- 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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- Trading N and O. Part 4: Asymmetric synthesis of syn-β-substituted-α-amino acids
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A total of nine enantiopure syn-β-substituted-α-amino acids have been synthesised, comprising both syn-β-hydroxy-α-amino acids and syn-β-fluoro-α-amino acids. The key step in the synthetic strategy towards these syn-β-substituted-α-amino acids involves a stereospecific rearrangement, which proceeds via the intermediacy of the corresponding aziridinium ions. The requisite enantiopure syn-α-hydroxy-β-amino esters were prepared via asymmetric aminohydroxylation of the corresponding α,β-unsaturated esters followed by epimerisation of the resultant anti-α-hydroxy-β-amino esters at the C(2)-position. Subsequent activation of the α-hydroxy moiety as a leaving group followed by displacement by the β-amino substituent gave the corresponding aziridinium species. Regioselective in situ ring-opening of the aziridinium intermediates with either water or fluoride gave the corresponding syn-β-hydroxy-α-amino ester or syn-β-fluoro-α-amino ester, respectively, and N-deprotection and ester hydrolysis afforded the target syn-β-substituted-α-amino acids as single diastereoisomers in good overall yield.
- Davies, Stephen G.,Fletcher, Ai M.,Greenaway, Catherine J.,Kennedy, Matthew S.,Mayer, Christoph,Roberts, Paul M.,Thomson, James E.
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p. 5049 - 5061
(2018/05/08)
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- Bench-Stable and Recoverable Palladium(I) Dimer as an Efficient Catalyst for Heck Cross-Coupling
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The application of air- and moisture-stable dinuclear palladium(I) complex [Pd(μ-I)(Pt-Bu3)]2 as an efficient catalyst for the Heck cross-coupling reaction of aryl iodides and bromides with acrylates and styrenes is described. The de
- Sperger, Theresa,Stirner, Christopher K.,Schoenebeck, Franziska
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supporting information
p. 115 - 120
(2016/12/24)
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- 2-Hydroxy-1,10-phenanthroline vs 1,10-Phenanthroline: Significant ligand acceleration effects in the Palladium-Catalyzed Oxidative Heck reaction of arenes
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A series of bidentate monoanionic nitrogen ligands were designed and applied in the Pd-catalyzed oxidative Heck reaction of arenes with alkenes. Significant ligand-accelerated effects were observed, and direct C-H functionalized products were formed in high yields with meta-selectivity.
- Ying, Cheng-Hao,Yan, Shao-Bai,Duan, Wei-Liang
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supporting information
p. 500 - 503
(2014/04/03)
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- Asymmetric synthesis of β-fluoroaryl-β-amino acids
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The conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl) amide to a range of β-fluoroaryl-α,β-unsaturated esters gave the corresponding β-amino esters with high diastereoselectivity and in good isolated yields. Sequential treatment of the resulta
- Davies, Stephen G.,Fletcher, Ai M.,Lv, Linlu,Roberts, Paul M.,Thomson, James E.
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experimental part
p. 910 - 925
(2012/09/22)
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- Microwave-assisted copper-catalyzed heck reaction in PEG solvent
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A catalytic system made of a copper salt, potassium carbonate and PEG 3400 was developed to perform a Heck arylation under microwave activation. Copper iodide gave the best results in a short reaction time (30 min) and various substituted tert-butyl cinna
- Declerck, Valérie,Martinez, Jean,Lamaty, Frédéric
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p. 3029 - 3032
(2008/02/13)
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- N-4-PIPERIDINYL COMPOUNDS AS CCR5 MODULATORS
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The invention provides a compound of formula (I):[Chemical formula should be inserted here. Please see paper copy.] wherein R1, R2, R3, R3a, R4, R4a, R5, and R6 are as defined; or a pharmaceutically acceptable salt thereof or a solvate thereof; compositions containing these compounds, processes for preparing them and their use as modulators of chemokine activity (especially CCR5 activity).
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- 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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p. 3227 - 3231
(2007/10/03)
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- Asymmetric synthesis of β-haloaryl β-amino acid derivatives
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Lithium N-benzyl-N-α-methyl-4-methoxybenzylamide may be employed as a homochiral ammonia equivalent for the synthesis of homochiral β-haloaryl β-amino acid derivatives via a strategy involving its conjugate addition to α,β-unsaturated β-haloaryl acceptors and subsequent oxidative deprotection with ceric ammonium nitrate.
- Bull, Steven D.,Davies, Stephen G.,Delgado-Ballester, Santiago,Kelly, Peter M.,Kotchie, Luke J.,Gianotti, Massimo,Laderas, Mario,Smith, Andrew D.
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p. 3112 - 3121
(2007/10/03)
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