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Ruthenium/Imidazolylphosphine Catalysis: Hydrogenation of Aliphatic and Aromatic Nitriles to Form Amines 下载免费PDF全文
Svenja Werkmeister Dr. Kathrin Junge Bianca Wendt Dr. Anke Spannenberg Dr. Haijun Jiao Christoph Bornschein Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4227-4231
A convenient and efficient catalyst system for the hydrogenation of aliphatic nitriles towards the corresponding primary amines in high to excellent yields is presented. In addition, aromatic nitriles are reduced smoothly, too. The use of low catalyst loadings and molecular hydrogen make this protocol an attractive methodology. 相似文献
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Dr. Robert Langer Dr. Mark A. Iron Dr. Leonid Konstantinovski Dr. Yael Diskin‐Posner Dr. Gregory Leitus Yehoshoa Ben‐David Prof. Dr. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7196-7209
The new, structurally characterized hydrido carbonyl tetrahydridoborate iron pincer complex [(iPr‐PNP)Fe(H)(CO)(η1‐BH4)] ( 1 ) catalyzes the base‐free hydrogenation of ketones to their corresponding alcohols employing only 4.1 atm hydrogen pressure. Turnover numbers up to 1980 at complete conversion of ketone were reached with this system. Treatment of 1 with aniline (as a BH3 scavenger) resulted in a mixture of trans‐[(iPr‐PNP)Fe(H)2(CO)] ( 4 a ) and cis‐[(iPr‐PNP)Fe(H)2(CO)] ( 4 b ). The dihydrido complexes 4 a and 4 b do not react with acetophenone or benzaldehyde, indicating that these complexes are not intermediates in the catalytic reduction of ketones. NMR studies indicate that the tetrahydridoborate ligand in 1 dissociates prior to ketone reduction. DFT calculations show that the mechanism of the iron‐catalyzed hydrogenation of ketones involves alcohol‐assisted aromatization of the dearomatized complex [(iPr‐PNP*)Fe(H)(CO)] ( 7 ) to initially give the Fe0 complex [(iPr‐PNP)Fe(CO)] ( 21 ) and subsequently [(iPr‐PNP)Fe(CO)(EtOH)] ( 38 ). Concerted coordination of acetophenone and dual hydrogen‐atom transfer from the PNP arm and the coordinated ethanol to, respectively, the carbonyl carbon and oxygen atoms, leads to the dearomatized complex [(iPr‐PNP*)Fe(CO)(EtO)(MeCH(OH)Ph)] ( 32 ). The catalyst is regenerated by release of 1‐phenylethanol, followed by dihydrogen coordination and proton transfer to the coordinated ethoxide ligand. 相似文献
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Ruthenium(II) Complexes Containing Lutidine‐Derived Pincer CNC Ligands: Synthesis,Structure, and Catalytic Hydrogenation of CN bonds 下载免费PDF全文
Dr. Martín Hernández‐Juárez Dr. Joaquín López‐Serrano Dr. Patricia Lara Judith P. Morales‐Cerón Dr. Mónica Vaquero Dr. Eleuterio Álvarez Prof. Verónica Salazar Dr. Andrés Suárez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7540-7555
A series of Ru complexes containing lutidine‐derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver‐carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N‐heterocyclic carbene fragments. In the presence of tBuOK, the Ru‐CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand‐assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru‐CNC complex 5 e (BF4) is able to add aldimines to the metal–ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer‐sphere stepwise hydrogen transfer to the C?N bond assisted either by the pincer ligand or a second coordinated H2 molecule. 相似文献
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Philipp Melle Jan Thiede Daniela A. Hey Prof. Dr. Martin Albrecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(58):13226-13234
The rational optimization of homogeneous catalysts requires ligand platforms that are easily tailored to improve catalytic performance. Here, it is demonstrated that pyridylidene amides (PYAs) provide such a platform to custom-shape transfer hydrogenation catalysts with exceptional activity. Specifically, a series of meta-PYA pincer ligands with differently substituted PYA units has been synthezised and coordinated to ruthenium(II) centres to form bench-stable tris-acetonitrile complexes [Ru(R-PYA-pincer)(MeCN)3](PF6)2 (R=OMe, Me, H, Cl, CF3). Analytic studies including 1H NMR spectroscopy, cyclic voltammetry, and X-ray crystallography reveal a direct influence of the