Browsing by Subject "Organic compounds"

Now showing 1 - 3 of 3
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    Diastereoselective Intramolecular Heck Reaction Assisted by an Acetate Group: Synthesis of the Decahydrobenzofluorene Derivative Dasyscyphin E
    (American Chemical Society, 2017-08-15) Jimenez, Fermin; Fernandez, Antonio; Boulifa, Ettahir; Mansour, Ahmed Ibn; Alvarez-Manzaneda, Ramon; Chahboun, Rachid; Alvarez-Manzaneda, Enrique; Química Orgánica
    The first synthesis of antifungal sesquiterpene quinol dasyscyphin E was achieved starting from trans-communic acid. The process described involves the first diastereoselective synthesis of this type of compound by cyclization of an aryl bicyclosesquiterpene. The acid was efficiently transformed into a sesquiterpene synthon, which was converted into the corresponding bromoaryl sesquiterpene. The key step of synthetic sequence was the cyclization of the latter under Heck reaction conditions, which yielded the tetracyclic skeleton of the target compound with complete diastereoselectivity. The participation of an acetate group is decisive, both for the course of the Heck reaction and for the stereoselectivity of the process.
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    Kinetics and mechanistic insights into the acetate-assisted dimerization of terminal alkynes under ruthenium- and acid-promoted (RAP) catalysis
    (American Chemical Society, 2017-09-21) Salvio, Riccardo; Juliá Hernández, Francisco; Pisciottani, Luca; Mendoza-Meroño, Rafael; García-Granda, Santiago; Bassetti, Mauro; Química Inorgánica
    The mechanism of the dimerization of terminal aryl alkynes promoted by [{RuCl(μ-Cl)(η6-p-cymene)}2](1)/AcOH, under cooperative transition metal/Brønsted acid catalysis, has been investigated with regard to (i) the activation of the dinuclear ruthenium complex and (ii) the catalytic formation of the trans-1,4-diaryl-1,3-enyne products, by a detailed kinetic investigation of both processes. Complex 1 is subject to a slow solvolytic process in neat acetic acid or is transformed rapidly in the presence of sodium acetate to form the monomeric ruthenium(II) acetato complex [RuCl(η6-pcymene)(OAc)]. The latter is the active catalytic species promoting the alkyne dimerization process, via initial π-alkyne coordination and intramolecular C−H abstraction by the acetate ligand, as key steps of the catalytic cycle. The presence of additive acetate salts allows for the reaction to proceed at room temperature with short reaction times and high trans/cis stereoselectivity, thus rendering this catalytic system among the most active and selective procedures for the dimerization of terminal alkynes in a protic medium. The linear coupling of three molecules of phenylacetylene affords an organometallic ruthenium complex featuring a butenynyl ligand which has been characterized by X-ray crystallography.
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    Site-selective catalytic carboxylation of unsaturated hydrocarbons with CO2 and water
    (American Chemical Society, 2017-08-16) Gaydou, Morgane; Moragas, Toni; Juliá Hernández, Francisco; Martin, Ruben; Química Inorgánica
    A catalytic protocol that reliably predicts and controls the site-selective incorporation of CO2 to a wide range of unsaturated hydrocarbons utilizing water as formal hydride source is described. This platform unlocks an opportunity to catalytically repurpose three abundant, orthogonal feedstocks under mild conditions.