1,448 research outputs found
Graphene Oxide-Supported Oxime Palladacycles as Efficient Catalysts for the Suzuki–Miyaura Cross-Coupling Reaction of Aryl Bromides at Room Temperature under Aqueous Conditions
Palladacycles are highly efficient precatalysts in cross-coupling reactions whose immobilization on carbonaceous materials has been hardly studied. Herein, we report a detailed study on the synthesis and characterization of new oxime palladacycle-graphene oxide non-covalent materials along with their catalytic activity in the Suzuki–Miyaura reaction. Catalyst 1-GO, which has been fully characterized by ICP, XPS, TGA, and UV-Vis analyses has been demonstrated to be an efficient catalyst for the Suzuki–Miyaura coupling between aryl bromides and arylboronic acids using very low catalyst loadings (0.002 mol % of Pd) at room temperature under aqueous conditions.Financial support from the University of Alicante (UAUSTI16-03, UAUSTI16-10, VIGROB-173), the Spanish Ministerio de EconomÃa, Industria y Competitividad (CTQ2015-66624-P) is acknowledged
Organocatalytic Asymmetric α-Chlorination of 1,3-Dicarbonyl Compounds Catalyzed by 2-Aminobenzimidazole Derivatives
Bifunctional chiral 2-aminobenzimidazole derivatives 1 and 2 catalyze the enantioselective stereodivergent α-chlorination of β-ketoesters and 1,3-diketone derivatives with up to 50% ee using N-chlorosuccinimide (NCS) or 2,3,4,4,5,6-hexachloro-2,5-cyclohexadien-1-one as electrophilic chlorine sources.Financial support from the University of Alicante (VIGROB-173, VIGROB-285, GRE12-03, UAUSTI13-01, UAUSTI13-02), and Spanish Ministerio de EconomÃa y Competitividad (CTQ2011-24151) is acknowledged
Advanced Nuclear Magnetic Resonance
Transparencias en inglés de la asignatura "Resonancia Magnética Nuclear Avanzada" (Advanced Nuclear Magnetic Resonance) (36643) que se imparte en el Máster de QuÃmica Médica como asignatura optativa de 3 créditos ECTS. En esta asignatura se completa el estudio iniciado en la asignatura de quinto curso de la licenciatura en QuÃmica "Determinación estructural" (7448) y en la del Grado de QuÃmica de tercer curso "Determinación estructural de los compuestos orgánicos" (26030) en lo referente a técnicas bidimensionales de resonancia magnética nuclear. Además se proporcionan los conocimientos necesarios para poder interpretar RMN de otros núcleos activos en RMN no estudiados hasta el momento como 19F, 31P, 2H, 28Si y 15N asà como sus acoplamientos con los núcleos de 1H y 13C
Amino acid metabolism conflicts with protein diversity
The twenty protein coding amino acids are found in proteomes with different
relative abundances. The most abundant amino acid, leucine, is nearly an order
of magnitude more prevalent than the least abundant amino acid, cysteine. Amino
acid metabolic costs differ similarly, constraining their incorporation into
proteins. On the other hand, sequence diversity is necessary for protein
folding, function and evolution. Here we present a simple model for a
cost-diversity trade-off postulating that natural proteomes minimize amino acid
metabolic flux while maximizing sequence entropy. The model explains the
relative abundances of amino acids across a diverse set of proteomes. We found
that the data is remarkably well explained when the cost function accounts for
amino acid chemical decay. More than one hundred proteomes reach comparable
solutions to the trade-off by different combinations of cost and diversity.
Quantifying the interplay between proteome size and entropy shows that
proteomes can get optimally large and diverse
(S)-(1-Pyrrolidin-2-ylmethyl)quinuclidin-1-ium Bromide
(S)-(1-Pyrrolidin-2-ylmethyl)quinuclidine-1-ium bromide was synthesized in a six-step reaction process starting from l-proline and spectroscopically and thermally characterized.This research was funded by the Generalitat Valenciana (Project AICO 2021/013), the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN, Projects PGC2018-096616-B−I00 and PID2021-127332NB-I00) and the University of Alicante (Projects VIGROB-173 and grant UAUSTI 2021)
Microwave-assisted palladium-catalyzed highly regio- and stereoselective head to head dimerization of terminal aryl alkynes in water
A highly regio- and stereoselective oxime palladacycle/imidazolinium-catalyzed head to head dimerization of terminal aryl alkynes in water is presented. The reaction, which is carried out at 130 °C under microwave irradiation in the presence of 1,3-bis-(2,6-diisopropylphenyl)imidazolinium chloride as ligand, triethylamine as base, and TBAB as surfactant, allows the synthesis of (E)-1,4-enynes as single stereoisomers in good isolated yields.Financial support from the MINECO (CTQ2010-20387), the Generalitat Valenciana (PROMETEO/2009/038), and the University of Alicante (VIGROB-173, UAUSTI13-01) is acknowledged
Structural and adhesion properties of poly(ethyl 2-cyanoacrylate) post-cured at different temperatures and times
The structure and properties of poly(ethyl 2-cyanoacrylate)s (pECNs) cured at 25 °C during 24 hours, and post-cured at different temperatures (45-90 °C) and times (2-6 hours) were studied. Irrespective of the post-cure conditions, pECN was not fully polymerized and two different structures of different molecular weights and topographies were obtained. The post-cure decreased the shear strength values in joints made with aluminum and ethyl cyanoacrylate due to the decrease in the percentage of higher molecular weight polymeric chains and the formation of new short polymeric chains by unzipping de-polymerization mechanism, both contributed to decrease the mechanical properties. On the other hand, the post-cure changed the morphology of pECN because of nano-spheres were produced by curing at 25 °C which were not present after post-cure at 90 °C.This work was supported by the University of Alicante [VIGROB-001, VIGROB-173] and the Spanish Ministerio de EconomÃa y Competitividad [CTQ2015-66624-P]
Enantioselective Synthesis of Succinimides by Michael Addition of 1,3-Dicarbonyl Compounds to Maleimides Catalyzed by a Chiral Bis(2-aminobenzimidazole) Organocatalyst
A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.Financial support from the Ministerio de Educación y Ciencia (MEC) (project numbers CTQ2007-62771/BQU, CTQ2010-20387), from Consolider INGENIO 2010 (grant number CSD2007-00006), from the Generalitat Valenciana (PROMETEO/2009/038), from Fondos Europeos para el Desarrollo Regional (FEDER), from the University of Alicante, and from the European Union (EU) (ORCA Action CM0905) is acknowledged
- …