Browsing by Subject "Palladium"
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- PublicationOpen Access2-Arylacetamides as Versatile Precursors for 3-Aminoisocoumarin and Homophthalimide Derivatives: Palladium-Catalyzed Cascade Double Carbonylation Reactions(Wiley, 2016-07-11) Frutos-Pedreño, Roberto; García-López, José-Antonio; García-López, José-Antonio; Química Inorgánica
- PublicationOpen AccessInsertion Reactions of Isocyanides into the Metal-C(sp3) Bonds of Ylide Complexes(Elsevier, 2019-08-30) Chicote Olalla, María Teresa; Saura-Llamas, Isabel; García-Yuste, María Francisca; Bautista, Delia; Vicente, José; Química InorgánicaThe synthesis of the previously reported complexes [Pd(C,C-CHCO2R)2PPh2}(mu-Cl)]2 (R = Me (1), Et (2)) has been considerably improved by reacting the phosphonium salts [Ph2P(CH2CO2R)2]Cl with Pd(OAc)2. Complexes 1 and 2 react with isocyanides R'NC (R' = C6H4Me2-2,6 (Xy), C6H4I-2 and tBu) to give complexes of the type [Pd{C,C-{C(CO2R)=C(NHR')}(CHCO2R)PPh2}Cl(CNR')], resulting from the insertion of the unsaturated molecule in one of their Pd-C bonds and the hydrogen transfer from the methine CH to the iminobenzoyl nitrogen. These are the first insertion reactions observed in the Pd-C bond of a P-ylide complex. The crystal structure of the complex [Pd{C,C-{C(CO2Me)=C(NHXy)}(CHCO2Me)PPh2}Cl(CNXy)] (3) is reported.
- PublicationOpen AccessNorbornadiene as a Building Block for the Synthesis of Linked Benzazocinones and Benzazocinium Salts through Tetranuclear Carbopalladated Intermediates.(ACS, 2017-01-23) García-López, José Antonio; Frutos-Pedreño, Roberto; Bautista, Delia; Saura-Llamas, Isabel; Vicente, José; Química InorgánicaThe six-membered C,N-palladacycle [Pd(C,N-C6H4CH2CMe2NH2-2)(mu-Cl)]2, derived from phentermine, reacts with norbornadiene to give a di- or tetra-nuclear complex arising from the double insertion of the same molecule of the strained alkene into one or two distinct Pd-aryl bonds. The tetranuclear complex has been characterized by X-ray diffraction studies and exhibits a very unusual cisoid geometry in both, the disposition of the C,N-chelate ligands and the position of the palladium centers. The newly formed Pd–alkyl bonds are still reactive towards the insertion of unsaturated molecules and the tetranuclear complex reacts with CO or isocyanides to give double benzazocinones or benzazocinium salts with a cisoid geometry, after depalladation of the corresponding organometallic intermediates, which have been isolated in some cases. When the related palladacycles derived from phenethylamine or N-methyl-phenethylamine are used as starting materials, polymeric compounds are obtained, from which double benzazocinones or benzazocinium salts with a transoid geometry are obtained after CO or RNC insertion and subsequent depalladation. The presence of substituents on the alpha-carbon atom of the chelated amine influences the regiochemistry of the double carbopalladation of the norbornadiene.
- PublicationOpen AccessPalladium-Mediated Functionalization of Benzofuran and Benzothiophene Cores(ACS, 2018-12-24) Pérez-Gómez, Marta; Hernández-Ponte, Sergio; García-López, José Antonio; Frutos-Pedreño, Roberto; Bautista, Delia; Saura-Llamas, Isabel; Vicente, José; Química InorgánicaThe palladation reactions of 2-heteroaromatic primary phenethylamines bearing a benzofuran and benzothiophene nuclei have been studied. We have assessed the reactivity of the corresponding dimeric six-membered palladacycles (arising from C-H metalation) toward neutral ligands and unsaturated species. The insertion reactions of isocyanides into the Pd-C bond of the aforementioned palladacycles allowed the isolation of the corresponding iminoacyl intermediates, which could later be decomposed to give the amidine derivatives containing these relevant heterocyclic cores. In contrast, the carbonylation and alkenylation reactions led to straightforward formation of lactams and alkenylated organic derivatives. Interestingly, an unusual hydrogen-bond-promoted E-to-Z isomerization equilibrium of the resulting olefins was observed. Furthermore, we have studied the conditions to perform the alkenylation of the N-Boc derivatives of these substrates in a catalytic fashion. All the organometallic complexes (arising from the C-H activation of the heteroaromatic cores and insertion of isocyanides) and organic products (arising form the decomposition reactions) have been fully characterized, including the X-ray crystal structures of several organometallic and organic derivatives.
