Synthesis of Methyl 5-(<i>N</i>-Benzoyl-<i>N</i>- methylamino)-2-methylpenta-2,4-dienoate by Ring-Opening Acylation of an <i>N</i>-Alkyltetrahydropyridine

Synthesis of Methyl 5-(N-Benzoyl-N- methylamino)-2-methylpenta-2,4-dienoate by Ring-Opening Acylation of an N-Alkyltetrahydropyridin

Water Oxidation on Spinel NiCo₂O₄ Nanoneedles Anode: Microstructures, Specific Surface Character, and the Enhanced Electrocatalytic Performance

Aiming to improve the electrochemical catalytic performance of the spinel NiCo2O4 as water oxidation catalyst, solvothermal method was employed in this work to fabricate NiCo2O4 directly on conductive substrate FTO as integrated anode. By simply altering the solvent in the precursor solution, NiCo2O4 with different morphology was obtained. The electrocatalytic water oxidation behavior of both NiCo2O4 nanoneedles (NNs) and NiCo2O4 nanosheets (NSs) were investigated in analytical scale, and the results showed that NiCo2O4 NNs exhibited enhanced catalytic performance with lower onset potential, larger current density, and faster kinetics in water oxidation process compared with NiCo2O4 NSs. Meanwhile, both the anodes presented excellent stability in the basic conditions which favored oxygen evolution. The reasons for the superior catalytic activity of NiCo2O4 NNs were also discussed in depth by investigating the surface elements composition and distribution, as well as the different chemical state of the surface adsorbed oxygen. It suggested that the NiCo2O4 NNs anode surface which was better hydroxylated and had more physic- and chemisorbed water was beneficial for enhanced water oxidation performance. It was believed that the present work may provide valuable experimental foundation and an exemplary method for improving the activity of water oxidation catalyst

Direct Synthesis of G-2N

The synthesis of angularly fused quinone natural products has been achieved using a photoenolization reaction and a Diels−Alder reaction in the key carbon−carbon bond forming steps

Selective Fowler Reductions: Asymmetric Total Syntheses of Isofagomine and Other 1-Azasugars from Methyl Nicotinate

An efficient, high-yielding strategy has been developed for the asymmetric synthesis of 1-N-iminosugars (1-azasugars), a new class of glycosidase inhibitors with promising biomedical applications. A highly regioselective procedure for the 1,2-reduction of substituted pyridines was employed to transform methyl nicotinate into several representative 1-azasugars

Chiral Recognition and Enantioselective Photoelectrochemical Oxidation toward Amino Acids on Single-Crystalline ZnO

A novel chiral photoanode was fabricated by in situ constructing surface molecular imprinting (MI) sites on vertically aligned single-crystalline (SC) ZnO, employing the l- or d-amino acid enantiomer as templates. The photoelectrochemical (PEC) experiments showed that the photoanode exhibited chiral recognition and enantioselective PEC oxidation ability to the template enantiomer, compared with the other one. The photocurrent response of l-Phe on the l-SC photoanode was 4.8 times the value of d-Phe. A similar result on the d-SC photoanode could also be observed. Moreover, it was found that the recognition factor obtained on the SC photoanode was 2.7-fold that of the polycrystalline counterpart. It was presumed that the enhanced PEC enantioselectivity may be attributed to the high-quality imprinting expression on the rigid surface of SC ZnO, on which the stereoselective adsorption ability was approximately 1.7 times that of the polycrystalline ZnO. The favorable photocatalytic activity of the one-dimensional SC photoanode further amplified the PEC chiral recognition ability by about 37%. Finally, the kinetics of PEC oxidation of the two enantiomers in racemic solution was investigated, and the rate constant on the proposed photoanode to the template enantiomer was above 1.75-fold that to the other enantiomer

Selective Fowler Reductions: Asymmetric Total Syntheses of Isofagomine and Other 1-Azasugars from Methyl Nicotinate

An efficient, high-yielding strategy has been developed for the asymmetric synthesis of 1-N-iminosugars (1-azasugars), a new class of glycosidase inhibitors with promising biomedical applications. A highly regioselective procedure for the 1,2-reduction of substituted pyridines was employed to transform methyl nicotinate into several representative 1-azasugars

Identification of the Oxygen Activation Site in Monomeric Sarcosine Oxidase: Role of Lys265 in Catalysis

