7 results on '"Pd-catalyst"'
Search Results
2. Focusing on the Catal. of the Pd- and Ni-Catalyzed Hirao Reactions
- Author
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György Keglevich, Réka Henyecz, and Zoltán Mucsi
- Subjects
catalyst formation ,Pharmaceutical Science ,mechanism ,Review ,Medicinal chemistry ,Reductive elimination ,Catalysis ,Analytical Chemistry ,lcsh:QD241-441 ,chemistry.chemical_compound ,lcsh:Organic chemistry ,Nickel ,Drug Discovery ,ligation ,Ni-catalyst ,Physical and Theoretical Chemistry ,Pd-catalyst ,P–C coupling ,Chemistry ,Ligand ,Aryl ,Organic Chemistry ,Oxidative addition ,Catalytic cycle ,Models, Chemical ,Chemistry (miscellaneous) ,Reagent ,Alkoxy group ,Hirao reaction ,Molecular Medicine ,Oxidation-Reduction ,Palladium - Abstract
The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the “(HOY2P)2Pd(0)” species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the “(HOY2P)(−OY2P)Ni(II)Cl−” form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations.
- Published
- 2020
3. Palladium-catalyzed N-arylation of O-methylamidoximes
- Author
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Anbazhagan, Mariappan, Stephens, Chad E., and Boykin, David W.
- Subjects
- *
ARYLATION , *ORGANIC compounds , *PALLADIUM catalysts , *CATALYSIS - Abstract
Pd-catalyzed coupling of O-methylbenzamidoximes gave N-aryl O-methylbenzamidoximes using aryl halides with electron attracting or moderate electron donating groups. Under the same conditions, benzamidoxime failed to undergo coupling and O-acetylbenzamidoxime underwent cyclization to form the corresponding [1,2,4]oxadiazole. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
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4. New Developments on the Hirao Reactions, Especially from 'Green' Point of View
- Author
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György Keglevich and Réka Henyecz
- Subjects
Denticity ,Aryl ,Organic Chemistry ,Phosphinates ,Biochemistry ,Combinatorial chemistry ,Article ,Catalysis ,Green synthesis ,chemistry.chemical_compound ,chemistry ,Hirao reaction ,Pd-catalyst ,Phosphonates ,P-C coupling ,Phosphine ,Phosphine oxides - Abstract
Background: The Hirao reaction discovered ca. 35 years ago is an important P–C coupling protocol between dialkyl phosphites and aryl halides in the presence of Pd(PPh3)4 as the catalyst and a base to provide aryl phosphonates. Then, the reaction was extended to other Preagents, such as secondary phosphine oxides and H-phosphinates and to other aryl and hetaryl derivatives to afford also phosphinic esters and tertiary phosphine oxides. Instead of the Pd(PPh3)4 catalyst, Pd(OAc)2 and Ni-salts were also applied as catalyst precursors together with a number of mono- and bidentate P-ligands. Objective: In our review, we undertook to summarize the target reaction with a special stress on the developments attained in the last 6 years, hence this paper is an update of our earlier reviews in a similar topic. Conclusion: “Greener” syntheses aimed at utilizing phase transfer catalytic and microwave-assisted approaches, even under “P-ligand-free. or even solvent-free conditions are the up-to date versions of the classical Hirao reaction. The mechanism of the reaction is also in the focus these days.
- Published
- 2019
5. Organoborane coupling reactions (Suzuki coupling)
- Author
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Akira Suzuki
- Subjects
chemistry.chemical_classification ,Steric effects ,Aqueous solution ,Base (chemistry) ,General Physics and Astronomy ,Review ,General Medicine ,biaryl synthesis ,organoboron compounds ,Combinatorial chemistry ,Coupling reaction ,Catalysis ,chemistry ,Suzuki reaction ,cross-coupling reaction ,synthesis of conjugated alkadienes and alkenynes ,Electrophile ,Stereoselectivity ,Pd-catalyst ,General Agricultural and Biological Sciences - Abstract
The palladium-catalyzed cross-coupling reaction between different types of organoboron compounds with sp2-, sp3-, and sp-hybridized carbon-boron compounds and various organic electrophiles in the presence of base provides a powerful and useful synthetic methodology for the formation of carbon-carbon bonds. The coupling reaction offers several advantages: (1) Availability of reactants (2) Mild reaction conditions (3) Water stability (4) Easy use of the reaction both in aqueous and heterogeneous conditions (5) Tolerance of a broad range of functional groups (6) High regio- and stereoselectivity (7) Insignificant effect toward steric hindrance (8) Use of very small amounts of catalysts (9) Utilization as one-pot synthesis (10) Non-toxic reaction (Communicated by Teruaki MUKAIYAMA, M.J.A.)
