A total synthesis of verbenachalcone, a bioactive diaryl ether from Verbena littoralis

Verbenachalcone 1, isolated from the aerial part of Verbena littoralis H. B. K. (Verbenaceae), has successfully been synthesized by employing anodic oxidation of the phenol derivative 3, as the key step. The bromine and chlorine substituents of 3 effected regioselective introduction of a methoxy group, as well as modulating the oxidation reaction. A flow-cell type apparatus of anodic oxidation provided the desired diaryl ether 4 in good yield.     

工业用加氢脱氮催化剂所含MoS2的形貌

用透射电镜（ＴＥＭ）观察了Ａ，Ｂ两种工业用加氢脱氮（ＨＤＮ）催化剂所含活性相基础物ＭｏＳ２的形貌，并根据ＴＥＭ图像测量了ＭｏＳ２六角形晶体的对角线长度（Ｌ）和层数（Ｎ）．由此计算相应平均值工和Ｎ及晶体分布密度（Ｓ），并绘制了Ｌ的分布曲线．使用前，高活性Ａ催化剂的Ｌ值比Ｂ催化剂小，而Ｓ值则比其大．长期运转后，两种催化剂的Ｌ值都增大，Ｓ值都减小，但Ａ催化剂的变化明显小于Ｂ催化剂．由ＴＥＭ结果表明，ＭＯＳ２晶体的分散状态是影响Ｍｏ－Ｎｉ／Ａｌ２Ｏ３ＨＤＮ催化剂活性的因素之一．     

Stereoselective Michael Addition and Michael-aldol Tandem Reaction of Diorganyl Diselenides or Disulfides with Conjugated Alkynones Mediated by Samarium Diiodide

Stereoselective Michael addition and Michael-aldol tandem reaction of diorganyl diselenides and disulfides with conjugated alkynones mediated by samarium diiodide were studied. The reaction temperature was critical for the stereoselectivity, β-Organylselenoalkenones or β-organylthioalkenones and γ-organylselenoallylic alcohols or γ-organylthioallylic alcohols were prepared in good yields.     

Perfluoroalkylation of 2-Thiopyrimidine Derivatives

The method of perfluoroalkylation of heterocyclic thiols and disulfides by thermolytic reaction with xenon(II) bisperfluoroalkylcarboxylates has been extended to sulfur-containing pyrimidines, including 2-mercaptopyrimidines, symmetrical disulfides, and S-trifluoroacetyl derivatives obtained from the corresponding thiols. The main reaction products are 2-SC_nF_2n+1 (n = 1, 2)-substituted pyrimidines. Their formation proceeds only via disulfides into which the initial thiols and S-trifluoroacetyl derivatives are converted in the reaction medium. Side reactions occurred in the case of trifluoromethylation linked with the perfluoroalkylation of the pyrimidine nucleus at the free 5 position (in the case of the 4,6-dimethyl derivative), or at position 4 or 4 and 5 (for unsubstituted pyrimidine). In addition, the introduction of the CF₃ group at one of the methyl substituents was confirmed by the formation of CH₂CF₃ fragment.     

Cu-nanoparticle catalyzed O-arylation of phenols with aryl halides via Ullmann coupling

Recyclable Cu-nanoparticles provide an efficient, economic, and novel method for the synthesis of diaryl ethers via Ullmann type coupling. This method provides a wide range of substrate applicability and avoids the use of a heavy metal co-catalyst and gives diaryl ethers in satisfactory yields.     

PVC-based bis(2-nitrophenyl)disulfide sensor for zinc ions

A PVC membrane electrode based on bis(2-nitrophenyl)disulfide carrier exhibits a very good response for Zn²⁺ in a wide concentration range (from 2.9×10⁻⁷ to 3.2×10⁻² mol l⁻¹) with a slope of 29.9±0.4 mV per decade of Zn²⁺ concentration. The response time of the sensor is about 10 s and the membrane can be used for more than 3 months without any observed divergence in potentials. The proposed sensor exhibits very good selectivity for Zn²⁺ over many cations and can be used in a wide pH range (2-9). This assembly served also as an indicator electrode in potentiometric titrations involving zinc ions and direct potentiometric determination of zinc ions in real and synthetic samples.     

