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     

Preparation of Polymer-Supported Chiral 1,2-Diamine as an Efficient Ligand for Asymmetric Hydrogenation Catalyst

An enantiopure 1,2-diamine having two phenolic hydroxy groups was synthesized, and attached to chloromethylated poly(styrene) through a benzyl ether linkage. The polymer-supported Ru precatalysts were prepared from the polymeric chiral 1,2-diamine and RuCl₂/BINAP complex. In the presence of t-BuOK the polymeric catalyst system worked well in asymmetric hydrogenation of aromatic ketones in a mixed solvent of 2-propanol and DMF. The insoluble polymeric catalyst was readily separated from the reaction mixture and reused at least several times without loss of the catalytic activity.     

Synthesis of cis-1,2-diol-type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation

Two cis-1,2-diol-type chiral ligands (T ₁ and T ₂ ) and their tri-coordinated chiral dioxaborinane (T _(1–2) B _(1–2) ) and four-coordinated chiral dioxaborinane adducts with 4-tert-butyl pyridine sustained by N → B dative bonds (T _(1–2) B _(1–2) -N) were synthesized and characterized by various spectroscopic techniques such as NMR (¹H, ¹³C, and ¹¹B), FT-IR and UV–Vis spectroscopy, LC–MS/MS, and elemental analysis. It was suggested that both ferrocene and trifluoromethyl groups played key roles in the catalytic and biological studies because they could tune the solubility of the chiral dioxaborinane complexes and adjust the strength of intermolecular interactions. To assess the biological activities of newly synthesized chiral dioxaborinane compounds, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, reducing power, antibacterial, DNA binding, and DNA cleavage activities were tested. Then, all chiral dioxaborinane complexes were investigated as catalysts for the asymmetric transfer hydrogenation of various ketones under suitable conditions. The results indicated that the chiral dioxaborinane catalysts performed well with high yields.     

手性磷酸酯配体的设计合成及其在不对称加氢中的应用研究新进展

合成对映体纯的药品、农用化学品及风味调料,对化学家来说是个巨大的挑战．目前采用多种不同的方法可以合成这些光学纯化合物,从工业化生产的角度来看,不对称催化反应作为获得光学纯化合物的一种手段,在众多方法中最具经济效益,同时也最具挑战性．该领域的大量出版物,     

Two precatalysts for application in asymmetric homogeneous hydrogenation

The title compounds, [(1R,1′R,2R,2′R)‐2,2′‐bis(diphenylphosphanyl)‐1,1′‐dicyclopentane](η⁴‐norbornadiene)rhodium(I) tetrafluoridoborate, [Rh(C₃₄H₃₆P₂)(C₇H₈)]BF₄, (I), and [(1R,1′R,2R,2′R)‐2,2′‐bis(diphenylphosphanyl)‐1,1′‐dicyclopentane][η⁴‐(Z,Z)‐cycloocta‐1,5‐diene]rhodium(I) tetrafluoridoborate dichloromethane monosolvate, [Rh(C₃₄H₃₆P₂)(C₈H₁₂)]BF₄·CH₂Cl₂, (II), are applied as precatalysts in asymmetric homogeneous hydrogenation, e.g. in the reduction of dehydroamino acids, affording excellent enantiomeric excesses [Zhu, Cao, Jiang & Zhang (1997). J. Am. Chem. Soc. 119 , 1799–1800].     

Tunable dendritic ligands of chiral 1,2-diamine and their application in asymmetric transfer hydrogenation

Tunable dendritic N-mono-sulfonyl ligands have been designed and synthesized via direct N-mono-sulfonylization of the chiral dendritic vicinal diamines and their ruthenium complexes demonstrated high catalytic and recyclable activities with comparable enantioselectivities to Noyori–Ikariya’s TsDPEN-Ru in the asymmetric transfer hydrogenation of an extended range of substrates, such as ketones, keto esters, and olefins.     

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.     

Enantioselective synthesis of cis-1,2-disubstituted cyclopentanes and cyclohexanes by Suzuki-Miyaura cross-coupling and iridium-catalyzed asymmetric hydrogenation

A series of 1,2-disubstituted cyclohexene derivatives was prepared through Suzuki-Miyaura cross-coupling of 2-bromo-1-cyclohexenecarbaldehyde or 2-carbomethoxy-1-cyclohexen-1-yl triflate with arylboronates. These tetra-substituted cyclic alkenes were subjected to Ir-catalyzed asymmetric hydrogenation. In this way cis-1-methoxymethyl-2-arylcyclohexanes were obtained in high yield with excellent enantio- and diastereoselectivities (up to >99% ee, >99% cis) by using phosphinomethyloxazolines as ligands. Asymmetric hydrogenation of analogous cyclopentene derivatives, prepared by Suzuki-Miyaura cross-coupling, proved to be more difficult and proceeded with lower enantioselectivities of up to 88% ee. The synthetic potential of this cross-coupling/asymmetric-hydrogenation strategy was demonstrated by an enantioselective route to chiral hexahydrofluorenones.     

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.     

手性1,2-二苯基-1,2-乙二胺及其衍生物在不对称合成中的应用

含有C2 对称轴的1,2-二胺在不对称合成中得到了广泛的应用.综述了手性1,2-二苯基-1,2-乙二胺及其衍生物的合成,以及作为手性辅助基和手性配体在不对称合成中的应用.     

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。     

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.     

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.