Electrochemical Oxidative Sulfonylation-Azidation of Alkenes.

A novel electrochemical oxidative sulfonylation-azidation of alkenes is accomplished by using sulfonyl hydrazide and trimethylsilyl azide (TMSN3) for the one-pot and green synthesis of ß-azidoarylsulfone, which involves the direct construction of new C-S and C-N bonds. Notably, neither exogenous oxidants/additives nor metal catalysts are required for this method. In addition, this electrochemical strategy features mild conditions and wide substrate scope and has been proved to be a radical pathway by mechanistic studies.

Phenolylazoindole scaffold for facilely synthesized and bis-functional photoswitches combining controllable fluorescence and antifungal properties using theoretical methods.

Functionalization is a major challenge for the application of photoswitches. With the aim to develop novel bis-functional azo photoswitches with stationary photophysical properties, a series of phenolylazoindole derivatives were designed, synthesized, and characterized via NMR spectroscopy studies and high-resolution mass spectrometry (HRMS). Herein, UV/Vis and 1H NMR spectra revealed that the photostationary state (PSS) proportions for PSScis and PSStrans were 76-80% and 68-81%, respectively. Furthermore, the thermal half-lives (t1/2) of compounds A2-A4 and B2 ranged from 0.9 to 5.3 h, affected by the diverse substituents at the R1 and R2 positions. The results indicated that azo photoswitches based on the phenolylazoindole scaffold had stationary photophysical properties and wouldn't be excessively affected by modifying the functional groups. Compounds A4 and B2, which were modified with an aryl group, also exhibited fluorescence emission properties (the quantum yields of A4 and B2 were 2.32% and 13.34%) through the modification of the flexible conjugated structure (benzene) at the R2 position. Significantly, compound C1 was obtained via modification with a pharmacophore in order to acquire antifungal activities against three plant fungi, Rhizoctonia solani (R. solani), Botrytis cinerea (B. cinerea), and Fusarium graminearum (F. graminearum). Strikingly, the inhibitory activity of the cis-isomer of compound C1towards R. solani (53.3%) was significantly better than that of the trans-isomer (34.2%) at 50 µg mL-1. In order to further reveal the antifungal mechanism, molecular docking simulations demonstrated that compound C1 effectively integrates into the cavity of succinate dehydrogenase (SDH); the optically controlled cis-isomer showed a lower binding energy with SDH than that of the trans-isomer. This research confirmed that phenolylazoindole photoswitches can be appropriately applied as molecular regulatory devices and functional photoswitch molecules via bis-functionalization.

Enhancing the Iodine Adsorption Capacity of Pyrene-Based Covalent Organic Frameworks by Regulating the Pore Environment.

Regulating of pore environment is an efficient way to improve the performance of covalent organic frameworks (COFs) for specific application requirements. Herein, the design and synthesis of two pyrene-based 2D COFs with -H or -Me substituents, TFFPy-PPD-COF and TFFPy-TMPD-COF are reported. Both of them show long order structure and high porosity, in which TFFPy-PPD-COF displays a larger pore volume and bigger BET surface area (2587 m2 g-1 , 1.17 cm3 g-1 ). Interestingly, TFPPy-TMPD-COF exhibits a much higher vapor iodine capacity (4.8 g g-1 ) than TFPPy-PPD-COF (2.9 g g-1 ), in contrast to their pore volume size. By using multiple techniques, the better performance of TFPPy-TMPD-COF in iodine capture is ascribed to the altered pore environment by introducing methyl groups, which contributes to the formation of polyiodide anions and enhances the interactions between the frameworks and iodine. These results will be helpful for understanding the effect of pore environment in COFs for iodine uptake and constructing novel structure with high iodine capture performance.

MiR-669b-5p inhibits the Alzheimer's disease development via regulation of CHEK2 in Neuro2a APPSwe/Δ9 cells.

DNA damage of neurons is accumulated in Alzheimer's disease (AD). DNA damage-activated Checkpoint kinase 2 (CHEK2) is evaluated in Aß-treated Neuro2a APPSwe/Δ9 cells, and the miR-669b-5p was specifically down-regulated. However, the underlying molecular mechanism between CHEK2 and miR-669b-5p in Neuro2a APPSwe/Δ9 cells remains unclear. This research discovers that in A-treated Neuro2a APPSwe/Δ9 cells, CHEK2 expression and miR-669b-5p expression were inversely correlated. In addition, miR-669b-5p mimics increased cell survival and proliferation in Neuro2a APPSwe/Δ9 cells while decreasing the production of inflammatory cytokines and cell death. Furthermore, it is observed that CHEK2 was a miR-669b-5p downstream target gene and that CHEK2 restored the miR-669b-5p's functions. According to this research, miR-669b-5p is a potential therapy for Alzheimer's patients since it slows the advancement of the disease.

