Copper‐Catalyzed One‐Pot Denitrogenative–Dehydrogenative–Decarboxylative Coupling of β‐Ketoacids with Trifluorodiazoethane: Facile Access to Trifluoromethylated Aldol Products

A novel copper‐catalyzed one‐pot cross‐coupling of β‐ketoacids with in situ generated trifluorodiazoethane has been developed. This reaction provides a direct and efficient method, in which one C?C bond and one C?O bond were formed in a carbenoid center with concomitant denitrogenation–dehydrogenation–decarboxylation, to afford trifluoromethylated aldol products. In several preliminary experiments, good to high enantioselectivities were also obtained.     

Tailoring 3,3′‐Dihydroxyisorenieratene to Hydroxystilbene: Finding a Resveratrol Analogue with Increased Antiproliferation Activity and Cell Selectivity

Four novel compounds were designed by “tailoring” 3,3′‐dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2′,3′,6′‐hexamethyl‐4,4′‐dihydroxy‐trans‐stilbene) was concisely synthesized in a one‐pot Stille–Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI‐H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol‐inspired antiproliferative agents.     

Molecular dynamics simulation study of xyloglucan adsorption on cellulose surfaces: effects of surface hydrophobicity and side-chain variation

The effect of surface hydrophobicity and side-chain variation on xyloglucan adsorption onto cellulose microfibrils (CMF) is investigated via molecular dynamics simulations. A molecular model of CMF with (100), (010), (1–10), (110) and (200) crystal faces was built. We considered xylogluco-oligosaccharides (XGO) with three repeating units, namely (XXXG)_3, (XXLG)₃, and (XXFG)₃ (where each (1,4)-β-d-glucosyl residue in the backbone is given a one-letter code according to its substituents: G = β-d-Glc; X = α-d-Xyl-(1,6)-β-d-Glc; L = β-d-Gal-(1,2)-α-d-Xyl-(1,6)-β-d-Glc; F = α-l-Fuc-(1,2)-β-d-Gal-(1,2)-α-d-Xyl-(1,6)-β-d-Glc). Our work shows that (XXXG)₃ binds more favorably to the CMF (100) and (200) hydrophobic surfaces than to the (110), (010) and (1–10) hydrophilic surfaces. The origin of this behavior is attributed to the topography of hydrophobic CMF surface, which stabilizes (XXXG)₃ in flat conformation. In contrast, on the rough hydrophilic CMF surface (XXXG)₃ adopts a less favorable random-coil conformation to facilitate more hydrogen bonds with the surface. Extending the xyloglucan side chains from (XXXG)₃ to (XXLG)₃ hinders their stacking on the CMF hydrophobic surface. For (XXFG)₃, the interaction with the hydrophobic surface is as strong as (XXXG)₃. All three XGOs have similar binding to the hydrophilic surface. Steered molecular dynamics simulation was performed on an adhesive model where (XXXG)₃ was sandwiched between two CMF hydrophobic surfaces. Our analysis suggests that this sandwich structure might help provide mechanical strength for plant cell walls. Our study relates to a recently revised model of primary cell walls in which extensibility is largely determined by xyloglucan located in limited regions of tight contact between CMFs.     

水杨羟肟酸对氟碳铈矿的捕收机制研究

以水杨羟肟酸为捕收剂,通过浮选试验、溶液化学计算、动电位和红外光谱检测分析研究了氟碳铈矿的可浮性及药剂与矿物的作用机制。当水杨羟肟酸浓度为5×10-4mol·L-1时,氟碳铈矿在pH=7~10较宽的范围内有较好的可浮性,与矿物表面的稀土阳离子的水解产物种类及其浓度有关。pH=8~9范围内,稀土阳离子水解优势组分RE(OH)2+和RE(OH)+2吸附在氟碳铈矿表面是主要的正活性质点,有利于药剂的化学吸附。在pH=8.3时,水杨羟肟酸对氟碳铈矿捕收是化学吸附作用生成五元环螯合物的结果。     

动态光散射研究盐对Gemini表面活性剂网状聚集体的影响

以动态光散射为主要手段研究了盐对羧酸盐Gemini表面活性剂O,O′-双(2-月桂酸钠)-p-二苯氧(记为C12φ2C12)自组织的影响.结果表明盐的加入很容易使C12φ2C12的网状聚集体转变为小(流体力学半径Rh,app约几纳米)和大(Rh,app100 nm)两种尺寸共存的聚集体,1,6-二苯基-1,3,5-己三烯(DPH)探针增溶实验证实小尺寸聚集体为核-壳结构的似球胶束,流变学测量说明大尺寸聚集体可能已经是线型的核-壳胶束.这种行为被归结为初始的网状聚集体不稳定,添加的反离子与C12φ2C12头基结合破坏了网状结构的亲水亲油平衡,促使了它们的转变.盐效应规律表现为MgCl2NaCl、Bu4NBrMe4NBrEt4NBrPr4NBr,这里Bu4NBr不遵循上述静电力顺序的原因是它提供了携带的丁基与C12φ2C12烷烃链疏水相互作用的附加力.     

