Latest ArticlesThe Cu(I)-catalyzed [4 + 1] annulation of vinyl indoles and a carbene precursor is a powerful method for constructing cyclopentaindole derivatives. Density functional theory (DFT) calculations were used to elucidate the mechanism and regioselectivity of this reaction. After Cu-assisted indole C3-alkylation, direct 1,5-annulation was favored over the Cu-assisted annulation pathway. Furthermore, the regioselectivity for 1,5-annulation was attributed to the generated five-membered-ring product being more stable than the three-membered-ring product from 1,3-annulation, which was the kinetically favored pathway.
Herein, an efficient molecular oxygen-mediated method for the selective hydroxyalkylation and alkylation of quinoxalin-2(1H)-ones with alkylboronic acids under transition-metal free conditions has been developed. This strategy demonstrates a broad scope of quinoxalin-2(1H)-ones and alkylboronic acids, giving 3-hydroxyalkylquinoxalin-2(1H)-ones and 3-alkylquinoxalin-2(1H)-ones in moderate-to-good yield. Control experiments reveal that a radical pathway is involved.
Dimeric sesquiterpenoids possessing densely substituted 7-norbornenone/7-norbornenol motifs pose a considerable challenge for chemical synthesis. From a strategic perspective, one could envision intermolecular Diels−Alder cycloaddition as a straightforward method for assembling alkyl-substituted 7-norbornenones. However, this approach is hindered by lability of the required dienes, namely alkyl-substituted cyclopentadienones. Here we report a one-pot protocol for construction of alkyl-substituted 7-norbornenones from electron-deficient olefins and a cyclopentenone derivative. DDQ was found to be an effective oxidant for generating a cyclopentadienone intermediate in situ from the enone. A series of sterically congested 7-norbornenone-containing polycyclic compounds were prepared by using this protocol.
A catalytic asymmetric total synthesis of (+)-vincamine is presented. Key features of the synthesis include a Pd-catalyzed enantioselective decarboxylative allylation to form the C20 quaternary stereogenic center and a stereoselective iminium reduction to install the critical cis-C20/C21 relative stereochemisty.
The construction of all-carbon molecule frameworks remains challenging. Herein, we report a facile and efficient one-pot synthesis of a novel all-carbon stair containing dimerized pentalene core using inexpensive cyclopropyl alkyne catalyzed by in situ generated Cu(I) from the comproportionation reaction of Cu(II) salt and Cu powder under mild reaction conditions. The reaction proceeds via sequential acetylenic coupling, followed by cyclization and [2 + 2] cycloaddition to directly produce pentalene dimer, which is difficult to access by other established methods. Different mechanistic paths were studied for the pentalene formation using density functional theory, suggesting that the reaction also proceeds through acetylenic coupling followed by cyclization and [2 + 2] cycloaddition. Based on the activation energy barriers, Path 1 has the rate-determining step of 38.63 kcal/mol, which is the most thermodynamically preferred one among the four paths.
Point mutations can be used as biomarkers to perform diagnosis for diseases. In this study, a nanorobot for low-abundance point mutation enrichment was constructed using DNA origami. The novel design achieved limits of detection of 0.1% and 1% for synthesized DNA samples and clinical gene samples, respectively. Resettability was a key property of this method, which also involved a simpler process, lower cost and shorter detection duration than traditional enrichment methods. This novel DNA nanorobot may enable the detection of tumor markers, potentially facilitating early cancer diagnosis.
A novel meroterpenoid, named meroterpenthiazole A (1), was isolated from the deep-sea-derived Penicillium allii-sativi. Its structure was established by extensive spectroscopic and computational methods. Meroterpenthiazole A bears a rare benzothiazole moiety in nature. Compound 1 significantly inhibited retinoid X receptor (RXR)-α transcriptional effect (KD = 12.3 µmol/L) through a novel binding mechanism.
Due to the involvement of four-electron transfer process at photoanode, water oxidation is the rate-limiting step in water splitting reaction. To settle this dilemma, ZnCo2O4 nanoparticles are combined with BiVO4 to form a p-n ZnCo2O4/BiVO4 heterojunction photoanode, which is proved by an input voltage−output current test. The built-in electric field formed within the heterojunction structure promotes the effective separation of electrons and holes. ZnCo2O4 is also an effective water oxidation cocatalyst, since it could cause the holes entering the electrode/electrolyte interface rapidly for the subsequent water oxidation reaction. The photocurrent density of ZnCo2O4/BiVO4 composite photoanode reaches 3.0 mA/cm2 at 1.23 V vs. RHE in 0.5 mol/L sodium sulfate under AM 1.5G simulated sunlight, about 2.1 times greater than that of BiVO4 (1.4 mA/cm2). These results suggest the potential of ZnCo2O4 nanoparticles for improving photoelectrochemical water splitting anode materials.
Metal-organic frameworks (MOFs) as a type of crystalline heterogeneous catalysts have shown potential application in photocatalytic CO2 reduction. However, MOF catalysts with high efficiency and selectivity are still in pursuit. Herein, by a bimetallic strategy, the catalytic performance of a Co-MOF for photocatalytic CO2 reduction was enhanced. Specifically, the Co-MOF based on 4, 5-dicarboxylic acid (H3IDC) and 4, 4ʹ-bipydine (4, 4ʹ-bpy) can catalyze CO2 reduction to CO, with high efficiency but relatively low selectivity. After replacement of 2/3 Co(Ⅱ) with Ni(Ⅱ) within Co-MOF, the resulted isostructural Co1Ni2-MOF not only retains high efficiency for photocatalytic CO2 reduction, but also shows enhanced CO selectivity. The CO evolution rate reaches 1160 µmol g−1 h−1 and the CO selectivity reaches as high as 94.6%. The enhanced photocatalytic CO2 reduction performance is supported by theoretical calculation results. This case demonstrates that bimetallic strategy is an effective mean to optimize the catalytic performance of MOF catalysts for photochemical CO2 reduction.
Supported NiCu bimetallic catalysts have been produced in-situ on commercial Al2O3 by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing good activity and selectivity in the reforming reaction of n-heptane. The catalytic performance has been found to depend on the Cu/Ni ratio, revealing the synergic catalysis between homogeneously dispersed Ni and Cu sites. The good catalysis of NiCu bimetallic catalysts makes it possible to partly or even completely replace Pt with NiCu bimetallic catalysts.
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