- Imidazolylidene carbene ligated palladium catalysis of the Heck reaction in the presence of air.
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Five 1,3-disubstituted imidazolium salts were synthesized. Their Heck reaction activities were evaluated. A convenient, efficient and high yielding procedure based on these compounds for the arylation of olefins was developed. Heck reactions mediated by these palladium-N-heterocyclic carbene complexes were conducted under air and even in the presence of several common oxidants.
- Liu, Jingping,Zhao, Yuanhong,Zhou, Yongyun,Li, Liang,Zhang, Tony Y,Zhang, Hongbin
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- Non-Chelate-Assisted Palladium-Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C?H Activation Need Help?
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The pyridone fragment in the ligand [2, 2’-bipyridin]-6(1H)-one (bipy-6-OH) enables the oxidative Heck reaction of simple arenes with oxygen as the sole oxidant and no redox mediator. Arenes with either electron-donating or electron-withdrawing groups can be functionalized in this way. Experimental data on the reaction with toluene as the model arene shows that the C?H activation step is turnover limiting and that the ligand structure is crucial to facilitate the reaction, which supports the involvement of the pyridone fragment in the C?H activation step. In the case of fluoroarenes, the alkenylation of mono and 1,2-difluoro benzenes requires the presence of bipy-6-OH. In contrast, this ligand is detrimental for the alkenylation of 1,3-difluoro, tri, tetra and pentafluoro benzenes which can be carried out using just [Pd(OAc)2]. This correlates with the acidity of the fluoroarenes, the most acidic undergoing easier C?H activation so other steps of the reaction such as the coordination-insertion of the olefin become kinetically important for polyfluorinated arenes. The use of just a catalytic amount of sodium molybdate as a base proved to be optimal in all these reactions. (Figure presented.).
- Albéniz, Ana C.,Villalba, Francisco
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supporting information
p. 4795 - 4804
(2021/09/06)
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- Mizoroki–Heck Cross-Coupling of Acrylate Derivatives with Aryl Halides Catalyzed by Palladate Pre-Catalysts
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The Mizoroki–Heck (MH) reaction involving aryl halides with various acrylates and acrylamides has been studied using air and moisture-stable imidazolium-based palladate pre-catalysts. These pre-catalysts can be converted into Pd-NHC species (NHC = N-heterocyclic carbene) under catalytic conditions and are capable of facilitating the Mizoroki–Heck reaction of aryl halides with various acrylates. The effects of solvent, catalyst loading, temperature and bases on the reaction outcome have been investigated. Various coupling partners were tolerated under the optimal reaction conditions catalyzed by palladate 1, [SIPr·H][Pd(η3-2-Me-allyl)Cl2]. The efficiency of the optimized synthetic methodology was tested on various aryl halides and substituted acrylates as well as acrylamides. The MH reaction yielded the coupled products in good to excellent isolated yields (up to 98%).
- Islam, Mohammad Shahidul,Nahra, Fady,Tzouras, Nikolaos V.,Barakat, Assem,Cazin, Catherine S. J,Nolan, Steven P.,Al-Majid, Abdullah Mohammed
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supporting information
p. 4695 - 4699
(2019/11/13)
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- Ruthenium(II)-Catalyzed Decarboxylative C-H Activation: Versatile Routes to meta-Alkenylated Arenes
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Ruthenium(II) bis(carboxylate)s proved highly effective for two decarboxylative C-H alkenylation strategies. The decarboxylation proceeded efficiently at rather low temperatures. The unique versatility of the decarboxylative ruthenium(II) catalysis is reflected in the oxidative olefinations with alkenes as well as the redox-neutral hydroarylations of alkynes. Two birds with one Ru: Ruthenium(II) catalysis enabled decarboxylative C-H olefinations by carboxylate assistance at low temperature. It is applicable to both alkenes for oxidative olefinations, as well as alkynes for redox-neutral hydroarylations. Neither silver nor copper salts are required and meta-substituted products can be accessed with this method.
- Kumar, N. Y. Phani,Bechtoldt, Alexander,Raghuvanshi, Keshav,Ackermann, Lutz
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supporting information
p. 6929 - 6932
(2016/06/13)
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- Palladium-catalyzed Mizoroki-Heck type reaction with aryliodine diacetates using hydrazone ligand
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We developed a palladium-catalyzed Mizoroki-Heck type reaction of olefins with such hypervalent iodine reagents as iodobenzene diacetate in good to high yields using 2 mol% of a heterocyclic hydrazone (1b)-Pd(OAc)2 system in NMP under air at 90 °C. The Japan Institute of Heterocyclic Chemistry.
