in good yields. A one-pot process for in situ nitrone formation, a 1,5-hydride shift, and ring cyclization was also realized

    P<sup>III</sup>/P<sup>V</sup>‑Catalyzed Beckmann Reaction and Sequential [2,3]-Sigmatropic Rearrangement to Construct 2‑Amidopyridines

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    An organophosphorus catalytic method for the synthesis of substituted 2-amidopyridines is reported. The method employs a small-ring organophosphorus-based catalyst and a hydrosilane reductant to drive the conversion of ketoximes and pyridine-N-oxides into 2-amidopyridines through sequential Beckmann rearrangement followed by [2,3]-sigmatropic rearrangement. The readily available ketoximes could be activated to nitrilium ions in PIII/PV redox catalysis and could efficiently participate in the domino reaction of pyridine-N-oxides, thus providing various substituted 2-amidopyridines in moderate to excellent yields. This presented strategy features excellent functional group tolerance and a broad substrate scope
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