Oxo-tethered ruthenium(II) complex as a bifunctional catalyst for asymmetric transfer hydrogenation and H2 hydrogenation

Newly developed oxo-tethered Ru amido complexes (R,R)-1 and their HCl adducts (R,R)-2 exhibited excellent catalytic performance for both asymmetric transfer hydrogenation and the hydrogenation of ketonic substrates under neutral conditions without any cocatalysts to give chiral secondary alcohols with high levels of enantioselectivity.     

Asymmetric transfer hydrogenation of imines and iminiums catalyzed by a water-soluble catalyst in water

The first asymmetric transfer hydrogenation of cyclic imines and iminiums in water was successfully performed in high yields and enantioselectivities with sodium formate as the hydrogen source and CTAB as an additive catalyzed by a water-soluble and recyclable ruthenium(II) complex of the ligand (R,R)-2.     

Enantioselective total syntheses of the Ipecacuanha alkaloid emetine, the Alangium alkaloid tubulosine and a novel benzoquinolizidine alkaloid by using a domino process

The first enantioselective syntheses of the Ipecacuanha alkaloid emetine (1) and the Alangium alkaloid tubulosine (2) is described employing a domino Knoevenagel/hetero-Diels-Alder reaction and an enantioselective catalytic transfer hydrogenation of imines as key steps. Thus, hydrogenation of the imine 15 with the catalyst (R,R)-16 gives the tetrahydroisoquinoline 14 with 95 % ee which was transformed into the aldehyde (1S)-7. The three-component domino reaction of (1S)-7 with 6 and 8 led to 19, which in a second domino process was treated with K(2)CO(3) in methanol followed by a hydrogenation to give the benzoquinolizidine 4 together with the diastereomers 22 and 23 in a overall yield of 66 %. Further transformation of 4 with the amines 3 and 5 yielded enantiopure emetine (1) and tubulosine (2), respectively. In addition, starting from 19 the novel benzoquinolizidine alkaloid 34 was synthesised; this compound resembles the vallesiachotamine alkaloid dihydroantirhin 31, which has not been isolated so far but probably must also exist in nature.     

Dynamic kinetic resolution in the stereoselective synthesis of 4,5-diaryl cyclic sulfamidates by using chiral rhodium-catalyzed asymmetric transfer hydrogenation

The dynamic kinetic resolution of 4,5-diaryl cyclic sulfamidate imines was achieved via asymmetric transfer hydrogenation using a HCO(2)H/Et(3)N mixture as the hydrogen source and chiral Rh catalysts (R,R)- or (S,S)-RhCl(TsDPEN)Cp* affording the corresponding cyclic sulfamidates in good yields with up to >20 : 1 dr and up to >99% ee.     

Stereoselective synthesis of norephedrine and norpseudoephedrine by using asymmetric transfer hydrogenation accompanied by dynamic kinetic resolution

Each of the enantiomers of both norephedrine and norpseudoephedrine were stereoselectively prepared from the common, prochiral cyclic sulfamidate imine of racemic 1-hydroxy-1-phenyl-propan-2-one by employing asymmetric transfer hydrogenation (ATH) catalyzed by the well-defined chiral Rh-complexes, (S,S)- or (R,R)-Cp*RhCl(TsDPEN), and HCO(2)H/Et(3)N as the hydrogen source. The ATH processes are carried out under mild conditions (rt, 15 min) and are accompanied by dynamic kinetic resolution.     

