Solvent- and Ligand-free Diboration of Alkynes and Alkenes Catalyzed by Platinum Nanoparticles on Titania

Platinum nanoparticles supported on titania efficiently catalyzed the diboration of alkynes and alkenes under solvent- and ligand-free conditions in air. The cis-1,2-diborylalkenes and 1,2-diborylalkanes were obtained in moderate to excellent yields following, in most cases, a simple filtration workup protocol. The versatility of the cis-1,2-diboronvinyl compounds was demonstrated in a series of organic transformations, including the Suzuki–Miyaura cross coupling and the boron–halogen exchange.

Recent Advances in the Catalytic Enantioselective Reformatsky Reaction

This paper reviews the present state of the catalytic enantioselective Reformatsky reaction. Advancements in asymmetric versions of this reaction have recently led to a considerable extension of its scope and applicability, principally due to the use of highly active chiral ligands and very specific reaction conditions.

Catalyzed addition of acid chlorides to alkynes by unmodified nano-powder magnetite: synthesis of chlorovinyl ketones, furans, and related cyclopentenone derivatives

Inexpensive and commercially available nano-powder magnetite is an excellent catalyst for the addition of acid chlorides to internal and terminal alkynes, yielding the corresponding chlorovinyl ketones in good yields. The process has been applied to the synthesis of 5-chloro-4-arylcyclopent-2-enones, 3-aryl-1H-cyclopenta[a]naphthalen-1-ones, and (E)-3-alkylidene-2,3-dihydro-1H-cyclopenta[a]naphthalen-1-ones, just by changing the nature of the starting acid chloride or the alkyne. All tested processes elapse with an acceptable or excellent regio- and stereo-selectivity. Moreover, the use of the iridium impregnated on magnetite catalyst permits the integration of the chloroacylation process with a second dehydrochlorination–annulation process to yield, in one-pot, 1-aryl-2,4-dialkylfurans in good yields, independently of the nature of the starting reagents, and including the heteroaromatic ones.

Environmentally friendly and regioselective C3-alkylation of indoles with alcohols through a hydrogen autotransfer strategy

The direct alkylation of indoles using KOH and alcohols, as initial source of the electrophile, under solvent-free conditions is a safe and environmentally benign strategy for selective modification of these structures at the C3-position, without using hazardous and difficult to handle bromide or iodide derivatives or toxic and expensive transition metal catalysts. The protocol shows a broad scope, including halogenated indoles and secondary alcohols.

Copper-Impregnated Magnetite as a Heterogeneous Catalyst for the Homocoupling of Terminal Alkynes

Copper-impregnated magnetite is a versatile heterogeneous catalytic system for the synthesis of 1,3-diynes by the homocoupling of terminal alkynes. This catalyst does not require the use of pressurized oxygen as the oxidant and it does not need a solvent or harsh conditions to give the expected products. Moreover, the catalyst can be removed from the reaction medium simply by using a magnet. The reaction occurs at the lowest copper loading reported for any heterogeneous catalyst.

NHC-Ligand Effectiveness in the Fluorine-Free Hiyama Reaction of Aryl Halides

1-Benzyl-3-(2-hydroxy-2-phenylethyl)imidazolium chloride (5), which is a precursor of an N-heterocyclic carbene ligand, in combination with palladium acetate, has been employed as an effective catalyst for the fluorine-free Hiyama reaction. A systematic study of the catalytic mixture, by a 32 factorial design, has revealed that both the amount of palladium and the Pd/NHC precursor ratio are important factors for obtaining good yields of the coupling products, indicating an interaction between them. The best catalytic system involves mixing 0.1 mol-% palladium acetate in a 1:5 ratio (Pd/salt 5), which allows the effective coupling of a range of aryl bromides and chlorides with trimethoxy(phenyl)silane. The Hiyama reactions are carried out in NaOH solution (50 % H2O w/w), at 120 °C under microwave irradiation during 60 min.

