Palladium-Catalyzed Amination of Aryl Halides with Aqueous Ammonia and Hydroxide Base Enabled by Ligand Development.

The conversion of aryl halides to primary arylamines with a convenient and inexpensive source of ammonia has been a long-standing synthetic challenge. Aqueous ammonia would be the most convenient and least expensive form of ammonia, but such a palladium-catalyzed amination reaction with a high concentration of water faces challenges concerning catalyst stability and competing hydroxylation, and palladium-catalyzed reactions with this practical reagent are rare. Further, most reactions with ammonia to form primary amines are conducted with tert-butoxide base, but reactions with ammonium hydroxide would contain hydroxide as base. Thus, ammonia surrogates, ammonia in organic solvents, and ammonium salts have been used under anhydrous conditions instead with varying levels of selectivity for the primary amine. We report the palladium-catalyzed amination of aryl and heteroaryl chlorides and bromides with aqueous ammonia and a hydroxide base to form the primary arylamine with high selectivity. The palladium catalyst containing a new dialkyl biheteroaryl phosphine ligand (KPhos) suppresses both the formation of aryl alcohol and diarylamine side products. Mechanistic studies with a soluble hydroxide base revealed turnover-limiting reductive elimination of the arylamine and an equilibrium between arylpalladium amido and hydroxo complexes prior to the turnover-limiting step.

Chemical Modification of Oxidized Polyethylene Enables Access to Functional Polyethylenes with Greater Reuse.

Polyethylene is a commodity material that is widely used because of its low cost and valuable properties. However, the lack of functional groups in polyethylene limits its use in applications that include adhesives, gas barriers, and plastic blends. The inertness of polyethylene makes it difficult to install groups that would enhance its properties and enable programmed chemical decomposition. To overcome these deficiencies, the installation of pendent functional groups that imbue polyethylene with enhanced properties is an attractive strategy to overcome its inherent limitations. Here, we describe strategies to derivatize oxidized polyethylene that contains both ketones and alcohols to monofunctional variants with bulk properties superior to those of unmodified polyethylene. Iridium-catalyzed transfer dehydrogenation with acetone furnished polyethylenes with only ketones, and ruthenium-catalyzed hydrogenation with hydrogen furnished polyethylenes with only alcohols. We demonstrate that the ratio of these functional groups can be controlled by reduction with stoichiometric hydride-containing reagents. The ketones and alcohols serve as sites to introduce esters and oximes onto the polymer, thereby improving surface and bulk properties over those of polyethylene. These esters and oximes were removed by hydrolysis to regenerate the original oxygenated polyethylenes, showing how functionalization can lead to materials with circularity. Waste polyethylenes were equally amenable to oxidative functionalization and derivatization of the oxidized material, showing that this low- or negative-value feedstock can be used to prepare materials of higher value. Finally, the derivatized polymers with distinct solubilities were separated from mechanically mixed plastic blends by selective dissolution, demonstrating that functionalization can lead to novel approaches for distinguishing and separating polymers from a mixture.

Diverse functional polyethylenes by catalytic amination.

Functional polyethylenes possess valuable bulk and surface properties, but the limits of current synthetic methods narrow the range of accessible materials and prevent many envisioned applications. Instead, these materials are often used in composite films that are challenging to recycle. We report a Cu-catalyzed amination of polyethylenes to form mono- and bifunctional materials containing a series of polar groups and substituents. Designed catalysts with hydrophobic moieties enable the amination of linear and branched polyethylenes without chain scission or cross-linking, leading to polyethylenes with otherwise inaccessible combinations of functional groups and architectures. The resulting materials possess tunable bulk and surface properties, including toughness, adhesion to metal, paintability, and water solubility, which could unlock applications for functional polyethylenes and reduce the need for complex composites.

Understanding the Structural Evolution of IrFeCoNiCu High-Entropy Alloy Nanoparticles under the Acidic Oxygen Evolution Reaction.

High-entropy alloy (HEA) nanoparticles are promising catalyst candidates for the acidic oxygen evolution reaction (OER). Herein, we report the synthesis of IrFeCoNiCu-HEA nanoparticles on a carbon paper substrate via a microwave-assisted shock synthesis method. Under OER conditions in 0.1 M HClO4, the HEA nanoparticles exhibit excellent activity with an overpotential of ∼302 mV measured at 10 mA cm-2 and improved stability over 12 h of operation compared to the monometallic Ir counterpart. Importantly, an active Ir-rich shell layer with nanodomain features was observed to form on the surface of IrFeCoNiCu-HEA nanoparticles immediately after undergoing electrochemical activation, mainly due to the dissolution of the constituent 3d metals. The core of the particles was able to preserve the characteristic homogeneous single-phase HEA structure without significant phase separation or elemental segregation. This work illustrates that under acidic operating conditions, the near-surface structure of HEA nanoparticles is susceptible to a certain degree of structural dynamics.

