Catalytic Enantioselective Peroxidation of α,β-Unsaturated Aldehydes for the Asymmetric Synthesis of Biologically Important Chiral Endoperoxides

We have developed an unprecedented highly enantioselective catalytic peroxidation of enals. Critical to this development is the discovery that varying the structure of the hydroperoxide has a significant impact on the enantioselectivity of the organocatalytic asymmetric peroxidation. This novel transformation enabled the development of an enantioselective route toward the core structure shared by all members of the stolonoxide family of anticancer natural products, a connected <i>trans</i>-3,6-disubstituted-1,2-dioxane and <i>trans</i>-2,5-disubstituted-tetrahydrofuran ring system. Our route also features an unprecedented cyclization cascade of a chiral bis­(epoxy)­hydroperoxide. The new methodology and synthetic strategy established in this work should be applicable to the enantioselective synthesis of a broad range of chiral 1,2-dioxolanes and 1,2-dioxanes, thereby facilitating biological and medicinal chemistry studies of peroxy natural products

Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines

The first direct catalytic asymmetric synthesis of γ-amino ketones was realized by the development of a highly diastereoselective and enantioselective C–C bond-forming umpolung reaction of imines and enones under the catalysis of a new cinchona alkaloid-derived phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol %, the catalyst activates a broad range of trifluoromethyl imines and aldimines as nucleophiles to engage in chemo-, regio-, diastereo- and enantioselective C–C bond-forming reactions with acyclic and cyclic enones, thereby converting these readily available prochiral starting materials into highly enantiomerically enriched chiral γ-amino ketones in synthetically useful yields. Enabled by this unprecedented umpolung reaction of imines, conceptually new and concise routes were developed for the asymmetric synthesis of nitrogen-heterocycles such as pyrrolidines and indolizidines

Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines

The first direct catalytic asymmetric synthesis of γ-amino ketones was realized by the development of a highly diastereoselective and enantioselective C–C bond-forming umpolung reaction of imines and enones under the catalysis of a new cinchona alkaloid-derived phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol %, the catalyst activates a broad range of trifluoromethyl imines and aldimines as nucleophiles to engage in chemo-, regio-, diastereo- and enantioselective C–C bond-forming reactions with acyclic and cyclic enones, thereby converting these readily available prochiral starting materials into highly enantiomerically enriched chiral γ-amino ketones in synthetically useful yields. Enabled by this unprecedented umpolung reaction of imines, conceptually new and concise routes were developed for the asymmetric synthesis of nitrogen-heterocycles such as pyrrolidines and indolizidines

Polyfluorene Electrolytes Interfacial Layer for Efficient Polymer Solar Cells: Controllably Interfacial Dipoles by Regulation of Polar Groups

The polar groups in the conjugated polyelectrolytes (CPEs) can create the favorable dipoles at the electrode/active layer interface, which is critical for the CPEs to minimize the interfacial energy barrier in polymer solar cells (PSCs). Herein, a series of CPEs based on poly [(9,9-bis­(3′-(<i>N</i>,<i>N</i>-dimethylamino)­propyl)-2,7-fluorene)-<i>co</i>-2,7-(9,9-dioctylfluorene)] derivates (PFNs) (PFN₃₀, PFN₅₀, PFN₇₀, and PFN₁₀₀) with different mole ratio of polar groups (−N­(C₂H₅)₂) were designed and synthesized to investigate the effect of the numbers of polar groups on the interfacial dipoles. Controllably interfacial dipoles could be readily achieved by only tuning the numbers of −N­(C₂H₅)₂ in PFNs, as revealed by the work function of the PFNs modified ITO gradually reduced as the loadings of the −N­(C₂H₅)₂ increased. In addition, increasing the numbers of −N­(C₂H₅)₂ in PFNs were also favorable for developing the smooth and homogeneous morphology of the active layer. As a result, the content of the polar amine in the PFNs exerted great influence on the performance of polymer solar cells. Increasing the numbers of the pendent −N­(C₂H₅)₂ could effectively improve the power conversion efficiency (PCE) of the devices. Among these PFNs, PFN₁₀₀ with the highest content of −N­(C₂H₅)₂ polar groups delivered the device with the best PCE of 3.27%. It indicates tailoring the content of the polar groups in the CPEs interlayer is a facial and promising approach for interfacial engineering to developing high performance PSCs

