NH_2-Ga-MIL-53催化剂对Strecker反应的底物选择性（英文）

研究了金属有机骨架化合物NH_2-Ga-MIL-53对多种N-苯基亚胺底物的Strecker反应的催化性能,研究结果表明:(1) NH_2-Ga-MIL-53具有高度催化活性和良好的底物普适性;(2)亚胺底物上取代基的电子效应是影响催化反应速率的关键因素,在亚胺底物上引入给电子取代基团(如甲氧基和苯基)可以加快反应速率,引入吸电子取代基团(如三氟甲基和硝基)可降低反应速率;(3)亚胺底物上取代基的位置对于催化反应速率同样具有重要影响,在亚胺底物的邻位引入甲氧基取代基团时,反应速率加快得最明显;(4)作为非均相催化剂,NH_2-Ga-MIL-53可循环使用9次而不失活且保持骨架结构不变;(5) NH_2-Ga-MIL-53和GaMIL-53催化性能的对比结果表明,NH_2-Ga-MIL-53结构中的氨基可以作为路易斯碱活性中心协同路易斯酸催化中心(Ga~(3+))有效促进strecker反应的进行。此外,由NH_2-Ga-MIL-53、六水合硝酸镓和2-氨基对苯二甲酸对Strecker反应的催化效果的对比可知,NH_2-Ga-MIL-53的孔结构是提高反应产物专一性的重要因素。     

D-甘露醇衍生的手性亚磷酸酯配体：合成及应用于铑催化α-脱氢氨基酸酯不对称氢化

以1,2:5,6-双亚环己基-D-甘露醇为手性骨架,合成含有联苯基团的新型手性tropos配体;分别以1,2:5,6-双异丙叉-D-甘露醇和1,2:5,6-双亚环己基-D-甘露醇为原料,合成系列双齿亚磷酸酯配体,将这些配体应用于铑催化α-乙酰氨基肉桂酸甲酯5a和α-苯酰氨基肉桂酸甲酯5b氢化反应中,考察配体结构,溶剂,底物/催化剂的摩尔比对反应对映选择性的影响,优化了反应条件;在底物是α-乙酰胺基肉桂酸甲酯时,配体的双异丙叉骨架与(R)-联萘部分是匹配组合,反应对映选择性高达93.5%.在优化的反应条件下,尝试七个苯环含不同取代基团的底物,无论供电子基团在芳环的邻位还是对位,其氢化产物的对映选择性均高于相应位置为吸电子基团的.     

亚胺氯化物介导一锅法合成3-吸电子基团取代吲哚衍生物

以3-氰基/酯基吲哚为代表的3-吸电子基团取代吲哚结构存在于多种生物活性分子中, 常作为优势骨架构建类药性化合物库用于新药发现. 本文设计并发展了一种基于亚胺氯化物活性中间体的串联反应, 从邻卤苯乙腈/酯和酰胺出发, 在碱和CuBr催化下, 一锅法构建结构多样性3-吸电子基团取代吲哚骨架的新合成方法. 该反应原料简单易得、反应快速(5 min完成)、产率高、底物适用范围广并可克级放大, 具有原子经济性和步骤经济性, 是基于优势骨架的多样性导向的合成方法学(privileged substructure-based DOS)案例的重要补充.     

手性磷酸催化亚甲胺叶立德与吲哚-3-甲醇不对称[3+3]环加成反应:一步构建多取代四氢-β-咔啉

研究了手性磷酸催化醛、氨基丙二酸酯与3-吲哚基苯基取代甲醇的三组分不对称[3+3]环加成反应,立体选择性地一步构建多取代四氢-β-咔啉骨架.考察了不同取代的手性磷酸催化剂、溶剂等因素对反应的影响,对芳环上不同位置具有不同性质取代基的底物进行了扩展,获得中等到优秀的产率(70%～91%),对映选择性良好到优秀(80%～93%ee),反应对底物芳环上的吸电子基和给电子基都具有良好的容忍性.     