Extralobar pulmonary sequestration with an unusual venous drainage to the portal vein: preoperative diagnosis and excision by video-assisted thoracoscopy.

Pulmonary sequestration is an uncommon congenital malformation of the lung that can be classified as intralobar or extralobar (ELS). Approximately 90% of ELS occur in the left hemithorax. Approximately 10% of ELS may present below the diaphragm. Both types of sequestrations are characterized by pulmonary tissue that does not communicate with the bronchial tree. The arterial blood supply to 80% ELS is through a direct branch of the thoracic or abdominal aorta, in 15% via another systemic artery and 5% from the pulmonary artery. The venous drainage of ELS is variable, predominantly into the systemic circulation (via the azygos vein, hemiazygos vein, or inferior vena cava). Approximately 25% drain completely or partially through the pulmonary veins. We report an extremely rare case of ELS with unusual venous drainage to the portal vein.

Hierarchical zinc oxide materials with multiple porosity prepared by ultrafast temperature gradient chemical gas-phase synthesis.

The preparation of materials characterized by three types of porosity could be prepared by a continuous chemical gas-phase method. The multistep formation mechanism involves a critical temperature gradient and occurs within seconds. The resulting hollow aerogel materials show superior properties as gas sensors in comparison to materials constructed from compact nanoparticles.

A new class of surfactants with multinuclear, inorganic head groups.

The main ability of amphiphilic molecules is to alter the energy of interfaces. They aid in the formation of various materials characterized by a high surface to volume ratio. Furthermore, amphiphiles tend to self-organize into structures of higher complexity. In the current study anionic surfactants containing a purely inorganic multinuclear head group of the polytungstate type R-[PW(11)O(39)](3-) were synthesized. Alkyl chains of different length were attached to the head group via siloxy bridges. Furthermore, the counterions could be varied. Ultimately, a heteropolyacid surfactant (H(+) as the counterion) could be prepared. The self-assembly behavior of the polyoxometalate surfactants into micelles and even lyotropic phases was studied. For instance, the formation of a phase with P6/mm symmetry containing hexagonally packed cylinders has been observed. Finally, it was possible to extend the functionality of classical amphiphiles. The polyoxometalate amphiphiles have been used for the emulsification of and, at the same time, as the initiator for the cationic polymerization of styrene. As a result, interesting organic-inorganic hybrid polymer latexes with surfaces containing heteropolyacid entities were prepared.

Chromium containing zinc oxide materials from organobimetallic precursors.

Zinc oxide has become one of the most important semiconductor materials and it possesses a multitude of properties and applications. An even wider spectrum of properties can be envisioned if an additional element is introduced. On the cation side there is large interest in the combination of ZnO with paramagnetic metal centres like Cr(III). Two new single source precursors containing "ZnO" and chromium in the ratios 1 : 1 and 1 : 2 are presented. Advantages and disadvantages of using these precursors are reported. One of the advantages is that the geometric organization of the magnetic centres in the ZnO matrix can be preorganized on the molecular scale.

Intrauterine intussusception: a rare cause of intestinal atresia.

Intrauterine intussusception is an uncommon cause of intestinal atresia. We report a case of ileal atresia owing to antenatal intussusception revealed as an intraluminal polypoid lesion after surgical intervention.

Double cervical cyst derived from a single thyroglossal duct tract.

Thyroglossal duct cysts are one of the most common congenital cervical pathologic findings in children. This type of cyst can be located anywhere between the base of the tongue and the sternal manubrium. We report the case of a patient with a double thyroglossal cyst, one located in the hyoid region and the other in the thyroid gland. The 2 cysts were connected by a permeable tract, which confirms that an involution failure of the embryonic remains of the thyroglossal duct was responsible for the development of the cyst. Intrathyroid cysts of the thyroglossal duct, though uncommon, should be included in the differential diagnosis of thyroid cysts in children.

