Reductive Coupling of P(O)-H Compounds and Aldehydes for the General Synthesis of Phosphines and Phosphine Oxides.

A novel strategy for the selective construction of a C(sp3)-P(III) or -P(V) bond from >P(O)-H compounds and aldehydes is disclosed. By using the H3PO3/I2 system, various secondary phosphine oxides could react with both aromatic and aliphatic aldehydes to afford valuable phosphines (isolated as sulfides) and phosphine oxides in good yields. This method features a wide substrate scope and simple reaction conditions and avoids the use of toxic halides and metals.

A ternary nucleotide-lanthanide coordination nanoprobe for ratiometric fluorescence detection of ciprofloxacin.

Ciprofloxacin (CIP) is a widely used broad-spectrum antibiotic and has been associated with various side effects, making its accurate detection crucial for patient safety, drug quality compliance, and environmental and food safety. This study presents the development of a ternary nucleotide-lanthanide coordination nanoprobe, GMP-Tb-BDC (GMP: guanosine 5'-monophosphate, BDC: 2-amino-1,4-benzenedicarboxylic acid), for the sensitive and ratiometric detection of CIP. The GMP-Tb-BDC nanoprobe was constructed by incorporating the blue-emissive ligand BDC into the Tb/GMP coordination polymers. Upon the addition of CIP, the fluorescence of terbium ion (Tb3+ ) was significantly enhanced due to the coordination and fluorescence sensitization properties of CIP, while the emission of the BDC ligand remained unchanged. The nanoprobe demonstrated good linearity in the concentration range of 0-10 µM CIP. By leveraging mobile phone software to analyze the color signals, rapid on-site analysis of CIP was achieved. Furthermore, the nanoprobe exhibited accurate analysis of CIP in actual drug and milk samples. This study showcases the potential of the GMP-Tb-BDC nanoprobe for practical applications in CIP detection.

Trivalent Organostibines: Sb,N Ligands in Double N-Arylation of Primary Amines toward Functionalized Carbazoles.

A Sb,N ligand (L-Sb) for Pd-catalyzed double N-arylation of primary amines was developed. This trivalent ligand L-Sb, containing a 5,6,7,12-tetrahydrodibenzo[c,f][1,5]azastibocine skeleton and stable under air and moisture, could be synthesized facilely on a gram scale from chlorostibine (1) and cyclopentylmagnesium bromide. L-Sb showed excellent catalytic performance in Pd2(dba)3-catalyzed double N-arylation of 2,2'-dibromo-1,1'-biphenyl (2) with primary amines (3), affording functionalized carbazoles in good yields. This Pd2(dba)3/L-Sb-catalyzed double N-arylation, the first example of the application of trivalent organostibines as a ligand in N-arylation, featured the following advantages: small catalyst loading, wide functional group tolerance, good yields, and ease of gram-scale synthesis.

Niobium Oxide Anode with Lattice Structure Self-Optimization for High-Power and Nearly Zero-Degeneration Battery Operation.

Li+ insertion-induced structure transformation in crystalline electrodes vitally influence the energy density and cycle life of secondary lithium-ion battery. However, the influence mechanism of structure transformation-induced Li+ migration on the electrochemical performance of micro-crystal materials is still unclear and the strategy to profit from such structure transformation remains exploited. Here, an interesting self-optimization of structure evolution during electrochemical cycling in Nb2 O5 micro-crystal with rich domain boundaries is demonstrated, which greatly improves the charge transfer property and mechanical strength. The lattice rearrangement activates the Li+ diffusion kinetics and hinders the particle crack, thus enabling a nearly zero-degeneration operation after 8000 cycles. Full cell paired with lithium cobalt oxides displays an exceptionally high capacity of 176 mA h g-1 at 8000 mA g-1 and excellent long-term durability at 6000 mA g-1 with 63% capacity retention over 2000 cycles. Interestingly, a unique fingerprint based on the intensity ratio of two X-ray diffraction peaks is successfully extracted as a measure of Nb2 O5 electrochemical performance. The structure self-optimization for fast charge transfer and high mechanical strength exemplifies a new battery electrode design concept and opens up a vast space of strategy to develop high-performance lithium-ion batteries with high energy density and ultra-long cycle life.

Study on the Mechanism of Ru-Catalyzed Cyclization of Aromatic Amides with Allylphosphine Oxides.

