Copper‐Mediated Aminoquinoline‐Directed Radiofluorination of Aromatic C−H Bonds with K18F

A Cu‐mediated ortho‐C?H radiofluorination of aromatic carboxylic acids that are protected as 8‐aminoquinoline benzamides is described. The method uses K¹⁸F and is compatible with a wide range of functional groups. The reaction is showcased in the high specific activity automated synthesis of the RARβ2 agonist [¹⁸F]AC261066.     

An Investigation of Molecular Reorientation in Crystalline Pyrazine by Pulse NMR and The Atom-Atom Approximation for Intermolecular Forces

Proton NMR relaxation times (T ₁, at 9.2 MHz and 18.5 MHz, and T ₁ at 18.5 MHz) have been measured for crystalline pyrazine over the temperature range 293 K to the melting point at 327 K. No evidence of a discontinuity in these data is evident at either 29°C or 35°C, where previous workers have found evidence of a phase transition using infrared, Raman, ¹⁴N NQR, calorimetric and other techniques. This result was valid for both unpurified samples and for samples obtained as the result of fractional sublimation. With the assistance of potential energy calculations using the atom-atom approximation for intermolecular forces, the nature of the motional process responsible for the spin-lattice relaxation has been proposed to be an in-plane flip by 180 degrees; this proposal appears to be consistent with all experimental information available for the low-temperature phase stable below 29°C. In addition, the nature of the first phase transition at 29°C has been similarly investigated; it is suggested that this involves an inplane rotation by 90 degrees of just one of the two molecules in the unit cell. Again, this suggestion seems capable of rationalising all available information concerning this transition, although it is possibly not unique in this regard.     

Merging visible-light photocatalysis and transition-metal catalysis in the copper-catalyzed trifluoromethylation of boronic acids with CF3I

This communication describes the development of a mild method for the cross-coupling of arylboronic acids with CF(3)I via the merger of photoredox and Cu catalysis. This method has been applied to the trifluoromethylation of electronically diverse aromatic and heteroaromatic substrates and tolerates many common functional groups.     

Progress toward the development of a point-of-care photonic crystal ammonia sensor

We have developed an ammonia-sensitive material by coupling the Berthelot reaction to our polymerized crystalline colloidal array (PCCA) technology. The material consists of a periodic array of highly charged colloidal particles (110 nm diameter) embedded in a poly(hydroxyethyl acrylate) hydrogel. The particles have a lattice spacing such that they Bragg-diffract visible light. In the Berthelot reaction, ammonia, hypochlorite, and phenol react to produce the dye molecule indophenol blue in an aqueous solution. We use this reaction in our sensor by covalently attaching 3-aminophenol to the hydrogel backbone, which forms cross-links through the Berthelot mechanism. Ammonia reacts with hypochlorite, forming monochloramine, which then reacts with a pendant aminophenol to form a benzoquinone chlorimine. The benzoquinone chlorimine reacts with another pendant aminophenol to form a cross-link. The creation of new cross-links causes the hydrogel to shrink, which reduces the lattice spacing of the embedded colloidal array. This volume change results in a blue-shift in the diffracted light proportional to the concentration of NH₃ in the sample. We demonstrate that the NH₃ photonic crystal sensing material is capable of quantitative determination of concentrations in the physiological range (50–350 μmol NH₃ L⁻¹) in human blood serum.     

Light-induced structural changes in chiral liquid crystals

Novel light-sensitive chiral dopants are studied as a light-sensitive component in chiral liquid crystals which may be used in tunable optical devices. Light-induced cis-trans- isomerization of chiral dopants results in changes of helical twisting power which translates into variations of helical pitch. Due to the light absorption in the liquid crystal cell the pitch variation is non-uniform across the cell, which leads, at first, to a deformation of cholesteric layers, and then to the formation of cholesteric bubbles. The sequence of structural changes has a distinct visual pattern and occurs at the surface close to the UV light source. Small deformations of cholesteric layers and bubbles are unstable and disappear after removing UV irradiation. The increasing size of the cholesteric bubbles results in better stability; large bubbles do not disappear after removing UV light. A theoretical model is suggested to describe the undulations of cholesteric layers.     

EELV secondary payload adapter (ESPA) static qualification tests,part 4 of 4

Experimental Techniques -     

Operational risk modelling and organizational learning in structured finance operations: a Bayesian network approach

This paper describes the development of a tool, based on a Bayesian network model, that provides posteriori predictions of operational risk events, aggregate operational loss distributions, and Operational Value-at-Risk, for a structured finance operations unit located within one of Australia's major banks. The Bayesian network, based on a previously developed causal framework, has been designed to model the smaller and more frequent, attritional operational loss events. Given the limited availability of risk factor event information and operational loss data, we rely on the elicitation of subjective probabilities, sourced from domain experts. Parameter sensitivity analysis is performed to validate and check the model's robustness against the beliefs of risk management and operational staff. To ensure that the domain's evolving risk profile is captured through time, a formal approach to organizational learning is investigated that employs the automatic parameter adaption features of the Bayesian network model. A hypothetical case study is then described to demonstrate model adaption and the application of the tool to operational loss forecasting by a business unit risk manager.