共查询到20条相似文献,搜索用时 10 毫秒
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William A. Carole Dr. Thomas J. Colacot 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(23):7686-7695
The behavior of palladium acetate is reviewed with respect to its synthesis, characterization, structure (in both solution and solid state), and activation pathways. In addition, comparisons of catalytic activities between pure palladium acetate and two common byproducts, Pd3(OAc)5(NO2) and polymeric [Pd(OAc)2]n, typically present in commercially available material are reviewed. Hence, this minireview serves as a concise guide for the users of palladium acetate from both academia and industry. 相似文献
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Synthesis of 2‐Alkynoates by Palladium(II)‐Catalyzed Oxidative Carbonylation of Terminal Alkynes and Alcohols 下载免费PDF全文
Qun Cao N. Louise Hughes Dr. Mark J. Muldoon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11982-11985
A homogeneous PdII catalyst, utilizing a simple and inexpensive amine ligand (TMEDA), allows 2‐alkynoates to be prepared in high yields by an oxidative carbonylation of terminal alkynes and alcohols. The catalyst system overcomes many of the limitations of previous palladium carbonylation catalysts. It has an increased substrate scope, avoids large excesses of alcohol substrate and uses a desirable solvent. The catalyst employs oxygen as the terminal oxidant and can be operated under safer gas mixtures. 相似文献
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Stahl SS 《Angewandte Chemie (International ed. in English)》2004,43(26):3400-3420
Selective aerobic oxidation of organic molecules is a fundamental and practical challenge in modern chemistry. Effective solutions to this problem must overcome the intrinsic reactivity and selectivity challenges posed by the chemistry of molecular oxygen, and they must find application in diverse classes of oxidation reactions. Palladium oxidase catalysis combines the versatility of Pd(II)-mediated oxidation of organic substrates with dioxygen-coupled oxidation of the reduced palladium catalyst to enable a broad range of selective aerobic oxidation reactions. Recent developments revealed that cocatalysts (e.g. Cu(II), polyoxometalates, and benzoquinone) are not essential for efficient oxidation of Pd(0) by molecular oxygen. Oxidatively stable ligands play an important role in these reactions by minimizing catalyst decomposition, promoting the direct reaction between palladium and dioxygen, modulating organic substrate reactivity and permitting asymmetric catalysis. 相似文献
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Brian V. Popp Dr. Shannon S. Stahl Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(12):2915-2922
Aerobic oxidation : Mechanisms of aerobic oxidation of the PdII(OAc)2/pyridine catalyst system were evaluated by using density functional theory methods. The results reveal that labile monodentate ligands, such as pyridine, favor a catalyst reoxidation pathway that proceeds via Pd0, rather than direct reaction of O2 with a PdII–hydride intermediate (see scheme).
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Kilian Muñiz Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(50):9412-9423
Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd0/PdII cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)‐promoted reactions at a given point of the catalytic cycle by selective metal oxidation. The resulting higher‐oxidation‐state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher oxidation state is of significant synthetic potential. 相似文献
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Reiko Jennerjahn Irene Piras Ralf Jackstell Dr. Robert Franke Dr. Klaus‐Diether Wiese Dr. Matthias Beller Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(26):6383-6388
A novel selective palladium catalyst system based on bidentate 2,2′‐heteroarylarylphosphines and p‐TsOH has been developed for hydroformylation reactions (see scheme). By applying optimal conditions good to excellent regioselectivity is obtained for the hydroformylation of aliphatic and aromatic olefins. It is shown that a low acid concentration is crucial for obtaining high degrees of the linear isomer.
