Advances in Catalyst Systems for the Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

Hydrogenation of prochiral ketones using chiral transition-metal catalysts represents the cleanest way to access enantiomerically enriched secondary alcohols, which are important building blocks in fine chemicals synthesis. Despite excellent activity, selectivity and compatibility of metal complexes with variety of functional groups, no universal catalysts exist. In this article we summarize the advances in catalyst systems for the asymmetric homogenous and heterogenous hydrogenation of ketones that have been made in past decade. The development of catalysts is oriented in reaching as high as activity with low catalyst loadings, using “greener’’ conditions, and ensuring good recyclability of catalysts. Even though ruthenium complexes represent the largest part of the catalysts, other metals rapidly penetrate this field.     

Rhodium‐Catalyzed Hydrogenation of Alkenes by Rhodium/Tris(fluoroalkoxy)phosphane Complexes in Fluorous Biphasic System

The reaction of [Ir(μ‐Cl)(COD)]₂ with various fluorous derivatives of triphenylphosphane containing a para‐, meta‐, or ortho‐(1H,1H‐perfluoroalkoxy)‐substituted fluorous phosphane P(C₆H₄‐ORf)₃ (Rf=CH₂C₇F₁₅, CH₂CH₂CH₂C₈F₁₇) and CO (1 atm) gives the corresponding trans‐[Ir(μ‐Cl)(CO){P(C₆H₄ORf)₃}₂]. The IR ν_CO values of these complexes give some information on the donor/acceptor properties of the phosphanes. These fluorous derivatives of triphenylphosphane, as well as a phosphane bearing two (1H,1H‐perfluoroalkyloxy) chains at the 3,5‐positions, were used in association with [Rh(μ‐Cl)(COD)]₂ or [Rh(COD)₂]PF₆ in the reduction of methyl cinnamate, 2‐cyclohexen‐1‐one, cinnamaldehyde, and methyl α‐acetamidocinnamate in a two‐phase system D‐100/ethanol under 1 bar hydrogen at room temperature. Some differences in catalytic activity were observed in the reduction of methyl cinnamate, the most active catalyst being the rhodium complex containing the phosphane with the p‐fluorous ponytail. Recycling of the fluorous catalyst was possible, particularly using the p‐substituted phosphane, where no significant loss of catalyst or activity was observed, and generally with very low leaching of rhodium or phosphane in the organic phase.     

毛细管气相色谱法测定三(3-羟丙基)膦反应液中丙烯醇的含量

建立了毛细管气相色谱测定三(3-羟丙基)膦反应液中丙烯醇含量的方法,采用35m×0.32 mm×0.3 μm PEG-20M毛细管色谱柱分离,FID检测器.在优化的条件下,以内标标准曲线法(正丁醇作为内标物)定量,测定的相对标准偏差为1.52％～2.50％,平均回收率为98.8％～100.6％,该方法具有简便、快速、准确的特点.     

改性骨架镍催化邻硝基氯苯加氢制备2，2’-二氯氢化偶氮苯

通过对骨架镍催化剂添加第三金属M(Mo,Ti,Cr)制备改性骨架镍催化剂,并采用间歇加压釜式反应器对改性骨架镍催化剂进行活性评价,考察了不同添加金属、反应压力、温度、碱量、催化剂循环套用次数等工艺条件对催化加氢法制备2,2'-二氯氢化偶氮苯的影响。实验得到优惠的反应条件为:使用Mo-Ni-Al改性骨架镍催化剂,反应温度350K,反应压力0.8MPa,30%的氢氧化钠溶液40mL。邻氯硝基苯的转化率达99.5%,2,2'-二氯氢化偶氮苯的收率可达90.5%。同时催化剂循环套用5次后其催化活性基本保持不变。结果表明,改性骨架镍催化剂较之普通骨架镍催化剂的活性、选择性及稳定性都有明显的提高,具有良好的工业应用前景。     

