A practical, one-pot synthesis of highly substituted thiophenes and benzo[b]thiophenes from bromoenynes and o-alkynylbromobenzenes

An efficient synthesis of thiophenes and benzo[b]thiophenes has been developed from easily available bromoenynes and o-alkynylbromobenzene derivatives. This novel one-pot procedure involves a Pd-catalyzed C-S bond formation using a hydrogen sulfide surrogate followed by a heterocyclization reaction. Moreover, in situ functionalization with selected electrophiles further expands the potential of this methodology to the preparation of the corresponding highly substituted sulfur heterocycles.     

Automatic filtration and filter flush for robust online solid-phase extraction liquid chromatography

Online solid-phase extraction-liquid chromatography (SPE-LC) with microbore or capillary columns was significantly improved regarding robustness, as an easily installed automatic filtration and filter flushing (AFFL) procedure was added to avoid system clogging. Specifically, an injected sample is passed through a union containing a stainless steel filter prior to SPE trapping. The filter stops any particulate matter from reaching the SPE. When the SPE is subsequently connected to the LC column by column switching, a separate pump backflushes the filter-union, removing the particulate matter off the filter after each injection. This feature greatly reduced backpressure buildup over the entire system.     

Ferritin and metallothionein: dangerous liaisons

Ferritin (Ft) interaction with the Zn-complexes of mammalian MT1, MT2 and MT3 metallothioneins (MT) leads to simultaneous Fe(II) and Zn(II) release.     

Competition between H···π and H···O interactions in furan heterodimers

Here the interactions of furan with HZ (Z = CCH, CCF, CN, Cl, and F) are studied using a variety of electron correlation methods (MP2, CCSD(T), DFT-SAPT) and correlation-consistent triple- and quadruple-ζ basis sets including complete basis set (CBS) extrapolation. For Fu-HF all methods agree that a n-type structure with a hydrogen bridge between the oxygen lone-pair of furan and the hydrogen atom of HF is the global minimum structure. It is found to be significantly more stable than a π-type structure where the hydrogen atom of HF points toward the π system of furan. For the other four dimers MP2 and DFT-SAPT predict the π-type structure to be somewhat more stable, while CCSD(T) favors the n-type structure as the global minimum for Fu-HCl and predicts both structures as nearly isoenergetic for Fu-HCCH and Fu-HCCF. From a geometrical point of view, the Fu-HCN dimer structures are more related to those of the Fu-HCl complex than to Fu-HCCH. The different behavior of HCCF and HF upon complexation with furan evidence the effect of the presence of a π system in the aggregation of fluorine derivatives. It is shown that aggregates of furan cannot be understood by means of dipole-dipole and electrostatic analysis only. Yet, through a combined and detailed analysis of DFT-SAPT energy contributions and resonance effects on the molecular charge distributions a consistent explanation of the aggregation of furan with both π electron rich molecules and halogen hydrides is provided.     

From catʼs eyes to multiple disjoint natural convection flow in tall tilted cavities: A direct primitive variables approach

Natural convection fluid flow in air-filled tall tilted cavities is studied numerically with a new direct projection method on the Boussinesq approximation in primitive variables. The study deals with “cat?s eyes” instabilities and multiple disjoint cells as the aspect ratio A and the angle of inclination ?   of the cavity vary. The flows are validated with those reported before using the stream function-vorticity variables. New cases, A=12$A=12$ and 20 varying ?, lead to get more insight on the physical phenomenon.     

The phenoxyl radical-water complex--a matrix isolation and computational study

The phenoxyl radical 1 was generated in high yields by flash vacuum pyrolysis of allyl phenyl ether 2 with subsequent trapping of the products in argon at 3 K. In water-doped argon matrices, an OH···O complex between 1 and water is formed that could be characterized by IR spectroscopy. Several isotopomers of the complex were generated, and the IR spectra compared to results of density functional theory calculations. Other dimers between 1 and water were not found under these conditions. QM/MM calculations in simulated argon matrices reveal that an OH···π complex is unstable even at a time scale of picoseconds. This finding has implications on the related interaction between the tyrosyl radical and the water in biological systems.     

Influence of POSS structure on the fire retardant properties of epoxy hybrid networks

Monofunctional Polyhedral Oligomeric Silsesquioxanes (POSS), differing in chemical structure, were introduced into an epoxy-amine formulation in order to obtain hybrid organic/inorganic epoxy networks. The process developed allows the POSS to be either covalently bonded to the network and organized in small amorphous domains, or completely dispersed in larger crystalline domains. Morphology, thermal and fire retardant properties were studied through electron microscopy, DSC, TGA, cone calorimeter experiments and UL94 tests. It was demonstrated that POSS nanoclusters induced an effective fire retardant effect, which was controlled by several factors. It was shown that POSS bearing phenyl ligands were far more effective than POSS with isobutyl ligands, and that the presence of a chemical linkage between the phenyl-based POSS clusters and the matrix favoured the dispersion of the nanoclusters, resulting in enhanced fire retardancy. The fire retardant effect was only slightly enhanced by increasing the amount of POSS nanoclusters.     

Characterization of the Trans-Epithelial Transport of Green Tea (C. sinensis) Catechin Extracts with In Vitro Inhibitory Effect against the SARS-CoV-2 Papain-like Protease Activity

This work describes an untargeted analytical approach for the screening, identification, and characterization of the trans-epithelial transport of green tea (Camellia sinensis) catechin extracts with in vitro inhibitory effect against the SARS-CoV-2 papain-like protease (PLpro) activity. After specific catechin extraction, a chromatographic separation obtained six fractions were carried out. The fractions were assessed in vitro against the PLpro target. Fraction 5 showed the highest inhibitory activity against the SARS-CoV-2 PLpro (IC₅₀ of 0.125 μg mL⁻¹). The untargeted characterization revealed that (−)-epicatechin-3-gallate (ECG) was the most abundant compound in the fraction and the primary molecule absorbed by differentiated Caco-2 cells. Results indicated that fraction 5 was approximately 10 times more active than ECG (IC₅₀ value equal to 11.62 ± 0.47 μg mL⁻¹) to inhibit the PLpro target. Overall, our findings highlight the synergistic effects of the various components of the crude extract compared to isolated ECG.