substituents on the electronic properties of the ruthenium center. The complexes are active in the catalytic transfer hydrogenation of ketones, with activities directly encoded by the PYA substitution pattern. Their perfomance improves further upon exchange of an ancillary MeCN ligand with PPh3. While complexes [Ru(R-PYA-pincer)(PPh3)(MeCN)2](PF6)2 were only isolated for R=H, Me, an in situ protocol was developed to generate these complexes in situ for R=OMe, Cl, CF3 by using a 1:2 ratio of the complexes and PPh3. This in situ protocol together with a short catalyst pre-activation provided highly active catalytic systems. The most active pre-catalyst featured the methoxy-substituted PYA ligand and reached turnover frenquencies of 210 000 h−1 under an exceptionally low catalyst loading of 25 ppm for the benchmark substrate benzophenone, representing one of the most active transfer hydrogenation systems known to date. 相似文献
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Asymmetric Hydrogenation of α,β‐Unsaturated Nitriles with Base‐Activated Iridium N,P Ligand Complexes 下载免费PDF全文
Marc‐André Müller Prof. Dr. Andreas Pfaltz 《Angewandte Chemie (International ed. in English)》2014,53(33):8668-8671
Although many chiral catalysts are known that allow highly enantioselective hydrogenation of a wide range of olefins, no suitable catalysts for the asymmetric hydrogenation of α,β‐unsaturated nitriles have been reported so far. We have found that Ir N,P ligand complexes, which under normal conditions do not show any reactivity towards α,β‐unsaturated nitriles, become highly active catalysts upon addition of N,N‐diisopropylethylamine. The base‐activated catalysts enable conjugate reduction of α,β‐unsaturated nitriles with H2 at low catalyst loadings, affording the corresponding saturated nitriles with high conversion and excellent enantioselectivity. In contrast, alkenes lacking a conjugated cyano group do not react under these conditions, making it possible to selectively reduce the conjugated C?C bond of an α,β‐unsaturated nitrile, while leaving other types of C?C bonds in the molecule intact. 相似文献
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Protic NNN and NCN Pincer‐Type Ruthenium Complexes Featuring (Trifluoromethyl)pyrazole Arms: Synthesis and Application to Catalytic Hydrogen Evolution from Formic Acid 下载免费PDF全文
Yoshiko Nakahara Tatsuro Toda Prof. Dr. Asuka Matsunami Prof. Dr. Yoshihito Kayaki Prof. Dr. Shigeki Kuwata 《化学:亚洲杂志》2018,13(1):73-80
NNN and NCN pincer‐type ruthenium(II) complexes featuring two protic pyrazol‐3‐yl arms with a trifluoromethyl (CF3) group at the 5‐position were synthesized and structurally characterized to evaluate the impact of the substitution on the properties and catalysis. The increased Brønsted acidity by the highly electron‐withdrawing CF3 pendants was demonstrated by protonation–deprotonation experiments. By contrast, the IR spectra of the carbonyl derivatives as well as the cyclic voltammogram indicated that the electron density of the ruthenium atom is negligibly influenced by the CF3 group. Catalysis of these complexes in the decomposition of formic acid to dihydrogen and carbon dioxide was also examined. The NNN pincer‐type complex 1 a with the CF3 group exhibited a higher catalytic activity than the tBu‐substituted analogue 1 b . In addition, the bis(CF3‐pyrazolato) ammine derivative 4 catalyzed the reaction even in the absence of base additives. 相似文献
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Tomohiro Maegawa Dr. Akira Akashi Kiichiro Yaguchi Yohei Iwasaki Masahiro Shigetsura Yasunari Monguchi Dr. Hironao Sajiki Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(28):6953-6963
An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the aromatic ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H2 pressures (<10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compounds in good to excellent yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity. 相似文献
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Transfer Hydrogenation of Ketones Catalyzed by Surface‐Active Ruthenium and Rhodium Complexes in Water 下载免费PDF全文
Dr. Alexander M. Kalsin Dr. Tat'yana A. Peganova Dr. Valentin V. Novikov Alexandra I. Zhamoytina Dr. Luca Gonsalvi Dr. Maurizio Peruzzini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):846-854
