SN2-Selective allylic substitution of chiral γ-aryl substituted allylic picolinates with alkynylcopper reagents

Substitution of γ-aryl secondary allylic picolinates with alkynyl copper reagents was studied. The copper reagent, prepared from TMSCCMgBr and CuBr·Me₂S in 2:1, was subjected to substitution of the picolinate derived from (E)-3-phenyl-1-methyl-2-propenyl alcohol at 0 °C for 1 h in THF to produce a mixture of α- and γ-products and the alcohol in 67:20:13, while the reagent in 3 or 4:1 ratio gave the α-product with 90-91% selectivity. On the contrary, reaction in CH₂Cl₂-THF (6-8:1) at 0 °C for 1 h furnished the α-product with 99% regioselectivity. The effect of CH₂Cl₂ was also demonstrated with eight more examples. Furthermore, 99% inversion was determined by transformation to the literature compound and by chiral HPLC.     

Studies on the Reduction of the Nitro Group in 4-Nitroindazoles by Anhydrous SnCl2 in Different Alcohols

The bakers' yeast reduction of a number of alkyl levulinates occurs in good to moderate yields to give the corresponding (S) alcohols in > 98% ee. The (S) alcohol la has been converted to synthetically useful (S)- or (R)-4- methylbutyro-lactone and (S)-(+)-l,4-pentanediol in good yields.     

An Extractive Spectrophotometric Method for the Determination of Nitrite Using Fluorescein Amine Isomer I

ABSTRACT

A sensitive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I is described. The method is based on the formation of azido derivative of fluorescein amine isomer I, which is selectively extracted into 20% iso amyl alcohol in toluene and is stripped to aqueous phase using NaOH. Formation of the azido derivative depends on nitrite concentration and the system obeys Beer's law in the range 0-0.4 ppm of nitrite at 495 nm. The molar absorptivity of the colour system is 6.67 × 10⁴ L mol^-1 cm^-1 with a relative standard deviation of 3% for 10 determinations at 1 μg of nitrite. The proposed method is successfully applied for the determination of nitrite and nitrate in soil, water and radiator coolant sample, NO₂ gas in a laboratory fume cupboard is determined after fixing it as nitrite in sodium arsenite absorber solution.     

一种SO2固定及用于制备BaSO3或BaSO4的方法

在常温常压下,由乙二胺（EDA）和乙二醇及其衍生物（EGs）组成的混合体系可捕集SO₂并转化为一种SO₂储集材料（SO₂SM）。EDA+EGs体系呈现了强的捕集性能（0.364~0.662 g_SO2·g_absorbent^-1）。FTIR,XPS和XRD结果确证了SO₂SM为一种烷基亚硫酸盐。以EG-SO₂SM为原料制备具有多种形貌的BaSO₃或BaSO₄,在此过程中,EG-SO₂SM不仅提供了原材料,而且可以释放EDA和EG用作表面活性剂,调控晶体的结晶化过程。     

一种SO2固定及用于制备BaSO3或BaSO4的方法

在常温常压下,由乙二胺（EDA）和乙二醇及其衍生物（EGs）组成的混合体系可捕集SO₂并转化为一种SO₂储集材料（SO₂SM）。EDA+EGs体系呈现了强的捕集性能（0.364~0.662 g_SO2·gabsorbent^-1）。FTIR,XPS和XRD结果确证了SO₂SM为一种烷基亚硫酸盐。以EG-SO₂SM为原料制备具有多种形貌的BaSO₃或BaSO₄,在此过程中,EG-SO₂SM不仅提供了原材料,而且可以释放EDA和EG用作表面活性剂,调控晶体的结晶化过程。     

环己酮与丙烯酸甲酯及(S)-3-(2′-氧环己基)-丙酸与醇的酯化反应

在(R)TTCA·K催化下由环己酮直接与丙烯酸甲酯进行Michael加成反应得到了(S)-3-(2′-氧环己基)-丙酸甲酯, [α]20D-4.14(41.5% e.e.).     

SnCl2/PdCl2-mediated aldehyde allylation in fully aqueous media

Catalyzed by PdCl₂, SnCl₂ can efficiently mediate the allylation of various aldehydes with allyl chloride or bromide, but not with allyl alcohol, in fully aqueous media. The yield of the reaction is very high (90-100%), and the reaction is operationally simple, environmental benign and easy to scale up.     

ASSOCIATION STRUCTURES OF MIXED BLOCK COPOLYMERS OF DIFFERENT POLAR CHAIN LENGTH

The amphiphilic association structures in the system water-phenethyl alcohol and two triblock copolymers (L101: EO_4.5PO₅₉EO_4.5 and F108: EO_132.5PO₅₀EO_132.5) (EO=ethylene oxide, PO=propylene oxide) were investigated by optical observation, measurements of surface tension, quasi-elastic light scattering and electric conductance. The results showed a most drastic influence of small amounts of the long polar chain block copolymer on the phase regions in the system water-phenethyl alcohol - (EO)₅(PO)₅₆(EO)₅ with 0.1% of the long polar chain compound added to the short chain one giving a most pronounced change in the phase regions.     