- PublicationOpen AccessPd(II)-catalyzed deprotection of acetals and ketals containing acid sensitive functional groups(Elsevier, 2014-02-05) Juliá Hernández, Francisco; Arcas, Aurelia; Vicente, José; Química InorgánicaThe pincer complex [Pd(C1,O1,N1-L)(NCMe)]ClO4 (L = monoanionic ligand resulting from deprotonation of the acetyl group of the dimethyl monoketal of 2,6-diacetylpyridine) is used for the high-yield and selective catalytic hydrolysis of aliphatic, aromatic, cyclic and acyclic dimethyl-acetals, - ketals and dioxolanes, even in the presence of large substituents. Other protecting groups, as THP or TBDMS, or very acid-sensitive alcohols were not affected. The catalyst is easily prepared in high yield from Pd(AcO)2 and 2,6-diacetylpyridinium perchlorate stable to air and moisture, easily and fully recoverable and reusable.
- PublicationOpen AccessPd-catalyzed cascade reactions involving skipped dienes: from double carbopalladation to remote C–C cleavage(2019-08-05) Azizollahi, Hamid; P. Mehta, Vaibhav; García-López, José-Antonio; Química InorgánicaWe report two ligand-controlled cascade reactions relying on the intramolecular carbopalladation of skipped dienes. The use of a bulky monodentate phosphine ligand affords [4,5]-spirocycles via sequential double carbopalladation, however bidentate phosphines promote a remote β-C-elimination process which does not rely on the use of strained or sterically hindered substrates
- PublicationOpen AccessRoom-temperature direct β-arylation of thiophenes and benzo[b]thiophenes and kinetic evidence for a Heck-type pathway(American Chemical Society, 2016-01-20) Colletto, Chiara; Islam, Saidul; Juliá Hernández, Francisco; Larrosa, Igor; Química InorgánicaThe first example of a regioselective β-arylation of benzo[b]thiophenes and thiophenes at room temperature with aryl iodides as coupling partners is reported. This methodology stands out for its operational simplicity: no prefunctionalization of either starting material is required, the reaction is insensitive to air and moisture, and it proceeds at room temperature. The mild conditions afford wide functional group tolerance, often with complete regioselectivity and high yields, resulting in a highly efficient catalytic system. Initial mechanistic studies, including 13C and 2 H KIEs, suggest that this process occurs via a concerted carbo-palladation across the thiophene double bond, followed by a base-assisted anti-elimination.
- PublicationOpen AccessRu-catalyzed C–H arylation of fluoroarenes with aryl halides(American Chemical Society, 2016-03-04) Simonetti, Marco; Perry, Gregory J. P.; Cambeiro, Xacobe C.; Juliá Hernández, Francisco; Arokianathar, Jude N.; Larrosa, Igor; Química InorgánicaAlthough the ruthenium-catalyzed C−H arylation of arenes bearing directing groups with haloarenes is wellknown, this process has never been achieved in the absence of directing groups. We report the first example of such a process and show that unexpectedly the reaction only takes place in the presence of catalytic amounts of a benzoic acid. Furthermore, contrary to other transition metals, the arylation site selectivity is governed by both electronic and steric factors. Stoichiometric and NMR mechanistic studies support a catalytic cycle that involves a well-defined η6-arene-ligandfree Ru(II) catalyst. Indeed, upon initial pivalate-assisted C−H activation, the aryl-Ru(II) intermediate generated is able to react with an aryl bromide coupling partner only in the presence of a benzoate additive. In contrast, directing-group-containing substrates (such as 2-phenylpyridine) do not require a benzoate additive. Deuterium labeling and kinetic isotope effect experiments indicate that C−H activation is both reversible and kinetically significant. Computational studies support a concerted metalation−deprotonation (CMD)-type ruthenation mode and shed light on the unusual arylation regioselectivity.
