Concise Stereoselective Synthesis of Oxaspirocycles with 1‐Tosyl‐1,2,3‐triazoles: Application to the Total Syntheses of (±)‐Tuberostemospiroline and (±)‐Stemona‐lactam R

A 4‐substituted‐1‐tosyl‐1,2,3‐triazole‐based stereoselective synthesis of structurally diverse oxaspirocycles is reported. The synthesis involves Rh‐catalyzed loss of nitrogen from 4‐substituted‐1‐tosyl‐1,2,3‐triazoles, Grignard reaction, and a ring‐closing metathesis reaction as key steps. By employing readily available and stable 4‐substituted‐1‐tosyl‐1,2,3‐triazoles as surrogates of diazo compounds and nitrogen sources, two types of oxaspirocycles were obtained. The latter compounds, which contain adjacent nitrogen stereocenters, could serve as the core structures of many natural products. This chemistry has been successfully applied to the total syntheses of (±)‐tuberostemospiroline and (±)‐stemona‐lactam R.     

Cu–Al Spinel Oxide as an Efficient Catalyst for Methanol Steam Reforming

Cu–Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper‐sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl₂O₄ releases active copper gradually. The catalyst CA2.5‐900, calcined at 900 °C with n(Al)/n(Cu)=2.5, has a higher CuAl₂O₄ content, higher BET surface area, and smaller CuAl₂O₄ crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5‐900 showed better catalytic performance than the commercial Cu–Zn–Al catalyst.     

Facile “Living” Radical Polymerization of Methyl Methacrylate in the Presence of Iniferter Agents: Homogeneous and Highly Efficient Catalysis from Copper(II) Acetate

A facile homogeneous polymerization system involving the iniferter agent 1‐cyano‐1‐methylethyl diethyldithiocarbamate (MANDC) and copper(II) acetate (Cu(OAc)₂) is successfully developed in bulk using methyl methacylate (MMA) as a model monomer. The detailed polymerization kinetics with different molar ratios (e.g., [MMA]₀/[MANDC]₀/[Cu(OAc)₂]₀ = 500/1/x (x = 0.1, 0.2, 0.5, 1.0)) demonstrate that this system has the typical “living”/controlled features of “living” radical polymerization, even with ppm level catalyst Cu(OAc)₂, first order polymerization kinetics, a linear increase in molecular weight with monomer conversion and narrow molecular weight distributions for the resultant PMMA. ¹H NMR spectra and chain‐extension experiments further confirm the “living” characteristics of this process. A plausible mechanism is discussed.

     

One‐Step In Situ Biosynthesis of Graphene Oxide–Bacterial Cellulose Nanocomposite Hydrogels

Graphene oxide–bacterial cellulose (GO/BC) nanocomposite hydrogels with well‐dispersed GO in the network of BC are successfully developed using a facile one‐step in situ biosynthesis by adding GO suspension into the culture medium of BC. During the biosynthesis process, the crystallinity index of BC decreases and GO is partially reduced. The experimental results indicate that GO nanosheets are uniformly dispersed and well‐bound to the BC matrix and that the 3D porous structure of BC is sustained. This is responsible for efficient load transfer between the GO reinforcement and BC matrix. Compared with the pure BC, the tensile strength and Young's modulus of the GO/BC nanocomposite hydrogel containing 0.48 wt% GO are significantly improved by about 38 and 120%, respectively. The GO/BC nanocomposite hydrogels are promising as a new material for tissue engineering scaffolds.

     

Effect of nitrogen-doping temperature on the structure and photocatalytic activity of the B,N-doped TiO2

B,N-TiO₂ photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH₃ at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO₂ were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV-visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO₂ lattice either interstitially or substitutionally or both, while the Ti-O-B-N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550 °C. Higher temperature may form many oxygen vacancies and Ti³⁺ species, resulting in the decrease of photocatalytic activity in visible light.     