Ligand and substrate effects on the mechanism of rhodium-catalyzed hydrogenation of enamides

The rhodium-catalyzed hydrogenation reaction of enamides is studied computationally using the B3LYP/LACVP** level of theory for a range of ligands and substrates. Two model bidentate phosphine ligands, 1,2-bis(dimethylphosphino)ethane (DMPE) and (Z)-1,2-bis(dimethylphosphino) ethene (ZDMP), and two chiral bidentate phosphine ligands, (R,R)-MeDuPHOS and (R,R)-tetramethylbisoxaphospinane (TMBOP), are investigated in the hydrogenation of alpha-formamidoacrylonitrile as a model substrate. The ZDMP ligand is then studied for three additional substrates: N-(2-propenyl)formamide, (Z)-3-formamido-2-butenenitrile, and (E)-3-formamido-2-butenenitrile. The potential-energy surfaces calculated for the four ligands and alpha-formamidoacrylonitrile are in general agreement with previous computational studies using QM/MM (ONIOM) methods but show consistently higher relative barriers rather than lower. The calculated potential-energy surfaces of hydrogenations of various substrates with a common ligand indicate a mechanistic change based on substrate. The sequence of hydrogen transfer to the two olefinic carbons is calculated to change based on substrate electronics. This has a significant impact on the origins of enantioselectivity for such varied substrates as the first hydride transfer to the substrate is calculated to be irreversible for all substrates, independent of whether it occurs at the alpha or beta carbon of the olefin.     

新型手性胺膦-铱体系催化芳香酮的不对称转移氢化

合成了含-CH_3取代基的PNNP型手性双胺双膦配体, 并采用核磁共振、质谱、红外光谱及圆二色光谱等方法对其进行了表征. 在异丙醇溶液中, 考察了该配体与[IrHCI_2(COD)]_2组成的手性胺膦-铱体系对多种芳香酮的不对称转移氢化性能. 结果表明, 该手性胺膦-铱体系是催化多种芳香酮不对称氢转移氢化的优秀催化剂. 在室温下, 用该体系催化1,1-二苯基丙酮时, 可得到99%的转化率和99% ee的对映选择性.     

锰配合物催化CO2加氢生成甲酸的理论研究

采用密度泛函理论(DFT)对锰配合物催化二氧化碳加氢生成甲酸的反应进行了理论研究. 整个催化循环主要包括氢气活化和二氧化碳氢化2个阶段. 计算结果表明, 甲酸的参与明显降低了氢气活化的反应能垒; 二氧化碳的氢化过程遵循外层机理并且氢转移是分步进行的, 决速步骤为氢负离子的转移过程, 自由能垒为21.0 kJ/mol. 对配合物中硫原子上的取代基R进行了调变, 研究结果表明, 当R为吸电子基团时能降低氢气裂解和二氧化碳氢化过程中质子转移的能垒, 而当R为推电子基团时有利于氢负离子的转移,当R=CF₃时整个反应的能量跨度(80.4 kJ/mol)最小.     

A remarkably effective catalyst for the asymmetric transfer hydrogenation of aromatic ketones in water and air

A Rh(III) complex generated in situ from [Cp*RhCl2]2 and (1R,2R)-N-(p-toluenesulfonyl)-1,2-cyclohexanediamine (TsCYDN) serves as a remarkably effective, robust catalyst for the asymmetric transfer hydrogenation of aromatic ketones by HCOONa in water in air, affording alcohols in up to 99% ee.     

手性联萘基-2,2'-联吡啶及其衍生物的合成及其在不对称合成中的应用

利用Kröhnke方法,以芳基乙酮为原料一锅法简洁地合成了6-芳基-6'-溴-2,2'-联吡啶2b~2d。 通过(R)-3-(4,4,5,5-四甲基-1,3,2-二噁唑硼烷基)-2,2'-乙氧基-1,1'-联萘((R)-1)与6-溴-2,2'-联吡啶及其衍生物2a~2d的Suzuki偶联, 合成了4种手性6-[3-((R)-2,2'-二乙氧基-1,1'-联萘)基]-2,2'-联吡啶(R)-3a~3d。 将配体(R)-3a~3d应用于苯乙酮的不对称氢转移反应中,配体(R)-3a给出92%的转化率和4%的对映体过量(ee)值。     

Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors

Metal-free transfer hydrogenation of polarized olefins (RR'C=CEE': R, R' = H or organyl, E, E' = CN or CO(2)Me) using amine borane adducts RR'NH-BH(3) (R = R' = H, AB; R = Me, R' = H, MAB; R = (t)Bu, R' = H, tBAB; R = R' = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the H(N) transfer is in agreement with a concerted transition state. The very reactive intermediate [NH(2)=BH(2)] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy(2)BNH(2). The final product borazine (BHNH)(3) is assumed to be formed by dehydrocoupling of [NH(2)=BH(2)] or its solvent stabilized derivative [NH(2)=BH(2)]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH(2)NH(2))(3) which is the trimerization product of [NH(2)=BH(2)].     