- Published
- 2004
6. Liquid-phase Hydrogenation of Phenol to Cyclohexanone over Supported Palladium Catalysts
- Author
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Lihui Fan, Dongbin Liu, Nasarul Wahab, Luyang Zhang, Mahmud Hasan, and Yanming Shen
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pd-catalyst ,liquid-phase ,Inorganic chemistry ,Cyclohexanone ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Chemical engineering ,Specific surface area ,phenol ,Phenol ,Chemical reaction engineering ,010405 organic chemistry ,Process Chemistry and Technology ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,TP155-156 ,hydrogenation ,cyclohexanone ,0210 nano-technology ,Selectivity ,Dispersion (chemistry) ,Nuclear chemistry ,Palladium - Abstract
The ZSM-5, g-Al2O3, SiO2 and MgO supported Pd-catalysts were prepared for the phenol hydrogenation to cyclohexanone in liquid-phase. The natures of these catalysts were characterized by XRD, N2 adsorption-desorption analysis, H2-TPR, CO2-TPD and NH3-TPD. The catalytic performance of the supported Pd-catalyst for phenol hydrogenation to cyclohexanone is closely related to nature of the support and the size of Pd nanoparticles. The Pd/MgO catalyst which possesses higher basicity shows higher cyclohexanone selectivity, but lower phenol conversion owing to the lower specific surface area. The Pd/SiO2 catalyst prepared by precipitation gives higher cyclohexanone selectivity and phenol conversion, due to the moderate amount of Lewis acidic sites, and the smaller size and higher dispersion of Pd nanoparticles on the surface. Under the reaction temperature of 135 oC and H2 pressure of 1 MPa, after reacting for 3.5 h, the phenol conversion of 71.62% and the cyclohexanone selectivity of 90.77% can be obtained over 0.5 wt% Pd/SiO2 catalyst. Copyright © 2016 BCREC GROUP. All rights reservedReceived: 7th March 2016; Revised: 13rd May 2016; Accepted: 7th June 2016How to Cite: Fan, L., Zhang, L., Shen, Y., Liu, D., Wahab, N., Hasan, M.M. (2016). Liquid-phase Hydrogenation of Phenol to Cyclohexanone over Supported Palladium Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3): 354-362 (doi: 10.9767/bcrec.11.3.575.354-362)Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.575.354-362
- Published
- 2016
7. Pd-catalyzed synthesis of beta-biarylacryl ferrocenes via Suzuki cross-coupling
- Author
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Ru-Xiang Lin, Zhen-Ping Yang, Chen-Ze Qi, and Qing-Bao Song
- Subjects
Boron Compounds ,Materials science ,Metallocenes ,Pd-Catalyst ,Pharmaceutical Science ,Infrared spectroscopy ,Coupling reaction ,Catalysis ,Article ,Analytical Chemistry ,Suzuki Cross- coupling Reaction ,lcsh:QD241-441 ,Nonlinear optical ,Biarenes ,Ferrocenyl ,Suzuki reaction ,lcsh:Organic chemistry ,Drug Discovery ,Molecule ,Organic chemistry ,Ferrous Compounds ,Physical and Theoretical Chemistry ,Molecular Structure ,Spectrum Analysis ,Organic Chemistry ,Chromophore ,Combinatorial chemistry ,Coupling (physics) ,Chemistry (miscellaneous) ,Molecular Medicine ,Palladium - Abstract
Some novel β-biarylacryl ferrocene derivatives were synthesized via Pd-catalytic Suzuki cross-coupling reactions of β-(2-bromophenyl)acrylferrocene and arylboronic acids. The structures were determined with elemental analyses, IR spectra, and 1 H-NMR spectra. Keywords: Pd-Catalyst; Biarenes; Ferrocenyl; Suzuki Cross- coupling Reaction. Introduction Over the last two decades, molecular-based second-order nonlinear optical (NLO) chromophores have attracted much interest because of their potential applications in emerging opto-electronic technologies [1-5]. These efforts have mainly focused on organic systems. More recently, organometallic molecules have been investigated as well [3-5]. In comparison to common organic molecules, they offer a large variety of novel structures. The possibility of high environmental stability and diversity of tunable electronic behaviors by virtue of the coordinated metal center might bring about NLO materials with unique characteristics such as magnetic and electro-chemical properties.
- Published
- 2004
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