取代席夫碱铜金属卟啉的微波辅助合成

微波辅助合成了取代席夫碱铜金属卟啉。 实验结果表明,取代苯甲醛与四(对氨基苯基)铜金属卟啉的缩合反应速率和产率与芳香醛取代基的种类有关,含吸电子基团的芳香醛大于含给电子基团的芳香醛,且随吸电子性的增强而增加,随给电子性的增强而减少。 水杨醛席夫碱铜金属卟啉侧链可与铜离子在碱性条件下形成铜配合物,其催化氧化环己烷的转化率达到了7.68%,环己酮的选择性达到了60.87%。     

MIL-53系列金属有机骨架化合物的合成及在Strecker反应中的催化性能

通过改变金属中心和配体官能团，合成了4个MIL-53系列金属有机骨架化合物NH₂-MIL-53（Sc），NH₂-MIL-53（Al），MIL-53（Sc）和NO₂-MIL-53（Sc）；研究了它们在合成α-氨基腈的Strecker反应中的催化性能.结果表明，NH₂-MIL-53（Sc）对于Strecker反应具有优异的催化性能，并具有可重复使用性.通过对比NH₂-MIL-53（Sc）和NH₂-MIL-53（Al）的催化性能，分析了金属离子半径和金属中心不饱和配位点对Strecker反应的影响.通过对比NH₂-MIL-53（Sc）与MIL-53（Sc）的催化性能，证明了作为路易斯碱中心的氨基可通过与路易斯酸中心的协同作用，有效促进Strecker反应的进行.通过对比NO₂-MIL-53（Sc）与MIL-53（Sc）的催化性能，认为催化剂结构上的硝基对于Strecker反应的进行具有重要影响.最后，通过对比NH₂-MIL-53（Sc）、硝酸钪和2-氨基对苯二甲酸（ATA）配体对催化性能的影响，总结出催化剂在纳米尺度的孔道结构是提高Strecker反应选择性的关键因素.     

二聚(2,5-噻吩乙烯撑)基态和激发态的电子结构: 桥基和芳环取代的影响

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)方法, 在B3LYP/TZVP水平下, 研究了一系列给电子基团(—NH2, —OCH3和—CH3)和吸电子基团(—CCH, —CN和—NO2)在二聚(2,5-噻吩乙烯撑)(2TV)的桥基和芳环上取代对基态和激发态电子结构的影响. 结果表明, 取代基的给/吸电子能力和取代位置对衍生物的几何结构以及吸收发射光谱均有重要影响, 其中氨基(—NH2)和硝基(—NO2)取代对2TV电子结构的影响较为显著. 此外, 对于桥基和芳环取代, 随着取代基吸电子能力的增强, 衍生物的前线分子轨道HOMO和LUMO的能级均呈逐渐降低的趋势.     

Lewis碱协助的 Lewis酸催化醇脱水合成烯烃及二氢吡喃开环合成2-肉桂基取代1,3-二羰基化合物

醇脱水是合成烯烃的重要方法之一。全球每年约有15%的苯乙烯是通过1-苯乙醇在酸性条件下脱水反应生产。虽然人们对该反应进行了较为深入的研究,但是当使用活性较高的1-苯乙醇衍生物为底物时,由于得到的取代苯乙烯产物具有较高的反应性,在脱水过程中会发生聚合而导致反应选择性降低,因此有必要探索适宜在高活性1-苯基乙醇脱水反应中应用的催化剂体系。
　　本文借助酸碱协同催化方法考察了1-(4-甲氧基苯基)乙醇制备4-甲氧基苯乙烯的反应。发现三苯基磷与 AlCl3构建的 Lewis碱/Lewis酸协同催化体系在硝基甲烷中可以接近定量的收率得到4-甲氧基苯乙烯。 Lewis碱/Lewis酸协同催化体系有效避免了4-甲氧基苯乙烯的二聚现象。底物拓展研究显示该方法具有很好的底物普适性,对多种取代苯乙烯的收率均超过80%。机理研究表明,1-(4-甲氧基苯基)乙醇在酸作用下先生成碳正离子,三苯基磷作为偶极性的电子给体不但能在一定程度上稳定该苄基碳正离子,而且抑制了其与4-甲氧基苯乙烯之间的亲电反应,进而最大化了脱质子生成4-甲氧基苯乙烯的选择性。
　　将Lewis碱协助的 Lewis酸催化提高反应选择性策略用于2-苯基-3,4-二氢吡喃衍生物合成2-肉桂基-1,3-二羰基化合物的开环反应。该类取代二氢吡喃在酸催化剂作用下也可生成苄基碳正离子,但是该中间体易受分子间和分子内亲电反应影响,反应选择性不高。而当使用单质碘/三苯基磷协同催化体系时,2-苯基-3,4-二氢吡喃衍生物能高选择性地实现开环反应,得到反式2-肉桂基-1,3-二羰基化合物。该类1,3-二羰基化合物具有丰富的反应性,是一类重要的合成子。     