The mechanism of Ru-catalyzed cyclization of aromatic amides with allylphosphine oxides is studied by density functional theory calculation (DFT). The results show that, first, a 5-membered Ru ring intermediate is formed by N-H and C-H diprotons via the concerted metalation-deprotonation mechanism (CMD) and then the allylphosphine oxide is inserted through the ring-extending reaction to form a 7-membered ring intermediate. Next, reduction elimination is followed via intramolecular hydrogen transfer isomerization. At last, with the assistance of acetic acid, Ru (II) → Ru (IV) → Ru (II) complexes occur from the 7-membered Ru ring intermediate, and the final product is formed by reduction elimination and protonation reaction, while the catalyst is released to participate in the next cycle.

Thioalkynes in Ring Forming Reactions.

Organic cycles play an important role in chemistry, pharmacology and material science for their unique properties. Construction of organic cycles from thioalkynes attracted increasing attention due to the facile access of thioalkynes. 2H-Azirines were synthesized successfully from thioalkynyl oxime ethers. Cyclobutanes were formed through chiral titanium catalyzed cycloaddition of thioalkynes. Cyclopentenes were afforded by annulation of thioalkynes. Thioalkynes could be also applied to synthesize thiophenes, oxazoles, benzo[b]thiophenes, 2H-chromenes, 2-phenylbenzothiazoles, diazacyclobutene, etc. In this review, construction of organic cycles from thioalkynes were highlighted. Firstly, the property and application of organic cyclic compounds were simply introduced. After presenting the general methods to access organic cycles, applications of thioalkynes as synthons to prepare organic cycles were classified and presented in detail. Based on different kinds of organic cycles obtained from thioalkynes, organic reactions for synthesis of three-, four-, five-, six-membered as well as fused cycles would be summarized and the plausible reaction mechanisms could be presented if available.

Azaindole derivatives as potential kinase inhibitors and their SARs elucidation.

Currently, heterocycles have occupied an important position in the fields of drug design. Among them, azaindole moiety is regarded as one privileged scaffold to develop therapeutic agents. Since two nitrogen atoms of azaindole increase the possibility to form hydrogen bonds in the adenosine triphosphate (ATP)-binding site, azaindole derivatives are important sources of kinase inhibitors. Moreover, some of them have been on the market or in clinical trials for the treatment of some kinase-related diseases (e.g., vemurafenib, pexidartinib, decernotinib). In this review, we focused on the recent development of azaindole derivatives as potential kinase inhibitors based on kinase targets, such as adaptor-associated kinase 1 (AAK1), anaplastic lymphoma kinase (ALK), AXL, cell division cycle 7 (Cdc7), cyclin-dependent kinases (CDKs), dual-specificity tyrosine (Y)-phosphorylation regulated kinase 1A (DYRK1A), fibroblast growth factor receptor 4 (FGFR4), phosphatidylinositol 3-kinase (PI3K) and proviral insertion site in moloney murine leukemia virus (PIM) kinases. Meanwhile, the structure-activity relationships (SARs) of most azaindole derivatives were also elucidated. In addition, the binding modes of some azaindoles complexed with kinases were also investigated during the SARs elucidation. This review may offer an insight for medicinal chemists to rationally design more potent kinase inhibitors bearing the azaindole scaffold.

A near-infrared ratiometric fluorescent probe for hydrazine and its application for gaseous sensing and cell imaging.

Hydrazine (N2H4) is a widely used raw material in the chemical industry, but at the same time hydrazine has extremely high toxicity. Therefore, the development of efficient detection methods is crucial for monitoring hydrazine in the environment and evaluating the biological toxicity of hydrazine. This study reports a near-infrared ratiometric fluorescent probe (DCPBCl2-Hz) for the detection of hydrazine by coupling a chlorine-substituted D-π-A fluorophore (DCPBCl2) to the recognition group acetyl. Due to the halogen effect of chlorine substitution, the fluorophore has an elevated fluorescence efficiency and a lowered pKa value and is suitable for physiological pH conditions. Hydrazine can specifically react with the acetyl group of the fluorescent probe to release the fluorophore DCPBCl2, so the fluorescence emission of the probe system significantly shifted from 490 nm to 660 nm. The fluorescent probe has many advantages, such as good selectivity, high sensitivity, large Stokes shift, and wide applicable pH range. The probe-loaded silica plates can realize convenient sensing gaseous hydrazine with content down to 1 ppm (mg/m3). Subsequently, DCPBCl2-Hz was successfully applied to detect hydrazine in soils. In addition, the probe can also penetrate living cells and allow the visualization of intracellular hydrazine. It can be anticipated that probe DCPBCl2-Hz will be a useful tool for sensing hydrazine in biological and environmental applications.

