新型手性环状胺膦配体的设计合成及在酮的不对称还原中的应用

新型手性配体的设计合成是不对称催化研究的重要内容,其中手性胺膦配体因同时含有"软"的磷原子和"硬"的氮原子而具有丰富的配位化学性能和优秀的不对称诱导能力.本文总结了本研究组最近设计合成的手性环状胺膦配体的制备、表征及其在铁催化酮的不对称还原中的应用.手性1,2-环己二胺与双(2-甲酰基苯基)苯基膦通过[2+2]环缩合反应能够顺利获得手性22元环的亚胺膦配体21,该配体经Na BH4还原后生成大环胺膦配体22.利用手性大环胺膦配体22与Fe3(CO)12原位生成的催化体系,能够高活性、高对映选择性地实现包括杂环芳香酮在内50多种酮的不对称转移氢化和不对称氢化反应,其S/C(底物与催化剂的摩尔比)最高可达5000:1,产物手性芳香醇的光学纯度高达99%ee.     

Osmium pyme complexes for fast hydrogenation and asymmetric transfer hydrogenation of ketones

The osmium compound trans,cis-[OsCl2(PPh3)2(Pyme)] (1) (Pyme=1-(pyridin-2-yl)methanamine), obtained from [OsCl2(PPh3)3] and Pyme, thermally isomerizes to cis,cis-[OsCl2(PPh3)(2)(Pyme)] (2) in mesitylene at 150 degrees C. Reaction of [OsCl2(PPh3)3] with Ph2P(CH2)(4)PPh2 (dppb) and Pyme in mesitylene (150 degrees C, 4 h) leads to a mixture of trans-[OsCl2(dppb)(Pyme)] (3) and cis-[OsCl2(dppb)(Pyme)] (4) in about an 1:3 molar ratio. The complex trans-[OsCl2(dppb)(Pyet)] (5) (Pyet=2-(pyridin-2-yl)ethanamine) is formed by reaction of [OsCl2(PPh3)3] with dppb and Pyet in toluene at reflux. Compounds 1, 2, 5 and the mixture of isomers 3/4 efficiently catalyze the transfer hydrogenation (TH) of different ketones in refluxing 2-propanol and in the presence of NaOiPr (2.0 mol %). Interestingly, 3/4 has been proven to reduce different ketones (even bulky) by means of TH with a remarkably high turnover frequency (TOF up to 5.7 x 10(5) h(-1)) and at very low loading (0.05-0.001 mol %). The system 3/4 also efficiently catalyzes the hydrogenation of many ketones (H2, 5.0 atm) in ethanol with KOtBu (2.0 mol %) at 70 degrees C (TOF up to 1.5 x 10(4) h(-1)). The in-situ-generated catalysts prepared by the reaction of [OsCl2(PPh3)3] with Josiphos diphosphanes and (+/-)-1-alkyl-substituted Pyme ligands, promote the enantioselective TH of different ketones with 91-96 % ee (ee=enantiomeric excess) and with a TOF of up to 1.9 x 10(4) h(-1) at 60 degrees C.     

具有C~2-对称性的手性二茂铁Schiff碱的合成、表征 及其在不对称氢转移反应 中的应用

首次报道了(1R,2S)-二苯基乙二胺,(1S,2R)-环己二胺,(R)-(+)-联二萘胺与甲酰基二茂铁反应,生成三个具有C~2对称性的手性二茂铁Schiff碱1,2,3,通过IR,^1HNMR,元素分析和旋光度测定确定其结构。并且将其作为配体,分别与Rh,Ir,Ru等过渡金属“原位”形成配合物对苯乙酮的不对称氢转移反应进行了研究,考察了反应条件,配体结构对反应和产物构型的影响。     

Highly efficient catalysts derived from planar chiral ferrocenes for asymmetric transfer hydrogenation of ketones

Planar chiral ferrocenes 1 and its diastereoisomer 2 were found to be good lig-ands for the ruthenium catalyzed asymmetric transfer hydrogenation of ketones with i-PrOH as hydrogen source under refluxing in the presence of sodium hydroxide. The results showed that the absolute configuration of alcohol seemed to be governed by the central chirality in the oxazoline ring instead of the planar chirality. At a ratio of 1:2 for Ru:ligand, 3000:1 S/C and >100,000/h-1 TOF were observed for acetophenone. For propiophenone 99% yield and 85% e.e. were obtained     

A concise synthesis of a new xylyl-biaryl diphosphine ligand for asymmetric hydrogenation of ketones

A concise synthesis of a symmetrical biaryl diphosphine ligand bearing 3,5-dimethylphenyl substituents at phosphorus is described. The ruthenium catalysts [diphosphine RuCl₂ diamine] containing the new ligand Xyl-TetraPHEMP were found to be as active and as selective as the state-of-the-art catalysts for homogeneous asymmetric ketone hydrogenation.     