Gold Nanoclusters Grown on MoS2 Nanosheets by Pulsed Laser Deposition: An Enhanced Hydrogen Evolution Reaction

Au nanoparticles were decorated on a 2H MoS₂ surface to form an Au/MoS₂ composite by pulse laser deposition. Improved HER activity of Au/MoS₂ is evidenced by a positively shifted overpotential (−77 mV) at a current density of −10 mA cm⁻² compared with pure MoS₂ nanosheets. Experimental evidence shows that the interface between Au and MoS₂ provides more sites to combine protons to form an active H atom. The density functional theory calculations found that new Au active sites on the Au and MoS₂ interface with improved conductivity of the whole system are essential for enhancing HER activity of Au/MoS₂.     

Vulcanization of polypropylene

Dynamic covalent crosslinking of commodity thermoplastics is a desirable target in material development, as it promises to combine the enhanced mechanical properties and thermal/solvent stability of thermosets with reprocessability and plastic flow under certain conditions activating the bond exchange. Many attempts of this development suffer from the same two problems: enhanced cost due to complex and often toxic chemicals, and the effective melt-flow index being too low for practical use. Here we return to the origins of polymer networks, and mimic the vulcanization of natural rubber in the commodity polypropylene using elemental sulfur initiated by peroxide. Forming sulfur bridges allows easy catalyst-free reprocessability based on the disulfide bond exchange. We study a broad range of compositions and reaction conditions, finding optimal balance between the crosslinking and chain scission in the melt compounder, and demonstrating much enhanced characteristics of the resulting materials. We specifically discuss and evaluate the balance between the rubber-elastic network response at high temperatures and the plastic flow enabled by disulfide exchange, responsible for the reprocessing of our vitrimers.     

双二苯基膦甲烷和μ^4-S的四核铜(Ⅰ)配合物的 合成与结构

室温下,双核配合物[Cu(dppm)(NO~3)]~2与二硫化碳反应制备了四核铜(Ⅰ)配合物[Cu~4(S)(dppm)~4](PF~6)~2·CH~2Cl~2(dppm=双二苯基膦甲烷),并经光谱学方法表征了配合物的物理化学性质。X射线四圆衍射测定结果表明dppm属桥式双齿配位,S^2^-以μ^4形式与中心铜离子配位,PF~6^-位于配合物的外界,铜离子呈现三角平面配位构型。     

Catalytic oxidation of CS2 over atmospheric particles and oxide catalysts

The catalytic oxidization of CS₂ over atmospheric particles and some oxide catalysts was explored through FT-IR, MS and a fixed-bed stainless steel reactor. The results show that atmospheric particles and some oxide catalysts exhibited considerable oxidizing activities for CS₂ at ambient temperature. The reaction products are mainly COS and elemental sulfur, even CO₂ on some catalysts. Among the catalysts, CaO has the strongest catalytic activity for oxidizing CS₂. Fe₂O₃ is weaker than CaO. The catalytic activity for Al₂O₃ reduces considerably compared with the former two catalysts, and SiO₂ the weakest. Atmospheric particle samples’ catalytic activity is between Fe₂O₃’s and Al₂O₃’s. The atmospheric particle sample collected mainly consists of Ca(Al₂Si₂O₈) · 4H₂O, which is also the main component of cement. COS, the main product, is formed by the catalytic oxidization of CS₂ with adsorbed “molecular” oxygen over the catalysts’ surfaces. The concentration of adsorbed oxygen over catalysts’ surfaces may be the key factor contributed to the oxidizing activity. It is indicated that CS₂ could be catalytically oxidized over atmospheric particles, which induced that this reaction may be another important source of atmospheric COS from CS₂.