- PublicationOpen AccessLa serie RRC 458 de César(2019-01-16) Amela Valverde, LuisBreve estudio de una de las series militares más conocidas de C. Julio César (cos. I 59 a.C.), RRC 458/1, que fue acuñada en Oriente (quizás en la provincia de Asia) durante el año 47 a.C. y no en África, como se considera habitualmente.
- PublicationOpen AccessSynthesis and Reactivity of Model Intermediates Proposed for the Pd-Catalyzed Remote C−H Functionalization of N‐(2- Haloaryl)acrylamides(2017-11-14) Pérez-Gómez, Marta; Navarro, Leticia; Saura-Llamas, Isabel; Bautista, Delia; Lautens, Mark; García-López, José-Antonio; Química InorgánicaWe have studied the possible reaction pathways operating in the Pd-catalyzed remote C–H functionalization of N-(2-haloaryl)-acrylamides from an organometallic approach. We have isolated and characterized several reaction intermediates, such as σ-alkyl-Pd complexes and spiro C,C-palladacycles, and evaluated the role of the base and the auxiliary ligands coordinated to Pd in the remote C–H activation process. In addition, the reactivity of these intermediates toward different unsaturated species like benzyne, alkynes or isocyanides has been studied in order to gain further insight on the reaction mechanism leading to functionalized spiro-oxoindoles.
- PublicationOpen AccessSynthesis of [3.4]-Spirooxindoles through Cascade Carbopalladation of Skipped Dienes(Wiley, 2020-03-24) Azizollahi, Hamid; Pérez-Gómez, Marta; Mehta, V. P.; García-López, José-Antonio; García-López, José-Antonio; Química Inorgánica
- PublicationOpen AccessSynthesis of spiro-oxoindoles through Pd-catalyzed remote C–H alkylation using alpha-diazocarbonyl compounds(2017-02-10) Pérez-Gómez, Marta; Hernández-Ponte, Sergio; Bautista, Delia; García-López, José-Antonio; Química InorgánicaIn this communication we describe a new route to spiro-oxoindoles derivatives through a novel Pd-catalyzed cascade process. This reaction is based on the remote C–H activation performed by sigma-alkyl Pd(II) species generated in situ via intramolecular carbopalladation of alkenes, followed by insertion of a carbenoid coupling partner.
- PublicationOpen AccessTandem Remote Csp3−H Activation/Csp3−Csp3 Cleavage in Unstrained Aliphatic Chains Assisted by Palladium(II)(2019-02-06) Pérez-Gómez, Marta; Azizollahi, Hamid; Franzoni, Ivan; Larin, Egor M.; Lautens, Mark; García-López, José-Antonio; Química InorgánicaWe report here a proof of concept for the cleavage of unstrained remote Csp3–Csp3 bonds at room temperature assisted by a directing group, opening up new possibilities to use aliphatic carboxylic acids as suitable alkenyl coupling partners. This strategy involves the Pd-mediated Csp3–H activation directed by a tethered 8-aminoquinoline group, followed by a concerted asynchronous carbene insertion into the Pd–C bond, and an unexpected β-carbon-carbon bond splitting. The insertion of a coupling partner into a Pd–C bond is a novel route to promote C–C bond cleavage, which, in contrast to most common methodologies, does not rely on the use of strained carbocycles.
- PublicationOpen AccessTrapping σ-Alkyl–Palladium(II) Intermediates with Arynes Encompassing Intramolecular C-H Activation: Spirobiaryls through Pd-Catalyzed Cascade Reactions(Wiley, 2016-11-07) Pérez-Gómez, Marta; García-López, José-Antonio; García-López, José Antonio; Química Inorgánica
- PublicationOpen Accessσ-Alkyl-PdII Species for Remote C-H Functionalization(Wiley-VCH, 2017-04-07) García-López, José-Antonio; Mehta, V. P.; García-López, José-Antonio; Mehta, V. P.; Química Inorgánica