8 research outputs found

    Preparation of Chiral 3-Arylpyrrolidines via the Enantioselective 1,4-Addition of Arylboronic Acids to Fumaric Esters Catalyzed by Rh(I)/Chiral Diene Complexes

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    A highly efficient rhodium-catalyzed protocol for the preparation of 2-arylsuccinic esters and 3-arylpyrrolidines of high optical purity has been achieved. In the presence of 1 mol % of a chiral diene/Rh(I) catalyst, asymmetric addition of various arylboronic acids to di-<i>tert</i>-butyl fumarate (<b>3c</b>) provides the corresponding adducts in up to 99% yield and 94→99.5% ee. Excellent enantioselectivities were also observed in the regio- and enantioselective conjugate addition of phenylboronic acid (<b>4a</b>) to compound <b>3e</b>

    Aerobic Oxidative Coupling of 2‑Naphthol Derivatives Catalyzed by a Hexanuclear Bis(μ-hydroxo)copper(II) Catalyst

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    A novel hexanuclear bis­(μ-hydroxo)­copper­(II) complex, [<b>L</b><sub>3</sub>(Cu<sub>2</sub>(μ-OH)<sub>2</sub>)<sub>3</sub>]­(ClO<sub>4</sub>)<sub>6</sub> (<b>1</b>), was synthesized with dinucleating ligand <i>N</i>,<i>N</i>,<i>N</i>,<i>N</i>-tetra­(pyridin-2-ylmethyl)-<i>m</i>-xylene diamine (<b>L</b>). Complex <b>1</b> is fully characterized by X-ray crystallography and magnetic susceptibility in the solid state and UV–vis and electron paramagnetic resonance spectroscopy in solution. The molecular structure of <b>1</b> possesses three dicopper cores, in which two copper centers are bridged by two hydroxide groups and separated by a distance ranging from 2.8852(15) to 2.8937(10) Å. In addition, the three dicopper cores are linked by the dinucleating ligand between each pair of adjacent dicopper cores. Importantly, aerobic oxidative coupling of 2,4-di-<i>tert</i>-butylphenol, 2-naphthol, and six 2-naphthol derivatives was achieved in 33–96% yield using complex <b>1</b> as a catalyst

    Rhodium/Chiral Diene Complexes in the Catalytic Asymmetric Arylation of β‑Pyrazol-1-yl Acrylates

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    The asymmetric conjugate addition of arylboronic acids to substituted and unsubstituted β-pyrazol-1-yl (<i>E</i>)-<i>tert</i>-butyl acrylates <b>4</b> catalyzed by 5 mol % of the Rh­(I)/diene <b>2a</b> catalyst provided the corresponding addition products in 44–98% yield and 91–>99.5% ee. The method was applied to the formal synthesis of (3<i>S</i>)-3-aryl-3-(pyrazol-1-yl)­propanoic acid <b>1b</b> with agonistic activity toward the human GPR40 G-protein coupled receptor

    Rh-Catalyzed Enantioselective Allylation of <i>N</i>‑Tosyl- and <i>N</i>‑Nosylaldimines: Total Synthesis of (−)-Crispine A

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    The unprecedented development of asymmetric Rh-catalyzed 1,2-allylation of <i>N</i>-Ts- and <i>N</i>-Ns-aldimines is achieved. This protocol utilizes potassium allyltrifluoroborates and various aldimines to generate enantioenriched homoallylic amines in the presence of 3.0 mol % of Rh­(I)/<b>L1b</b> catalyst with up to 90% yield, 98% ee (R = H), and 10:1 diastereoselectivity (R = Me or Ph), yielding the same major diastereomer when using potassium (<i>E</i>)- and (<i>Z</i>)-crotyltrifluoroborate. Its synthetic utility is also illustrated in the total synthesis of (−)-crispine A

    Rh(I)-Catalyzed 1,4-Conjugate Addition of Alkenylboronic Acids to a Cyclopentenone Useful for the Synthesis of Prostaglandins

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    An efficient and <i>trans</i>-diastereoselective Rh­(I)-catalyzed 1,4-conjugate addition reaction of alkenylboronic acids and a homochiral (<i>R</i>)-4-silyloxycyclopentenone useful for the synthesis of derivatives of prostaglandins E and F is described for the first time. The reaction functions under mild conditions and is particularly rapid (≤6 h) under low power (50 W) microwave irradiation at 30 °C in MeOH in the presence of a catalytic amount of KOH. Under these conditions, 3 mol % of [RhCl­(COD)]<sub>2</sub> is typically required to produce high yields. The method also functions without microwave irradiation at 3 °C in the presence of a stoichiometric amount of KOH. Under these conditions, only 1.5 mol % of [RhCl­(COD)]<sub>2</sub> is needed, but the reaction is considerably slower. The method accepts a range of aryl- and alkyl-substituted alkenylboronic acids, and its utility has been demonstrated by the synthesis of PGF<sub>2α</sub> (dinoprost) and tafluprost

    Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to β‑Nitroolefins: Formal Synthesis of (<i>S</i>)‑SKF 38393

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    An efficient enantioselective addition of an array of arylboronic acids to various β-nitrostyrenes catalyzed by a novel and reactive rhodium–diene catalyst (S/C up to 1000) was developed, providing β,β-diarylnitroethanes in good to high yields (62–99%) with excellent enantioselectivities (85–97% ee). The method was extended to 2-heteroarylnitroolefins and 2-alkylnitroolefins similarly providing the desired products with high enantioselectivities and yields. The usefulness of this method was demonstrated in the formal synthesis of the enantiomer of the dopamine receptor agonist and antagonist, SKF 38393

    Enantioselective and Rapid Rh-Catalyzed Arylation of <i>N</i>‑Tosyl- and <i>N</i>‑Nosylaldimines in Methanol

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    Enantiomerically enriched tosyl-protected diarylmethylamines were rapidly prepared by the asymmetric addition of arylboronic acids to <i>N</i>-tosylaldimines under mild conditions in the presence of a catalyst prepared in situ from Rh­(I) and a chiral diene ligand. This methodology offers access to diarylmethylamines in good yields with excellent chiral purity at room temperature using MeOH as a solvent and NEt<sub>3</sub> as a base. Its synthetic utility was demonstrated by the preparation of (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline (<b>14</b>), an antagonist of the <i>N</i>-methyl-d-aspartate (NMDA) receptor

    Enantioselective and Rapid Rh-Catalyzed Arylation of <i>N</i>‑Tosyl- and <i>N</i>‑Nosylaldimines in Methanol

    No full text
    Enantiomerically enriched tosyl-protected diarylmethylamines were rapidly prepared by the asymmetric addition of arylboronic acids to <i>N</i>-tosylaldimines under mild conditions in the presence of a catalyst prepared in situ from Rh­(I) and a chiral diene ligand. This methodology offers access to diarylmethylamines in good yields with excellent chiral purity at room temperature using MeOH as a solvent and NEt<sub>3</sub> as a base. Its synthetic utility was demonstrated by the preparation of (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline (<b>14</b>), an antagonist of the <i>N</i>-methyl-d-aspartate (NMDA) receptor
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