球磨时间对Cu/SiO_2规整结构催化剂草酸酯加氢性能与涂层黏结性影响

将蒸氨法制备的Cu/Si O2催化剂原粉球磨不同的时间获得一系列球磨胶,再涂覆到堇青石载体上获得系列的规整结构催化剂,并对球磨胶及催化剂进行表征。N2物理吸附、压汞法、N2O滴定及X射线衍射表征结果表明,不同球磨时间的催化剂的物化性能和相结构变化不大;激光粒度仪和扫描电镜表征结果表明,延长球磨时间可以降低球磨胶的粒度,改善催化剂的表面形貌,提高涂层黏结性。而涂层黏结性强的Cu/Si O2规整结构催化剂在草酸酯加氢制乙二醇反应中表现出较高的催化性能。     

热稳定性增强的铈改性Cu/SiO_2催化剂及在草酸酯加氢制乙二醇反应中的应用

采用蒸氨法制备了一系列铈改性的Cu/Si O2催化剂,并对该催化剂在草酸二甲酯(DMO)加氢制乙二醇反应中的催化活性及热稳定性进行了考察。研究发现铈的加入对于催化剂表面铜物种的分布有显著的影响,而Cu+的含量是影响加氢活性的主要因素,铈通过影响催化剂中Cu+的含量而影响催化剂的反应活性。此外,催化剂表征结果表明铈可以提高铜物种与载体间的相互作用,同时4价铈的氧化性阻碍了Cu+的进一步还原,从而使得催化剂表面大部分的Cu+在热冲击以及还原后得以保留。因此,相比于铜硅催化剂,铈改性催化剂(Cu-1.0Ce/Si O2)在草酸酯加氢制乙二醇反应中表现出较强的热稳定性。     

Facile Rh-C Bond Cleavage of Rhodium(III) Benzyl Porphyrin Complex in DMSO with Strong Bases

Rhodium-carbon bond cleavage represents an essential step for small molecule activation and transformation by rhodium porphyrin complexes. This article reports on a new method for the cleavage of porphyrin rhodium(III)-carbon bonds in DMSO solvent with strong bases. UV-Vis, in situ ¹H NMR spectrum and GC-MS analysis confirmed generation of rhodium(I) species and monodeuterated toluene. Mechanistic studies revealed that strongly reducing CD₃SOCD₂⁻, formed in situ from DMSO-d₆ and strong bases, promoted Rh-C bond cleavage.     

Kinetics and Mechanisms of Homogeneous Catalytic Reactions. Part 11. Regioselective Hydrogenation of Quinoline Catalyzed by Rhodium Systems Containing 1,2-Bis(diphenylphosphino)ethane

Abstract  

The system prepared in situ by addition of two equivalents of 1,2-bis(diphenylphosphino)ethane (dppe) to Rh₂Cl₂(COE)₄ (COE = cyclooctene) showed to be an efficient and regioselective precatalyst for the hydrogenation of quinoline (Q). This reaction showed to be independent of the Q concentration and of fractional order on H₂ and catalyst concentrations (1.5 and 0.6, respectively). The fractional order on catalyst concentration indicates that several catalytic species with different activities are present in the reaction medium; however, the cationic species [Rh (dppe)₂]⁺ was the only phosphorous-containing compound detected by ³¹P{¹H} NMR. For the acac salt of this cationic bis(dppe) complex, a kinetic study led to the rate law r = {K₁k₂/(1 + K₁[H₂])}[M][H₂]²; [M(Q)(κ²-dppe)(κ¹-dppe)]⁺ was proposed as the catalytically active species (CAS) of the cycle. The general mechanism involves a reversible oxidative addition of H₂ to generate a dihydrido complex, which transfers the hydride ligands to the coordinated Q to yield species containing a 1,2-dihydroquinoline (DHQ) ligand, followed by a second oxidative addition of H₂, considered as the rate-determining step of the cycle; hydrogen transfer toward the DHQ ligand yields THQ, regenerates the CAS and restarts the catalytic cycle.     