Osmium Catalyst for the Borrowing Hydrogen Methodology: α-Alkylation of Arylacetonitriles and Methyl Ketones

Complex [Os(η6-p-cymene)(OH)(IPr)]OTf is an efficient catalyst precursor for the α-alkylation of arylacetonitriles and methyl ketones with alcohols, which works with turnover frequencies between 675 and 176 h–1 for nitriles and between 194 and 28 h–1 for ketones.

Intramolecular Bromoamination of Conjugated N-Tosylaminodienes Using N-Bromosuccinimide. Synthesis of Bromoallyl-Substituted N-Heterocycles and Their Applications as Building Blocks

The bromonium-promoted cyclization of conjugated aminodienes is described. The reaction proceeds smoothly in the presence of N-bromosuccinimide as halonium promoter, and using N-tosyl-protected aminodienes as substrates, to give the corresponding halocyclization products in high yields and with high diastereoselectivities. It can be envisaged that the formation of these products is the result of an SN2′-type ring-opening of a terminal bromonium intermediate in a 5-exo-trig or 6-exo-trig cyclization mode. The presence of an allyl bromide moiety in the haloamination products makes these molecules highly attractive from a synthetic point of view, as it opens the way for further transformations. Thus, allylic substitution reactions with different nucleophiles (acetate, azide, cyanide, and malonate), palladium-catalysed Suzuki coupling, and silver-mediated bromine displacement reactions were carried out successfully.

Copper-Catalyzed Asymmetric Alkylation of β-Keto Esters with Xanthydrols

The copper(II) triflate-tert-butyl-bisoxazoline [Cu(OTf)2-t-Bu-BOX]-catalyzed asymmetric alkylation of β-keto esters using free benzylic alcohols such as xanthydrols, as alkylating agents, is herein described for the first time. This green protocol renders in general the corresponding products with good results in terms of both yields and enantioselectivities using different keto esters, even when quaternary stereocenters were created. The scope, limitations and mechanistic aspects of the process are also discussed.

Direct Nucleophilic Substitution of Free Allylic Alcohols in Water Catalyzed by FeCl3⋅6 H2O: Which is the Real Catalyst?

The allylic substitution reaction, and particularly the direct allylic amination reaction, of free allylic alcohols in water catalyzed by FeCl3⋅6 H2O is described. This novel environmentally-friendly methodology allows the use of a wide variety of nitrogenated nucleophiles such as sulfonamides, carbamates, benzamides, anilines, benzotriazoles, and azides, generally giving good yields of the corresponding substitution products. The synthetic applicability of the process is also demonstrated because the reaction can be performed on gram-scale. Additionally, carbon nucleophiles such as silylated nucleophiles, aromatic compounds, and malonates also proved to be suitable for this transformation. Finally, the nature of the catalytic species present in aqueous media is unveiled, pointing towards the formation of hexaaquo iron(III) complexes.

Role of potassium orbitals in the metallic behavior of K3picene

Detailed electronic structure calculations of picene clusters doped by potassium modeling the crystalline K3picene structure show that while two electrons are completely transferred from potassium atoms to the lowest-energy unoccupied molecular orbital of pristine picene, the third one remains closely attached to both material components. Multiconfigurational analysis is necessary to show that many structures of almost degenerate total energies compete to define the cluster ground state. Our results prove that the 4s orbital of potassium should be included in any interaction model describing the material. We propose a quarter-filled two-orbital model as the most simple model capable of describing the electronic structure of K-intercalated picene. Precise solutions obtained by a development of the Lanczos method show low-energy electronic excitations involving orbitals located at different positions. Consequently, metallic transport is possible in spite of the clear dominance of interaction over hopping.

First aromatic ring acetamidation by anodic oxidation

Anodic oxidation of 1-(trifluoromethyl)benzene in dry acetonitrile/Bu4NBF4 under constant potential conditions led to 2-(trifluoromethyl) acetanilide in 86% yield. Other experimental conditions, as the use of constant current or the change in the supporting electrolyte were considered.