铱催化的MBH乙酸酯与吲哚酮类化合物的烯丙基化反应

研究了一种新的铱催化的Morita-Baylis-Hillman(MBH)乙酸酯与3-苯基取代的吲哚酮的烯丙基烷基化反应, 发现铱催化的区域选择明显不同于钯催化的反应, 直接、 高效地合成了一类未见报道的具有新结构的 3,3-二取代的吲哚酮类化合物. 通过对亚磷酰胺、 双膦及单膦等配体、 金属源、 溶剂、 碱以及反应温度的筛选, 获得了适合该反应的催化体系及最优条件: 以[Ir(COD)Cl]₂(摩尔分数5%)和亚磷酰胺配体(L6, 摩尔分数10%)为催化剂, CH₃CN为溶剂, Cs₂CO₃为碱, 于?30 ℃反应25 h. 在最优条件下, 对不同类型取代基的底物进行了考察, 发现底物普适性良好, 产率最低为84%, 最高可达98%. 同时还发现, 底物取代基的电性对反应产率影响不大, 一些其它类型的双膦和单膦配体对催化反应也有较好的催化效果.     

Schiff碱配合物拟酶催化反应的取代基效应研究

系统地研究了新型Ｓｃｈｉｆｆ碱双核配合物在拟酶催化ＰｈＩＯ单加氧化环己烷反应中的取代基效应,结果表明,这些配合物的环外苯基及环上亚苯基上吸电子取代基均能提高配合物的催化活性,而给电子取代基作用相反;环上亚苯基上的取代基效应比环外苯基上的取代基效应更明显,催化反应表观速率常数ｋ与环外苯基上的取代基特性常数σ（σｍ或σｐ）及环上亚苯基上的取代基特性常数（σｍ＋σｐ）呈良好的线性关系;ｌｇｋ＝０．１６５８σ－６．０９０及ｌｇｋ＝０．７３９４「（σｍ＋σｐ）／２」－６．４７８。     

In Situ Formation of Frustrated Lewis Pairs in a Water‐Tolerant Metal‐Organic Framework for the Transformation of CO2

Frustrated Lewis pairs (FLPs) consist of sterically hindered Lewis acids and Lewis bases, which provide high catalytic activity towards non‐metal‐mediated activation of “inert” small molecules, including CO₂ among others. One critical issue of homogeneous FLPs, however, is their instability upon recycling, leading to catalytic deactivation. Herein, we provide a solution to this issue by incorporating a bulky Lewis acid‐functionalized ligand into a water‐tolerant metal‐organic framework (MOF), named SION‐105 , and employing Lewis basic diamine substrates for the in situ formation of FLPs within the MOF. Using CO₂ as a C1‐feedstock, this combination allows for the efficient transformation of a variety of diamine substrates into benzimidazoles. SION‐105 can be easily recycled by washing with MeOH and reused multiple times without losing its identity and catalytic activity, highlighting the advantage of the MOF approach in FLP chemistry.     

Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration

The reaction of the V-shaped linker molecule 5-hydroxyisophthalic acid (H₂L⁰), with Al or Ga nitrate under almost identical reaction conditions leads to the nitration of the linker and subsequent formation of metal–organic frameworks (MOFs) with CAU-10 or MIL-53 type structure of composition [Al(OH)(L)], denoted as Al-CAU-10-L^{0, 2, 4, 6} or [Ga(OH)(L)], denoted as Ga-MIL-53-L². The Al-MOF contains the original linker L⁰ as well as three different nitration products (L², L⁴ and L^4/6), whereas the Ga-MOF mainly incorporates the linker L². The compositions were deduced by ¹H NMR spectroscopy and confirmed by Rietveld refinement. In situ and ex situ studies were carried out to follow the nitration and crystallization, as well as the composition of the MOFs. The crystal structures were refined against powder X-ray diffraction (PXRD) data. As anticipated, the use of the V-shaped linker results in the formation of the CAU-10 type structure in the Al-MOF. Unexpectedly, the Ga-MOF crystallizes in a MIL-53 type structure, which is usually observed with linear or slightly bent linker molecules. To study the structure directing effect of the in situ nitrated linker, pure 2-nitrobenzene-1,3-dicarboxylic acid (m-H₂BDC-NO₂) was employed which exclusively led to the formation of [Ga(OH)(C₈H₃NO₆)] (Ga-MIL-53-m-BDC-NO₂), which is isoreticular to Ga-MIL-53-L². Density Functional Theory (DFT) calculations confirmed the higher stability of Ga-MIL-53-L² compared to Ga-CAU-10-L² and grand canonical Monte Carlo simulations (GCMC) are in agreement with the observed water adsorption isotherms of Ga-MIL-53-L².     

Immobilization of phosphotungstic acid in an amino‐containing metal–organic framework for oxidative desulfurization

A composite material has been successfully synthesized using an amino‐containing metal–organic framework (NH₂‐MOF) and phosphotungstic acid (PTA). This composite was characterized using X‐ray diffraction, high‐resolution transmission electron microscopy, nitrogen adsorption–desorption measurements, Fourier transform infrared spectroscopy and X‐ray fluorescence. Characterization results confirmed the immobilization and good distribution of PTA in the NH₂‐MOF. The PTA/NH₂‐MOF was subsequently applied in the oxidative desulfurization of dibenzothiophene (DBT) with H₂O₂ as the oxidant in n‐octane under atmospheric conditions. Under optimal reaction conditions, the oxidative desulfurization conversion of DBT reached 100%, and there was no significant decrease of the catalytic activity after four recycles. Kinetic experiments were also performed for the reaction at various temperatures, which indicated that oxidative reaction rates followed pseudo first‐order kinetics, and the apparent activation energy for the desulfurization reaction was 34.1 kJ mol^?1. The results indicated that this material exhibited excellent catalytic performance for oxidative desulfurization of DBT. Copyright © 2016 John Wiley & Sons, Ltd.     

Regioselectivity of methoxydebromination of substituted pentabromobenzenes C6Br5X in pyridine

The kinetics and regioselectivity of methoxydebromination of some substituted pentabromobenzenes C₆Br₅X (X = NO₂, CN, NH₂, MeNH, and MeO) were studied in pyridine at 115°C. The partial rate factors (k _f) were calculated for different positions of the polybrominated ring in these compounds. The effect of substituents X on methoxydebromination at themeta- andpara-positions is satisfactorily described only by the Hammett substituent constants ( = 2.22,r = 0.96). This allows one to conclude that direct polar conjugation of the substituents contributes only slightly to the transition state of the reaction. Theorthobromine atoms have a significant steric effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1784–1788, September, 1995.     

Analytical application of ion-molecule reactions. Reactions of various substituted cyclopropane molecular ions with ammonia

By ion cyclotron resonance it is found that various substituted cy clopropanes after ionization react with ammonia to give products which allow identification of the degree and kind ofsubstitution on the cyclopropl ring. For example, cyclopropyle reacts to give [CH₂NH₂]⁺ (m/e 30), methylcyclopropane gives [CH₂NH₂]⁺ (m/e 30) and the ethyl substituted [CH(C₂H₃)NH₂]⁺ (m/e 44) and ethylopropane gives [CH₂NH₂]⁺ (m/e 30) and the ethyl substituted [CH(C₂H₅)NH₂]⁺ (m/e 58). It is suggested that reactions of stable molecular ions with reagent neutrals may be a source of highly specific structural information for organic compounds.     

