- 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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- Synthesis of Indoles by Reductive Cyclization of Nitro Compounds Using Formate Esters as CO Surrogates
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Alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of 2-nitrostyrenes to give indoles. Whereas the use of alkyl formates requires the presence of a ruthenium catalyst such as Ru3(CO)12, the reaction with phenyl formate can be performed by using a Pd/phenanthroline complex alone. Phenyl formate was found to be the most effective CO source and the desired products were obtained in excellent yields, often higher than those previously reported using pressurized CO. The reaction tolerates many functional groups, including sensitive ones like a free aldehydic group or a pendant pyrrole. Detailed experiments and kinetic studies allow to conclude that the activation of phenyl formate is base-catalyzed and that the metal doesn't play a role in the decarbonylation step. The reactions can be performed in a single thick-walled glass tube with as little as 0.2 mol-% palladium catalyst and even on a 2 g scale. The same protocol can be extended to other nitro compounds, affording different heterocycles.
- Ahmed Fouad, Manar,Ferretti, Francesco,Formenti, Dario,Milani, Fabio,Ragaini, Fabio
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supporting information
p. 4876 - 4894
(2021/09/20)
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- Palladium-Based Catalysts Supported by Unsymmetrical XYC–1 Type Pincer Ligands: C5 Arylation of Imidazoles and Synthesis of Octinoxate Utilizing the Mizoroki–Heck Reaction
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A series of new unsymmetrical (XYC–1 type) palladacycles (C1–C4) were designed and synthesized with simple anchoring ligands L1–4H (L1H = 2-((2-(4-methoxybenzylidene)-1-phenylhydrazinyl)methyl)pyridine, L2H = N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono)methyl)aniline, L3H = N,N-diethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono)methyl) aniline and L4H = 4-(4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono) methyl)phenyl)morpholine H = dissociable proton). Molecular structure of catalysts (C1–C4) were further established by single X-ray crystallographic studies. The catalytic performance of palladacycles (C1–C4) was explored with the direct Csp2–H arylation of imidazoles with aryl halide derivatives. These palladacycles were also applied for investigating of Mizoroki–Heck reactions with aryl halides and acrylate derivatives. During catalytic cycle in situ generated Pd(0) nanoparticles were characterized by XPS, SEM and TEM analysis and possible reaction pathways were proposed. The catalyst was employed as a pre-catalyst for the gram-scale synthesis of octinoxate, which is utilized as a UV-B sunscreen agent.
- Maji, Ankur,Singh, Ovender,Singh, Sain,Mohanty, Aurobinda,Maji, Pradip K.,Ghosh, Kaushik
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p. 1596 - 1611
(2020/04/29)
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- Tandem Wittig – Reductive annulation decarboxylation approach for the synthesis of indole and 2-substituted indoles
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A simple tandem Wittig reaction-reductive decarboxylation route is established for the synthesis of indoles from commercially available o-nitrobenzaldehydes and a stable phosphorane. The method allows access to indoles in a very fast manner without involving any metal or expensive reagents or inert atmosphere. Also 2-substituted indoles are obtained which forms an important core of many biological active compounds.
- Volvoikar, Prajesh S.,Tilve
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p. 1851 - 1854
(2018/04/14)
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- DIPHENYL UREA DERIVATIVES AS FORMYL PEPTIDE RECEPTOR MODULATORS
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The present invention relates to diphenyl urea derivatives, processes for preparing them, pharmaceutical compositions containing them and their use as pharmaceuticals as modulators of the N-formyl peptide receptor 2.
- -
-
Paragraph 0119-0121
(2015/03/28)
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- Palladium/norbornene-mediated tandem C-H amination/C-I alkenylation reaction of aryl iodides with secondary cyclic O-benzoyl hydroxylamines and activated terminal olefins
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A novel palladium-catalyzed norbornene-mediated three-component reaction for the construction of ortho-alkenyl aromatic tertiary amines has been achieved, which represents a useful extension of the Catellani-type tandem ortho-selective C-H amination trans
- Chen, Zhi-Yuan,Ye, Chang-Qing,Zhu, Hui,Zeng, Xing-Ping,Yuan, Jian-Jun
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supporting information
p. 4237 - 4241
(2014/05/06)
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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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- Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage
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The unactivated carbon-nitrogen bond of various aryl hydrazines was cleaved under very mild conditions by Pd(0) with the assistance of Pd(II). The in situ generated aryl palladium complex readily takes part in the C-C bond formation with olefins. This study offered a new mode of C-Pd bond formation, which will spur the development of palladium-catalyzed cross-coupling in the future.
- Zhu, Ming-Kui,Zhao, Jun-Feng,Loh, Teck-Peng
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supporting information; experimental part
p. 6308 - 6311
(2012/01/06)
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- Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF2
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A new protocol for the decarboxylative Heck vinylation of benzoic acids is disclosed. In the presence of a catalyst system generated in situ from Pd(OAc)2 (2 mol %), CuF2 (2 equiv), and benzoquinone (0.5 equiv) in NMP, a wide range of olefins were coupled with various 2-nitrobenzoates at 130 °C with the release of carbon dioxide to afford the corresponding vinyl arenes in good yields.
