铁催化烯基芳烃的氢芳基化、甲基芳基化和二芳基化制备非对称1,1-二芳基烷烃的反应（英文）

报道了一种新型的铁催化的烯基芳烃的氢芳基化、甲基芳基化和双芳基化的反应.富电子的苯甲醚以及1,3,5-三甲氧基苯在温和条件下和烯基芳烃反应得到非对称的1,1-二芳基烷烃.其中,在氢芳基化反应中,苯甲酰基过氧化物被用作氧化剂;在甲基芳基化和双芳基化反应中,叔丁基过氧酯是氧化剂.

在含水介质中钯高效催化咪唑并[1,2-a]吡啶类化合物与芳基氯代物的碳氢芳基化反应（英文）

3-芳基咪唑并[1,2-a]吡啶骨架广泛存在于药物结构中,在药物学方面具有重要的地位及在材料化学、有机化学等方面也具有潜在的应用价值.在含水介质中,利用醋酸钯催化咪唑并[1,2-a]吡啶及其衍生物与芳基/杂芳基氯代物的碳氢芳基化反应,简便、高效地合成系列3-芳基咪唑并[1,2-a]吡啶类化合物,并以较好至优秀的收率获得芳基化产品.该方法采用廉价易得的芳基/杂芳基氯代物和咪唑并[1,2-a]吡啶类化合物为偶联反应的底物,且底物的范围能够拓展至缺电子、富电子的芳基氯代物和杂芳基氯代物及多种基团取代的咪唑并[1,2-a]吡啶类化合物.

1,1’-双(二苯基膦基)二茂铁介导的芳烃碳氢键芳基化反应制备联芳基骨架（英文）

联芳基骨架的合成过去主要依赖于过渡金属催化的交叉偶联反应和碳氢键芳基化反应。近年来,碱促进的芳基卤化物与非活化芳烃的自由基芳香取代反应(BHAS)得到了广泛的关注,为合成联芳基骨架提供了更简洁的策略。在本文中,我们报道了使用叔丁醇钾作碱和电子供体,dppf(1,1’-双(二苯基膦基)二茂铁)介导的非活化芳烃与芳基碘的直接芳基化反应。在标准反应条件下,一系列具有不同取代基团的芳基碘化物和芳烃都能顺利反应,以良好的收率和区域选择性生成芳基化产物。分子内芳基化反应也可以顺利进行:该反应经历了单电子转移(SET)/引发、5-exo-trig自由基加成、扩环、去质子化和芳构化/链增长等步骤。机理研究表明,dppf骨架中的二苯基膦基团通过与叔丁醇阴离子作用提高其单电子还原能力,是顺利引发反应的关键。同时,同位素效应实验结果表明叔丁醇钾与环己二烯基自由基中间体的去质子化过程是整个反应中的决速步。

Ni@Pd core-shell nanoparticles supported on a metal-organic framework as highly efficient catalysts for nitroarenes reduction

Ni@Pd core-shell nanoparticles with a mean particle size of 8–9 nm were prepared by solvothermal reduction of bivalent nickel and palladium in oleylamine and trioctylphosphine.Subsequently,the first-ever deposition of Ni@Pd core-shell nanoparticles having different compositions on a metal-organic framework（MIL-101）was accomplished by wet impregnation in n-hexane.The Ni@Pd/MIL-101 materials were characterized by powder X-ray diffraction,Fourier transform infrared spectroscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy and also investigated as catalysts for the hydrogenation of nitrobenzene under mild reaction conditions.At 30 °C and 0.1 MPa of H2 pressure,the Ni@Pd/MIL-101 gives a TOF as high as 375 h–1 for the hydrogenation of nitrobenzene and is applicable to a wide range of substituted nitroarenes.The exceptional performance of this catalyst is believed to result from the significant Ni-Pd interaction in the core-shell structure,together with promotion of the conversions of aromatics by uncoordinated Lewis acidic Cr sites on the MIL-101 support.

Carbon film encapsulated Fe_2O_3: An efficient catalyst for hydrogenation of nitroarenes

Iron catalysis has attracted a wealth of interdependent research for its abundance,low price,and nontoxicity.Herein,a convenient and stable iron oxide(Fe2O3)‐based catalyst,in which active Fe2O3nanoparticles(NPs)were embedded into carbon films,was prepared via the pyrolysis of iron‐polyaniline complexes on carbon particles.The obtained catalyst shows a large surface area,uniform pore channel distribution,with the Fe2O3NPs homogeneously dispersed across the hybrid material.Scanning electron microscopy,Raman spectroscopy and X‐ray diffraction analyses of the catalyst prepared at900°C(Fe2O3@G‐C‐900)and an acid‐pretreated commercial activated carbon confirmed that additional carbon materials formed on the pristine carbon particles.Observation of high‐resolution transmission electron microscopy images also revealed that the Fe2O3NPs in the hybrid were encapsulated by a thin carbon film.The Fe2O3@G‐C‐900composite was highly active and stable for the direct selective hydrogenation of nitroarenes to anilines under mild conditions,where previously noble metals were required.The synthetic strategy and the structure of the iron oxide‐based composite may lead to the advancement of cost‐effective and sustainable industrial processes.