水热-溶胶-凝胶法合成多壁碳纳米管-Na3V2（PO4）3复合物及其作为锂离子电池正极材料的性能

采用水热和溶胶-凝胶相结合的方法,制备了具有良好电化学性能的新型多壁碳纳米管-Na₃V₂（PO₄）₃（MWCNT-NVP）复合材料（MWCNT的质量分数为8.74%）. 通过场发射扫描电子显微镜表征可知,MWCNT分散在NVP纳米颗粒之间,并起到“电子导电线”的作用. 与纯Na₃V₂（PO₄）₃相比,MWCNT-NVP具有更高的比容量和更优异的循环性能. 在0.2C（35.2 mA·g^-1）的电流密度下,3.0-4.5 V的电压范围内,MWCNT-NVP的初始比容量为82.2 mAh·g^-1. 循环100次以后,比容量为72.3 mAh·g^-1. 在1.0-3.0 V充放电时,MWCNT-NVP的初始容量为100.6 mAh·g^-1. 100次循环以后,其容量保持率高达90%. 同时,交流阻抗测试表明,由于MWCNT的存在,MWCNT-NVP的导电性有了显著的提高. 以上结果表明,MWCNT-NVP是一种良好的锂离子电池电极材料.     

高活性硫化铅电极的制备及在量子点敏化太阳能电池中的应用

为了提高量子点敏化纳晶薄膜太阳能电池的光电转换效率,我们通过连续在酸和多硫溶液中处理铅片制备了对多硫电解液具有高电催化活性的硫化铅电极.通过电化学阻抗谱测试评价所制备硫化铅电极的催化活性,从而确定制备高效硫化铅电极的最佳条件.以在最佳条件下制备的硫化铅为对电极、CdSe量子点敏化TiO2纳晶薄膜为工作电极和多硫电解液组装成量子点敏化太阳能电池.光电性能测试结果表明所制备的电极具有良好的催化活性和光电转换性能.与已报导的方法相比,新方法大幅度地减少制备过程所需的时间,但却提高了所制备的硫化铅对电极的催化活性.通过X射线衍射和扫描电镜测试表征了硫化铅的生成过程,探讨了催化活性提高的原因.     

SnO_2/TiO_2纳米管复合光催化剂的性能及失活再生

基于微波水热法和微乳液法合成SnO2/TiO2纳米管复合光催化剂.通过X射线衍射(XRD)、配有能量色散X射线光谱仪(EDX)的透射电镜(TEM)和电化学手段对光催化剂进行表征.以甲苯为模型污染物,考察光催化剂在紫外光(UV)和真空远紫外光(VUV)下的性能及失活再生.结果表明,SnO2/TiO2纳米管复合光催化剂形成三元异质结(锐钛矿相TiO2(A-TiO2)/金红石相TiO2(R-TiO2)、A-TiO2/SnO2和R-TiO2/SnO2异质结),促使光生电子-空穴对的有效分离,提高光催化活性.SnO2/TiO2表现出最佳的光催化性能,UV和VUV条件下的甲苯降解率均达100%,CO2生成速率(k2)均为P25的3倍左右.但由于UV光照矿化能力不足,中间产物易在催化剂表面累积.随着UV光照时间的增加,SnO2/TiO2逐渐失活,20 h后k2由138.5 mg·m-3·h-1下降到76.1 mg·m-3·h-1.利用VUV再生失活的SnO2/TiO2,过程中产生的·OH、O2-·、O(1D)、O(3P)、O3等活性物质可氧化吸附于催化剂活性位的难降解中间产物,使催化剂得以再生,12 h后k2恢复到143.6 mg·m-3·h-1.UV和VUV的协同效应使UV降解耦合VUV再生成为一种可持续的光催化降解污染物模式.     

Enhanced Anticancer Efficacy by ATP‐Mediated Liposomal Drug Delivery

A liposome‐based co‐delivery system composed of a fusogenic liposome encapsulating ATP‐responsive elements with chemotherapeutics and a liposome containing ATP was developed for ATP‐mediated drug release triggered by liposomal fusion. The fusogenic liposome had a protein–DNA complex core containing an ATP‐responsive DNA scaffold with doxorubicin (DOX) and could release DOX through a conformational change from the duplex to the aptamer/ATP complex in the presence of ATP. A cell‐penetrating peptide‐modified fusogenic liposomal membrane was coated on the core, which had an acid‐triggered fusogenic potential with the ATP‐loaded liposomes or endosomes/lysosomes. Directly delivering extrinsic liposomal ATP promoted the drug release from the fusogenic liposome in the acidic intracellular compartments upon a pH‐sensitive membrane fusion and anticancer efficacy was enhanced both in vitro and in vivo.     

Oxidative Cross‐Coupling of Allenyl Ketones and Organoboronic Acids: Expeditious Synthesis of Highly Substituted Furans

Allenyl ketones are employed as coupling partners in palladium‐catalyzed oxidative cross‐coupling reactions with organoboronic acids. This reaction constitutes an efficient methodology for the synthesis of highly substituted furan derivatives. Palladium‐carbene migratory insertion is proposed as the key step in this transformation.