辛可尼定修饰的铂纳米簇合物催化丙酮酸甲酯不对称加氢反应的研究

研究了辛可尼定(cinchonidine)作手性修饰剂修饰的氧化铝负载铂纳米簇合物(Pt-PVP-γ-Al2O3)催化丙酮酸甲酯不对称氢化反应,采用甲醇的碱溶液做溶剂,着重考察了低温条件下催化剂的活性和对映选择性的变化.优化的反应条件为0℃,5.0MPaH2,[cinchonidine]=3.24×10-3mol/L,[KOH]=0.02mol/L,1h内丙酮酸甲酯不对称加氢的转化率为32.2%,对映选择性达到52.2%;     

L-脯氨酸修饰的铱催化苯乙酮及其衍生物不对称加氢反应

在温和条件下制备了L-脯氨酸稳定并修饰的负载型金属铱催化剂,用于苯乙酮及其衍生物不对称催化加氢反应. 考察了L-脯氨酸的量、溶剂、碱以及碱的量和氢气压力对苯乙酮不对称催化加氢反应的影响. 结果显示,该催化剂催化苯乙酮不对称加氢反应获得了92.1%的转化率和32.9%的对映选择性(e.e.),催化2′-(三氟甲基)苯乙醇的对映选择性为39.3,这一结果高于目前报道的天然手性修饰剂修饰的负载型金属催化剂. 该催化循环使用5次, 对映选择性只有小幅度下降.     

金鸡纳碱衍生物修饰的负载钌-铑双金属催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的1.0%Ru+0.2%Rh/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了修饰剂种类及浓度、碱添加剂种类及浓度、溶剂、氢气压力等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru+0.2%Rh/γ-Al2O3-tpp催化剂具有较好的修饰作用,在优化反应条件下苯乙酮加氢反应的对映选择性高达84%.     

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by Cinchona-and PPh3-Modified RuRh/y-Al2O3

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的1.0%Ru＋0.2%Rh/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了修饰剂种类及浓度、碱添加剂种类及浓度、溶剂、氢气压力等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru＋0.2%Rh/γ-Al2O3-tpp催化剂具有较好的修饰作用,在优化反应条件下苯乙酮加氢反应的对映选择性高达84%.     

奎宁修饰的纳米铑簇合物催化丙酮酸乙酯对映选择性加氢反应研究

研究了奎宁作手性修饰剂修饰的负载型纳米铑簇合物催化剂 (Rh/ PVP-γ-Al2 O3)催化丙酮酸乙酯不对称氢化反应 ,在该反应中手性修饰剂奎宁不仅具有手性诱导作用 ,而且还有明显加速反应的作用 ;载体γ-Al2 O3在促进提高催化剂活性和对映选择性方面也有很重要的影响 .在优化的反应条件 [2 0℃ ,7.0 MPaH2 ,c(奎宁 ) =3 .86× 1 0 - 3mol/ L,四氢呋喃作溶剂 ]下 ,丙酮酸乙酯不对称加氢的转化频率 (TOF)为871 h- 1 ,对映选择性达到了 5 4.7% ;反应温度降低到 3℃时 ,对映选择性达到 5 9.2 % .     

金鸡纳碱衍生物修饰的负载钌催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦(tpp)稳定的1.0%Ru/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了稳定剂种类、修饰剂种类、金属负载量、溶剂、碱添加剂种类等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru/γ-Al2O3/2tpp催化剂具有较好的修饰作用,在优化的反应条件下苯乙酮及其衍生物加氢反应的对映选择性达78%～98%,2-乙酰基噻吩加氢反应的对映选择性可达80%,2-乙酰基呋喃加氢反应的对映选择性可达75%.     

手性修饰的介孔碳材料MPC-61负载铂催化剂上α-酮酸酯的不对称氢化反应

采用氯铂酸乙醇溶液和氯铂酸水溶液为前体,通过浸渍法制备了介孔碳材料MPC-61负载Pt质量分数分别为4%和10%的Pt/MPC-61催化剂,并利用XRD,TEM,N2吸附-脱附和CO化学吸附等手段对催化剂进行了表征.考察了经过手性分子辛可尼定修饰后的Pt/MPC-61催化剂在丙酮酸乙酯不对称氢化反应中的催化性能.以氯铂...     