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Prof. Uwe H. F. Bunz Dr. Jens U. Engelhart 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4680-4689
Novel synthetic methodologies allow increasingly efficient access to known organic materials, as well as the preparation of otherwise inaccessible species. Pd‐catalyzed coupling of aromatic dihalides to ortho‐diaminoarenes furnishes embedded stable N,N′‐dihydropyrazines expediently and in often excellent yields. The embedded N,N′‐dihydropyrazines can then be oxidized by MnO2 to give substituted azatetracenes, azapentacenes, azahexacenes, and azaheptacenes, which are soluble, processable, and stable. This powerful Pd‐catalyzed methodology allows the preparation of azaacenes, including diaza‐, tetraaza‐ and hexaazaacenes. In combination with a suitable Pd precursor, Buchwald‐type biarylphosphines have been shown to give excellent results. Activated dihalides such as 2,3‐dihaloquinoxalines are coupled easily under simplified conditions, whereas 2,3‐dibromoacenes require more stringent conditions and advanced catalyst precursors. Pd catalysts effect the assembly of azaacenes with otherwise difficult to obtain substitution patterns. High yields and flexibility make this method most attractive. 相似文献
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IntroductionInthepastdecade ,itwasfoundthattwoaminoacidresidues ,SerandHis ,workastheactivesitesintheser ineprotease .1 3 Inourpreviouswork ,adipeptideseryl histidine (Ser His)wasfoundtohavetheproteinandnu cleosidescleavageactivity .4 7p Nitrophenylacetate (p NPA)w… 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
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Francis Bru Dr. Mathieu Lesieur Dr. Albert Poater Prof. Dr. Alexandra M. Z. Slawin Prof. Dr. Luigi Cavallo Prof. Dr. Catherine S. J. Cazin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202201917
The synthesis and isolation of [Pd(NHC)(PhC≡CPh)] complexes are reported. These new 14-electron Pd(0)-complexes are key synthons leading to known palladium(0) and palladium(II) species, as well as permitting access to unprecedented mixed NHC-phosphite palladium(0) complexes. This motif permits the facile catalytic hydrosilylation of allenes. DFT calculations have allowed the characterization of the relatively weak interaction between the metal and the diphenylacetylene ligand, with a comparison with a series of ligands with more or less coordinating power, bearing varied structural and electronic properties. 相似文献
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Dr. Paolo Zardi Dr. Thierry Roisnel Dr. Rafael Gramage-Doria 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(2):627-634
Inspired by enzymes such as cytochrome P-450, the study of the reactivity of metalloporphyrins continues to attract major interest in the field of homogeneous catalysis. However, little is known about benefitting from the substrate-recognition properties of porphyrins containing additional, catalytically relevant active sites. Herein, such an approach is introduced by using supramolecular ligands derived from metalloporphyrins customized with rigid, palladium-coordinating nitrile groups. According to different studies (NMR and UV/Vis spectroscopy, XRD, control experiments), the supramolecular ligands are able to accommodate pyridine derivatives as substrates inside the porphyrin pocket while the reactivity occurs at the peripheral side. By simply tuning a remote metal center, different binding events result in different catalyst reactivity, and this enzyme-like feature leads to high degrees of substrate selectivity in representative palladium-catalyzed Suzuki–Miyaura reactions. 相似文献
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乙酸乙酯的水解实验是现行高中有机化学教学内容中的重要实验,教材中提出通过观察酯层消失的时间差异来判断水解速率的差别,在实际操作过程中实验效果并不理想。借助手持技术分别探究了乙酸乙酯在中性、酸性、碱性、不同温度条件下的水解速率情况,并借助相关知识理论分析了乙酸乙酯在酸性和碱性条件下水解速率的差异,旨在帮助教师和学生深度理解乙酸乙酯发生水解的条件及规律。 相似文献
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Dr. Nikolay Tarabanko Viktor A. Golubkov Valentin V. Sychev Prof. Valery E. Tarabanko Prof. Oxana P. Taran 《Chemphyschem》2022,23(3):e202100804
Double activation catalysis was experimentally observed in hydrolysis of cellobiose catalyzed simultaneously with phthalic and hydrochloric acids, confirming earlier theoretical prediction known from literature. Both acids can catalyze the reaction individually, and contribution of the double-activation pathway to the total reaction rate declines as temperature increases. In fact, above a certain temperature, the hydrolysis rate in presence of both acids becomes lower than the sum of the rates for the two acids acting individually. A kinetic model is proposed to explain this transition between double-activated catalysis and inhibition. The trend of declining contribution of cooperative catalytic pathway with rising temperature is theorized to be generally applicable for any reaction with a pathway involving simultaneous action of two catalysts when either of them can individually catalyze the reaction. 相似文献
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