共查询到20条相似文献,搜索用时 15 毫秒
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Dr. S. M. A. Hakim Siddiki Dr. Abeda Sultana Touchy Dr. Kenichi Kon Prof. Ken‐ichi Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):6111-6119
Carbon‐supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant‐free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate‐limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. 相似文献
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Dr. Xinjiang Cui Dr. Yuehui Li Dr. Christoph Topf Dr. Kathrin Junge Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2015,54(36):10596-10599
The “green” reduction of carboxylic acids to alcohols is a challenging task in organic chemistry. Herein, we describe a general protocol for generation of alcohols by catalytic hydrogenation of carboxylic acids. Key to success is the use of a combination of Ru(acac)3, triphos and Lewis acids. The novel method showed broad substrate tolerance and a variety of aliphatic carboxylic acids including biomass‐derived compounds can be smoothly reduced. 相似文献
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Pincer‐Type Complexes for Catalytic (De)Hydrogenation and Transfer (De)Hydrogenation Reactions: Recent Progress 下载免费PDF全文
Dr. Svenja Werkmeister Jacob Neumann Dr. Kathrin Junge Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12226-12250
Pincer complexes are becoming increasingly important for organometallic chemistry and organic synthesis. Since numerous applications for such catalysts have been developed in recent decades, this Minireview covers progress in their use as catalysts for (de)hydrogenation and transfer (de)hydrogenation reactions during the last four years. Aside from noble‐metal‐based pincer complexes, the corresponding base metal complexes are also highlighted and their applications summarized. 相似文献
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Hölscher M Prechtl MH Leitner W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(23):6636-6643
The potential of pincer complexes [M(H)(2)(H(2))(PXP)] (M=Fe, Ru, Os; X=N, O, S) to coordinate, activate, and thus catalyze the reaction of N(2) with classical or nonclassical hydrogen centers present at the metal center, with the aim of forming NH(3) with H(2) as the only other reagent, was explored by means of DF (density functional) calculations. Screening of various complexes for their ability to perform initial hydrogen transfer to coordinated N(2) showed ruthenium pincer complexes to be more promising than the corresponding iron and osmium analogues. The ligand backbone influences the reaction dramatically: the presence of pyridine and thioether groups as backbones in the ligand result in inactive catalysts, whereas ether groups such as gamma-pyran and furan enable the reaction and result in unprecedented low activation barriers (23.7 and 22.1 kcal mol(-1), respectively), low enough to be interesting for practical application. Catalytic cycles were calculated for [Ru(H)(2)(H(2))(POP)] catalysts (POP=2,5-bis(dimethylphosphanylmethyl)furan and 2,6-bis(dimethylphosphanylmethyl)-gamma-pyran). The height of activation barriers for the furan system is somewhat more advantageous. Formation of inactive metal nitrides has not been observed. SCRF calculations were used to introduce solvent (toluene) effects. The Gibbs free energies of activation of the numerous single reaction steps do not change significantly when solvent is included. The reaction steps associated with the formation of the active catalyst from precursors [M(H)(2)(H(2))(PXP)] were also calculated. The otherwise inactive pyridine ligand system allows for the generation of the active catalyst species, whereas the ether ligand systems show activation barriers that could prohibit practical application. Consequently the generation of the active catalyst species needs to be addressed in further studies. 相似文献
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Selective Hydrogen Generation from Formic Acid with Well‐Defined Complexes of Ruthenium and Phosphorus–Nitrogen PN3‐Pincer Ligand 下载免费PDF全文
Dr. Yupeng Pan Dr. Cheng‐Ling Pan Yufan Zhang Dr. Huaifeng Li Dr. Shixiong Min Dr. Xunmun Guo Dr. Bin Zheng Dr. Hailong Chen Addison Anders Prof. Zhiping Lai Prof. Junrong Zheng Prof. Kuo‐Wei Huang 《化学:亚洲杂志》2016,11(9):1357-1360
An unsymmetrically protonated PN3‐pincer complex in which ruthenium is coordinated by one nitrogen and two phosphorus atoms was employed for the selective generation of hydrogen from formic acid. Mechanistic studies suggest that the imine arm participates in the formic acid activation/deprotonation step. A long life time of 150 h with a turnover number over 1 million was achieved. 相似文献
