Metal‐Free Hydrogenation of Unsaturated Hydrocarbons Employing Molecular Hydrogen

The metal‐free activation of hydrogen by frustrated Lewis pairs (FLPs) is a valuable method for the hydrogenation of polarized unsaturated molecules ranging from imines, enamines, and silyl enol ethers to heterocycles. However, one of the most important applications of hydrogenation technology is the conversion of unsaturated hydrocarbons into alkanes or alkenes. Despite the fast development of the FLP chemistry, such reactions proved as highly challenging. This Minireview provides an overview of the basic concepts of FLP chemistry, the challenge in the hydrogenation of unsaturated hydrocarbons, and first solutions to this central transformation.     

Highly Efficient and Stereoselective Construction of Bispirooxindole Derivatives via a Three-Component 1,3-Dipolar Cycloaddition Reaction

A highly regio- and stereoselective synthesis of bispirooxindoles by 1,3-dipolar cycloaddition of in situ generated azomethine ylides from isatin and proline to different electron-deficient alkenes has been developed. The synthesis affords the desired bispiro scaffold compounds in excellent yields with high regioselectivity under mild conditions. The stereochemistry was determined by single-crystal X-ray analysis.     

Platinum(II) Olefin Hydroarylation Catalysts: Tuning Selectivity for the anti‐Markovnikov Product

Pt^II complexes containing unsymmetrical (pyridyl)pyrrolide ligands are shown to catalyze the hydroarylation of unactivated alkenes with selectivity for the anti‐Markovnikov product. Substitution on the pyrrolide portion of the ligand allows effective tuning of the selectivity to anti‐Markovnikov alkylarene products, whereas substitution on the pyridyl portion can promote competitive alkenylarene production.     

RhIII‐Catalyzed Hydroacylation Reactions between N‐Sulfonyl 2‐Aminobenzaldehydes and Olefins

Metal‐catalyzed hydroacylation of olefins represents an important atom‐economic synthetic process in C?H activation. For the first time highly efficient Rh^IIICp*‐catalyzed hydroacylation was realized in the coupling of N‐sulfonyl 2‐aminobenzaldehydes with both conjugated and aliphatic olefins, leading to the synthesis of various aryl ketones. Occasionally, oxidative coupling occurred when a silver(I) oxidant was used.     

The sol-gel derived Co-Mn/TiO_2 catalysts for light olefins production

In this research work,two 30%(Co-Mn)/TiO2catalysts were prepared using sol-gel(catalyst A)and coprecipitation(catalyst B)methods.The activity and selectivity to C2~4light olefins in Fischer-Tropsch synthesis(FTS)has been studied in a fixed-bed reactor under different operational conditions.These operational conditions were:temperature220~280℃,and total pressure from0.1~0.6 MPa.The optimum operating conditions were investigated after steady state.As the results shown,the catalyst A was more selective to C2~4olefins(58.7%in 260℃)and catalyst B was more selective to C5+hydrocarbons.Characterization of both catalysts was carried out by using X-ray diffraction(XRD),scanning electron microscopy(SEM)and N2adsorption-desorption measurements methods.     

Fe/SiO_2纳米复合物上合成气制低碳烯烃催化性能研究

分别采用一步合成法和常规共沉淀法制备了Fe/SiO2催化剂,通过N2物理吸附、X射线衍射、透射电镜、傅里叶变换红外光谱和程序升温还原等方法对催化剂进行了表征,并在固定床反应器中对其费托合成制低碳烯烃的催化性能进行了评价。结果表明,与共沉淀铁基催化剂不同,采用一步合成法制备的纳米复合物主要由Fe3O4相构成,形貌呈规则球形,平均粒径为30 nm,尺寸分布窄,更容易还原。一步合成法制得的Fe/SiO2催化剂对费托合成反应具有较高的活性和低碳烯烃选择性、较低的甲烷选择性和良好的稳定性。     

Copper‐Catalyzed Trifluoromethylation of Internal Olefinic CH Bonds: Efficient Routes to Trifluoromethylated Tetrasubstituted Olefins and N‐Heterocycles

