三氟甲磺酸铜(Ⅱ)催化的苯乙烯基重氮乙酸甲酯和芳胺的插入反应

在三氟甲磺酸铜催化下,苯烯基重氮甲酯和苯胺(2)在多种溶剂下发生插入反应,主要产物是α,β-不饱和γ-氨基酸衍生物.以二氯甲烷为溶剂时,产物的区域选择性随2上取代基不同而发生变化.通过在铜催化剂中加入配体,可以获得低的对映选择性.     

铜催化炔烃的双官能团化反应研究进展

炔烃的双官能团化反应近年来受到广大科研工作者的关注,其已经发展为一种简单、高效、原子经济性高,能够同时引入各类不同官能团的重要方法。近年来,许多关于铜催化炔烃的双官能团化反应研究见诸报道。本文针对近年来铜催化炔烃的双官能团化反应的研究进行了归纳与总结。     

三氟甲磺酸铜(Ⅱ)催化的硫醇对烯酮的共轭加成反应

硫醚是一类具有重要生物和生理活性的化合物,常见于药物以及天然产物中,其高效合成方法是有机化学研究热点之一.硫-共轭加成特别是有机小分子催化的加成反应的研究比较充分,已被证明是一种合成硫醚分子的有效手段.然而,科研工作者对于过渡金属催化的硫-共轭加成反应的研究相对较少,仍需要大量探索.本工作通过借助三氟甲磺酸铜的催化,实...     

三氟甲磺酸铜催化新型苯并恶唑烷衍生物的合成

以三氟甲磺酸铜［Cu(OTf)₂］为催化剂,取代邻氨基苯酚(1a~1g)和取代联苯甲酰(2a~2g)为原料,合成了7个苯并恶唑烷衍生物（3a~3g,其中3b~3g为新化合物）,其结构经¹H NMR, ¹³C NMR, IR和HR-MS(ESI)表征。以3a的合成为例,研究了催化剂、溶剂、催化剂用量、物料比γ［n(1) : n(2)］和反应温度对3产率的影响。结果表明：在最佳反应条件［8 mmol%Cu(OTf)₂, 1,2-二氯乙烷为溶剂,1a~1g1.5 mmol, γ=3:1,于70 ℃反应10 h］下,3a~3g产率62%~91%。     

钯催化炔烃羰基化反应新进展

综述了过渡金属钯催化的炔烃羰基化反应最新研究进展，深入讨论了影响钯催 化的炔烃碳基化反应的区域选择性和立体选择性的两大因素：溶剂效应与酸碱效应。     

铜催化芳基(或烷基)卤化物选择性烯丙基化反应研究

以溴代芳烃和烯丙基乙酸酯为反应原料,发展了一种铜催化高效构建碳碳键的交叉偶联方法.该方法通过“一锅法”策略,有效避免了预制金属有机试剂的使用,在较温和条件下即可实现烯丙基类化合物的高区域选择性制备.     

利用选择性转移氢化反应合成含卤素或杂环的饱和酮

在金属前体[IrCl(COD)]2, 1,2-双(二苯基膦)乙烷(dppe)和碳酸铯的催化下,用异丙醇做氢源时,含卤素或杂环的α,β-不饱和酮可以选择性地发生1,4-还原得到饱和酮,产率高达90%.反应中未出现卤素被还原和催化剂中毒的现象.     

硅卡宾铁(0)氮气配合物催化的炔烃选择性硼氢化反应

硅卡宾（R₂Si：,silylene）是卡宾的相似体,可以作为配体与金属形成配合物.由于硅的原子半径比碳大,硅卡宾可与Lewis碱配位形成三配位甚至四配位的化合物同时保持很强的配位能力.因此,硅卡宾兼具卡宾和膦配体的结构特征,在稳定新颖的金属配合物及均相催化领域或具有更大的调控空间.本工作报道硅卡宾铁氮气配合物[PhC （t-BuN）₂SiCH₂C （t-Bu） NAr]FeN₂（D,Ar＝2,6-（i-Pr）₂C₆H₃）催化的炔烃的选择性硼氢化反应.研究发现,该配合物对炔烃的硼氢化反应具有很好的区域及立体选择性,主要生成E式构型产物并表现出很好的官能团耐受性.该研究表明,硅卡宾对过渡金属催化具有很好的调控作用,具有很好的研究潜力.     