Photocatalytic hydrogen-evolution dimerization of styrenes to synthesize 1,2-dihydro-1-arylnaphthalene derivatives using Acr^+-Mes and cobaloxime catalysts

We report a hydrogen-evolution dimerization of styrenes via the synergistic merger of Acr＋-Mes photocatalyst and cobaloxime proton reduction catalysts. By utilizing this dual catalyst system, 1,2-dihydro-1-arylnaphthalene derivatives can be directly constructed from commercially available styrenes. Our reaction proceeds smoothly under mild conditions without the need for oxidants or hydrogen atom transfer reagents, and the sole byproduct is hydrogen gas. Mechanistic investigation suggests that the reaction is initiated by photoinduced electron transfer under visible-light irradiation.

Synergism of Pt nanoparticles and iron oxide support for chemoselective hydrogenation of nitroarenes under mild conditions

An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors andα-Fe2O3 as a support.The catalyst with Pt content as low as 0.2 wt%exhibits high activities,chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes.The conversion of nitrobenzene can reach 3170 molconv h^–1 molPt^–1 under mild conditions(30°C,5 bar),which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions.The spatial separation of the active sites for H2 dissociation and hydrogenation should be responsible for the high chemoselectivity,which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles.The unique surface properties ofα-Fe2O3 play an important role in the reaction process.It provides active sites for hydrogen spillover and reactant adsorption,and ultimately completes the hydrogenation of the nitro group on the catalyst surface.

Chemoselective transfer hydrogenation to nitroarenes mediated by oxygen-implanted MoS_2

We present an efficient approach for the chemoselective synthesis of arylamines from nitroarenes and formate over an oxygen-implanted MoS2 catalyst（O-MoS2）.O-MoS2 was prepared by incomplete sul idation and reduction of an ammonium molybdate precursor.A number of Mo-O bonds were implanted in the as-synthesized ultrathin O-MoS2 nanosheets.As a consequence of the different coordination geometries of O（Mo O2） and S（MoS2）,and lengths of the Mo-O and Mo-S bonds,the implanted Mo-O bonds induced obvious defects and more coordinatively unsaturated（CUS） Mo sites in O-MoS2,as confirmed by X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,high resolution transmission electron microscopy,and extended X-ray absorption fine structure characterization of various MoS2-based materials.O-MoS2 with abundant CUS Mo sites was found to efficiently catalyze the chemoselective reduction of nitroarenes to arylamines.

Cobalt nanoparticles encapsulated in nitrogen-doped carbon for room-temperature selective hydrogenation of nitroarenes

Here,we report cobalt nanoparticles encapsulated in nitrogen‐doped carbon(Co@NC)that exhibit excellent catalytic activity and chemoselectivity for room‐temperature hydrogenation of nitroarenes.Co@NC was synthesized by pyrolyzing a mixture of a cobalt salt,an inexpensive organic molecule,and carbon nitride.Using the Co@NC catalyst,a turnover frequency of^12.3 h?1 and selectivity for 4‐aminophenol of>99.9%were achieved for hydrogenation of 4‐nitrophenol at room temperature and 10 bar H2 pressure.The excellent catalytic performance can be attributed to the cooperative effect of hydrogen activation by electron‐deficient Co nanoparticles and energetically preferred adsorption of the nitro group of nitroarenes to electron‐rich N‐doped carbon.In addition,there is electron transfer from the Co nanoparticles to N‐doped carbon,which further enhances the functionality of the metal center and carbon support.The catalyst also exhibits stable recycling performance and high activity for nitroaromatics with various substituents.

EPR and DFT Study of the Polycyclic Aromatic Radical Cations from Friedel-Crafts Alkylation Reactions

Electron paramagnetic resonance and electron-nuclear double resonance methods were used to study the polycyclic aromatic radical cations produced in a Friedel-Crafts alkylating sys- tem, with m-xylene, or p-xylene and alkyl chloride. The results indicate that the observed electron paramagnetic resonance spectra are due to polycyclic aromatic radicals formed from the parent hydrocarbons. It is suggested that benzyl halides produced in the Friedel-Crafts alkylation reactions undergo Scholl self-condensation to give polycyclic aromatic hydrocar- bons, which are converted into corresponding polycyclic aromatic radical cations in the presence of AlCl3. The identification of observed two radicals 2,6-dimethylanthracene and 1,4,5,8-tetramethylanthraeene were supported by density functional theory calculations using the B3LYP/6-31G（d,p）//B3LYP/6-31G（d） approach. The theoretical coupling constants support the experimental assignment of the observed radicals.