Alcohol-Soluble n‑Type Conjugated Polyelectrolyte as Electron Transport Layer for Polymer Solar Cells

A novel alcohol-soluble n-type conjugated polyelectrolyte (n-CPE) poly-2,5-bis­(2-octyldodecyl)-3,6-bis­(thiophen-2-yl)-pyrrolo­[3,4-<i>c</i>]­pyrrole-1,4-dione-<i>alt</i>-2,5-bis­[6-(<i>N</i>,<i>N</i>,<i>N</i>-trimethyl­ammonium)­hexyl]-3,6-bis­(thiophen-2-yl)-pyrrolo­[3,4-<i>c</i>]­pyrrole-1,4-dione (PDPPNBr) is synthesized for applications as an electron transport layer (ETL) in an inverted polymer solar cells (PSCs) device. Because of the electron-deficient nature of diketopyrrolopyrrole (DPP) backbone and its planar structure, PDPPNBr is endowed with high conductivity and electron mobility. The interfacial dipole moment created by n-CPE PDPPNBr can substantially reduce the work function of ITO and induce a better energy alignment in the device, facilitating electron extraction and decreasing exctions recombination at active layer/cathode interface. As a result, the power conversion efficiency (PCE) of the inverted devices based poly­(3-hexylthiophene) (P3HT):(6,6)-phenyl-C₆₁ butyric acid methyl ester (PC₆₁BM) active layer with PDPPNBr as ETL achieves a value of 4.03%, with 25% improvement than that of the control device with ZnO ETL. Moreover, the universal PDPPNBr ETL also delivers a notable PCE of 8.02% in the devices based on polythieno­[3,4-<i>b</i>]-thiophene-<i>co</i>-benzo­dithiophene (PTB7):(6,6)-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). To our best knowledge, this is the first time that n-type conjugated polyelectrolyte-based cathode interlayer is reported. Quite different from the traditional p-type conjugated and nonconjugated polyelectrolytes ETLs, n-CPE PDPPNBr as ETL could function efficiently with a thickness approximate 30 nm because of the high conductivity and electron mobility. Furthermore, the PDPPNBr interlayer also can ensure the device with the improved long-term stability. The successful application of this alcohol solution processed n-type conjugated polyelectrolyte indicates that the electron-deficient planar structure with high electron mobility could be very promising in developing high performance and environmentally friendly polymer solar cells

Ambient Electrochemical Ammonia Synthesis With High Selectivity On Fe/Fe Oxide Catalyst

Electrochemical reduction of N2 to NH3 under ambient conditions can provide an alternative to the Haber-Bosch process for distributed NH3 production that can be powered by renewable electricity. The major challenge for realizing such a process is to develop efficient electrocatalysts for the N2 reduction reaction (N2RR), as typical catalysts show a low activity and selectivity due to the barrier for N2 activation and the competing hydrogen evolution reaction (HER). Here we report an Fe/Fe3O4 catalyst for ambient electrochemical NH3 synthesis, which was prepared by oxidizing an Fe foil at 300 °C followed by in situ electrochemical reduction. The Fe/Fe3O4 catalyst exhibits a Faradaic efficiency of 8.29% for NH3 production at -0.3 V vs the reversible hydrogen electrode in phosphate buffer solution, which is around 120 times higher than that of the original Fe foil. The high selectivity is enabled by an enhancement of the intrinsic (surface-area-normalized) N2RR activity by up to 9-fold as well as an effective suppression of the HER activity. The N2RR selectivity of the Fe/Fe3O4 catalyst is also higher than that of Fe, Fe3O4, and Fe2O3 nanoparticles, suggesting Fe/Fe oxide composite to be an efficient catalyst for ambient electrochemical NH3 synthesis

Unexpected Role of <i>p</i>‑Toluenesulfonylmethyl Isocyanide as a Sulfonylating Agent in Reactions with α‑Bromocarbonyl Compounds

The reactions of <i>p</i>-toluenesulfonylmethyl isocyanide (TosMIC) with α-bromocarbonyl compounds leading efficiently to α-sulfonated ketones, esters, and amides were reported, in which an explicit new role of TosMIC as the sulfonylating agent was uncovered for the first time. Mechanistic study by control experiments and DFT calculations suggested that the reaction is initiated by Cu­(OTf)₂-catalyzed hydration of TosMIC to form a formamide intermediate, which undergoes facile C–S bond cleavage under the mediation of a Cs₂CO₃ additive