Synthesis mechanism of four metallic Cyclo-N5- energetic materials: A theoretical Perspective.

In the past five years, over 20 types of cyclo-N5- energetic materials (EMs) have been successfully synthesized. Metallic cyclo-N5- EMs exhibit higher density and performance compared to non-metallic cyclo-N5- EMs. However, the mechanisms for such metallic cyclo-N5- EMs remain unexplored. Herein, we performed a thorough quantum chemistry study on the mechanistic pathway for the cyclo-N5- trapped by metal cations in four cyclo-N5- EMs: [Na(H2O) (N5)] · 2H2O, [M(H2O)4(N5)2] · 4H2O (M = Mn, Fe, and Co), by density functional theory methods and transition state theory. During the synthesis process, the cyclo-N5- in the precursor hybrid aromatic compound is susceptible to electrophilic attack by metal cations. This attack disrupts the hydrogen bond interaction surrounding the cyclo-N5-, ultimately leading to the formation of either an ionic bond or a coordination bond between the metal cation and the cyclo-N5-, resulting in an electrophilic substitution reaction. In addition, solvent effects reduce the energy of the ionic bond, thereby promoting the reaction. Our findings will provide valuable insights for future route design and contribute to enhancing the synthesis yield of cyclo-N5- EMs in both theoretical and experimental aspects.

Palladium-catalyzed C(sp3)-H nitrooxylation of masked alcohols.

A palladium-catalyzed ß-C(sp3)-H nitrooxylation of aliphatic alcohols with AgNO2 is reported. An 8-formylquinoline-derived oxime is installed as an exo-type directing group for sp3 C-H activation and selectfluor acts as the oxidant. The reaction tolerates a variety of functional groups and shows good selectivity for ß-C-H nitrooxylation of alcohols.

Symmetrical cyclo-N5- hydrogen bonds: stabilization mechanism of four non-metallic cyclo-pentazolate energetic salts.

Pairing different cations (R+) to stabilize cyclo-N5- is the main synthesis path for non-metallic cyclo-pentazolate (cyclo-N5-) salts. As novel energetic materials (EMs), crystalline packing-force of cyclo-N5- salts has been a puzzle, and whether cyclo-N5- is protonated also is a controversial issue. In this paper, four non-metallic cyclo-N5- salts, PHAC, N2H5N5, NH3OHN5, and NH4N5, are quantitatively studied by coupling first-principle method and bond-strength analyzing technology. Different from the traditional CHON-EMs (molecular crystal) and azide-EMs (ionic crystal), the four salts are stabilized by 3D hydrogen bond (HB) networks. One new type of hydrogen bond, protonated HB (p-H, R-H⋯N5-), is discovered to be a key stabilizing factor for cyclo-N5-. Proton competition mechanism between R and cyclo-N5- in p-H HB showed that cyclo-N5- cannot be protonated into HN5. In general, p-H HB can be adopted to estimate the stability of novel non-metallic cyclo-N5- EMs. Such findings have great significance for future design and performance prediction of novel cyclo-N5- EMs in both theoretical and experimental aspects.

Thermal Decomposition Mechanism and Energy Release Law of Novel Cyclo-N5--Based Nitrogen-Rich Energetic Salt.

Detonation energy of novel cyclo-N5--based nitrogen-rich energetic salts is expected to exceed 3 times the equivalent of TNT. PHAC([(N5)6(H3O)3(NH4)4Cl]) was selected as the prototype to investigate the thermal decomposition reaction of PHAC in the solid phase for the first time by the first-principles molecular dynamics method. At about 38 ps, the final state of the reaction was reached. It was found that there were mainly five final products, among which the proportion of N2 molecules was the maximum and accounted for 60% (mole fraction) of all final products. The reaction pathways of PHAC were analyzed, and more than 30 elementary reactions were found. The initial reaction of the PHAC thermal decomposition was the ring-opening of cyclo-N5- ion and proton transfer. The energy release of PHAC thermal decomposition is divided into two stages. The first stage is a slow release of energy before the formation of the HN3 molecule. The second stage is the rapid release of energy after the formation of HN3 molecules. The HN3 molecule is an essential junction, and the unimolecular dissociation of HN3 is the rate-determining step. Such an understanding of reaction mechanism and energy release law greatly promotes the application and synthesis of novel cyclo-N5--based nitrogen-rich energetic salts.