Process-Divergent Syntheses of 4- and 5-Sulfur-Functionalized 1,2,3-Triazoles via Copper-Catalyzed Azide-Alkyne Cycloadditions of 1-Phosphinyl-2-sulfanylethynes.

4-Sulfanyl-substituted 1,2,3-triazoles were provided regioselectively with good yields and broad scope via consecutive t-BuOK-promoted dephosphinylation of 1-phosphinyl-2-sulfanylethynes and copper-catalyzed azide-alkyne cycloadditions (CuAAC) with alkyl azides. Unsymmetrically substituted ditriazoles were successfully obtained using a tandem dephosphinylative CuAAC protocol with diazides. Direct CuAAC of the 1-phosphinyl-2-sulfanylethynes with azides afforded regioisomeric mixtures of 4-phosphinyl-5-sulfanyl- and 5-phosphinyl-4-sulfanyl-1,2,3-triazoles that were easily separable from one another. When the phosphinyl- and sulfanyl-substituted triazoles were treated with t-BuOK, the dephosphination proceeded smoothly, yielding the corresponding 5- and 4-sulfanyltriazoles, respectively. 5-(1-Aryl-1-hydroxymethyl)-4-sulfanyltriazoles were synthesized by stepwise treatment of 5-phosphinyl-4-sulfanyltriazole with MeMgBr and arylaldehydes. Additionally, Ph2P(O) and RS groups in the triazoles were easily converted to Ph2P and RSO2 by PhSiH3-reduction and m-CPBA-oxidation, respectively. Following the dephosphinylative CuAAC of 1-phosphinyl-2-(4-t-butylphenylsulfanyl)ethyne with aryl azides and m-CPBA-oxidation, potent antagonists of pregnane X receptor LC-58 and LC-59 were successfully produced.

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering.

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.

Benzoxazine: A Privileged Scaffold in Medicinal Chemistry.

BACKGROUND: Benzoxazine is one of the most important privileged scaffolds in medicinal chemistry. Compounds bearing benzoxazine moiety usually have a variety of biological activities, such as anti-inflammatory, anti-microbial, anti-tuberculosis, anti- oxidant and anti-cancer activities. The fascinating bioactivity profile of benzoxazine scaffold in various fields has prompted medicinal chemists to design and discover novel benzoxazine derivatives as potential therapeutic candidates with the desired biological properties. OBJECTIVE: This review aimed to provide a comprehensive elucidation on the recent advances of benzoxazine derivatives in medicinal chemistry. METHODS: We have searched the recent literature about benzoxazine derivatives from the online resources and databases, such as PubMed, SciFinder and Google Scholar. RESULTS: Many benzoxazine derivatives with a wide range of bioactivities, such as anti- microbial, anti-cancer, anti-tuberculosis, anti-oxidant and anti-inflammatory, were summed up. Many compounds displayed good biological activities. CONCLUSION: Benzoxazine is a versatile structure and building block in medicinal chemistry. Benzoxazine derivatives have gained considerable attention from medicinal chemists due to their various pharmacological properties and multiple modification sites. This review might help medicinal chemists to seek new drug candidates with better bioactivities and pharmacokinetics properties.

Enhanced NO2 Sensing Performance of ZnO-SnO2 Heterojunction Derived from Metal-Organic Frameworks.

Nitrogen dioxide (NO2) is the major reason for acid rain and respiratory illness in humans. Therefore, rapid, portable, and effective detection of NO2 is essential. Herein, a novel and simple method to construct a ZnO-SnO2 heterojunction is fabricated by pyrolysis of bimetallic metal organic frameworks. The sensitivity of ZnO-SnO2 heterojunction towards 0.2 ppm NO2 under 180 °C is 37, which is 3 times that of pure ZnO and SnO2. The construction of heterojunction speeds up the response-recovery process, and this kind of material exhibits lower detection limit. The construction of heterojunction can significantly improve the NO2 sensitivity. The selectivity, stability, and moisture resistance of ZnO-SnO2 heterojunction are carried out. This could enable the realization of highly selective and sensitive portable detection of NO2.

Zirconium-Based Catalysts in Organic Synthesis.

