Phosphorous-filled nanobrick wall multilayer thin film eliminates polyurethane melt dripping and reduces heat release associated with fire

Unique trilayer (TL) thin films of sodium montmorillonite (MMT), poly(allylamine hydrochloride) (PAH) and poly(sodium phosphate) (PSP) are prepared via layer-by-layer (LbL) assembly. This three-component nanocoating completely shuts down melt dripping and reduces heat release of open-celled flexible polyurethane (PU) foam when exposed to direct flame due to a synergistic interaction between PSP and the thermally shielding clay platelets in the condensed phase. Post burn scanning electron microscopy reveals the nanocoating's swollen morphology is able to maintain foam shape, cellular structure, and porosity. Cone calorimetry reveals that 4 TL coated foams (<3 wt% addition) have a peak heat release rate that is reduced by 54% relative to the uncoated control. Using LbL assembly, this work combines two common flame-retarding mechanisms (thermal shielding clay and intumescing PAH/PSP) in a single coating system and provides a foundational platform for new environmentally-benign flame retardant strategies for various substrates (e.g., foam found in home furnishings).     

Aromatic Nucleophilic Substitution: The Reaction of Sodium 2,2,2-Trifluoroethoxide with Chlorobenzonitriles in HMPA

The preparation¹ of fluorinated compounds continues to be of significant interest to organic chemists due to their diverse and important application as polymers, blood substitutes, pharmaceuticals and pesticides. Considerable attention has been directed to the formation of fluoroalkoxy benzenes with the majority of the synthetic routes involving the reaction of an electrophilic haloalkyl fluoride with a nucleophilic phenol derivative^1,2. In a somewhat related procedure, Mendel³ has prepared ortho-2,2,2-trifluoroethoxy methyl benzoate by reacting ortho-hydroxy methyl benzoate with 2,2,2-trifluoroethyl trifluoromethylsulfonate in a potassium carbonate/acetone mixture.     

A [4 + 4] annulation strategy for the synthesis of eight-membered carbocycles based on intramolecular cycloadditions of conjugated enynes

A [4+4] annulation strategy for the synthesis of eight-membered carbocycles is reported that proceeds via a cascade involving two pericyclic processes. In the first step, the [4+2] cycloaddition of a conjugated enyne with an electron-deficient cyclobutene generates a strained six-membered cyclic allene that isomerizes to the corresponding 1,3-cyclohexadiene. In the second step, this bicyclo[4.2.0]octa-2,4-diene intermediate undergoes thermal or acid-promoted 6-electron electrocyclic ring opening to furnish a 2,4,6-cyclooctatrienone. The latter transformation represents the first example of the promotion of 6-electron electrocyclic ring opening reactions by acid.     

Synthesis of polycyclic benzofused nitrogen heterocycles via a tandem ynamide benzannulation/ring-closing metathesis strategy. Application in a formal total synthesis of (+)-FR900482

A two-stage "tandem strategy" for the synthesis of benzofused nitrogen heterocycles is described that is particularly useful for the construction of systems with a high level of substitution on the benzenoid ring. The first stage in the strategy involves a benzannulation based on the reaction of cyclobutenones with ynamides. This cascade process proceeds via a sequence of four pericyclic reactions and furnishes a multiply substituted aniline derivative which can bear a variety of functionalized substituents at the position ortho to the nitrogen. In the second stage of the tandem strategy, ring-closing metathesis generates the nitrogen heterocyclic ring. This two-step sequence provides efficient access to highly substituted dihydroquinolines, benzazepines, benzazocines, and related benzofused nitrogen heterocyclic systems. The application of this chemistry in a concise formal total synthesis of the anticancer agents (+)-FR900482 and (+)-FR66979 is described.     

Relating structural aspects of bimetallic Pt(3)Cr(1)/C nanoparticles to their electrocatalytic activity, stability, and selectivity in the oxygen reduction reaction

Two methods were used to prepare bimetallic Pt(3)Cr(1)/C nanocatalysts with similar composition but different alloying extent (structure). We investigated how these differences in alloying extent affect the catalytic activity, stability and selectivity in the oxygen reduction reaction (ORR). One method, based on slow thermal decomposition of the Cr precursor at a rate that matches that of chemical reduction of the Pt precursor, allows fine control of the composition of the Pt(3)Cr(1)/C alloy, whereas the second approach, using the ethylene glycol method, results in considerable deviation (>25 %) from the projected composition. Consequently, these two methods lead to variations in the alloying extent that strongly influence the Pt d-band vacancy and the Pt electroactive surface area (Pt ESCA). This relationship was systematically evaluated by transmission electron microscopy, X-ray absorption near edge structure spectroscopy, and electrochemical analysis. The ORR activity depends on two effects that nullify each other, namely, the number of active Pt sites and their activity. The Pt-site activity is more dominant in governing the ORR activity. The selectivity of the nanocatalyst towards the ORR and the competitive methanol oxidation reaction (MOR) depend on these two effects acting in cooperation to give enhanced ORR activity with suppressed MOR. The number of active Pt sites is associated with the Pt ESCA value, while Pt-site activity is associated with the alloying extent and Pt d-band vacancy (electronic) effects. The presence of Cr atoms in Pt(3)Cr(1)/C enhances stability during electrochemical treatment. Overall, the Pt(3)Cr(1)/C catalyst prepared by controlled-composition synthesis was shown to be superior in ORR activity, selectivity and stability owing to its favorable alloying extent, Pt d-band vacancy, and Pt ESCA.     

Nanoscale imaging with resonant coherent X rays: extension of multiple-wavelength anomalous diffraction to nonperiodic structures

The methodology of multiple-wavelength anomalous diffraction, widely used for macromolecular structure determination, is extended to the imaging of nonperiodic nanostructures. We demonstrate the solution of the phase problem by a combination of two resonantly recorded coherent scattering patterns at the carbon K edge (285 eV). Our approach merges iterative phase retrieval and x-ray holography approaches, yielding unique and rapid reconstructions. The element, chemical, and magnetic state specificity of our method further renders it widely applicable to a broad range of nanostructures, providing a spatial resolution that is limited, in principle, by wavelength only.     

CCR1 antagonists

CCR1 (CC Chemokine receptor 1) is a widely studied G protein-coupled receptor target expressed on multiple types of leukocytes. It is implicated in initiating and exacerbating inflammatory conditions and thus is viewed as a good target for autoimmune and inflammatory therapeutic applications. Numerous CCR1 antagonists have been reported. Although some early CCR1 antagonists lacked the species cross reactivity that made in vivo animal model study difficult, efforts have been made to improve the compound potency in rodents. Recent identification of new and improved CCR1 antagonists has resulted in promising, in vivo efficacy in a variety of animal models of disease. While several early compounds have been withdrawn from clinical trials due to lack of efficacy, work continues to evaluate CCR1 antagonists in preclinical and clinical settings.