Controlled synthesis of monodispersed AgGaS2 3D nanoflowers and the shape evolution from nanoflowers to colloids

Monodispersed AgGaS₂ three-dimensional (3D) nanoflowers have been successfully synthesized in a “soft-chemical” system with the mixture of 1-octyl alcohol and cyclohexane as reaction medium and oleylamine as surfactant. The crystal phase, morphology and chemical composition of the as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HTEM), respectively. Results reveal that the as-synthesized AgGaS₂ nanoflowers are in tetragonal structure with 3D flower-like shape. Controlled experiments demonstrated that the shape transformation of AgGaS₂ nanocrystals from 3D nanoflowers (50 nm) to nanoparticles (10-20 nm) could be readily realized by tuning the reaction parameters, e.g., the ratio of octanol to cyclohexane, the length of carbon chain of fatty alcohol, the concentration of oleylamine, etc. The UV-vis and PL spectra of the obtained AgGaS₂ nanoflowers and colloids were researched. In addition, the photoelectron energy conversion (SPV) of AgGaS₂ nanoflowers was further researched by the surface photovoltage spectra.     

Synthesis and gas sensitivities of SnO2 nanorods and hollow microspheres

SnO₂ urchin-like structures composed of nanorods with diameters of 10-15 nm and lengths of 50-70 nm have been hydrothermally synthesized via a H₂O₂-assisted route without any surfactant, using SnCl₂ as raw material. With the addition of methenamine (HMT), SnO₂ hollow microspheres with diameters of 2-3 μm and shell thickness of 60-140 nm were also prepared. The as-obtained products were examined using diverse techniques including X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-resolution TEM and photoluminescence spectra. The gas sensitivity experiments have demonstrated that the as-synthesized SnO₂ materials exhibit good sensitivity to alcohol vapors, which may offer potential applications in gas sensors.     

LiFePO4的软化学合成及锂快离子导体修饰

采用溶剂热法制备正极材料LiFePO_4,采用溶胶凝胶法制备Li_(0.5)La_(0.5)TiO_3(LLTO)粉体,并通过酒精悬浮法对LiFePO_4进行修饰,修饰量为LiFePO_4质量的1%~4%,获得了薄壁蜂窝状自组装结构的LiFePO_4上修饰有球状LLTO纳米颗粒的复合正极材料。通过进行充放电测试、交流阻抗测试及循环伏安测试,研究了不同修饰量对电池的充放电比容量、循环性能及可逆性的影响,发现当LLTO含量为3%(w/w)时,以2C和5C倍率放电相对于没有修饰LLTO的LiFePO_4的比容量分别提高29.7%和31.6%,30次循环之后,容量损失率较未改性前减小4.13%,循环伏安曲线上氧化还原峰之间的电位差仅为0.117 V,以3%的LLTO修饰改性的LiFePO_4显著提高了电池的倍率性能、循环性能和低温性能。     

A novel gaseous pinacolyl alcohol sensor utilizing cataluminescence on alumina nanowires prepared by supercritical fluid drying

A cataluminescence (CTL) sensor using Al₂O₃ nanowires as the sensing material was developed for the determination of trace pinacolyl alcohol in air samples based on the catalytic chemiluminescence (CL) of pinacolyl alcohol on Al₂O₃ nanowires. Eight catalysts were examined and the CL intensity on Al₂O₃ nanowires prepared by supercritical fluid drying was the strongest. This novel CL sensor showed high sensitivity and selectivity to gaseous pinacolyl alcohol at optimal temperature of 340 °C. Quantitative analysis was performed at a wavelength of 460 nm. The linear range of CTL intensity versus concentration of gaseous pinacolyl alcohol was 0.09 × 10⁻⁶ to 2.56 × 10⁻⁶ g mL⁻¹ (r = 0.9983, n = 6) with a detection limit (3σ) of 0.0053 × 10⁻⁶ g mL⁻¹. None or only very low levels of interference were observed while the foreign substances such as water vapor, ethanol, ammonia, chloroform, benzene, nitrogen dioxide, methylbenzene, hydrochloric acid, methanol and butanol were passing through the sensor. The response time of the sensor is less than 100 s, and the sensor had a long lifetime more than 60 h. The sensor would be potentially applied to analysis of the nerve agents such as Soman.     

天然产物(±)-Aiphanol的全合成研究

以醛1和5为起始原料,经几步反应后用Ag₂O偶联,得到含苯并二氧六环骨架的化合物7,化合物7经过选择性保护酚羟基,再用NaIO₄/OsO₄(cat.)氧化断裂双键,得到关键中间体9,化合物9和10经过Wittig-Horner反应,并用苯硫酚和AIBN实现了顺式双键向反式的转化,脱去保护基后完成了具有新颖结构的天然产物(±)-Aiphanol(12)的合成.     