Zirconium is a silvery-white malleable and ductile metal at room temperature with a crustal abundance of 162 ppm. Its compounds, showing Lewis acidic behavior and high catalytic performance, have been recognized as a relatively cheap, low-toxicity, stable, green, and efficient catalysts for various important organic transformations. Commercially available inorganic zirconium chloride was widely applied as a catalyst to accelerate amination, Michael addition, and oxidation reactions. Well-designed zirconocene perfluorosulfonates can be applied in allylation, acylation, esterification, etc. N-Chelating oganozirconium complexes accelerate polymerization, hydroaminoalkylation, and CO2 fixation efficiently. In this review, the applications of both commercially available and synthesized zirconium catalysts in organic reactions in the last 5 years are highlighted. Firstly, the properties and application of zirconium and its compounds are simply introduced. After presenting the superiority of zirconium compounds, their applications as catalysts to accelerate organic transformations are classified and presented in detail. On the basis of different kinds of zirconium catalysts, organic reactions accelerated by inorganic zirconium catalysts, zirconium catalysts bearing Cp, and organozirconium catalysts without Cp are summarized, and the plausible reaction mechanisms are presented if available.

Enhancing Li-Ion Transport in Solid Electrolytes by Confined Water.

Developing new oxide solid electrolytes with fast Li-ion transport and high stability is an important step to realize high-performance solid-state Li-ion batteries. Hydrate materials containing confined water widely exist in nature or can be easily synthesized. However, they have seldom been explored as Li-ion solid electrolytes due to the stereotype that the presence of water limits the electrochemical stability window of a solid electrolyte. In this work, it is demonstrated that confined water can enhance Li-ion transport while not compromising the stability window of solid electrolytes using Li-H-Ti-O quaternary compounds as an example system. Three Li-H-Ti-O quaternary compounds containing different amounts of confined water are synthesized, and their ionic conductivity and electrochemical stability are compared. The compound containing structural pseudo-water is demonstrated to have an ionic conductivity that is 2-3 order of magnitude higher than the water-free Li4 Ti5 O12 and similar stability window. A solid-state battery is made with this new compound as the solid electrolyte, and good rate and cycling performance are achieved, which demonstrates the promise of using such confined-water-containing compounds as Li-ion solid electrolytes. The knowledge and insights gained in this work open a new direction for designing solid electrolytes for future solid-state Li-ion batteries. Broadly, by confining water into solid crystal structures, new design freedoms for tailing the properties of ceramic materials are introduced, which creates new opportunities in designing novel materials to address critical problems in various engineering fields.

One-pot synthesis of phosphorylnaphth[2,1-d]oxazoles and products as P,N-ligands in C-N and C-C formation.

Phosphanylnaphtho[2,1-d]oxazoles were synthesized successfully through one-pot phosphonation of naphthoquinone with diaryl(alkyl)phosphine oxides and Cu-catalyzed oxidative condensation with imines, followed by methylation and reduction. Upon applying 4-phosphanylnaphtho[2,1-d]oxazole as a P,N-chelating ligand, Pd-catalyzed C-N formation of amines or nitrobenzene as well as Ni-catalyzed C-C formation and the synthesis of quinoline proceeded successfully. The reaction was facilely scaled up to give N-benzylaniline 15a in a gram scale synthesis. This research provided a facile and convenient protocol to synthesize phosphanylnaphtho[2,1-d]oxazoles, which could be applied as an efficient P,N-ligand in transition-metal-catalyzed C-N and C-C formation to produce the desired products in high yields with wide functional group tolerance under small catalyst loading, solvent-free conditions in many reactions.

Target-Induced In Situ Formation of Organic Photosensitizer: A New Strategy for Photoelectrochemical Sensing.

Small-molecule photosensitizers have great application prospects in photoelectrochemical (PEC) sensing due to their defined composition, diversified structure, and adjustable photophysical properties. Herein, we propose a new strategy for PEC analysis based on the target-induced in situ formation of the organic photosensitizer. Taking thiophenol (PhSH) as a model analyte, we designed and synthesized a 2,4-dinitrophenyl (DNP)-caged coumarin precursor (Dye-PhSH), which was then covalently coupled onto the TiO2 nanoarray substrate to obtain the working photoanode. Due to the intramolecular photoinduced electron transfer process, Dye-PhSH has only a very weak photoelectric response. Upon reacting with the target, Dye-PhSH undergoes a tandem reaction of the detachment of the DNP moiety and the intramolecular cyclization process, which leads to a coumarin dye with a pronounced photoelectric effect, thus achieving a highly selective turn-on PEC response to PhSH. For the first time, this study was to construct a PEC sensor by exploiting specific organic reactions for the in situ generation of small molecule-based photoactive material. It can be anticipated that the proposed strategy will expand the paradigm of PEC sensing and holds great potential for detecting various other analytes.

Mitochondria-targeted phosphorescent cyclometalated iridium(III) complex for bioimaging of H2S.