Congreso de Estudiantes de Química de la Comunidad Valenciana. Otra forma de aprender es posible

En abril de 2013 se celebró en la Universidad de Alicante el I Congreso de Estudiantes de Química de la Comunidad Valenciana. Estas jornadas presentan como principal novedad que la totalidad del comité organizador está compuesto por estudiantes de Química (cinco de la Universidad de Alicante y dos de la Universidad de Valencia) apoyados por un comité científico formado por profesores de ambas universidades. Estos estudiantes habían participado en años anteriores en redes de innovación docente o proyectos similares, mostrando interés por proponer alternativas a las clases magistrales para la adquisición de competencias, tanto de tipo transversal como específicas de la titulación. El congreso se enfocó teniendo en cuenta tres puntos básicos que son de especial interés para estudiantes de Química: (i) Salidas profesionales; (ii) Búsqueda activa de empleo y como enfrentarse a una entrevista de trabajo; (iii) Estudios de postgrado. Además, los más de 100 estudiantes que participaron en las jornadas ya sea mediante una comunicación oral, un póster o una actividad de divulgación científica se mostraron muy satisfechos con la experiencia. Actividades de este tipo y su gran acogida son capaces de mostrarnos, tanto a estudiantes como profesores, que existen formas de aprendizaje fuera de las aulas que permiten la adquisición de competencias transversales y específicas.

Influencia del proceso de evaluación continua en la calificación final de asignaturas de grado del área de Química Orgánica

En la presente memoria se detallan los resultados del análisis comparativo del proceso de evaluación continua, así como su influencia en la calificación final del alumno, en diferentes asignaturas de grado adscritas al área de conocimiento de Química Orgánica: Grado de Biología y Ciencias del Mar, asignatura Química, código 26510; Grado de Química, asignatura Determinación Estructural de Compuestos Orgánicos, código 26030; Grado en Óptica y Optometría, asignatura Química, código 24014 y Grado en Ingeniería Química, asignatura Química Orgánica Aplicada, código 34513. Dicho análisis comparativo es fruto de los resultados obtenidos por el alumno en las diversas metodologías y estrategias docentes aplicadas en el proceso de evaluación continua que, como se verá, repercuten de manera notable en la calificación final de las asignaturas. También se pretende evaluar el rendimiento y competencias conseguidas por el alumno, destacando ventajas e inconvenientes de la evaluación continua durante el desarrollo de la asignatura. Y como último fin de este estudio se debatirá sobre las estrategias que hayan resultado más efectivas para su posible implantación en sucesivos cursos académicos.

Coordinación docente de cuarto curso de Grado en Óptica y Optometría

En el marco del proyecto de Redes de Investigación en Docencia Universitaria 2012-13 de la Universidad de Alicante se creó una red de trabajo formada por los profesores encargados de la docencia del cuarto curso de Grado en Óptica y Optometría. La experiencia adquirida durante la implementación de los tres primeros cursos de dicho Grado ha puesto de manifiesto la necesidad de que exista un trabajo previo de desarrollo de contenidos y de organización temporal. El objetivo principal de esta red ha sido la coordinación entre los profesores de las diferentes asignaturas para evitar repeticiones y asegurar la consecución de las competencias previstas, así como una buena distribución de la carga docente y de las pruebas de evaluación. Para ello, se debatieron las propuestas de las diferentes asignaturas y se estableció un cronograma global del curso ubicando todas las actividades docentes que contribuyen con un peso determinado a la calificación final. Con este cronograma se pudo visualizar la carga de trabajo del alumno semanalmente, así como debatir las dificultades a las que se enfrenta para superar las diversas pruebas de evaluación continua en una determinada asignatura y cómo éstas afectan al rendimiento del resto de asignaturas.