2‐Substituted dATP Derivatives as Building Blocks for Polymerase‐Catalyzed Synthesis of DNA Modified in the Minor Groove

2′‐Deoxyadenosine triphosphate (dATP) derivatives bearing diverse substituents (Cl, NH₂, CH₃, vinyl, ethynyl, and phenyl) at position 2 were prepared and tested as substrates for DNA polymerases. The 2‐phenyl‐dATP was not a substrate for DNA polymerases, but the dATPs bearing smaller substituents were good substrates in primer‐extension experiments, producing DNA substituted in the minor groove. The vinyl‐modified DNA was applied in thiol–ene addition and the ethynyl‐modified DNA was applied in a CuAAC click reaction to form DNA labelled with fluorescent dyes in the minor groove     

Sustainable Catalysis: Rational Pd Loading on MIL‐101Cr‐NH2 for More Efficient and Recyclable Suzuki–Miyaura Reactions

Palladium nanoparticles have been immobilized into an amino‐functionalized metal–organic framework (MOF), MIL‐101Cr‐NH₂, to form Pd@MIL‐101Cr‐NH₂. Four materials with different loadings of palladium have been prepared (denoted as 4‐, 8‐, 12‐, and 16 wt %Pd@MIL‐101Cr‐NH₂). The effects of catalyst loading and the size and distribution of the Pd nanoparticles on the catalytic performance have been studied. The catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier‐transform infrared (FTIR) spectroscopy, powder X‐ray diffraction (PXRD), N₂‐sorption isotherms, elemental analysis, and thermogravimetric analysis (TGA). To better characterize the palladium nanoparticles and their distribution in MIL‐101Cr‐NH₂, electron tomography was employed to reconstruct the 3D volume of 8 wt %Pd@MIL‐101Cr‐NH₂ particles. The pair distribution functions (PDFs) of the samples were extracted from total scattering experiments using high‐energy X‐rays (60 keV). The catalytic activity of the four MOF materials with different loadings of palladium nanoparticles was studied in the Suzuki–Miyaura cross‐coupling reaction. The best catalytic performance was obtained with the MOF that contained 8 wt % palladium nanoparticles. The metallic palladium nanoparticles were homogeneously distributed, with an average size of 2.6 nm. Excellent yields were obtained for a wide scope of substrates under remarkably mild conditions (water, aerobic conditions, room temperature, catalyst loading as low as 0.15 mol %). The material can be recycled at least 10 times without alteration of its catalytic properties.     

Cobalt imine–pyridine–carbonyl complex functionalized metal–organic frameworks as catalysts for alkene epoxidation

Aerobic epoxidation of alkene is a green and economical route to produce epoxides. For such reaction, transition metal complexes exhibit favorable catalytic activity. In this work, NH₂-MIL-101, a stable metal–organic framework (MOF) material with large surface area and high pore volume, was functionalized with pyridine-2,6-dicarbaldehyde and Co(NO₃)₂, to realize the immobilization of Co(II) via imine–pyridine–carbonyl (N,N,O) tridentate ligands bonding to MOF skeleton. The modified materials were applied as heterogeneous catalysts for the aerobic epoxidation of cyclohexene at ambient temperature, and multiple factors were studied to explore their influences on catalytic effects. Under the optimal reaction conditions, satisfactory substrate conversion and epoxide selectivity were reached. In addition, this catalytic system is suitable for a variety of alkene substrates. Furthermore, recycle experiments and infrared spectroscopy characterization illustrated that the coordination surroundings of Co are altering smoothly during the reaction process, thus having an impact on the performance of catalyst.

     

Influence of the Base on Pd@MIL‐101‐NH2(Cr) as Catalyst for the Suzuki–Miyaura Cross‐Coupling Reaction

The chemical stability of metal–organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki–Miyaura cross‐coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL‐101‐NH₂(Cr). Four bases were compared for the reaction: K₂CO₃, KF, Cs₂CO₃ and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N₂ sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL‐101‐NH₂(Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.