2-氧代-4-苯基丁酸乙酯不对称加氢反应的动力学和机理探讨

 采用 10,11-二氢辛可尼定修饰的Pt/γ-Al2O3 催化 2-氧代-4-苯基丁酸乙酯不对称加氢合成 (R)-2-羟基-4-苯基丁酸乙酯,考察了修饰剂用量、底物浓度、氢压和反应温度对加氢反应速率和光学选择性的影响. 结果表明,修饰剂用量和底物浓度在适中范围内对反应速率和光学选择性均较为有利;提高氢压和温度均能显著加快反应速率,但氢压对光学选择性影响不大,温度升高则不利于目标产物的生成. 根据反应动力学特征,认为修饰剂喹啉环平行吸附于Pt表面,被质子化后与以si面吸附在催化剂表面的底物作用,经过立体选择生成单一对映体. 用提出的反应机理推导出不对称加氢反应速率方程,可以较好地描述实验结果.     

金鸡纳碱衍生物修饰的负载铱催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂, 研究了三苯基膦稳定的Ir/SiO₂催化剂催化芳香酮多相不对称加氢. 通过电感耦合等离子体原子发射发谱(ICP-AES)、高分辨透射电镜(HRTEM)、X 射线光电子能谱(XPS)、Brunauer-Emmett-Teller (BET)比表面积测试等固体表面分析手段对负载铱催化体系进行了表征; 利用红外(IR)光谱、固体核磁共振(NMR)等分析手段初步表征了负载铱多相催化体系中手性修饰剂-金属-稳定剂在载体上的相互作用; 利用“均相与多相催化体系的对比”、“催化剂稳定性实验”、“汞中毒实验”等方法阐明了手性修饰的负载铱催化体系是多相催化体系. 还考察了稳定剂种类、修饰剂种类、金属负载量、溶剂、碱添加剂种类等因素对不对称加氢反应的影响. 结果表明, 金鸡纳碱衍生物对Ir/SiO₂催化剂具有较好的修饰作用, 在优化反应条件下苯乙酮及其衍生物加氢反应的对映选择性为52%-96%, 4-乙酰基吡啶、2-乙酰基噻吩及2-乙酰基呋喃加氢反应的对映选择性可分别达到74%、75%及63%.     

手性二胺修饰的Ru-TPP/γ-Al2O3催化苄叉丙酮不对称加氢反应

在温和条件下制备了三苯基膦(TPP)作保护剂的负载钌催化剂Ru-TPP/γ-Al2O3,以(1S,2S)-1,2-二苯基乙二胺,(S)-1,1-二(对甲氧苯基)-2-异丙基乙二胺,(8S,9S)-9-氨基(9-脱氧)二氢辛可尼定和(1S,2S)-环己二胺为手性修饰剂,考察了Ru-TPP/γ-Al2O3在苄叉丙酮不对称加氢反应中的催化性能.结果表明,以(1S,2S)-1,2-二苯基乙二胺作为修饰剂时,催化剂具有较高的活性和选择性.在有K2CO3存在的异丙醇和水的混合溶液中,在氢气压力4MPa,40℃和8h的条件下,苄叉丙酮的转化率达到了99%,对羰基加氢的选择性大于98%,不饱和醇的光学纯度ee值为47%.     

Enantioselective hydrogenation of ethyl pyruvate catalyzed by PVP-stabilized rhodium nanoclusters

The enantioselective hydrogenation of ethyl pyruvate catalyzed by polyvinylpyrrolidone-stabilized rhodium nanocluster (Rh/PVP) modified by cinchonidine and quinine was studied. The results show that cinchonidine and quinine not only can induce the enantioselectivity in the hydrogenation of ethyl pyruvate, but also can greatly accelerate the reaction. Under the optimum conditions, 298 K, 5 MPa of hydrogen pressure and 4.3×10⁻³ mol/l of cinchonidine in tetrahydrofuran, the enantiomeric excess of R-(+)-ethyl lactate and turnover frequency (TOF) of ethyl pyruvate reach up to 42.2% e.e. and 941 h⁻¹, respectively. The rate of hydrogenation is faster by a factor of about 50 in the presence of cinchonidine than that without it. Quinine exhibits the similar effect.     

Enantioselective hydrogenation of ethyl pyruvate catalyzed by alumina support rhodium modified with quinine

Alumina supported rhodium catalyst using cinchonidine as a stabilizer exhibited excellent performance in the asymmetric hydrogenation of ethyl pyruvate with the addition of quinine. Quinine as a chiral modifier can not only induce the enantioselectivity, but also greatly accelerate the reaction. Under the optimum conditions: 293 K, 7.0 MPa of hydrogen pressure and 4.6 × 10⁻³ mol/L of quinine concentration in THF, TOF of Rh/2(cinchonidine)-γ-Al₂O₃ as catalyst and ee value of (R)-ethyl lactate can achieve 894 h⁻¹ and 71.6% ee, respectively.     

