Pd/C as a Catalyst for Completely Regioselective CH Functionalization of Thiophenes under Mild Conditions

The completely C3‐selective arylation of thiophenes and benzo[b]thiophenes was achieved by using Pd/C as a heterogeneous catalyst without ligands or additives under mild reaction conditions. The practicability of this transformation is demonstrated by notable functional group tolerance and the insensitivity of the reaction to H₂O and air. This method is also applicable to nitrogen‐ and oxygen‐containing heterocycles, yielding the corresponding C2‐arylated products. Three‐phase tests along with Hg‐poisoning and hot‐filtration tests suggest that the catalytically active species is heterogeneous in nature.     

Magnolol and honokiol included green emissive terbium sol–gel materials and their recognition behaviors

Magnolol and honokiol as pharmaceutical ligands have been introduced into terbium complex systems for the first time and two hybrid organic–inorganic materials were successfully prepared. Both of them can sensitize terbium characteristic green emission effectively based on intra-molecular energy transfer channel. Moreover, they selectively recognized Cu²⁺ and Fe³⁺ through luminescence quenching effects. The photophysical properties and morphological structures were extensively investigated.     

Synthesis of Site‐Specifically Phosphate‐Caged siRNAs and Evaluation of Their RNAi Activity and Stability

A complete set of new photolabile nucleoside phosphoramidites were synthesized, then site‐specifically incorporated into sense or antisense strands of siRNA for phosphate caging. Single caging modification was made along siRNA strands and their photomodulation of gene silencing were examined by using the firefly luciferase reporter gene. Several key phosphate positions were then identified. Furthermore, multiple caging modifications at these key positions led to significantly enhanced photomodulation of gene silencing activity, suggesting a synergistic effect. The caging group on both the terminally phosphate‐caged siRNA and the single‐stranded caged RNA has comparatively high stability, whereas hydrolysis of the caged group from the internally caged siRNA was observed, irrespective of the presence of Mg²⁺. Molecular dynamic simulations demonstrated that enhanced hydrolysis of the caging group on internally phosphate‐caged siRNAs was due to easy fragmentation of the caging group upon formation of the pentavalent intermediate of the phosphotriester with attack by water. The caging group in the terminally phosphate‐caged siRNA or single‐stranded caged RNA prefers to form π–π stacks with nearby nucleobases. In addition to providing explanations for previous observations, this study sheds further light on the design of caged oligonucleotides and indicates the direction of future development of nucleic acid drugs with phosphate modifications.     

MnO2‐Modified Persistent Luminescence Nanoparticles for Detection and Imaging of Glutathione in Living Cells and In Vivo

Persistent luminescence nanoparticles (PLNPs) hold great promise for the detection and imaging of biomolecules. Herein, we have demonstrated a novel nanoprobe, based on the manganese dioxide (MnO₂)‐modified PLNPs, that can detect and image glutathione in living cells and in vivo. The persistent luminescence of the PLNPs can be efficiently quenched by the MnO₂ nanosheets. In the presence of glutathione (GSH), MnO₂ was reduced to Mn²⁺ and the luminescence of PLNPs can be restored. The persistent luminescence property can allow detection and imaging without external excitation and avoid the background noise originating from the in situ excitation. This strategy can offer a promising platform for detection and imaging of reactive species in living cells or in vivo.     

Size‐Regulable Vesicles Based on Anion–π Interactions

Taking tetraoxacalix[2]arene[2]triazine as a functionalization platform, a series of new amphiphilic molecules were synthesized in 18 to 53 % yields by using a fragment coupling protocol. These amphiphilic molecules self‐assembled into stable vesicles in a mixture of THF and water, with the surface of the vesicles engineered by electron‐deficient cavities. Various anions are able to selectively influence the size of self‐assembled vesicles, following the order of F^?<ClO₄^?<SCN^?<BF₄^?<Br^?<Cl^?<NO₃^?, as revealed by DLS measurements. Such a sequence was independent with the hydration cost and in agreement with the binding strength of anions with tetraoxacalix[2]arene[2]triazine host molecule, indicating that the anion–π interaction most probably competed over other possible weak interactions and accounted for this interesting selectivity. In addition, the chloride permeation process across the membrane of the vesicles was also preliminarily studied by means of fluorescent experiments. This study, in addition to providing the potentiality of heteracalixaromatics as new models to construct functional vesicles, opens a new avenue to study the anion–π interactions in aqueous and also potentially in living systems.     

Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide

A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO₂ under very mild conditions (1 atm CO₂, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high M_n value of 28 600 and a relatively narrow polydispersity (M_w/M_n ratio) of 1.43 were also achieved.     

Gold‐Catalyzed Cycloisomerization of Yne‐Vinylidenecyclopropanes: A Three‐Carbon Synthon for [3+2] Cycloadditions

A novel type of yne‐vinylidenecyclopropanes (VDCPs) has been synthesized and applied in gold‐catalyzed cycloisomerization reactions. It was found that these compounds can undergo an intramolecular cycloisomerization and perform as a three‐carbon synthon for [3+2] cycloaddition under gold catalysis to give fused [4.3.0] and [5.3.0] bicyclic derivatives and VDCP rearranged products in moderated to good yields under mild conditions. The substrate scope of these novel transformations has been explored and plausible reaction mechanisms have been presented on the basis of deuterium labeling experiments and DFT calculations.     

Elements analysis of infant milk formula by ICP-OES: a comparison of pretreatment methods

Sample pretreatments are critical steps for achieving true and precise results in element analysis for infant milk formula. In this study, we made a comparative study of four pretreatment methods: dry ashing (DA), wet ashing (WA), microwave ashing (MA) and slurry dispersion analysis. Nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) were determined by inductively coupled plasma optical emission spectrometry. Infant formula (GBW08509) with certified values was used for assessment of trueness and precision. The data showed that all relative standard deviations (RSD) of the observed values were <15 %. In contrast to other pretreatment, results for MA had the lowest RSD (≤5 %) for all the elements. For Cu and Mn, there was no significant difference between measurement results and certified values in four pretreatments. But, after DA and WA the results for Ca, K, Na, P and Zn differed significantly from the certified values.     

Thermal Ethane Activation by Bare [V2O5]+ and [Nb2O5]+ Cluster Cations: on the Origin of Their Different Reactivities

The gas‐phase reactivity of [V₂O₅]⁺ and [Nb₂O₅]⁺ towards ethane has been investigated by means of mass spectrometry and density functional theory (DFT) calculations. The two metal oxides give rise to the formation of quite different reaction products; for example, the direct room‐temperature conversions C₂H₆→C₂H₅OH or C₂H₆→CH₃CHO are brought about solely by [V₂O₅]⁺. In distinct contrast, for the couple [Nb₂O₅]⁺/C₂H₆, one observes only single and double hydrogen‐atom abstraction from the hydrocarbon. DFT calculations reveal that different modes of attack in the initial phase of C?H bond activation together with quite different bond‐dissociation energies of the M?O bonds cause the rather varying reactivities of [V₂O₅]⁺ and [Nb₂O₅]⁺ towards ethane. The gas‐phase generation of acetaldehyde from ethane by bare [V₂O₅]⁺ may provide mechanistic insight in the related vanadium‐catalyzed large‐scale process.     

The Divergent Synthesis of Nitrogen Heterocycles by Rhodium(II)‐Catalyzed Cycloadditions of 1‐Sulfonyl 1,2,3‐Triazoles with 1,3‐Dienes

The first rhodium(II)‐catalyzed aza‐[4+3] cycloadditions of 1‐sulfonyl 1,2,3‐triazoles with 1,3‐dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5‐dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza‐[3+2] cycloadditions, thus leading to 2,3‐dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza‐heterocycles from common rhodium(II) iminocarbene intermediates.