Effect of the structure of the diamine backbone of P-N-N-P ligands in iron(II) complexes on catalytic activity in the transfer hydrogenation of acetophenone

The asymmetric transfer hydrogenation of aromatic ketones can be efficiently accomplished using catalysts that are based on platinum group metals which are more toxic and less abundant than iron. For that reason the discovery of iron based catalysts for the use in this transformation is important. To address this issue, we synthesized a new series of iron(II)-based precatalysts trans-[Fe(Br)(CO)(PPh(2)CH(2)CH═NCHRCHRN═CHCH(2)PPh(2))]BPh(4) (5a-5d) containing P-N-N-P ligands with the diamines (R,R)-1,2-diaminocyclohexane (a), (R,R)-1,2-diphenyl-1,2-diaminoethane (b), (R,R)-1,2-di(4-methoxyphenyl)-1,2-diaminoethane (c), and ethylenediamine (d) incorporated in the backbone using a convenient one-pot synthesis using readily available starting materials. All of the complexes, when activated with a base, show a very high activity in the transfer hydrogenation catalysis of acetophenone, using 2-propanol as a reducing agent under mild conditions. A comparison of the TOF of complexes 5a-5d show that the catalytic activity of complexes increase as the size of the substituents in the backbone of ligands increases (d < a < b = c).     

手性胺修饰的羟基磷灰石负载RuCl_2(TPP)_3催化不对称氢化苯乙酮

采用共沉淀法制备了手性胺(L-脯氨酸、D-脯氨酸、(1R,2R)-1,2-二苯基乙二胺二磺酸钠((1R,2R)-DPENDS)、(1S,2S)-1,2-二苯基乙二胺二磺酸钠((1S,2S)-DPENDS))修饰的羟基磷灰石(HAP).并采用傅里叶变换红外(FT-IR)光谱,扫描电子显微镜(SEM),X射线衍射(XRD)和比表面积测定(BET)等仪器分析手段对其进行表征.以手性胺修饰的羟基磷灰石做载体负载RuCl2(TPP)3催化苯乙酮不对称加氢反应,详细考察温度、压力、碱的浓度、手性胺负载量等条件对催化反应的影响.在氢气压力为5.0 MPa、30℃条件下反应4 h,苯乙酮的不对称加氢反应,可获得99.9%转化率和77.8%对映选择性,其结果优于对应的均相催化反应.实验结果证明,催化反应在载体表面完成,催化剂通过简单离心分离可循环使用.     

Asymmetric transfer hydrogenation of alpha-aminoalkyl alpha'-chloromethyl ketones with chiral Rh complexes

Asymmetric transfer hydrogenation of N-substituted (3S)-3-amino-1-chloro-4-phenyl-2-butanones in the presence of CpRhCl[(R,R)-Tsdpen] (S/C = 1000) with a mixture of formic acid/triethylamine gave N-substituted (2R,3S)-3-amino-1-chloro-2-hydroxy-4-phenylbutanes with up to 93% de in a quantitative yield, and reduction with the enantiomeric catalyst CpRhCl[(S,S)-Tsdpen] gave (2S,3S)-diastereomeric alcohol with up to 96% de.     

Asymmetric transfer hydrogenation of benzaldehydes

A combined system of RuCl[(R, R)-YCH(C(6)H(5))CH(C(6)H(5))NH(2)](eta(6)-arene) (Y = NSO(2)C(6)H(4)-4-CH(3) or O) and t-C(4)H(9)OK catalyzes the asymmetric transfer hydrogenation of various benzaldehyde-1-d derivatives with 2-propanol to yield (R)-benzyl-1-d alcohols in 95-99% ee and with >99% isotopic purity. Reaction of benzaldehydes with a DCO(2)D-triethylamine mixture and the R,R catalyst affords the S deuterated alcohols in 97-99% ee.     