固体酸催化合成三(三溴苯氧基)异氰脲酸酯及其阻燃聚氨酯脲的研究

以异氰脲酸(CA)和三溴苯酚(TBP)为原料,用SO42-/MxOy型固体酸作催化剂合成三(三溴苯氧基)异氰脲酸酯(TTBPC)。利用红外光谱(FT-IR)、差示扫描量热法(DSC)和热重(TG)对其结构及热稳定性、热分解行为进行了表征,并研究了添加该阻燃剂的聚氨酯脲(PUU)的力学性能与阻燃性能,结果表明此阻燃剂能够增加PUU的力学性能,且能阻止其燃烧。     

Study on Deactivation by Sulfur and Regeneration of Pd/C Catalyst in Hydrogenation of N-(3-nitro-4-methoxyphenyl) Acetamide

Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials. For instance, the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide. In this study, the chemisorption of sulfur on the surface of deactivated Pd/C was detected by energy dispersive spectrometer and X-ray photoelectron spectroscopy. Sulfur compounds poison the Pd/C catalyst and increase the formation of azo deposit, reducing the activity of catalyst. We report a mild method to regenerate the Pd/C catalyst: wash the deposit by N,N-dimethylformamide and oxidize the chemisorbed sulfur by hot air. The regenerated Pd/C catalyst can be reused at least ten runs with stable activity.     

水溶性meso-四(4-甲氧基-3-磺酸苯基)卟啉及其金属化合物合成新方法研究

采用浓硫酸和少量发烟硫酸在常温下合成了水溶性的四(4-甲氧基-3-磺酸基苯基)卟啉及其铁、钻、铜、锌、锰和镍金属化合物,采用核磁、质谱、紫外和元素分析仪对其结构进行了表征.该方法采用一定比例的浓硫酸和发烟硫酸混合物在常温下与卟啉反应,产物收率均超过98%.替代了文献中所采用的氯磺酸和硅烷氯磺酸酯等稳定性差且易于产生HC...     

The Iron(II) Complex [Fe(CF3SO3)2(mcp)] as a Convenient,Readily Available Catalyst for the Selective Oxidation of Methylenic Sites in Alkanes

The efficient and selective oxidation of secondary C H sites of alkanes is achieved by using low catalyst loadings of a non‐expensive, readily available iron catalyst [Fe(II)(CF₃SO₃)₂(mcp)], { Fe‐mcp , [mcp=N,N′‐dimethyl‐N,N′‐bis(2‐pyridylmethyl)cyclohexane‐trans‐1,2‐diamine]}, and hydrogen peroxide (H₂O₂) as oxidant, via a simple reaction protocol. Natural products are selectively oxidized and isolated in synthetically amenable yields. The easy access to large quantities of the catalyst and the simplicity of the C H oxidation procedure make this system a particularly convenient tool to carry out alkane C H oxidation reactions on the preparative scale, and in short reaction times.

     

催化加氢法绿色合成肛N-(3-氨基-4-甲氧基苯基)乙酰胺

N-(3-氨基-4-甲氧基苯基)乙酰胺是生产偶氮型分散染料的一类重要中间体.现有的工业生产方法仍全部采用铁粉还原.笔者开发了一种高效的Pd/C催化剂,分别选用甲醇和水作为反应溶剂,实现了高活性、高选择性和高稳定性地催化加氢制备Ⅳ-(3-氨基-4-甲氧基苯基)乙酰胺.为了抑制原料和产物在水溶液中的副反应.添加少量碱性助剂可以提高目标产物的选择性,最高达到99.3%.     

On the Use of Ruthenium Dioxide in 1-n-Butyl-3-Methylimidazolium Ionic Liquids as Catalyst Precursor for Hydrogenation Reactions

The H₂ reduction of RuO₂ hydrate “dissolved” in 1-n-butyl-3-methylimidazolium ionic liquids with different counterions, hexafluorophosphate (BMI ? PF₆), tetrafluoroborate (BMI ? BF₄) and trifluoromethane sulfonate (BMI ? SO₃CF₃), is a simple and reproducible method for the preparation of ruthenium nanoparticles of 2.0–2.5?nm diameter size and with a narrow size distribution. The Ru nanoparticles were characterized by TEM and XRD. The isolated Ru nanoparticles are reoxidized in air, whereas they are less prone to oxidation when imbibed in the ionic liquids. These nanoparticles are active catalysts for the solventless or liquid–liquid biphasic hydrogenation of olefins under mild reaction conditions (4 atm, 75°C). The catalytic system composed of nanoparticles dispersed in BMI ? PF₆ ionic liquid is very stable and can be reused several times without any significant loss in the catalytic activity. Total turnover numbers greater than 110 000 (based on total Ru) or 320 000 (corrected for exposed Ru atoms) were attained within 80?h for the hydrogenation of 1-hexene.     