Hydrogen production via autothermal reforming of ethanol over noble metal catalysts supported on oxides

Hydrogen was produced over noble metal (Ir, Ru, Rh, Pd) catalysts supported on various oxides, including γ-Al₂O₃, CeO₂, ZrO₂ and La₂O₃, via the autothermal reforming reaction of ethanol (ATRE) and oxidative reforming reaction of ethanol (OSRE). The conversion of ethanol and selectivites for hydrogen and byproducts such as methane, ethylene and acetaldehyde were studied. It was found that lanthana alone possessed considerable activity for the ATRE reaction, which could be used as a functional support for ATRE catalysts. It was demonstrated that Ir/La₂O₃ prevented the formation of methane, and Rh/La₂O₃ encumbered the production of ethylene and acetaldehyde. ATRE reaction was carried out over La₂O₃-supported catalysts (Ir/La₂O₃) with good stability on stream, high conversion, and excellent hydrogen selectivity approaching thermodynamic limit under autothermal condition. Typically, 3.4 H₂ molecules can be extracted from a pair of ethanol and water molecules over Ir(5wt%)/La₂O₃. The results presented in this paper indicate that Ir/La₂O₃ can be used as a promising catalyst for hydrogen production via ATRE reaction from renewable ethanol.     

负载酞菁铁的氮掺杂中空碳球的电催化氧还原性能（英文）

开发低成本、高性能的氧还原反应（ORR）催化剂是当前的研究热点.虽然酞菁铁（FePc）在几十年前就被证明能高效地电催化氧还原反应,但由于其电子传导性和稳定性较差,无法取代商用的Pt/C催化剂.氮掺杂碳材料不仅化学性质稳定、电子传导性好,还有一定的氧还原催化活性.本文首先制备了聚苯乙烯@聚多巴胺球前驱体,经过高温碳化后制得了氮掺杂中空碳球,进而负载酞菁铁后制备了负载酞菁铁的氮掺杂中空碳球复合材料（FePc-NHCS）.通过调整煅烧温度和酞菁铁的负载量,可进一步调控FePc-NHCS的多孔结构、石墨化程度、氮掺杂的种类与含量及酞菁铁的负载状态.优化后的FePc-NHCS在碱性电解质中显示出优异的ORR催化活性,其半波电位和稳定性均高于商用Pt/C催化剂.研究结果表明,掺杂与复合是增强单项催化组分活性的有效途径.此外,通过调控催化剂的结构和组分也能有效地优化催化剂的氧化还原性能.     

Nicotine Inhibits the Cytotoxicity and Genotoxicity of NNK Mediated by CYP2A13 in BEAS-2B Cells

Both tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and nicotine can be metabolized by cytochrome P450 2A13 (CYP2A13). Previous studies have shown that nicotine has a potential inhibitory effect on the toxicity of NNK. However, due to the lack of CYP2A13 activity in conventional lung cell lines, there had been no systematic in vitro investigation for the key target organ, the lung. Here, BEAS-2B cells stably expressing CYP2A13 (B-2A13 cells) were constructed to investigate the effects of nicotine on the cytotoxicity and genotoxicity of NNK. The results showed more sensitivity for NNK-induced cytotoxicity in B-2A13 cells than in BEAS-2B and B-vector cells. NNK significantly induced DNA damage, cell cycle arrest, and chromosomal damage in B-2A13 cells, but had no significant effect on BEAS-2B cells and the vector control cells. The combination of different concentration gradient of nicotine without cytotoxic effects and a single concentration of NNK reduced or even counteracted the cytotoxicity and multi-dimensional genotoxicity in a dose-dependent manner. In conclusion, CYP2A13 caused the cytotoxicity and genotoxicity of NNK in BEAS-2B cells, and the addition of nicotine could inhibit the toxicity of NNK.     

Synthesis and Characterization of a Novel Class of PPV Derivatives Covalently Linked to C60

Poly(phenylenevinylene) (PPV) derivatives covalently linked to fullerene C₆₀ (PPV‐1‐C₆₀ and PPV‐2‐C₆₀) were synthesized by cycloaddition reaction between C₆₀ and azide group‐containing PPV derivatives. By tuning the initial feed ratio of the azido monomer, the content of C₆₀ in the copolymers was controlled. The copolymers were partially soluble in common organic solvents and were characterized by means of ¹H NMR, FT‐IR, UV‐Vis and fluorescence spectroscopy, as well as by GPC, TGA and cyclic voltammetry techniques.     

红外热成像技术在中医领域的研究综述

检索中国科技期刊近5年已发表的红外热成像检测技术在中医领域的研究文献51篇,从红外成像检测在辅助中医诊断、指导临床治疗与疗效评估,以及对中医基础理论的研究等方面,陈述红外热成像技术在中医领域目前研究现状,分析其在中医领域应用的优势特点,并对未来研究方向提出建议.