Chiral spirooxindoles are privileged heterocyclic motifs, which are widely found in natural alkaloids and pharmaceuticals. Moreover, the construction of chiral spiro-cyclic frameworks is a ...long-lasting challenge in organic synthesis. The past four years have witnessed significant developments in this field, and this feature article outlines the recent progress in the catalytic asymmetric synthesis of spirooxindoles, including the contributions of our group. The catalytic asymmetric construction of spirooxindoles has greatly benefited from the utilization of oxindole derivatives as starting materials, including isatin derivatives, methyleneindolinones, indolin-2-one derivatives and isatin-derived 3-indolylmethanols. This article is divided into sections according to the size and type of the generated spiro-ring fused at the C3-position of the oxindole core (from three-membered to seven-membered spiro-rings), and representative examples are given with illustrations. In addition, the enantioselective construction of bispirooxindole frameworks is also discussed in the last section.
The past four years have witnessed significant developments in the field of the catalytic asymmetric synthesis of spirooxindoles, and this feature article outlines the recent progress in this area, including the contributions of our group. This article is divided into sections according to the size and type of the generated spiro-ring fused at the C3-position of the oxindole core.
Exploring high‐efficiency and stable halide perovskite‐based photocatalysts for the selective reduction of CO2 to methane is a challenge because of the intrinsic photo‐ and chemical instability of ...halide perovskites. In this study, halide perovskites (Cs3Bi2Br9 and Cs2AgBiBr6) were grown in situ in mesoporous TiO2 frameworks for an efficient CO2 reduction. Benchmarked CH4 production rates of 32.9 and 24.2 μmol g−1 h−1 with selectivities of 88.7 % and 84.2 %, were achieved, respectively, which are better than most reported halide perovskite photocatalysts. Focused ion‐beam sliced‐imaging techniques were used to directly image the hyperdispersed perovskite nanodots confined in mesopores with tunable sizes ranging from 3.8 to 9.9 nm. In situ X‐ray photoelectronic spectroscopy and Kelvin probe force microscopy showed that the built‐in electric field between the perovskite nanodots and mesoporous titania channels efficiently promoted photo‐induced charge transfer. Density functional theory calculations indicate that the high methane selectivity was attributed to the Bi‐adsorption‐mediated hydrogenation of *CO to *HCO that dominates CO desorption.
Halide perovskites (Cs3Bi2Br9, Cs2AgBiBr6) are grown in situ in a mesoporous titania framework for efficient CO2 reduction reaction (CO2RR). A benchmarked production rate of CH4 (32.9 and 24.2 μmol g−1 h−1) is achieved with selectivity values of 88.7 % and 84.2 %, respectively. In situ X‐ray photoelectronic spectroscopy and Kelvin probe force microscopy reveal that the inner surface built‐in electric field between the perovskite nanodots and mesoporous titania channels can efficiently promote photo‐induced charge transfer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The first catalytic asymmetric construction of 3,3′‐bisindole skeletons bearing both axial and central chirality has been established by organocatalytic asymmetric addition reactions of 2‐substituted ...3,3′‐bisindoles with 3‐indolylmethanols (up to 98 % yield, all >95:5 d.r., >99 % ee). This reaction also represents the first highly enantioselective construction of axially chiral 3,3′‐bisindole skeletons, and utilizes the strategy of introducing a bulky group to the ortho‐position of prochiral 3,3′‐bisindoles. This reaction not only provides a good example for simultaneously controlling axial and central chirality in one operation, but also serves as a new strategy for catalytic enantioselective construction of axially chiral 3,3′‐bisindole backbones from prochiral substrates.