催化加氢法绿色合成N-(3-氨基-4-甲氧基苯基)乙酰胺

N-(3-氨基-4-甲氧基苯基)乙酰胺是生产偶氮型分散染料的一类重要中间体。现有的工业生产方法仍全部采用铁粉还原。笔者开发了一种高效的Pd/C催化剂,分别选用甲醇和水作为反应溶剂,实现了高活性、高选择性和高稳定性地催化加氢制备N-(3-氨基-4-甲氧基苯基)乙酰胺。为了抑制原料和产物在水溶液中的副反应,添加少量碱性助剂可以提高目标产物的选择性,最高达到99.3%。     

Controlled Reversible Anchoring of η6‐Arene/TsDPEN‐ Ruthenium(II) Complex onto Magnetic Nanoparticles: A New Strategy for Catalyst Separation and Recycling

A new catalyst separation and recycling protocol combining magnetic nanoparticles and host‐guest assembly was developed. The catalyst, (η⁶‐arene)[N‐(para‐toluenesulfonyl)‐1,2‐diphenylethylenediamine]ruthenium trifluoromethanesulfonate [Ru(OTf)(TsDPEN)(η⁶‐arene)] bearing a dialkylammonium salt tag, was easily separated from the reaction mixtures by magnet‐assisted decantation, on basis of the formation of a pseudorotaxane complex by using dibenzo[24]crown‐8‐modified Fe₃O₄ nanoparticles. The ruthenium catalyst has been successfully reused at least 5 times with the retention of enantioselectivity but at the expense of relatively low catalytic activities in the asymmetric hydrogenation of 2‐methylquinoline.     

Study of Photoluminescence Excitation Spectra of Tris(8-hydroxyquinoline)aluminum(III) (Alq3) in Solutions and Films

Absorption, photoluminescence, and photoluminescence excitation (PLE) spectra have been investigated for tris(8-hydroxyquinoline)aluminum(III) (Alq₃) in solution at various Alq₃ concentrations and in doped and neat films. The redshifted PLE spectra, with respect to the absorption spectra, are obtained, together with a dip located near the absorption band peak. The dip becomes deeper with increasing concentration. It is found that the unusual PLE spectra are caused by the penetration depth effect, not by previously suggested microcrystallites of Alq₃.     

Pd/Al2O3液相选择加氢催化剂抗硫性能研究

研究了助剂对Pd/Al2O3催化剂裂化汽油液相选择加氢活性及其抗硫性能的影响。着重探讨了Co助剂的作用规律。结果表明，助剂对Pd/Al2O3催化剂的加氢活性有不同影响，其中加入Ag、Cu和Co助剂时，可以提高催化剂加氢活性，而Co助剂的提高最为明显，通过对催化剂进行XPS和反应后催化剂硫含量的分析，表明Co助剂改善Pd/Al2O3催化剂液相加氢活性的作用有两方面，一是与Pd金属产生电子相互作用，改变其电子状态，减弱对硫化物的吸附；二是Co具有吸硫作用，使部分硫化物吸附在助剂Co上，从而减少了在活性中心Pd上的吸附，导致Pd－Co/Al2O3催化剂具有良好的液相选择加氢活性。     

双膦胺配体氮原子上取代基的空间和电子效应对于乙烯四聚催化体系的影响

在乙酰丙酮铬、甲基铝氧烷（MAO）、配体三元催化体系中,以乙烯为原料在高压下齐聚生成1-辛烯．主要考察N原子上取代基不同的PNP配体对催化荆活性及1-辛烯选择性的影响结果表明．苯环取代基为3．5-二甲基的配体效果较为理想,其活性达到4990kg／（mol·h）．对1-辛烯选择性为72．31％。PNP配体中苯环取代基上间、对位给电子基团有助于提高催化活性和1-辛烯选择性．而空间位阻较大的基团和吸电子基团则不利于催化反应。