钌(Ⅱ)卟啉催化顺式二苯乙烯类化合物的选择性合成

由芳醛制得的腙盐在钌(Ⅱ)卟啉催化下发生自身偶合，以较高收率合成了二苯乙烯类化合物(～90％的顺式选择性)。部分中间体及目标化合物的结构经^1H NMR，^13C NMR和MS表征。     

Copper(II)/Palladium(II) catalysed highly selective cross-coupling of terminal alkynes in supercritical carbon dioxide

An efficient protocol for the synthesis of unsymmetrical 1,3-diynes was developed using supercritical carbon dioxide (ScCO₂) as the solvent. The direct coupling of two different terminal alkynes is catalysed by a bimetallic catalyst, CuCl₂·2H₂O/Pd(NH₃)₄Cl₂·H₂O, in the presence of the base tetramethylethylenediamine (TMEDA) and O₂. In pure ScCO₂, our bimetallic catalytic system maintains high activity over a wide substrate scope to provide unsymmetrical 1,3-diynes in good to excellent yields. In the proposed reaction mechanism, the synergistic cooperation between copper(II) and palladium(II) centres is responsible for the superior selectivity of the cross-coupling.     

New iminophosphine–Ru(II) complexes and their application in hydrogenation and transfer hydrogenation

Ruthenium complexes [RuCl₂L₂] were prepared by treating [RuCl₂(p‐cymene)]₂ with structurally similar N‐(2‐(diphenylphosphino)benzylidene)‐3‐methylpyridin‐2‐amine, 4‐(2‐(diphenylphosphino)benzylideneamino)‐3‐methylphenol and 4‐(2‐(2‐(diphenylphosphino)benzylideneamino)ethyl)phenol refluxed in toluene. These complexes were used as catalysts for the transfer hydrogenation of acetophenones in 2‐propanol and for the direct hydrogenation of styrenes under hydrogen pressure. The results of the catalytic studies provide evidence that these complexes function as excellent catalysts for hydrogenation and transfer hydrogenation. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel cyclohexyl‐based aminophosphine ligands and use of their Ru(II) complexes in transfer hydrogenation of ketones

Two new aminophosphines – furfuryl‐(N‐dicyclohexylphosphino)amine, [Cy₂PNHCH₂–C₄H₃O] ( 1 ) and thiophene‐(N‐dicyclohexylphosphino)amine, [Cy₂PNHCH₂–C₄H₃S] ( 2 ) – were prepared by the reaction of chlorodicyclohexylphosphine with furfurylamine and thiophene‐2‐methylamine. Reaction of the aminophosphines with [Ru(η⁶‐p‐cymene)(μ‐Cl)Cl]₂ or [Ru(η⁶‐benzene)(μ‐Cl)Cl]₂ gave corresponding complexes [Ru(Cy₂PNHCH₂–C₄H₃O)(η⁶‐p‐cymene)Cl₂] ( 1a ), [Ru(Cy₂PNHCH₂–C₄H₃O)(η⁶‐benzene)Cl₂] ( 1b ), [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐p‐cymene)Cl₂] ( 2a ) and [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐benzene)Cl₂] ( 2b ), respectively, which are suitable catalyst precursors for the transfer hydrogenation of ketones. In particular, [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐benzene)Cl₂] acts as a good catalyst, giving the corresponding alcohols in 98–99% yield in 30 min at 82 °C (up to time of flight ≤ 588 h^?1). Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

The application of tunable tridendate P‐based ligands for the Ru(II)‐catalysed transfer hydrogenation of various ketones

Two novel versatile tridendate aminophosphine–phosphinite and phosphinite ligands were prepared and their trinuclear neutral ruthenium(II) dichloro complexes were found to be effective catalysts for the transfer hydrogenation of various ketones in excellent conversions up to 99% in the presence of 2‐propanol/NaOH in 0.1 M isopropanol solution. Particularly, [Ru₃(PPh₂OC₂H₄)₂ N–PPh₂(η⁶‐p‐cymene)₃Cl₆] acts as an excellent catalyst giving the corresponding alcohols in excellent conversion up to 99% (turnover frequency ≤ 1176 h^?1). A comparison of the catalytic properties of the complexes is also discussed briefly. Furthermore, the structures of these ligands and their corresponding complexes have also been clarified using a combination of multinuclear NMR spectroscopy, infrared spectroscopy and elemental analysis. ¹H–¹³C HETCOR or ¹H–¹H COSY correlation experiments were used to confirm the spectral assignments. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrogenation versus transfer hydrogenation of ketones: two established ruthenium systems catalyze both