New synthetic route to the important (S)-5-(1-(tert-butoxycarbonyl)pyrrolidin-2-yl)-2-methylthiophene-3-carboxylic acid intermediate for the synthesis of a novel glucokinase activator

To obtain an efficient and practical route to a novel glucokinase activator, we investigated a novel synthetic method for the preparation of its key intermediate (S)-5-(1-(tert-butoxycarbonyl)pyrrolidin-2-yl)-2-methylthiophene-3-carboxylic acid through the asymmetric transfer hydrogenation of a pyrroline derivative. The hydrogenation of this pyrroline derivative using the iridium (III)-prolinamide complex Cp*IrCl[(R)-PA] at atmospheric pressure provided an initial intermediate in approximately 50% ee. Further purification via recrystallization provided the desired key intermediate in an excellent enantiopurity, which was applicable to practical use.     

Novel chiral multidentate P3N4-type ligand for asymmetric transfer hydrogenation of aromatic ketones

Novel chiral multidentate P₃N₄-type ligand has been synthesized and characterized by NMR and HRMS. Using i-PrOH as solvent and hydrogen source, asymmetric transfer hydrogenation of various ketones was investigated. The catalyst generated in situ from chiral multidentate aminophosphine ligand (R,R,R,R)-3 and IrCl(CO)(PPh₃)₂ exhibited highly catalytic activity and excellent enantioselectivity under mild conditions, achieving the corresponding chiral alcohols with up to 99% yield and 99% ee.     

Enantioselective synthesis of vicinal halohydrins via dynamic kinetic resolution

[reaction: see text] Expanding the scope of enantioselective catalysis via DKR, transfer hydrogenation of a variety of cyclic alpha-halo ketones was accomplished using the Noyori/Ikariya (R,R)- or (S,S)-I catalysts and either HCO(2)H/Et(3)N or HCO(2)Na/n-Bu(4)NBr in H(2)O/CH(2)Cl(2) as the hydrogen sources. Good yields of vicinal bromo-, chloro-, and fluorohydrins with excellent de and ee levels were achieved in most cases after a simple tuning of reaction conditions.     

Synthesis of novel chiral tetraaza ligands and their application in enantioselective transfer hydrogenation of ketones

Novel chiral tetraaza ligands(R)-N,N′-bis[2-(piperidin-1-yl)benzylidene]propane-l,2-diamine 6 and(S)-N-[2-(piperidin-l- yl)benzylidene]-3-{[2-(piperidin-1-yl)benzylidene]amino}-alanine sodium salt 7 have been synthesized and fully characterized by NMR,IR,MS and CD spectra.The catalytic property of the ligands was investigated in Ir-catalyzed enantioselective transfer hydrogenation of ketones.The corresponding optical active alcohols were obtained with high yields and moderate ees under mild reaction conditions.     

erythro-1-Naphthyl-1-(2-piperidyl)methanol: synthesis,resolution, NMR relative configuration,and VCD absolute configuration

The erythro isomer of 1-naphthyl-1-(2-piperidyl)methanol 4, an efficient chiral modifier for asymmetric heterogeneous hydrogenation, was obtained as the major isomer (95%) in two steps while the threo isomer can be obtained as the major isomer (67%) in three steps. erythro-4 and threo-4 were resolved on a CHIRALCEL OD-RH column. It has been shown by VCD that the diastereomer determined as the erythro by NMR was indeed the erythro and that the first eluted (-)-enantiomer on CHIRALCEL OD-R or -RH columns has the (1R,2S) configuration. The VCD studies identify the presence of at least five conformers in CDCl(3) solution. Moreover, this (-)-(1R,2S) absolute configuration found by VCD is consistent with the expected stereo-outcome of catalytic hydrogenation of pyruvate into lactate, which supported the (+)-(1S,2R) assignment.