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Cover Picture: Selective Hydrogen Generation from Formic Acid with Well‐Defined Complexes of Ruthenium and Phosphorus–Nitrogen PN3‐Pincer Ligand (Chem. Asian J. 9/2016) 下载免费PDF全文
Dr. Yupeng Pan Dr. Cheng‐Ling Pan Yufan Zhang Dr. Huaifeng Li Dr. Shixiong Min Dr. Xunmun Guo Dr. Bin Zheng Dr. Hailong Chen Addison Anders Prof. Zhiping Lai Prof. Junrong Zheng Prof. Kuo‐Wei Huang 《化学:亚洲杂志》2016,11(9):1294-1294
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Julia Kaufmann Elisabeth Jäckel Dr. Edgar Haak 《Angewandte Chemie (International ed. in English)》2018,57(20):5908-5911
Cascade transformations forming multiple bonds and one‐pot procedures provide rapid access to natural‐product‐like scaffolds from simple precursors. These atom‐economic processes are valuable tools in organic synthesis and drug discovery. Herein, we report on ruthenium‐catalyzed cascade annulations of indole with readily available propargyl alcohols. These provide rapid access to diverse carbazoles, cyclohepta[b]indoles, and further fused polycycles with high selectivity. A bifunctional ruthenium complex featuring a redox‐coupled cyclopentadienone ligand acts as a common catalyst for the different cascade processes. 相似文献
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Nora Thies Dr. Cristian G. Hrib Prof. Dr. Edgar Haak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6302-6308
Several ruthenium‐catalyzed atom‐economic transformations of propargyl alcohols with pyrroles or indoles leading to alkylated, propargylated, or annulated heteroaromatics are reported. The mechanistically distinct reactions are catalyzed by a single ruthenium(0) complex containing a redox‐coupled dienone ligand. The mode of activation regarding the propargyl alcohols determines the reaction pathway and depends on the alcohols’ substitution pattern. Secondary substrates form alkenyl complexes by a 1,2‐hydrogen shift, whereas the transformation of tertiary substrates involves allenylidene intermediates. 1‐Vinyl propargyl alcohols are converted by a cascade allylation/cyclization sequence. The environmentally benign processes are of broad scope and allow the selective synthesis of highly functionalized pyrroles and indoles generating water as the only waste product. 相似文献
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Dr. Jacorien Coetzee Dr. Deborah L. Dodds Prof. Jürgen Klankermayer Sandra Brosinski Prof. Walter Leitner Prof. Alexandra M. Z. Slawin Prof. David J. Cole‐Hamilton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):11039-11050
Hydrogenation of amides in the presence of [Ru(acac)3] (acacH=2,4‐pentanedione), triphos [1,1,1‐tris‐ (diphenylphosphinomethyl)ethane] and methanesulfonic acid (MSA) produces secondary and tertiary amines with selectivities as high as 93 % provided that there is at least one aromatic ring on N. The system is also active for the synthesis of primary amines. In an attempt to probe the role of MSA and the mechanism of the reaction, a range of methanesulfonato complexes has been prepared from [Ru(acac)3], triphos and MSA, or from reactions of [RuX(OAc)(triphos)] (X=H or OAc) or [RuH2(CO)(triphos)] with MSA. Crystallographically characterised complexes include: [Ru(OAc‐κ1O)2(H2O)(triphos)], [Ru(OAc‐κ2O,O′)(CH3SO3‐κ1O)(triphos)], [Ru(CH3SO3‐κ1O)2(H2O)(triphos)] and [Ru2(μ‐CH3SO3)3(triphos)2][CH3SO3], whereas other complexes, such as [Ru(OAc‐κ1O)(OAc‐κ2O,O′)(triphos)], [Ru(CH3SO3‐κ1O)(CH3SO3‐κ2O,O′)(triphos)], H[Ru(CH3SO3‐κ1O)3(triphos)], [RuH(CH3SO3‐κ1O)(CO)(triphos)] and [RuH(CH3SO3‐κ2O,O′)(triphos)] have been characterised spectroscopically. The interactions between these various complexes and their relevance to the catalytic reactions are discussed. 相似文献
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Kjellgren J Aydin J Wallner OA Saltanova IV Szabó KJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(18):5260-5268
Palladium-catalyzed cross-coupling of vinyl epoxides and aziridines with organoboronic acids was performed by using 0.5-2.5 mol % pincer-complex catalyst. The reactions proceed under mild conditions affording allyl alcohols and amines with high regioselectivity and in good to excellent yields. Under the applied reaction conditions aromatic chloro-, bromo- and iodo substituents are tolerated. Our results indicate that the mechanism of the pincer complex catalyzed and the corresponding palladium(0) catalyzed process is substantially different. It was concluded that the transformations proceed via transmetalation of the organoboronic acids to the pincer-complex catalyst followed by an S(N)2'-type opening of the vinyl epoxide or aziridine substrate. In this process the palladium atom is kept in oxidation state +2 under the entire catalytic process, and therefore oxidative side reactions can be avoided. 相似文献