Crystal structure of chiral binaphthol lanthanide complexes and their catalysis in asymmetric transfer hydrogenation of acetophenone

Heterometallic [(THF)₂Na]₃[Ln(R‐Binolate)₃(H₂O)] [Ln = Sm ( 1 ) and Gd ( 2 )] has been synthesized by the reactions of either LnCl₃ or LnBr₃ with 3 equiv. Na(R‐HBinolate) and characterized by X‐ray crystallographic analysis. Structural analyses proposed that 1 and 2 are isomorphous complexes, crystallizing in the hexagonal space group P6₃ with C₃ symmetry. The coordination geometry of the lanthanide ions in 1 and 2 can be best approximated as a mono‐capped triangle antiprism. When complexes 1 and 2 were employed as catalysts in the Meerwein–Ponndorf–Verley (MPV) reactions of acetophenone, the S‐phenylethanol was separated in 94 and 85% enantiomeric excess (e.e.) for 1 and 2 , respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Efficient iridium and rhodium‐catalyzed asymmetric transfer hydrogenation using 9‐amino(9‐deoxy) cinchona alkaloids as chiral ligands

9‐Amino (9‐deoxy) cinchona alkaloids, derived from natural cinchona alkaloids, were applied in asymmetric transfer hydrogenation in both iridium and rhodium catalytic systems using i‐propanol as the hydrogen source. A series of aromatic ketones was examined, and good to excellent conversions and enantioselectivities were observed. The best results were achieved using 9‐amino(9‐deoxy) epicinchonine 2a as the ligand and [Ir(COD)Cl]₂ as the metal precursor, and for the isobutylphenone, the conversion and enantioselectivity were obtained in 90 and 97% e.e. respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

Novel benzoferrocenyl chiral ligands: Synthesis and evaluation of their suitability for asymmetric catalysis

Four benzoferrocenyl phosphorus chiral ligands were conveniently prepared in good overall yields. These ligands were found to be stable in solid form and in solution. Two of the four ligands were resolved by chiral HPLC. Unlike a reported bis(phosphino-η⁵-indenyl)iron(II) complex, in which the indenyl ligands undergo ring flipping through an η¹-intermediate, these two ligands were found to be configurationally stable in solution and in solid state. The suitability of these ligands for enantioselective catalysis was assessed in studies on allylic alkylation reactions. When the two less sterically hindered ligands were used, excellent chemical yields were obtained, but the other two more sterically hindered ones gave lower yields. When the two enantiopure ligands were used, enantioselectivity of up to 51% ee was observed. These findings suggest that benzoferrocene derivatives may be used as chiral ligands for asymmetric catalysis.     

Preparation of the enantiopure 1,2-diamine monomer and its polymerization: The efficient polymeric chiral ligand of an asymmetric hydrogenation catalyst

An enantiopure 1,2-diamine monomer possessing a p-vinylbenzyl group as a polymerizable group was synthesized from chiral 1,2-bis(p-hydroxyphenyl)-N,N′-bis(tert-butoxycarbonyl)-1,2-diaminoethane. The chiral monomer was copolymerized with styrene, and this was followed by the deprotection of the tert-butoxycarbonyl group, which yielded the polymer-supported chiral 1,2-diamine. The polymeric catalyst system was established with the polymeric chiral 1,2-diamine complexed with 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl/RuCl₂. In the presence of potassium tert-butoxide (t-BuOK), the polymeric catalyst system worked well in the asymmetric hydrogenation of aromatic ketones. The corresponding chiral secondary alcohols were obtained in quantitative yields with a high level of enantioselectivity. The insolubility of the catalyst, caused by the crosslinked structure of the polymer, made it recyclable. The polymeric catalyst was reused several times without a loss of catalytic activity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4556–4562, 2004     

Polyethylene glycol‐bound Ru catalyst for asymmetric transfer hydrogenation of aromatic ketones in water

A new polyethylene glycol‐supported chiral monosulfonamide was synthesized from (R,R)‐1,2‐diaminocyclohexane and shown to act as a ligand for ruthenium(II)‐catalyzed asymmetric transfer hydrogenation of aromatic ketones in neat water using sodium formate as the hydrogen source. Good enantioselectivities were obtained and the catalyst could be easily separated from the reaction mixture and reused several times. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and application of chiral N-heterocyclic carbene-oxazoline ligands: iridium-catalyzed enantioselective hydrogenation