The selective visualization of H2S in mitochondria is still a challenge, but it correlates closely with mitochondrial damage and some related diseases. In this work, a cyclometalated iridium complex Ir-DNB, [Ir(ppy)2(N^N)](PF6) (ppy = 2-phenylpyridine, N^N = (4'-methyl-[2,2'-bipyridin]-4-yl)methyl 2-((2,4-dinitrophenyl) thio)benzoate) has been explored for the detection of mitochondrial H2S. Adding H2S to a solution of complex Ir-DNB results in a clearly luminescence enhancement, and displays high selectivity and sensitivity. Moreover, this complex displays negligible toxicity and good mitochondrial localization to HeLa cells, and has also been successfully used for endogenous and exogenous H2S imaging in vitro and in vivo.

Sulfonamide derivatives as potential anti-cancer agents and their SARs elucidation.

Currently, the arise of drug resistance and undesirable off-target effects of anti-cancer agents are major challenges for cancer treatment, which energizes medicinal chemists to develop more anti-cancer agents with high efficiency and low toxicity continuously. Sulfonamide derivatives are a class of promising compounds with diverse biological activities including anti-cancer, and parts of them have been marketed for cancer therapy, such as Belinostat, ABT-199 and Amsacrine. In this review, we summed up the recent advances of sulfonamide derivatives as potential anti-cancer agents based on the anti-cancer targets, such as aromatase, carbonic anhydrase (CA), anti-apoptotic B-cell lymphoma-2 (Bcl-2) proteins, topoisomerase and phosphatidylinositol 3-kinase (PI3K), and elucidated the corresponding structure-activity relationships (SARs) of most sulfonamide derivatives. We hope this review could provide a clear insight for medicinal chemists in the rational design of more potent and bio-target specific anti-cancer agents.

Room-Temperature Hydrogen-Sensing Capabilities of Pt-SnO2 and Pt-ZnO Composite Nanoceramics Occur via Two Different Mechanisms.

Impressive room-temperature gas-sensing capabilities have been reported for nanomaterials of many metal oxides, including SnO2, ZnO, TiO2, WO3, and Fe2O3, while little attention has been paid to the intrinsic difference among them. Pt-SnO2 and Pt-ZnO composite nanoceramics have been prepared through convenient pressing and sintering. The former shows strong and stable responses to hydrogen in 20% O2-N2 (synthetic air) at room temperature, while the responses to hydrogen in N2 cannot be stabilized in limited times; the latter shows strong and stable responses to hydrogen in N2, while the responses to hydrogen in synthetic air are greatly depressed. Further analyses reveal that for Pt-ZnO, the responses result from the reaction between hydrogen and oxygen chemisorbed on ZnO; while for Pt-SnO2, the responses result from two reactions of hydrogen, one is that with oxygen chemisorbed on SnO2 and the other is hydrogen chemisorption on SnO2. These results reveal two different room-temperature hydrogen-sensing mechanisms among MOXs, which results in highly contrasting room-temperature hydrogen-sensing capabilities attractive for sensing hydrogen in oxygen-contained and oxygen-free environments, separately.

Highly-Dispersed Submicrometer Single-Crystal Nickel-Rich Layered Cathode: Spray Synthesis and Accelerated Lithium-Ion Transport.

For conventional polycrystalline Ni-rich cathode material consisting of numerous primary particles in disordered orientation, the crystal anisotropy in charge/discharge process results in the poor rate capability and rapid capacity degradation. In this work, highly-dispersed submicron single-crystal LiNi0.8 Co0.15 Al0.05 O2 (SC-NCA) cathode is efficiently prepared by spray pyrolysis (SP) technique followed by a simple solid-state lithiation reaction. Porous Ni0.8 Co0.15 Al0.05 Ox precursor prepared via SP exhibits high chemical activity for lithiation reaction, enabling the fabrication of single-crystal cathode at a relatively low temperature. In this way, the contradiction between high crystallinity and cation disordering is well balanced. The resulted optimized SC-NCA shows polyhedral single-crystal morphology with moderate grain size (≈1 µm), which are beneficial to shortening the Li+ diffusion path and improving the structural stability. As cathode for lithium ion batteries, SC-NCA delivers a high discharge capacity of 202 and 140 mAh g-1 at 0.1 and 10 C, respectively, and maintains superior capacity retention of 161 mAh g-1 after 200 cycles at 1C. No micro-crack is observed in the cycled SC-NCA particles, indicating such single-crystal morphology can greatly relieve the anisotropic micro-strain. This effective, continuous and adaptable strategy for preparing single-crystal Ni-rich cathode without any additive may accelerate their practical application.