Tuning the Electronic Structure of Se via Constructing Rh-MoSe₂ Nanocomposite to Generate High-Performance Electrocatalysis for Hydrogen Evolution Reaction

As one of the most promising acid-stable catalysts for hydrogen evolution reaction (HER), MoSe₂ was hampered by the limited quantity of active sites and poor conductivity, which severely impede the efficiency of hydrogen production. Different from heteroatoms doping and conductivity improvement, to address this issues, the electronic structure of active edge sites Se in MoSe₂ were modulated by electron injection from ruthenium deposited on MoSe₂ nanosheets. The Rh-MoSe₂ nanocomposite exhibits great performance enhancement with a low onset potential of 3 mV and quite low overpotential of 31 mV (vs RHE), which is superior to almost all Rh-based and MoSe₂-based electrocatalysts. Experimental results and density functional theory (DFT) simulations reveal that the performance improvement stems from the modulated electronic structure of Se atoms at the edge sites by electron transfer from metal Rh to MoSe₂ support, which leads to a moderate Δ<i>G</i>_H* value of 0.09 eV compared to 0.83 eV for MoSe₂ and −0.26 eV for Rh

Image2_The hypoxia-related signature predicts prognosis, pyroptosis and drug sensitivity of osteosarcoma.TIF

Osteosarcoma (OS) is one of the most common types of solid sarcoma with a poor prognosis. Solid tumors are often exposed to hypoxic conditions, while hypoxia is regarded as a driving force in tumor recurrence, metastasis, progression, low chemosensitivity and poor prognosis. Pytoptosis is a gasdermin-mediated inflammatory cell death that plays an essential role in host defense against tumorigenesis. However, few studies have reported relationships among hypoxia, pyroptosis, tumor immune microenvironment, chemosensitivity, and prognosis in OS. In this study, gene and clinical data from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases were merged to develop a hypoxia risk model comprising four genes (PDK1, LOX, DCN, and HMOX1). The high hypoxia risk group had a poor prognosis and immunosuppressive status. Meanwhile, the infiltration of CD8+ T cells, activated memory CD4+ T cells, and related chemokines and genes were associated with clinical survival outcomes or chemosensitivity, the possible crucial driving forces of the OS hypoxia immune microenvironment that affect the development of pyroptosis. We established a pyroptosis risk model based on 14 pyroptosis-related genes to independently predict not only the prognosis but also the chemotherapy sensitivities. By exploring the various connections between the hypoxic immune microenvironment and pyroptosis, this study indicates that hypoxia could influence tumor immune microenvironment (TIM) remodeling and promote pyroptosis leading to poor prognosis and low chemosensitivity.</p

Image3_The hypoxia-related signature predicts prognosis, pyroptosis and drug sensitivity of osteosarcoma.TIFF

Osteosarcoma (OS) is one of the most common types of solid sarcoma with a poor prognosis. Solid tumors are often exposed to hypoxic conditions, while hypoxia is regarded as a driving force in tumor recurrence, metastasis, progression, low chemosensitivity and poor prognosis. Pytoptosis is a gasdermin-mediated inflammatory cell death that plays an essential role in host defense against tumorigenesis. However, few studies have reported relationships among hypoxia, pyroptosis, tumor immune microenvironment, chemosensitivity, and prognosis in OS. In this study, gene and clinical data from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases were merged to develop a hypoxia risk model comprising four genes (PDK1, LOX, DCN, and HMOX1). The high hypoxia risk group had a poor prognosis and immunosuppressive status. Meanwhile, the infiltration of CD8+ T cells, activated memory CD4+ T cells, and related chemokines and genes were associated with clinical survival outcomes or chemosensitivity, the possible crucial driving forces of the OS hypoxia immune microenvironment that affect the development of pyroptosis. We established a pyroptosis risk model based on 14 pyroptosis-related genes to independently predict not only the prognosis but also the chemotherapy sensitivities. By exploring the various connections between the hypoxic immune microenvironment and pyroptosis, this study indicates that hypoxia could influence tumor immune microenvironment (TIM) remodeling and promote pyroptosis leading to poor prognosis and low chemosensitivity.</p