Theoretical Investigation of Energetic Salts with Pentazolate Anion.

Energetic salts based on pentazolate anion (cyclo-N5-) have attracted much attention due to their high nitrogen contents. However, it is an enormous challenge to efficiently screen out an appropriate cation that can match well with cyclo-N5-. The vertical electron affinity (VEA) of the cations and vertical ionization potential (VIP) of the anions for 135 energetic salts and some cyclo-N5- salts were calculated by the density functional theory (DFT). The magnitudes of VEA and VIP, and their matchability were analyzed. The results based on the calculations at the B3LYP/6-311++G(d,p) and B3LYP/aug-cc-pVTZ levels indicate that there is an excellent compatibility between cyclo-N5- and cation when the difference between the VEA of cation and the VIP of cyclo-N5- anion is -2.8 to -1.0 eV. The densities of the salts were predicted by the DFT method. Relationship between the calculated density and the experimental density was established as ρExpt = 1.111ρcal - 0.06067 with a correlation coefficient of 0.905. This regression equation could be in turn used to calibrate the calculated density of the cyclo-N5- energetic salts accurately. This work provides a favorable way to explore the energetic salts with excellent performance based on cyclo-N5-.

Synthesis and Characterization of cyclo-Pentazolate Salts of NH4+, NH3OH+, N2H5+, C(NH2)3+, and N(CH3)4.

A breakthrough in polynitrogen chemistry was recently achieved by our bulk synthesis of (N5)6(H3O)3(NH4)4Cl in which the cyclo-pentazolate anions were stabilized extensively by hydrogen bridges with the NH4+ and OH3+ cations. Significant efforts have been carried out to replace these nonenergetic cations and the Cl- anion by more energetic cations. In this paper, the metathetical syntheses of cyclo-pentazolate salts containing the simple nitrogen-rich cations NH4+, NH3OH+, N2H5+, C(NH2)3+, and N(CH3)4+ are reported. These salts were characterized by their crystal structures; vibrational, mass, and multinuclear NMR spectra; thermal stability measurements; sensitivity data; and performance calculations. It is shown that the cyclo-pentazolates are more energetic than the corresponding azides but are thermally less stable decomposing in the range of 80 °C to 105 °C. As explosives, the hydrazinium and hydroxyl ammonium salts are predicted to match the detonation pressure of RDX but exhibit significantly higher detonation velocities than RDX and HMX with comparable impact and friction sensitivities. Although the ammonium salt has a lower detonation pressure than RDX, its detonation velocity also exceeds those of RDX and HMX. As a rocket propellant, the hydrazinium and hydroxyl ammonium salts are predicted to exceed the performances of RDX and HMX. The crystal structures show that the cyclo-pentazolate anions are generally stabilized by hydrogen bonds to the cations, except for the N(CH3)4+ salt which also exhibits strong cation-π interactions. This difference in the anion stabilization is also detectable in the vibrational spectra which show for the N(CH3)4+ salt a decrease in the cyclo-N5- stretching vibrations of about 20 cm-1.

A Symmetric Co(N5 )2 (H2 O)4 ⋠4 H2 O High-Nitrogen Compound Formed by Cobalt(II) Cation Trapping of a Cyclo-N5- Anion.

The reactions of (N5 )6 (H3 O)3 (NH4 )4 Cl with Co(NO3 )2 ⋅6 H2 O at room temperature yielded Co(N5 )2 (H2 O)4 ⋅4 H2 O as an air-stable orange metal complex. The structure, as determined by single-crystal X-ray diffraction, has two planar cyclo-N5- rings and four bound water molecules symmetrically positioned around the central metal ion. Thermal analysis demonstrated the explosive properties of the material.

Construction of a conjugated covalent organic framework for iodine capture.

Radioactive iodine in the nuclear field is considered very dangerous nuclear waste because of its chemical toxicity, high mobility and long radioactive half-life. Herein, a conjugated two-dimensional covalent organic framework, TPB-TMPD-COF, has been designed and synthesized for iodine capture. TPB-TMPD-COF has been well characterized by several techniques and showed long order structure and a large surface area (1090 m2 g-1). Moreover, TPB-TMPD-COF shows a high iodine capture value at 4.75 g g-1 under 350 K and normal pressure conditions, benefitting from the increased density of adsorption sites. By using multiple techniques, the iodine vapor adsorbed into the pores may readily generate the electron transfer species (I3- and I5-) due to the strong interactions between imine groups and iodine molecules, which contributes to the high iodine uptake for TPB-TMPD-COF. Our study will stimulate the design and synthesis of COFs as a solid-phase adsorbent for iodine uptake.