An improved, high‐yield, one‐pot synthetic procedure for water‐soluble ligands functionalized with trialkyl ammonium side groups H2N(CH2)2NHSO2‐p‐C6H4CH2[NMe2(CnH2n+1)]+ ( [HL n ]+ ; n=8, 16) was developed. The corresponding new surface‐active complexes [(p‐cymene)RuCl( L n )] and [Cp*RhCl( L n )] (Cp*=η5‐C5Me5) were prepared and characterized. For n=16 micelles are formed in water at concentrations as low as 0.6 mM , as demonstrated by surface‐tension measurements. The complexes were used for catalytic transfer hydrogenation of ketones with formate in water. Highly active catalyst systems were obtained in the case of complexes bearing C16 tails due to their ability to be adsorbed at the water/substrate interface. The scope of these catalyst systems in aqueous solutions was extended from partially water soluble aryl alkyl ketones (acetophenone, butyrophenone) to hydrophobic dialkyl ketones (2‐dodecanone). 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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Tailor‐Made Ruthenium‐Triphos Catalysts for the Selective Homogeneous Hydrogenation of Lactams 下载免费PDF全文
Markus Meuresch Stefan Westhues Prof. Dr. Walter Leitner Prof. Dr. Jürgen Klankermayer 《Angewandte Chemie (International ed. in English)》2016,55(4):1392-1395
The development of a tailored tridentate ligand enabled the synthesis of a molecular ruthenium‐triphos catalyst, eliminating dimerization as the major deactivation pathway. The novel catalyst design showed strongly increased performance and facilitated the hydrogenation of highly challenging lactam substrates with unprecedented activity and selectivity. 相似文献
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Highly Enantioselective Hydrogenation of N‐Aryl Imines Derived from Acetophenones by Using Ru–Pybox Complexes under Hydrogenation or Transfer Hydrogenation Conditions in Isopropanol 下载免费PDF全文
Estefanía Menéndez‐Pedregal Dr. Mónica Vaquero Dr. Elena Lastra Prof. Pilar Gamasa Dr. Antonio Pizzano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):549-553
The asymmetric reduction of N‐aryl imines derived from acetophenones by using Ru complexes bearing both a pybox (2,6‐bis(oxazoline)pyridine) and a monodentate phosphite ligand has been described. The catalysts show good activity with a diverse range of substrates, and deliver the amine products in very high levels of enantioselectivity (up to 99 %) under both hydrogenation and transfer hydrogenation conditions in isopropanol. From deuteration studies, a very different labeling is observed under hydrogenation and transfer hydrogenation conditions, which demonstrates the different nature of the hydrogen source in both reactions. 相似文献
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Unprecedented Iron‐Catalyzed Ester Hydrogenation. Mild,Selective, and Efficient Hydrogenation of Trifluoroacetic Esters to Alcohols Catalyzed by an Iron Pincer Complex 下载免费PDF全文
Dr. Thomas Zell Yehoshoa Ben‐David Prof. Dr. David Milstein 《Angewandte Chemie (International ed. in English)》2014,53(18):4685-4689
The synthetically important, environmentally benign hydrogenation of esters to alcohols has been accomplished in recent years only with precious‐metal‐based catalysts. Here we present the first iron‐catalyzed hydrogenation of esters to the corresponding alcohols, proceeding selectively and efficiently in the presence of an iron pincer catalyst under remarkably mild conditions. 相似文献
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Hydrogenation of Sulfoxides to Sulfides under Mild Conditions Using Ruthenium Nanoparticle Catalysts 下载免费PDF全文
Dr. Takato Mitsudome Yusuke Takahashi Dr. Tomoo Mizugaki Prof. Dr. Koichiro Jitsukawa Prof. Dr. Kiyotomi Kaneda 《Angewandte Chemie (International ed. in English)》2014,53(32):8348-8351
The first demonstration of the hydrogenation of sulfoxides under atmospheric H2 pressure is reported. The highly efficient reaction is facilitated by a heterogeneous Ru nanoparticle catalyst. The mild reaction conditions enable the selective hydrogenation of a wide range of functionalized sulfoxides to the corresponding sulfides. The high redox ability of RuOx nanoparticles plays a key role in the hydrogenation. 相似文献