Tratamiento del pectus excavatum mediante toracoplastia percutánea videoasistida / Treatment of pectus excavatum with videoassisted percutaneous thoracoplasty

Fundamento. La deformación congénita más frecuentede la caja torácica es el pectus excavatum (PE): 95% de loscasos. PE es una malformación de los cartílagos costalesque comporta la respiración paradójica o invertida del pacientedesde la fase de la lactancia con hundimiento progresivodel esternón y deformación de toda la caja torácica.El tratamiento clásico del PE ha consistido entoracoplastia «a demanda» con resección subpericondralde todas las uniones costoesternales patológicas. La posibilidadde tratar esta afección mediante una técnica pocoinvasiva es una consideración que se debe evaluar.Objetivo. La finalidad de este trabajo es la presentaciónde nuestra experiencia en el tratamiento del PE mediantetoracoplastia percutánea videoasistida (TPV) segúnla técnica descrita por Nuss.Método. Desde el 14 de junio de 2001 a mayo de 2004hemos tratado 21 casos de PE grave mediante TPV. Todoslos casos correspondían a hombres de edades comprendidasentre 3 y 21 años (media edad: 10,4). Las exploracionescomplementarias requeridas son RX de tórax simple, pruebasde función respiratoria, ecocardiografía y TAC torácica conmedición de Indice de Haller (diámetro máximo LL / diámetromínimo del PE, considerando patológico un índice superior a3,2). El método quirúrgico se realiza bajo anestesia convencionale intubación orotraqueal. Con asistencia toracoscópicade 5 mm colocada en 7º espacio intercostal derecho seprocede a la reducción de la deformación y ferulización ortésicamediante una férula previamente configurada.Resultados. El tiempo medio ha sido de 65 minutos. Laspérdidas hemáticas son inapreciables (10-20 ml). Estanciamedia de 6.5 días. Como complicación se apreció un seroma en dos casos y granulomas en uno. La ortesis ha sido bientolerada en todos los casos, reintegrándose a su vida normala los 16 días de media. La férula ha sido ya retirada enseis pacientes por finalización del tratamiento. Todos loscasos se han reintegrado socialmente, y se ha conseguidouna adaptación rápida a la actividad física escolar. Seis pacientesque previamente presentaban cuadros bronconeumónicosde repetición no los han vuelto a sufrir. El resultadoestético es evidente desde la salida del quirófano, yaque únicamente se detectan tres pequeñas señales, quecon el tiempo se hacen imperceptibles. El beneficio económicose cifra en un 40% del procedimiento convencional.Conclusiones. Consideramos la TPV como un métodoatractivo del cual se pueden beneficiar todos los pacientesafectos de PE simétrico severo con independencia de suedad

Background. Pectus excavatum (PE) is the most commoncongenital malformation of the chest wall, accountingfor 95% of all cases. PE is a deformity of the cartilages ofthe chondrosternal joint that leads to inverted breathingand progressive chest deformity. Classic repair of PE is openthoracoplasty with subperichondral resection of the chondrosternaljoints. Alternative, less aggressive procedures,with minimally invasive techniques should be considered.Objective. The aim of this paper is to present our experiencein the treatment of PE with videoassisted percutaneousthoracoplasty (VPT), as previously described by Nuss.Patients and Methods. From June 2001 to May 2004,21 patients with severe PE were treated with VPT in our institution.All the patients were males, aged 3 to 21 years(mean 10.4 years). Chest XR, pulmonary function tests,echocardiography, and CT scan with measurement ofHaller index (LL diameter / AP diameter on the PE, andconsidering abnormal a ratio > 3.2) were the required diagnosticprocedures. Surgery was performed under generalanesthesia, with orotracheal intubation. The deformitywas corrected with the placement of previouslyconformed orthesis using videoassisted thoracoscopythrough the 7th intercostal space.Results. The mean duration of the intervention was 65minutes. Blood losses were minimal (10-20 ml), and themean length of hospitalization was 6.5 days (range 5 to 14days). Complications included seroma in 2 cases andwound granuloma in 1 case. The pectus bar was well toleratedin all patients, and normal activity was reached at amean of 16 days. The pectus bar was removed in 6 patientsonce the treatment was completed, and no recurrenceswere observed. Six patients that had history of recurrentbronchopulmonary infections prior to the correction are freeof symptoms. The good cosmetic outcome was apparent immediatelyafter surgery. Medical costs of this technique wereestimated to be 40% of the traditional techniques.Conclusions. The VPT is an effective minimally invasivesurgical technique that can be used in the treatment of allpatients with symmetric PE, regardless of age