Catalytic Hydrogenation of Aromatic Compounds in the Liquid Phase

Peculiarities of a liquid phase hydrogenation, namely lower diffusivity of components influencing the reaction rate and deactivation of catalysts by leaching, are discussed. A focus is on hydrogenation of aromatic compounds, whereas the following processes are evaluated： （l） partial hydrogenation of benzene to cyclohexene; （2） hydrogenation of aniline; （3） hydrogenation of diphenylamine; （4） preparation of aniline from nitrobenzene; （5） hydrogenation of chloronitrobenzenes; （6） hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture. Processes （1） and （6） are typically carried out in the water-oil system. Generally, this type of system allows reaching a higher selectivity to desired products. In the case of hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture, the water phase extracts a water soluble catalyst; which is recycled and used for condensation of aniline and nitrobenzene. Problems of reaction kinetics, as well as catalysts deactivation are here discussed.

Visible-Light-Induced Selective Hydrocarboxylation of Alkynes with Formate

An efficient and sustainable protocol for regioselective hydrocarboxylation of alkynes to construct diverse propionic acid derivatives is disclosed.Under photoinduced conditions,the anti-Markovnikov hydrocarboxylation of alkynes was realized with CO_(2) radical anion in-situ generated from formate as both a carbonyl source and a reductant.The collaboration between photosensitizer and hydrogen atom transfer catalyst promoted the catalytic cycle to work smoothly,giving a broad substrate scope including terminal and internal alkynes.The Giese radical addition of CO_(2) radical anion to the C—C triple bond is the key step to initiate the reaction.

钴催化C—H功能化反应机理的理论研究

通过密度泛函理论方法研究了金属钴催化的烯炔与醛的C—H功能化生成吡咯烷反应.计算表明该反应机理主要包括氧化环化、C—H键复分解和还原消除3个步骤.决速步骤为C—H键复分解,与实验上提出的C—H键断裂的推论吻合.对比反应生成的氢化芳基化产物和氢化酰基化产物所对应的决速步骤发现,生成氢化芳基化产物需要克服的能垒比生成氢化酰基化产物需要克服的能垒低,该结果与实验观察到的选择性一致.

Structure evolution of thiophene-containing conjugated polymer photocatalysts for high-efficiency photocatalytic hydrogen production

Conjugated polymer photocatalysts have received extensive attention in the field of photocatalytic hydrogen evolution owing to their tunable molecular structures and electronic properties.Herein,we developed three donoracceptor(D-A)type thiophene-containing narrow-band-gap conjugated polymers with pyrene as a donor and different fused-thiophene derivatives as acceptors via direct C-H arylation coupling polymerization.It was found that the band gap of the polymers can be tuned by adjusting the number of the fused-thiophene rings.The visible light absorption range can be extended by increasing the number of the thiophene rings,the planar molecular structure for both donor and acceptor units facilitates the charge transmission along the polymer skeleton,and the D-A type polymer structure promotes the dissociation of photo-induced electrons and holes.As a result,a high photocatalytic hydrogen evolution rate of 33.07 mmol h^(−1)g^(−1) was obtained by PyTP-2 with an optimized molecular structure under visible light irradiation(λ>420 nm)without the aid of Pt co-catalyst.In addition,PyTP-2 also shows a photocatalytic activity for oxygen evolution with an average oxygen evolution rate of 58.37µmol h^(−1)g^(−1).

Cobalt single atoms anchored on N-doped ultrathin carbon nanosheets for selective transfer hydrogenation of nitroarenes

Selective transfer hydrogenation of nitroarenes to amines with transition metal nanocatalysts is appealing due to its low-cost, moderate reaction conditions, good activity and excellent selectivity. Single-atom catalysts (SACs) possessing advantages of maximum atom efficiency and particular electronic structure are expected to be more effective for this reaction, yet no report about it. Herein, cobalt single atoms anchored on N-doped ultrathin carbon nanosheets (denoted as CoSAs/NCNS) were produced and demonstrated as an outstanding SAC for selective transfer hydrogenation of nitroarenes to amines with formic acid as hydrogen donor. The turnover frequency (TOF) reached 110.6 h^-1, which was 20 times higher than the best results of cobalt nanopartides reported in literatures under similar reaction conditions. Moreover, CoSAs/NCNS exhibited excellent selectivity for a variety of nitroarenes bearing other reducible functionalities, such as iodo, cyano, keto, vinyl, alkynyl and ester groups. The findings further highlight the ability and advantages of SACs in heterogeneous catalysis.