Two libraries of enantiomerically pure imidazolium salts bearing an oxazoline unit were synthesized. Deprotonation of the imidazolium salts and complexation of the resulting oxazoline-carbene ligands to iridium(I) was achieved in one step by mixing the imidazolium salts with NaOtBu and [(eta(4)-cod)IrCl](2) in THF at room temperature. The air-stable complexes were purified by flash chromatography. All complexes were analyzed by two-dimensional (2D) NMR methods and one compound from each family was characterized by X-ray structure analysis. The two libraries of iridium complexes were successfully tested in the asymmetric hydrogenation of unfunctionalized and functionalized olefins. Enantioselectivities of up to 90 % ee were obtained with trans-alpha-methylstilbene. Upon complexation of imidazolium salt 15 p with R(1) = phenyl, C-H bond activation of the phenyl ring gave rise to iridium(III) complex 17, which was fully characterized by NMR spectroscopy and X-ray structure analysis. Complex 17 proved to be catalytically inactive in the hydrogenation.     

Water-soluble chiral monosulfonamide-cyclohexane-1,2-diamine-RhCp complex and its application in the asymmetric transfer hydrogenation (ATH) of ketones

Monosulfonamide ligands with heteroatom/heterocyclic systems were derived from trans-(1R,2R)-cyclohexane-1,2-diamine and complexed with [Ru(benzene)Cl₂]₂, [Cp^∗RhCl₂]₂ in situ and used in the ATH of aromatic ketones with aqueous sodium formate as the hydrogen source. The chiral secondary alcohols were obtained with >93% enantioselectivity and >89% yield. Reduction in water was faster than in isopropanol/KOH. Addition of surfactants showed little or no effects.     

Enantioselective transfer hydrogenation of ketones with planar chiral ruthenocene-based phosphinooxazoline ligands

1,2-Disubstituted planar chiral ruthenocene-based phosphinooxazoline ligands (Rc-PHOX, 3 and 4) were synthesized easily and applied in the transfer hydrogenation of ketones to chiral alcohols using 2-propanol as a source of hydrogen with excellent enantioselectivity and high catalytic activity.     

Synthesis of novel chiral N, P-containing multidentate ligands and their applications in asymmetric transfer hydrogenation

Novel chiral PN₄-type multidentate aminophosphine ligands have been successfully synthesized by Schiff-base condensation of bis（o-formylphenyl）phenylphosphane and various chiral amino-sulfonamides.Their structures were fully characterized by IR,EI-MS and NMR.The catalytic systems,prepared in situ from the multidentate ligands and iridium（I） complexes,showed high activity in asymmetric transfer hydrogenation of propiophenone in 2-propanol solution,leading to corresponding optical alcohol with up to 75%ee.     

手性树状分子膦配体在不对称催化氢化中的应用

树状大分子作为一类组成精确的超支化结构大分子,近十多年来引起了科学家们的广泛关注.作为一类新型可溶性载体应用于均相催化剂,尤其是手性均相催化剂的负载化研究是树状大分子的重要应用领域之一.本文主要介绍了手性树状大分子膦配体,包括膦配体位于树状分子核心、末端和表面的几种类型,重点对它们与金属配合物形成的催化剂在不对称催化氢化反应中的应用研究进行总结,同时对负载催化剂的分离与回收、树状分子载体的结构和体积对催化剂性能的影响进行了讨论.     

Application of chiral thiazolidine ligands to asymmetric hydrosilation

Seven chiral thiazolidines bound rhodium complexes were synthesized and their catalytic asymmetric hydrosilation properties were investigated It was found through investigation that the configuration of newly formed chiral centre C2 of substituted chiral thiazolidines prepared from L-cysteine or its esters has no effect on the final results of catalytic asymmetric hydrosilation.The direct reason for causing this phenomenon is reported by the present quantitative results for the first time:the rapid racemation of chiral center C2 of chiral thiazolidine ligands takes place under the catalysis of rhodium(Ⅰ) complex [Rh(COD)CI]2     

Mixtures of chiral and achiral monodentate ligands in asymmetric Rh-catalyzed olefin hydrogenation: reversal of enantioselectivity

The recently described method of combinatorial asymmetric transition metal catalysis based on the use of mixtures of chiral monodentate P-ligands has been extended to include mixtures of chiral and achiral monodentate P-ligands, reversal of enantioselectivity in Rh-catalyzed olefin hydrogenation being possible in appropriate cases.