Intramolecular (4+3) cycloadditions of nitrogen-tethered epoxy enosilanes for the synthesis of heteropolycycles

Furans bearing epoxy enolsilane units linked by a nitrogen heteroatom tether undergo intramolecular (4 + 3) cycloadditions to generate bis-heteroatomic polycyclic adducts having piperidine moieties in their frameworks. The cycloadducts, ultimately derived from furfural, a renewal chemical feedstock, are obtained with up to 4:1 dr and with ee retained from the epoxide.     

Frontal free‐radical photopolymerization of thick samples: Applications to LED‐induced fiber‐reinforced polymers

Free‐radical photopolymerization is scarcely used for the manufacturing of fiber‐reinforced polymers. The main issue relies on the penetration depth of light which affects the conversion degree when photopolymerizing thick samples. Consequently, this could lead to inhomogeneous polymer properties. The ability of acylphosphine oxides to photobleach under near UV irradiation makes them of great interest for the curing of thick samples. Therefore, the influence of (2,4,6‐trimethylbenzoyl) phosphine oxide on the curing of composites under LED is investigated. Although that a frontal photopolymerization process can be evidenced, it was found that full photobleaching is hardly obtained at high concentration of photoinitiator. Six layers laminates made of unidirectional fiber glass and unsaturated polyester resin were prepared. The existence of an optimal range of concentration for which the conversion of the resin is the most homogeneous throughout its thickness was pointed out, a fact that is confirmed by dynamic mechanical analysis. Interestingly, this effect is reflected in the shrinkage of the resin as shown by direct measurements or deflection experiments. Mechanical analysis was undertaken whose results correlate well with the aforementioned study, demonstrating the occurrence of a balance between the concentration of photoinitiator and the mechanical properties of the samples. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 898–906     

Synthesis of Nitro-Aryl Functionalised 4-Amino-1,8-Naphthalimides and Their Evaluation as Fluorescent Hypoxia Sensors

Fluorescent sensors are a vital research tool, enabling the study of intricate cellular processes in a sensitive manner. The design and synthesis of responsive and targeted probes is necessary to allow such processes to be interrogated in the cellular environment. This remains a challenge, and requires methods for functionalisation of fluorophores with multiple appendages for sensing and targeting groups. Methods to synthesise more structurally complex derivatives of fluorophores will expand their potential scope. Most known 4-amino-1,8-naphthalimides are only functionalised at imide and 4-positions, and structural modifications at additional positions will increase the breadth of their utility as responsive sensors. In this work, methods for the incorporation of a hypoxia sensing group to 4-amino-1,8-naphthalimide were evaluated. An intermediate was developed that allowed us to incorporate a sensing group, targeting group, and ICT donor to the naphthalimide core in a modular fashion. Synthetic strategies for attaching the hypoxia sensing group and how they affected the fluorescence of the naphthalimide were evaluated by photophysical characterisation and time-dependent density functional theory. An extracellular hypoxia probe was then rationally designed that could selectively image the hypoxic and necrotic region of tumour spheroids. Our results demonstrate the versatility of the naphthalimide scaffold and expand its utility. This approach to probe design will enable the flexible, efficient generation of selective, targeted fluorescent sensors for various biological purposes.     

Desymmetrizing reductive aldol cyclizations of enethioate derivatives of 1,3-diones catalyzed by a chiral copper hydride

A range of enethioate derivatives of 1,3-diones underwent reductive aldol cyclizations catalyzed by a chiral copper hydride generated in situ from 5 mol% TaniaPhos (SL-T001-1), 5 mol% Cu(OAc)(2)·H(2)O, 5 mol% bipyridine and 2.0 equiv. of PhSiH(3), to furnish polycyclic β-hydroxythioester products bearing three newly established contiguous stereocenters, with >98:2 dr and in up to 94% yield and 98% ee. The use of an amine such as bipyridine or 2,6-lutidine as additive results in an increase of the overall reaction rate. The major bicyclic aldol product has all substituents cis and can be rationalized by a reductively generated (Z)-enolate reacting with the dione via a cyclic transition state.     

Facial selectivity and stereospecificity in the (4 + 3) cycloaddition of epoxy enol silanes

The scope of the (4 + 3) cycloaddition using epoxy enol silanes has been examined. Unhindered and nucleophilic dienes react to give the highest yields, but hindered dienes give rise to higher diastereoselectivities. Notably, the cycloaddition shows facial selectivity and stereospecificity for the stereochemistry of the epoxy enol silane.     