The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient Cu^II‐catalyzed trifluoromethylation of internal olefins, that is, α‐oxoketene dithioacetals, has been achieved by using Cu(OH)₂ as a catalyst and TMSCF₃ as a trifluoromethylating reagent. The push–pull effect from the polarized olefin substrates facilitates the internal olefinic C?H trifluoromethylation. Cyclic and acyclic dithioalkyl α‐oxoketene acetals were used as the substrates and various substituents were tolerated. The internal olefinic C?H bond cleavage was not involved in the rate‐determining step, and a mechanism that involves radicals is proposed based on a TEMPO‐quenching experiment of the trifluoromethylation reaction. Further derivatization of the resultant CF₃ olefins led to multifunctionalized tetrasubstituted CF₃ olefins and trifluoromethylated N‐heterocycles.     

Fe@Si/S-34催化剂的制备及其合成气制烯烃性能

合成气经费托合成反应直接制低碳烯烃是极具开发前景的合成气直接制烯烃技术,其关键是通过产物分布的调控提高低碳烯烃的选择性.本工作将疏水性Fe基费托合成催化剂与SAPO-34分子筛进行复合,制备了一系列不同SAPO-34分子筛含量的Fe@Si/S-34复合催化剂.采用X射线衍射、扫描电子显微镜、N₂吸附-脱附、NH₃程序升温脱附和水接触角测量仪考察了SAPO-34分子筛含量对催化剂物化性质的影响.结果表明SAPO-34分子筛的含量对催化剂的表面积、孔体积、酸性和疏水性具有显著的影响.随着SAPO-34分子筛含量的增加,催化剂的比表面积和总孔体积增加,弱酸和中强酸位点增加,疏水性减弱.催化性能评价结果表明,Fe@Si/S-34复合催化剂明显降低了C₅₊产物选择性,增加了C₂～C₄烃类的选择性,适量的SAPO-34分子筛能够显著提高C₂～C₄烯烃的选择性.本研究将Fe@Si催化剂的疏水性和SAPO-34分子筛对C₅₊烃的...     

Pd@Pt Core–Shell Nanoparticles with Branched Dandelion‐like Morphology as Highly Efficient Catalysts for Olefin Reduction

A facile synthesis based on the addition of ascorbic acid to a mixture of Na₂PdCl₄, K₂PtCl₆, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion‐like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core–shell NPs, which differs from the traditional seed‐mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion‐like Pd@Pt core–shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro–mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers.     

ZrCdOx/SAPO-18双功能催化剂催化CO2加氢合成低碳烯烃性能

采用并流共沉淀法制备了不同Zr/Cd原子比（n_Zr/n_Cd）的ZrCdO_x金属氧化物，并与水热法制备的不同硅铝比（n_SiO2/n_{Al2O3）的片状SAPO-18分子筛物理混合制得ZrCdOx/SAPO-18双功能催化剂，研究了其催化CO2加氢直接合成低碳烯烃性能。采用透射电子显微镜（TEM）、X射线衍射（XRD）、N2吸附-脱附、CO2程序升温脱附（CO2-TPD）、NH3程序升温脱附（NH3-TPD）和X射线光电子能谱（XPS）对催化剂进行了分析。与单一ZrO2相比，引入CdO使得ZrCdOx比表面积下降，当nZr/nCd=8时制备的Zr8Cd1氧化物呈现出无定形小颗粒状，Zr与Cd之间较强的协同作用使得ZrCdOx氧化物产生了更多的氧空位，有利于CO2的吸附活化。通过对Zr8Cd1金属氧化物与SAPO-18（硅铝比0.1）的质量比、工艺反应温度、压力和空速对催化性能影响的考察，获得了最佳反应条件。研究还发现，当SAPO-18的硅铝比从0.1降为0.01时，Brø；nsted酸含量降低，产物中烯烃/烷烃物质的量之比从18.6提高至37.2，但副产物CO含量迅速增加，低碳烯烃时空收率明显下降。}