Monomeric sarcosine oxidase (MSOX) catalyzes the oxidation of N-methylglycine and contains covalently bound FAD that is hydrogen bonded at position N(5) to Lys265 via a bridging water. Lys265 is absent in the homologous but oxygen-unreactive FAD site in heterotetrameric sarcosine oxidase. Isolated preparations of Lys265 mutants contain little or no flavin but can be covalently reconstituted with FAD. Mutation of Lys265 to a neutral residue (Ala, Gln, Met) causes a 6000- to 9000-fold decrease in apparent turnover rate whereas a 170-fold decrease is found with Lys265Arg. Substitution of Lys265 with Met or Arg causes only a modest decrease in the rate of sarcosine oxidation (9.0- or 3.8-fold, respectively), as judged by reductive half-reaction studies which show that the reactions proceed via an initial enzyme·sarcosine charge transfer complex and a novel spectral intermediate not detected with wild-type MSOX. Oxidation of reduced wild-type MSOX (k = 2.83 × 105 M−1 s−1) is more than 1000-fold faster than observed for the reaction of oxygen with free reduced flavin. Mutation of Lys265 to a neutral residue causes a dramatic 8000-fold decrease in oxygen reactivity whereas a 250-fold decrease is observed with Lys265Arg. The results provide definitive evidence for Lys265 as the site of oxygen activation and show that a single positively charged amino acid residue is entirely responsible for the rate acceleration observed with wild-type enzyme. Significantly, the active sites for sarcosine oxidation and oxygen reduction are located on opposite faces of the flavin ring

Novel Electrochemical Pretreatment for Preferential Removal of Nonylphenol in Industrial Wastewater: Biodegradability Improvement and Toxicity Reduction

Preferential pretreatment of nonylphenol (NP) before biological treatment is of great significance due to its horizontal gene transfer effect and endocrine disruption activity. A novel molecular imprinting high-index facet SnO2 (MI-SnO2, HIF) electrode is designed. NP was effectively removed from industrial wastewater at 1.8 V with totally suppressing human estrogen activity. The ratio of 5 day biological oxygen demand to chemical oxygen demand (BOD5/CODCr) was enhanced to 0.412 from 0.186 after preferential pretreatment. The effluent concentration of NP was 6.4 μg L–1 after further simulating anaerobic-anoxic-oxic treatment, which was about 1/10 of that without pretreatment. This preferential electrochemical pretreatment is interpreted as prior adsorption and enrichment of target pollutants on the MI-SnO2, HIF surface. The reactive oxygen species and subsequent oxidation products were investigated by in situ electron paramagnetic resonance and electrochemical infrared spectroscopy. The degradation pathway of NP was further analyzed by liquid chromatography–mass spectrometry. This unique pretreatment method for a complex tannery wastewater system has irreplaceable status because no methods with similar advantages have been reported, expecting to be widely used in preferential pretreatment of toxic contaminants blended with highly concentrated nontoxic organics

Fast Generation of Hydroxyl Radicals by Rerouting the Electron Transfer Pathway via Constructed Chemical Channels during the Photo-Electro-Reduction of Oxygen

A strategy for the fast generation of hydroxyl radicals (HO·) via photo-electro-reduction of oxygen by rerouting the electron transfer pathway was proposed. The rate-determining step of HO· production is the formation of H2O2 and the simultaneous reduction of H2O2. Engineering of F-TiO2 with single atom Pd bonded with four F and two O atoms favored the electrocatalytic 2-electron oxygen reduction to H2O2 with as high as 99% selectivity, while the additional channel bond HO–O···Pd–F–TiO2 facilitates the photogenerated electron transfer from the conduction band to single atom Pd to reduce Pd···O–OH to HO·. The optimized HO· production rate is 9.18 μ mol L–1 min–1, which is 2.6–52.5 times higher than that in traditional advanced oxidation processes. In the application of wastewater treatment, this proposed photoelectrocatalytic oxygen reduction method, respectively, shows fast kinetics of 0.324 and 0.175 min–1 for removing bisphenol A and acetaminophen. Around 93.2% total organic carbon and 99.3% acute toxicity removal were achieved. Additionally, the degradation efficiency was less affected by the water source and pH value because of the evitable usage of metallic active sites. This work represents a fundamental investigation on the generation rate of HO·, which would pave the way for the future development of photoelectrocatalytic technologies for water purification