Identification of catalyst surface species during asymmetric platinum-catalysed hydrogenation in a "supercritical" solvent

In situ attenuated total reflection infrared spectroscopy studies during the enantioselective hydrogenation of ethyl pyruvate in "supercritical" ethane over a chirally modified Pt/Al(2)O(3) catalyst show the preferential adsorption of ethyl pyruvate as cis-conformer and indicate a hydrogen bond interaction of this species with the co-adsorbed modifier cinchonidine.     

The first case of competitive heterogeneously catalyzed enantioselective hydrogenation of ketones

In competitive racemic hydrogenation of methyl benzoylformate (MBF) + ethyl pyruvate (EP) binary mixture over Pt/Al(2)O(3): k(MBF) > k(EP), but in competitive enantioselective hydrogenation k(MBF) < k(EP); the phenomenon verified for the first time is dependent on the adsorption strength of the surface complexes of various compositions (MBF-Pt, EP-Pt, MBF-CD-Pt, EP-CD-Pt, CD = cinchonidine).     

易分离的高效纳米铂氢化催化剂

近年来纳米贵金属的优异催化性能得到了人们的关注,但是纳米粒子在使用、贮藏过程中存在团聚现象。在制备过程中加入稳定剂可以延缓其团聚,但给纳米粒子的分离带来了困难。有献报道利用水溶性表面活性剂聚乙二醇(PEG)的乙二醇链段可以稳定Rh纳米粒子,可是因其分子量过     

Enantioselective electrocatalytic hydrogenation of ethyl pyruvate on carbon supported Pd electrodes

The electrocatalytic hydrogenation of ethyl pyruvate to yield S-ethyl lactate over palladium supported on carbon felt electrodes modified with cinchonidine has been found to yield an enantiomeric excess of 13%. The effect of electrode potential, ethyl pyruvate concentration and cinchonidine have been investigated. The experimental results reported in the present study are in good agreement with the previously reported heterogeneous enantioselective hydrogenation using molecular hydrogen at high pressure. The electrocatalytic driven reaction avoids the dissociation of molecular hydrogen and thus the use of high pressure hydrogen.     

手性修饰的介孔树脂材料负载铂催化剂上丙酮酸乙酯的不对称氢化反应

采用氯铂酸和二氯四氨合铂为前体通过浸渍法分别制备了介孔树脂材料FDU-14负载的质量分数为5%的铂催化剂Pt/FDU-14, 并利用XRD, TEM, N₂气吸附和CO化学吸附等手段对催化剂进行了表征. 考察了经过手性分子辛可尼定修饰后的Pt/FDU-14催化剂在丙酮酸乙酯不对称氢化反应中的催化性能. 以氯铂酸为前体制备的Pt/FDU-14催化剂因其具有较小的铂粒子和较高的分散度而表现出较高的活性, 乙酸溶剂中的初始活性(TOF)可以达到21902 mol/(mol?h); 而以二氯四氨合铂为前体制备的Pt/FDU-14催化剂则具有较强的手性诱导能力, 乙酸溶剂中(R)-(+)-乳酸乙酯的光学选择性可以达到81.4% e.e.. 更重要的是, 由于FDU-14具有较强的疏水性, Pt/FDU-14催化剂在水溶剂中也表现出较高的催化性能, 并且还可以重复使用10次以上.     

介孔修饰MCM-41负载Pt纳米催化剂高对映选择性催化酮不对称加氢(英文)

Catalysts containing metal nanotubes were prepared by the adsorption of platinum metal nano-tubes onto functionalized and modified silica surfaces(MCM-41 and fumed silica).(3- Chloropro-pyl)trimethoxysilane and cinchonidine were used for functionalization and modification, respec-tively. Potassium chloroplatinate was used as the metal precursor to impregnate platinum metal nanotubes on the pretreated functionalized and modified silica surfaces. The solid catalysts were characterized by ESEM, TEM, EDAX, and XPS. The MCM-41 supported platinum nanotube catalyst showed 98% to ~100% enantioselectivity towards the hydrogenation of a range of pharmaceuti-cally important chemicals such as methyl pyruvate, ethyl pyruvate, and acetophenone with nearly full conversion.     

Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine:A highly active and recyclable catalyst for aqueous biphasic hydrogenation of benzene

<正>Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine(PETPP,P[C_6H_4-p-(OCH_2CH_2)_nOH]_3) combining double stabilization effects demonstrated high activity and good recyclability in aqueous biphasic hydrogenation of benzene.The value of turnover frequency(TOF) was 3333 h~(-1).Furthermore,the rhodium nanoparticle catalyst could be easily recycled for five times without loss in activity.