- Goossen, Lukas J.,Zimmermann, Bettina,Knauber, Thomas
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experimental part
(2010/08/19)
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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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- An inexpensive and highly stable ligand 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazine for Mizoroki-Heck and room temperature Suzuki-Miyaura cross-coupling reactions
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A bulky, inexpensive and simple bidentate ligand 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazine (1) has been synthesized and characterized. The palladium catalyst was formed by combination of 1 with [Cl2Pd(COD)] in a ratio of 1:1, tested in the Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions. Coupling of a variety of aryl bromides with phenylboronic acid using methanol as solvent at room temperature, or at 60 °C, gave generally high yields of coupled products. Coupling of aryl chlorides with organoboron reagent at 110 °C in DMF afforded good yields of biaryls under aerobic conditions. This non-phosphorus, air and moisture stable catalyst also displays good activity for Mizoroki-Heck coupling reaction in methanol at 60 °C with various aryl chlorides and bromides.
- Mohanty, Sasmita,Suresh,Balakrishna, Maravanji S.,Mague, Joel. T.
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p. 240 - 247
(2008/09/16)
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- Wittig reactions in water media employing stabilized ylides with aldehydes. Synthesis of α,β-unsaturated esters from mixing aldehydes, α-bromoesters, and Ph3P in aqueous NaHCO3
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(Chemical Equation Presented) Water is demonstrated to be an effective medium for the Wittig reaction over a wide range of stabilized ylides and aldehydes. Despite sometimes poor solubility of the reactants, good chemical yields normally ranging from 80 to 98% and high E-selectivities (up to 99%) are achieved, and the rate of the reactions in water is unexpectedly accelerated. The efficiency of water as a medium in the Wittig reaction is compared to conventional organic solvents ranging from carbon tetrachloride to methanol. The aqueous Wittig reaction works best when large hydrophobic entities are present, such as aromatic, heterocyclic aromatic carboxaldehydes, and long-chain aliphatic aldehydes with triphenylphosphoranes. The E/Z-isomeric ratio of the Wittig products appears dependent on the electron-accepting/donating capacity and the location of the substituents present in the aromatic ring. The effect of additives, such as benzoic acid, LiCl, and sodium dodecyl sulfate (SDS), on the Wittig reaction has been explored. The Wittig reaction can also be conducted in the presence of acidic entities, such as phenols and carboxylic acids. In addition, large α-substituents in the aliphatic aldehydes do not jeopardize the reaction. It is also demonstrated that hydrates of aldehydes can be used directly in the aqueous Wittig reaction as substrates. The scope of the aqueous Wittig reaction is extended to 24 examples of one-pot mixtures of Ph3P, α-bromoesters, and aldehydes in sodium bicarbonate solution (at 20°C for 40 min to 3 h) to provide Wittig products of up to 99% yield and up to 98% E-selectivity. Since water is inexpensive, extremely easy to handle, and represents no environmental concerns, it should be considered a possible medium for new organic reactions.
- El-Batta, Amer,Jiang, Changchun,Zhao, Wen,Anness, Robert,Cooksy, Andrew L.,Bergdahl, Mikael
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p. 5244 - 5259
(2008/02/07)
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- One-pot enantioselective aziridination of olefins catalyzed by a copper(I) complex of a novel diimine ligand by using PhI(OAc)2 and sulfonamide as nitrene precursors
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A novel chiral C2-symmetric 1,4-diamine with multistereogenic centers at the backbone of the ligand has been synthesized from cheap natural product D-mannitol through multistep transformations. Its diimine derivative (3a) was found to be highly
- Wang, Xisheng,Ding, Kuiling
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p. 4568 - 4575
(2008/02/08)
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- Catalytic asymmetric synthesis with Rh-diene complexes: 1,4-Addition of arylboronic acids to unsaturated esters
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(Chemical Equation Presented) A general route to enantioenriched tert-butyl 3,3-diarylpropanoates is presented. These useful building blocks are prepared via an asymmetric rhodium-catalyzed conjugate addition of arylboronic acids to unsaturated tert-butyl
- Paquin, Jean-Francois,Stephenson, Corey R. J.,Defieber, Christian,Carreira, Erick M.
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p. 3821 - 3824
(2007/10/03)
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- CuI/Dabco as a highly active catalytic system for the Heck-type reaction
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An efficient catalytic system using CuI/Dabco (triethylenediamine) for the Heck-type cross-coupling reaction was developed. In the presence of 10 mol % of CuI and 20 mol % of Dabco, the coupling of various aromatic iodides and 1-((Z)-2-bromovinyl)benzene
- Li, Jin-Heng,Wang, De-Ping,Xie, Ye-Xiang
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p. 4941 - 4944
(2007/10/03)
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