Bulk up: The first catalytic asymmetric construction of 3,3′‐bisindole skeletons bearing axial and central chirality has been established by organocatalytic asymmetric addition reactions of 2‐substituted 3,3′‐bisindoles with electrophiles. This reaction also represents the first highly enantioselective construction of axially chiral 3,3′‐bisindole skeletons, and utilizes the strategy of introducing a bulky group to the ortho‐position of prochiral 3,3′‐bisindoles.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Indolylmethanols have emerged as versatile reactants in catalytic asymmetric reactions because of the facile generation of reactive intermediates from these compounds. The most common ...indolylmethanols are 3-indolylmethanols and 2-indolylmethanols, and the reaction types applicable to these heterocycles mainly include catalytic enantioselective substitutions and cyclizations. Using indolylmethanols as reactants in catalytic asymmetric reactions enables the enantioselective construction of a variety of indole-containing frameworks.
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A built‐in electric field in electrocatalyst can significantly accumulate higher concentration of NO3− ions near electrocatalyst surface region, thus facilitating mass transfer for efficient nitrate ...removal at ultra‐low concentration and electroreduction reaction (NO3RR). A model electrocatalyst is created by stacking CuCl (111) and rutile TiO2 (110) layers together, in which a built‐in electric field induced from the electron transfer from TiO2 to CuCl (CuCl_BEF) is successfully formed . This built‐in electric field effectively triggers interfacial accumulation of NO3− ions around the electrocatalyst. The electric field also raises the energy of key reaction intermediate *NO to lower the energy barrier of the rate determining step. A NH3 product selectivity of 98.6 %, a low NO2− production of <0.6 %, and mass‐specific ammonia production rate of 64.4 h−1 is achieved, which are all the best among studies reported at 100 mg L−1 of nitrate concentration to date.
An electrocatalyst is created by stacking CuCl (111) and rutile TiO2 (110) layers together. A built‐in electric field induced from the electron transfer from TiO2 to CuCl (CuCl_BEF) is thus formed, which triggers interfacial accumulation of NO3− ions around the electrocatalyst. A NH3 product selectivity of 98.6 %, a low NO2− production of <0.6 %, and mass‐specific ammonia production rate of 64.4 h−1 is achieved.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Nitrate electrocatalytic reduction (NO3RR) for ammonia production is a promising strategy to close the N‐cycle from nitration contamination, as well as an alternative to the Haber–Bosch process with ...less energy consumption and carbon dioxide release. However, current long‐term stability of NO3RR catalysts is usually tens of hours, far from the requirements for industrialization. Here, symmetry‐broken Cusingle‐atom catalysts are designed, and the catalytic activity is retained after operation for more than 2000 h, while an average ammonia production rate of 27.84 mg h−1 cm−2 at an industrial level current density of 366 mA cm−2 is achieved, obtaining a good balance between catalytic activity and long‐term stability. Coordination symmetry breaking is achieved by embedding one Cu atom in graphene nanosheets with two N and two O atoms in the cis‐configuration, effectively lowering the coordination symmetry, rendering the active site more polar, and accumulating more NO3− near the electrocatalyst surface. Additionally, the cis‐coordination splits the Cu 3d orbitals, which generates an orbital‐symmetry‐matched π‐complex of the key intermediate *ONH and reduces the energy barrier, compared with the σ‐complex generated with other catalysts. These results reveal the critical role of coordination symmetry in single‐atom catalysts, prompting the design of more coordination‐symmetry‐broken electrocatalysts toward possible industrialization.
A coordination‐symmetry‐breaking Cusingle‐atom catalyst enables a good balance between catalytic activity and long‐term stability in nitrate electroreduction to ammonia. The catalytic activity is retained after operation for more than 2000 h, while an average ammonia production rate of 27.84 mg h−1 cm−2 at an industrial level current density of 366 mA cm−2 is achieved.
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The enantioselective dearomatization of indoles by an organocatalytic (3+2) reaction has been established. The reaction makes use of simple indole derivatives as substrates, and employs azoalkenes ...reaction partners. A wide range of pyrroloindolines containing an all‐carbon quaternary stereogenic center were readily prepared in high yields and with excellent enantioselectivities.