- Mino, Takashi,Watanabe, Kohei,Abe, Taichi,Kogure, Taketo,Sakamoto, Masami
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p. 2015 - 2021
(2013/10/22)
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- Synthesis and ring openings of cinnamate-derived N-unfunctionalised aziridines
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Tert-Butyl cinnamates are aziridinated with high trans-selectivity by an N-N ylide generated in situ from N-methylmorpholine and O-diphenylphosphinyl hydroxylamine. The resulting N-unfunctionalised aziridines are shown to be versatile synthetic building b
- Armstrong, Alan,Ferguson, Alexandra
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supporting information
p. 1747 - 1752,6
(2020/09/16)
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- Manipulating micellar environments for enhancing transition metal-catalyzed cross-couplings in water at room temperature
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The remarkable effects of added salts on the properties of aqueous micelles derived from the amphiphile PTS are described. Most notably, Heck reactions run in the presence of NaCl lead to couplings on aryl bromides in water at room temperature. Olefin cross- and ring-closing metathesis reactions run in the presence of small amounts of pH-lowering KHSO4 are also accelerated, another phenomenon that does not apply to typical processes in organic media. These salt effects allow, in general, for synthetically valuable C-C bond-forming processes to be conducted under environmentally benign conditions. Recycling of the surfactant is also demonstrated.
- Lipshutz, Bruce H.,Ghorai, Subir,Leong, Wendy Wen Yi,Taft, Benjamin R.,Krogstad, Daniel V.
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experimental part
p. 5061 - 5073
(2011/08/06)
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- Cinnamoyl inhibitors of tissue transglutaminase
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(Figure Presented) Transglutaminases (TGases) catalyze the intermolecular cross-linking of certain proteins and tissue TGases (TG2) are involved in diverse biological processes. Unregulated, high TGase activities have been implicated in several physiological disorders, but few reversible inhibitors of TG2 have been reported. Herein, we report the synthesis of a series of novel trans-cinammoyl derivatives, discovered to be potent inhibitors of guinea pig liver transglutaminase. The most effective inhibitors evaluated can be sorted into two subclasses: substituted cinnamoyl benzotriazolyl amides and the 3-(substituted cinnamoyl)pyridines, referred to more commonly as azachalcones. Kinetic evaluation of both of these subclasses revealed that they display reversible inhibition and are competitive with acyl donor TGase substrates at IC50 values as low as 18 μM. An analysis of structure - activity relationships within these series of inhibitors permitted the identification of potentially important binding interactions. Further testing of some of the most potent inhibitors demonstrated their selectivity for TG2 and their potential for further development.
- Pardin, Christophe,Pelletier, Joelle N.,Lubell, William D.,Keillor, Jeffrey W.
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p. 5766 - 5775
(2008/12/22)
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- Asymmetric dehydration of β-hydroxy esters via kinetic resolution
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Catalytic asymmetric dehydration of β-hydroxy esters via kinetic resolution has been investigated. The kinetic resolution of rac-β-hydroxy esters in the presence of prolinol chiral ligand 2a and BrZnCH2CO2t-Bu can provide highly enan
- Kim, Yongtae,Choi, Eui Ta,Lee, Min Hee,Park, Yong Sun
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p. 2833 - 2835
(2007/10/03)
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- Biaryl synthesis via palladium-catalyzed aryne multicomponent coupling
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Aryl iodides have been introduced as electrophiles in the three-component Heck coupling of arynes. Following optimization studies to favor three- versus two-component coupling, the reaction proceeds in good yield to afford a variety of functionalized biaryls.
- Henderson, Jaclyn L.,Edwards, Andrew S.,Greaney, Michael F.
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p. 5589 - 5592
(2008/09/18)
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- Parallel synthesis of homochiral β-amino acids
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The parallel asymmetric synthesis of an array of 30 β-amino acids of high enantiomeric purity using the conjugate addition of homochiral lithium N-benzyl-N-(α-methylbenzyl)amide as the key step is accomplished. The experimental simplicity and highly practical nature of the protocol is demonstrated by the efficient parallel conversion of 15 α,β-unsaturated esters to both enantiomeric series of the corresponding β-amino acids in high overall yields and selectivities with minimal purification involved in each step of the reaction protocol.
- Davies, Stephen G.,Mulvaney, Andrew W.,Russell, Angela J.,Smith, Andrew D.
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p. 1554 - 1566
(2008/02/09)
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- Highly Efficient Heck Reactions of Aryl Bromides with n-Butyl Acrylate Mediated by a Palladium/Phosphine-Imidazolium Salt System
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matrix presented A new phosphine-imidazolium salt, L·HBr (1, L = (1-ethylenediphenylphosphino-3-(mesityl))imidazol-2-ylidene), has been prepared. A combination of 0.5 mol % of Pd(dba)2 and 0.5 mol % of L·HBr in the presence of 2 equiv of Cssub
- Yang, Chuluo,Lee, Hon Man,Nolan, Steven P.
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p. 1511 - 1514
(2007/10/03)
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