AlF3包覆对Li1.2Mn0.534Ni0.133Co0.133O2正极材料电化学性能的影响

通过共沉淀法制备锂离子电池富锂锰基正极材料Li1.2Mn0.534Ni0.133Co0.133O2,并对其进行AlF3包覆。实验结果表明,通过AlF3包覆,材料的电化学性能得到明显提高。在0.2C下,包覆前材料的首次放电比容量为253 mAh.g-1,首次充放电效率仅为88.8%。经过AlF3包覆,材料的首次放电比容量提高到294 mAh.g-1,首次充放电效率高达96.4%。同样,在1.0C下循环50次,未包覆材料的放电比容量由225 mAh.g-1降到185 mAh.g-1,容量保持率仅为82.2%。经过AlF3包覆,材料的放电比容量由230mAh.g-1仅降为222 mAh.g-1,容量保持率高达96.5%。     

ZrO_2负载Pt催化巴豆醛选择性加氢

以高比表面积ZrO2为载体,采用浸渍法制备了负载型Pt催化剂,应用于常压下气相巴豆醛加氢反应,考察了Pt负载量和H2还原温度等对巴豆醛选择性加氢性能的影响.实验结果表明,Pt负载量(质量分数)为3%的3Pt/ZrO2催化剂经500℃还原后,具有较高的巴豆醛选择性加氢性能:巴豆醛转化率为27%,巴豆醇的选择性为55%.X射线粉末衍射(XRD)分析,CO化学吸附,NH3程序升温脱附(NH3-TPD)表征结果表明Pt/ZrO2催化剂上Lewis强酸中心和适宜的Pt颗粒(约为8nm)有利于巴豆醛选择性加氢生成巴豆醇.     

纳米CuFe2O4-rGO复合材料的制备及电化学性能

采用溶剂热法成功制备了纳米CuFe₂O₄-rGO复合材料。通过X射线衍射（XRD）,扫描电子显微镜（SEM）、透射电子显微镜（TEM）和电化学工作站对样品的结构、形貌及电容特性进行表征。结果表明,CuFe₂O₄纳米粒子均匀地分散在石墨烯片层间,其中CuFe₂O₄-20% rGO复合材料具有最优的电化学性能,当电流密度1 A·g^-1时,其比电容为1 952.5 F·g^-1,当电流密度为1 A·g^-1时,CuFe₂O₄-20% rGO复合材料经1 000次充放电后的比电容保持率为86.17%。     

纳米CuFe_2O_4-rGO复合材料的制备及电化学性能

采用溶剂热法成功制备了纳米CuFe_2O_4-rGO复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学工作站对样品的结构、形貌及电容特性进行表征。结果表明,CuFe_2O_4纳米粒子均匀地分散在石墨烯片层间,其中CuFe_2O_4-20%rGO复合材料具有最优的电化学性能,当电流密度1 A·g~(-1)时,其比电容为1 952.5 F·g~(-1),当电流密度为1 A·g~(-1)时,CuFe_2O_4-20%rGO复合材料经1 000次充放电后的比电容保持率为86.17%。     

球磨辅助高温固相法制备Li1.0Na0.2Ni0.13Co0.13Mn0.54O2正极材料及其性能

以乙酸盐(乙酸锂、乙酸钠、乙酸钴、乙酸镍、乙酸锰等)为原材料,采用球磨辅助高温固相法制备Li_(1.0)Na_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2正极材料。借助XRD、SEM等表征材料的结构和形貌,利用循环伏安、恒流充放电、交流阻抗等方法研究材料的电化学性能。结果表明,钠的掺杂导致颗粒表面光滑度降低,形成Na_(0.77)Mn O_(2.05)新相。0.05C活化过程中,掺钠样品和未掺钠样品首次放电比容量分别为258.4 m Ah·g~(-1)和215.8 m Ah·g~(-1),库伦效率分别为75.2%和72.8%;2C放电比容量分别为116.3 m Ah·g~(-1)和106.2 m Ah·g~(-1)。研究发现,掺钠可减小首次充放电过程的不可逆容量,提高容量保持率;改善倍率性能与容量恢复特性;降低SEI膜阻抗和电荷转移阻抗;掺钠后样品首次循环就可以基本完成Li_2Mn O_3组分向稳定结构的转化,而未掺杂的样品需要两次循环才能逐步完成该过程;XPS结果表明,掺钠样品中Ni~(2+)、Co~(3+)、Mn~(4+)所占比例明显提高,改善了样品的稳定性和电化学性能;循环200次后的XRD结果表明掺钠与未掺钠材料在脱嵌锂反应中的相变化过程基本一致,良好有序的层状结构遭到破坏是循环过程中容量衰减的主要原因。