That simple: The enantioselective dearomatization of indoles by an organocatalytic (3+2) reaction has been established. The reaction makes use of simple indole derivatives as substrates and azoalkenes as 1,3‐diople reaction partners. A wide range of pyrroloindolines containing an all‐carbon quaternary stereogenic center were readily prepared in high yields and with excellent enantioselectivity.
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The first enantioselective construction of a new class of axially chiral naphthyl‐indole skeletons has been established by organocatalytic asymmetric coupling reactions of 2‐naphthols with ...2‐indolylmethanols (up to 99 % yield, 97:3 e.r.). This approach not only affords a new type of axially chiral heterobiaryl backbone, but also provides a new catalytic enantioselective strategy for constructing axially chiral biaryl scaffolds by making use of the C3‐electrophilicity of 2‐indolylmethanols.
Axed: The title compounds have been accessed by organocatalytic asymmetric coupling reactions of 2‐naphthols with 2‐indolylmethanols. This approach not only affords a new type of axially chiral heterobiaryl backbone, but also provides a new catalytic enantioselective strategy for constructing axially chiral biaryl scaffolds by making use of the C3‐electrophilicity of 2‐indolylmethanols. CPA=chiral phosphoric acid, M.S.=molecular sieves.
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Memristors are emerging as a rising star of new computing and information storage techniques. However, the practical applications are severely challenged by their instability toward harsh conditions, ...including high moisture, high temperatures, fire, ionizing irradiation, and mechanical bending. In this work, for the first time, lead‐free double perovskite Cs2AgBiBr6 is utilized for environmentally robust memristors, enabling highly efficient information storage. The memory performance of the typical indium‐tin‐oxide/Cs2AgBiBr6/Au sandwich‐like memristors is retained after 1000 switching cycles, 105 s of reading, and 104 times of mechanical bending, comparable to other halide perovskite memristors. Most importantly, the memristive behavior remains robust in harsh environments, including humidity up to 80%, temperatures as high as 453 K, an alcohol burner flame for 10 s, and 60Co γ‐ray irradiation for a dosage of 5 × 105 rad (SI), which is not achieved by any other memristors and commercial flash memory techniques. The realization of an environmentally robust memristor from Cs2AgBiBr6 with a high memory performance will inspire further development of robust electronics using lead‐free double perovskites.
Double perovskite Cs2AgBiBr6 is fabricated into an indium tin oxide/Cs2AgBiBr6/Au device for the first time. Ultrastable memristive behavior is obtained owing to the tough crystallinity of Cs2AgBiBr6. Humidity‐, high temperature‐, fire‐, and radiation‐resistant properties of Cs2AgBiBr6‐based devices promote memristive devices to work in harsh environments, where most perovskite‐based devices may fail to work.
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Microglia express constitutively a Nox2 enzyme that is involved in neuroinflammation by the generation of reactive oxygen species (ROS). Amyloid β (Aβ) plays a crucial role in Alzheimer's disease. ...However, the mechanism of Aβ-induced microglial dysfunction and redox-regulation of microgliosis in aging remains unclear. In this study, we examined Nox2-derived ROS in mediating microglial response to Aβ peptide 1-42 (Aβ
) stimulation in vitro, in aging-associated microgliosis in vivo and in post-mortem human samples. Compared to controls, Aβ
markedly induced BV2 cell ROS production, Nox2 expression, p47
and ERK1/2 phosphorylation, cell proliferation and IL-1β secretion. All these changes could be inhibited to the control levels in the presence of Nox2 inhibitor or superoxide scavenger. Compared to young (3-4 months) controls, midbrain tissues from wild-type aging mice (20-22 months) had significantly higher levels of Nox2-derived ROS production, Aβ deposition, microgliosis and IL-1β production. However, these aging-related changes were reduced or absent in Nox2 knockout aging mice. Clinical significance of aging-associated Nox2 activation, microgliosis and IL-1β production was investigated using post-mortem midbrain tissues of humans at young (25-38 years) and old age (61-85 years). In conclusion, Nox2-dependent redox-signalling is crucial in microglial response to Aβ
stimulation and in aging-associated microgliosis and brain inflammation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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