22 research outputs found

    Synthesis of Enantioenriched α,α-Dichloro- and α,α-Difluoro-β-Hydroxy Esters and Amides by Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation

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    A mild and convenient approach was developed to prepare a series of α,α-dihalogeno β-hydroxy esters or amides by using commercially available Noyori’s complex [RuCl­(<i>p</i>-cymene)­(<i>R</i>,<i>R</i>)-TsDPEN] as a catalyst (S/C = 100−200) in the asymmetric transfer hydrogenation of the corresponding ketones. Moderate to high yields (up to 99%) and excellent enantioselectivities (up to >99% ee) were achieved for a series of variously substituted dichloro and difluoro β-hydroxy esters and amides

    Ruthenium-Catalyzed [2 + 2 + 2] Cycloaddition Reaction Forming 2‑Aminopyridine Derivatives from α,ω-Diynes and Cyanamides

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    A novel, efficient, and mild synthetic route for the preparation of 2-aminopyridines via ruthenium-mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and cyanamides has been developed. This atom-economical catalytic process demonstrated remarkable regioselectivities to access pyridine derivatives of high synthetic utility

    HNTf<sub>2</sub>‑Catalyzed Regioselective Preparation of Polysubstituted Naphthalene Derivatives Through Alkyne–Aldehyde Coupling

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    We report herein the preparation of polysubstituted naphthalene derivatives by the original Brønsted-acid-catalyzed benzannulation reaction of phenylacetaldehydes with alkynes. This reaction, which was usually performed with Lewis acids under thermal activation, is efficiently promoted by 15 mol % of triflimide (HNTf<sub>2</sub>) at room temperature under metal-free and mild reaction conditions and leads with a perfect regioselectivity to a wide variety of diversely functionalized naphthalenes in 41–78% yield. A catalytic cycle is proposed together with some further applications of this catalytic system in the related benzannulation transformations of epoxide and acetal derivatives

    Access toward Fluorenone Derivatives through Solvent-Free Ruthenium Trichloride Mediated [2 + 2 + 2] Cycloadditions

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    An efficient and practical route for the preparation of highly substituted fluorenones and analogues via solvent-free ruthenium trichloride mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and alkynes has been developed. This green chemistry approach involves a solventless and atom-economical catalytic process to generate densely functionalized fluorenones and related derivatives of high synthetic utility

    Enantioselective Synthesis of 1-Aryl-tetrahydroisoquinolines through Iridium Catalyzed Asymmetric Hydrogenation

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    Asymmetric hydrogenation of 1-aryl-3,4-dihydroisoquinolines using the [IrCODCl]<sub>2</sub>/(<i>R</i>)-3,5-diMe-Synphos catalyst is reported. Under mild reaction conditions, this atom-economical process provides easy access to a variety of enantioenriched 1-aryl-1,2,3,4-tetrahydroisoquinoline derivatives, which are important pharmacophores found in several pharmaceutical drug candidates, in high yields and enantiomeric excesses up to 99% after a single crystallization

    Synthesis and Antiproliferative and Metabolic Evaluations of Novel Securinine Derivatives

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    New securinine analogues have been prepared by semisynthesis. Two series were developed using either Suzuki or Sonogashira cross coupling reactions. The <i>in vitro</i> cytotoxicity of the compounds was assayed against HCT-116 colon cancer cells. The most potent derivatives showed promising growth inhibition on four tumoral cell lines giving a valuable insight on the structure–activity relationship (SAR) of securinine. Moreover, high antiproliferative effect against A-375 (melanoma) was observed with IC<sub>50</sub> up to 60 nM

    Palladium-Catalyzed Efficient Enantioselective Synthesis of Chiral Allenes: Steric and Electronic Effects of Ligands

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    Asymmetric synthesis of chiral allenes starting from prochiral substrates under mild reaction conditions promoted by Pd-SYNPHOS catalyst is reported. This protocol provides an efficient access to various enantioenriched aryl- and alkyl- substituted allenes, which are versatile building blocks of high utility to both organic and medicinal chemists, in excellent isolated yields (up to 96%) and high enatiomeric ratio values (up to 95:5). In addition, a comparative study using several <i>C</i><sub>2</sub>-symmetric atropisomeric diphosphine ligands revealed the overwhelming impact of the steric and electronic properties of the ligands for the catalytic efficiency of this process

    Enantioselective Rhodium-Catalyzed Synthesis of α-Chloromethylene-γ-Butyrolactams from <i>N</i>-Allylic Alkynamides

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    The first enantioselective cycloisomerization with intramolecular halogen migration of various 1,6-enynes promoted by a cationic Rh-Synphos catalyst is reported. This method provides an efficient route to enantiomerically enriched γ-butyrolactam derivatives, which are important core scaffolds found in numerous natural products and biologically active molecules. Good yields and enantiomeric excesses up to 96% are achieved

    Heck Coupling Using a Vinyliodo-MIDA Boronate: An Efficient and Modular Access to Polyene Frameworks

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    A simple Heck coupling between an alkenyl iodo-boronate and a variety of terminal olefins is disclosed. This method gives access to a wide range of dienic moieties including valuable bis-functionalized dienes. The synthetic potential of the coupling reaction is demonstrated by a short and modular preparation of several tetraenic compounds
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