8 research outputs found

    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

    Cobalt-Catalyzed Intramolecular Alkyne/Benzocyclobutenone Coupling: C–C Bond Cleavage via a Tetrahedral Dicobalt Intermediate

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    A Co(0)-catalyzed intramolecular alkyne/benzocyclobutenone coupling through C–C cleavage of benzocyclobutenones is described. Co<sub>2</sub>(CO)<sub>8</sub>/P­[3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>]<sub>3</sub> was discovered to be an effective metal/ligand combination, which exhibits complementary catalytic activity to the previously established rhodium catalyst. In particular, the C8-substituted substrates failed in the Rh system, but succeeded with the Co catalysis. Experimental and computational studies show that the initially formed tetrahedral dicobalt-alkyne complex undergoes C1–C2 activation via oxidative addition with Co(0), followed by migratory insertion and reductive elimination to give the β-naphthol products

    Chromosome composition of F<sub>1</sub> hybrids and BC<sub>1</sub> progeny.

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    <p><b>Note:</b> The modal number of chromosomes is presented for the sugarcane clones analysed, since small variation of chromosome counts can occur due to the loss or the overlapping of a few chromosomes from the preparation.</p><p>Chromosome composition of F<sub>1</sub> hybrids and BC<sub>1</sub> progeny.</p

    Schematic of seven meiosis scenarios with two pairs of homologous chromosomes.

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    <p>(A) NM: normal meiosis; (B) FDR: first meiotic division restitution; (C) SDR: second meiotic division restitution; (D) NHC: nondisjunction of homologous chromosomes in first meiotic division; (E) NSC: nondisjunction of sister chromatids in second meiotic division; (F) NHC+SDR: nondisjunction of homologous chromosomes in first meiotic division and second division restitution; (G) FDR+NSC: first division restitution and nondisjunction of a chromosome with sister chromatids in the second meiotic division. For simplicity, recombination events are not illustrated in these meiosis schematics.</p

    Palladium-Catalyzed Carbene Migratory Insertion Using Conjugated Ene–Yne–Ketones as Carbene Precursors

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    Palladium-catalyzed cross-coupling reactions between benzyl, aryl, or allyl bromides and conjugated ene–yne–ketones lead to the formation of 2-alkenyl-substituted furans. This novel coupling reaction involves oxidative addition, alkyne activation–cyclization, palladium carbene migratory insertion, β-hydride elimination, and catalyst regeneration. Palladium (2-furyl)­carbene is proposed as the key intermediate, which is supported by DFT calculations. The palladium carbene character of the key intermediate is validated by three aspects, including bond lengths, Wiberg bond order indices, and molecular orbitals, by comparison to those reported for stable palladium carbene species. Computational studies also revealed that the rate-limiting step is ene–yne–ketone cyclization, which leads to the formation of the palladium (2-furyl)­carbene, while the subsequent carbene migratory insertion is a facile process with a low energy barrier (<5 kcal/mol)