A study of the accuracy of mobile technology for measuring urban noise pollution in large scale participatory sensing campaigns

The study reports on the relevancy and accuracy of using mobile phones in participatory noise pollution monitoring studies in an urban context. During one year, 60 participants used the same smartphone model to measure environmental noise at 28 different locations in Paris. All measurements were performed with the same calibrated application. The sound pressure level was recorded from the microphone every second during a 10-min period. The participants frequently measured the evolution of the sound level near two standard monitoring sound stations (in a square and near a boulevard), which enables the assessment of the accuracy and relevancy of collected acoustic measurements. The instantaneous A-weighting sound level, energy indicators such as L_A,eq, L_A10, L_A50 or L_A90 and event indicators such as the number of noise events exceeding a certain threshold L_α (NNEL ? L_α) were measured and compared with reference measurements. The results show that instantaneous sound levels measured with mobile phones correlate very well (r > 0.9, p < 0.05) with sound levels measured with a class 1 reference sound level meter with a root mean square error smaller than 3 dB(A). About 10% of the measurements for the boulevard location (respectively 20% for the square) were inaccurate (r < 0.3, p < 0.05). Nevertheless, mobile phone measurements are in agreement for the L_A50 and the L_A90 acoustic indicators with the fixed station (4-m high) measurements, with a median deviation smaller than 1.5 dB(A) for the boulevard (respectively 3 dB(A) for the square).     

Collision Cross Sections and Ion Mobility Separation of Fragment Ions from Complex N-Glycans

Ion mobility mass spectrometry (IM-MS) holds great potential for structural glycobiology, in particular in its ability to resolve glycan isomers. Generally, IM-MS has largely been applied to intact glycoconjugate ions with reports focusing on the separation of different adduct types. Here, we explore IM separation and report the collision cross section (CCS) of complex type N-glycans and their fragments in negative ion mode following collision-induced dissociation (CID). CCSs of isomeric fragment ions were found, in some cases, to reveal structural details that were not present in CID spectra themselves. Many fragment ions were confirmed as possessing multiple structure, details of which could be obtained by comparing their drift time profiles to different glycans. By using fragmentation both before and after mobility separation, information was gathered on the fragmentation pathways producing some of the ions. These results help demonstrate the utility of IM and will contribute to the growing use of IM-MS for glycomics.

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Design,Synthesis, and Self‐Assembly Behavior of Liquid‐Crystalline Bis‐[60]Fullerodendrimers

Bis‐[60]fullerodendrimers were synthesized by assembling [60]fullerene‐containing type I (terminal olefin) and type II (α,β‐unsaturated carbonyl olefin) olefins through the olefin cross‐metathesis reaction. The synthetic modular approach developed in this study allowed the preparation of mono‐[60]fullerodendrimers and their [60]fullerene‐free analogues. First‐ and second‐generation poly(aryl ester) dendrons carrying cyanobiphenyl mesogens were used as liquid‐crystalline promoters. The liquid‐crystalline properties were studied by polarized optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering. In agreement with the nature and structure of the dendrimers, nematic, smectic, and multisegregated lamellar phases were observed. Owing to its versatility and tolerance towards many functional groups, olefin cross‐metathesis proved to be a reaction of choice for the elaboration of molecular materials with complex architectures.     

Thermoelectric Generators Based on Ionic Liquids

Looking at energy harvesting using body or waste heat for portable electronic or on-board devices, Ionic liquids are interesting candidates as thermoactive materials in thermoelectric generators (TEGs) because of their outstanding properties. Two different kinds of ionic liquid, with alkylammonium and choline as cations, were studied, whereby different anions and redox couples were combined. This study focussed on the intention to find non-hazardous and environmentally friendly ionic liquids for TEGs to be selected among the thousands that can potentially be used. Seebeck coefficients (SEs) as high as ? 15 mV/K were measured, in a particular case for an electrode temperature difference of 20 K. The bottleneck of our TEG device is still the abundance of negative SE liquids matching the internal resistance with the existing positive SE-liquids at series connections. In this paper, we show further progress in finding increased negative SE liquids. For current extraction from the TEG, the ionic liquid must be blended with a redox couple, allowing carrier exchange in a cyclic process under a voltage which is incuced by the asymmetry of the generator in terms of hot and cold electrodes. In our study, two types of redox pairs were tested. It was observed that a high SE of an ionic liquid/redox blend is not a sufficient condition for high power output. It appears that more complex effects between the ionic liquid and the electrode determine the magnitude of the final current/power output. The physico-chemical understanding of such a TEG cell is not yet available.