Determination of estradiol valerate in pharmaceutical preparations and human serum by flow injection chemiluminescence.

A novel method for the detection of trace estradiol valerate (EV) in pharmaceutical preparations and human serum was developed by inhibition of luminol chemiluminescence (CL) by estradiol valerate on the zinc deuteroporphyrin (ZnDP)-enhanced luminol-K3 Fe(CN)6 chemiluminescence system. Under optimized experimental conditions, CL intensity and concentration of estradiol valerate had a good linear relationship in the ranges of 8.0 × 10(-8) to 1.0 × 10(-5) g/mL. Detection limit (3σ) was estimated to be 3.5 × 10(-8) g/mL. The proposed method was applied successfully for the determination of estradiol valerate in pharmaceutical preparations and human serum and recoveries were 97.0-105.0% and 95.5-106.0%, respectively. The possible mechanism of the CL system is discussed.

Synthesis and catalytic properties of a series of cobalt porphyrins as cytochrome P450 model: the effect of substituents on the catalytic activity.

A series of cobalt porphyrins derived from hemin was prepared as cytochrome P450 models. Effects of substituents at the cobalt deuteroporphyrin-propionate side chains are investigated in oxidation of toluene with air to benzaldehyde and benzyl alcohol without the use of solvent and sacrificial co-reductant. The catalytic activity of cobalt porphyrins depends on the type of substituents. When the electron-withdrawing groups like -Cl, -Br, were introduced into the double propionate side chains, they can increase the catalyst stability and selectivity to benzaldehyde. In comparison with these electron-withdrawing groups, the electron-donor groups, such as -CH3, -S-S- and -NH2 groups, can improve their catalytic activities. Moreover, the electron-donor group containing an unpaired electron (such as -S-S-, -NH2) is benefit for improving its catalytic efficiency and promoting the electron delivery. It can be concluded that the double propionate side chains in the deuteroporphyrin complex may participate in oxidation process and effect electron transfer from the high-valent metalloporphyrin species to the substrate.

Autophagy­regulating miRNAs: Novel therapeutic targets for Parkinson's disease (Review).

Parkinson's disease (PD) is a neurodegenerative disorder that has a high incidence during the aging process and is characterized by the loss of dopaminergic neurons in the substantia nigra, leading to motor dysfunctions and non­motor symptoms. Impaired clearance and excessive accumulation of aberrantly modified proteins or damaged organelles, such as aggregated α­synuclein and dysfunctional mitochondria, are regarded as the main causes of nigrostriatal neurodegeneration. As one of the major degradation pathways, autophagy can recycle these useless or toxic substances to maintain cellular homeostasis and it plays a crucial role in PD progression. MicroRNAs (miRNAs) are a group of small non­coding RNA molecules that regulate gene expression by silencing targeted mRNAs. Recent studies have illustrated that autophagy­regulating miRNA has been implicated in pathological processes of PD, including α­synuclein accumulation, mitochondrial damage, neuroinflammation and neuronal apoptosis, which suggests that targeting autophagy­regulating miRNAs may provide novel therapeutic strategies for this disease. The present review summarizes the role of autophagy in PD and emphasizes the role of miRNA­mediated autophagy in PD, for the development of promising interventions in this disease.

Novel salicylic acid derivatives connecting to five-membered cycle through an acyl hydrazone bond as multi-stimuli responsive fluorescent smart materials with photoswitching properties.

In order to exploit novel multi-stimuli responsive fluorescent materials, a series of novel fluorescent molecules of salicylic acid derivatives were designed and synthesized via introducing pyrazole or cyclopentane to the salicylic acid scaffold through a special Schiff base-acylhydrazone, and the molecular structures of representative compounds A2 and A4 were verified via single crystal X-ray diffraction. All title molecules could exhibit obvious solvatofluorochromism from cyan to indigo in several solutions with different polarity. The fluorescence titration data exhibited compound A2 and complex A2-Cu2+ with prime detection limits to Cu2+ (0.24 µM) and S2- ions (2.83 µM). The sensitive recognition of A2 to trifluoroacetic (TFA) and A2-TFA to triethylamine (TEA) were also confirmed via fluorescent titration experiments in various solutions, respectively. What's more, the 1H NMR and UV/Vis absorption spectra further explained the mechanism between molecules and ions or molecules and TFA/TEA. Besides, the photoswitching properties of the compounds A2 and A3 could be demonstrated via the irradiation of special wavelength light or heating accompanied with changes in quantum yields. In addition, these phenomena of multiple responses were explained via Density Functional Theory (DFT) based on the Gaussian calculations. Thus, this work provided a preliminary basis for the research of multi-stimuli responsive fluorescent molecules with photoswitching properties.