The established standard ketone hydrogenation (abbreviated HY herein) precatalyst [Ru(Cl)(2)((S)-tolbinap)[(S,S)-dpen]] ((S),(S,S)-1) has turned out also to be a precatalyst for ketone transfer hydrogenation (abbreviated TRHY herein) as tested on the substrate acetophenone (3) in iPrOH under standard conditions (45 degrees C, 45 bar H(2) or Ar at atmospheric pressure). HY works at a substrate catalyst ratio (s:c) of up to 10(6) and TRHY at s:c<10(4). Both produce (R)-1-phenylethan-1-ol ((R)-4), but the ee in HY are much higher (78-83 %) than in TRHY (4-62 %). In both modes, iPrOK is needed to generate the active catalysts, and the more there is (1-4500 equiv), the faster the catalytic reactions. The ee is about constant in HY and diminishes in TRHY as more iPrOK is added. The ketone TRHY precatalyst [Ru(Cl)(2)((S,S)-cyP(2)(NH)(2))] ((S,S)-2), established at s:c=200, has also turned out to be a ketone HY precatalyst at up to s:c=10(6), again as tested on 3 in iPrOH under standard conditions. The enantioselectivity is opposite in the two modes and only high in TRHY: with (S,S)-2, one obtains (R)-4 in up to 98 % ee in TRHY as reported and (S)-4 in 20-25 % ee in HY. iPrOK is again required to generate the active catalysts in both modes, and again, the more there is, the faster the catalytic reactions. The ee in TRHY are only high when 0.5-1 equivalents iPrOK are used and diminish when more is added, while the (low) ee is again about constant in HY as more iPrOK is added (0-4500 equiv). The new [Ru(H)(Cl)((S,S)-cyP(2)(NH)(2))] isomers (S,S)-9 A and (S,S)-9 B (mixture, exact structures unknown) are also precatalysts for the TRHY and HY of 3 under the same conditions, and (R)-4 is again produced in TRHY and (S)-4 in HY, but the lower ee shows that in TRHY (S,S)-9 A/(S,S)-9 B do not lead to the same catalysts as (S,S)-2. In contrast, the ee are in accord with (S,S)-9 A/(S,S)-9 B leading to the same catalysts as (S,S)-2 in HY. The kinetic rate law for the HY of 3 in iPrOH and in benzene using (S,S)-9 A/(S,S)-9 B/iPrOK or (S,S)-9 A/(S,S)-9 B/tBuOK is consistent with a fast, reversible addition of 3 to a five-coordinate amidohydride (S,S)-11 to give an (S,S)-11-substrate complex, in competition with the rate-determining addition of H(2) to (S,S)-11 to give a dihydride [Ru(H)(2)((S,S)-cyP(2)(NH)(2))] (S,S)-10, which in turn reacts rapidly with 3 to generate (S)-4 and (S,S)-11. The established achiral ketone TRHY precatalyst [Ru(Cl)(2)(ethP(2)(NH)(2))] (12) has turned out to be also a powerful precatalyst for the HY of 3 in iPrOH at s:c=10(6) and of some other substrates. Response to the presence of iPrOK is as before, except that 12 already functions well without it at up to s:c=10(6).     

13C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

Homogeneously catalyzed hydrogenations of unsaturated substrates with parahydrogen not only lead to strong polarization signals in ¹H NMR spectra, but also can give rise to strong heteronuclear polarization, especially if the hydrogenations are carried out in low magnetic fields. As a typical example, the polarization transfer from protons to carbon nuclei during the hydrogenation of alkynes is outlined for several substrates. In systems containing easily accessible triple bonds, e.g. phenylethyne or 3,3‐dimethyl‐1‐butyne, polarization transfer occurs to all carbon nuclei in the molecule. Accordingly, in NMR spectra recorded in situ all ¹³C resonances can be observed with good to excellent signal‐to‐noise ratios using only a single transient. The qualitative influence of symmetry and electronic aspects of the substrate and its hydrogenation product on the efficiency of the transfer of polarization to the ¹³C‐nuclei are discussed. Copyright © 2001 John Wiley & Sons, Ltd.