Nitrogen-rich polycyclic pentazolate salts as promising energetic materials: theoretical investigating.

Pentazolate (cyclo-N5-) salts are nitrogen-rich compounds with great development potential as energetic materials due to their full nitrogen anion. However, the densities of available N5- salts are generally low, which seriously lowers their performances. It is necessary to screen out cyclo-N5- salts with high density. To this end, eight new non-metallic cyclo-N5- salts based on fused heterocycle were designed. -NH2, -NO2, and -O- groups were introduced into the compounds to adjust and improve the detonation performance and impact sensitivity of cyclo-N5- salts. By theoretical calculations and Hirshfeld surface analyses, the densities, heats of formation, detonation performance, sensitivities, and crystal structures of the title compounds were predicted, and the contribution of hydrogen bond as well as π-π stacking to the stability of cyclo-N5- salt was revealed. The results indicate that the densities of title compounds are higher than 1.85 g cm‒3, and the sensitivities of these compounds are predicted to be lower than that of HMX. The detonation properties of a (D = 9.47 km s-1, P = 41.21 GPa) and d (D = 9.44 km s-1, P = 40.26 GPa) are better than those of HMX. These mean that using fused ring as a cation and introducing proper substituents are an effective method to improve cyclo-N5- salt's density and balance the detonation performance and sensitivity.

Hydrogen Bond and π-π Stacking Interaction: Stabilization Mechanism of Two Metal Cyclo-N5 --Containing Energetic Materials.

In recent years, cyclo-N5 - has attracted extensive attention because all-nitrogen high-energy-density materials (HEDMs) have been expected to reach a TNT equivalent of over 3.0. However, for cyclo-N5 --containing HEDMs, the stabilization mechanism has remained enigmatic. In this study, two typical cyclo-N5 --containing metal hydrates, [Na(H2O)(N5)]·2H2O (Na-cyclo-N5 -) and [Mg(H2O)6(N5)2]·4H2O (Mg-cyclo-N5 -), are selected to gain insights into the factors affecting their stability by the first-principles method. Both binding/lattice energy calculations and density of states analysis show that Mg-cyclo-N5 - is more stable than Na-cyclo-N5 -. Hydrogen bonding is the main stabilization mechanism for stabilizing crystals and cyclo-N5 -. Two types of hydrogen bonds, O-H···O and O-H···N, are clarified, which construct a 3D hydrogen bond network in Mg-cyclo-N5 - and an intralayer 2D hydrogen bond network in Na-cyclo-N5 -. Moreover, nonuniform stress causes distortion of cyclo-N5 -. Comparing the two samples, the distortion degree of cyclo-N5 - is higher in Na-cyclo-N5 -, which indicates that cyclo-N5 - decomposition is easier. These findings will enhance the future prospects for the design and synthesis of cyclo-N5 --containing HEDMs.

Theoretical research about nonmetallic energetic salts with pentazolate anion.

Significant progress has been made in the synthesis of nitrogen-rich high-energy salts by pairing pentazolate anion (cyclo-N5-) with different cations since cyclo-N5- was synthesized. It is difficult to screen out cyclo-N5- salts with high energy quickly and effectively in experiment, while theoretical research can realize this goal. Herein, nineteen high-energy salts, which were composed of tetrazole cation and cyclo-N5- anion, were designed. And their properties were studied via density functional theory and volume-based thermodynamic methods. The results indicate that most salts have high densities, low sensitivities, and good detonation properties. In particular, salt 14 (ρCalib = 1.802 g/cm3, ΔHf = 1058.4 kJ/mol, D = 9.38 km/s, P = 39.10 GPa, h50 = 44.92 cm) exhibits excellent detonation performance (approximating that of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)) superior to 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and lower impact sensitivity than CL-20 or HMX. Hence salt 14 is regarded as promising candidates for high-performance energetic materials.

Corrigendum: Exploration of High-Energy-Density Materials: Computational Insight into Energetic Derivatives Based on 1,2,4,5-Tetrahydro-1,2,4,5-tetrazine.

[This corrects the article DOI: 10.1002/open.201800161.].