- Recyclable Pd ionic catalyst coated on cordierite monolith for high TOF Heck coupling reaction
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Abstract : Pd 2 + ionic catalyst, Ti 0.97Pd 0.03O 1.97 was coated over cordierite monolith by solution combustion method. The catalyst coated on the cordierite is nano-crystalline as seen from XRD studies. Coated catalyst was used for Heck coupling reactions with different substrates of aryl halides and olefins. Thus handling nano-crystalline catalyst powder is avoided by fixing it on a solid catalyst cartridge. Heck coupled products were characterized using 1H NMR, 13C NMR, Mass and FTIR spectroscopy. This catalyst showed high selectivity towards Heck coupling reaction. Turnover frequencies (TOF) for each of the reactions were found to be very high. The catalyst was recycled up to 7 times with total TOF 3017 h - 1, which is found to be a new green technique in the Heck coupling reaction. Graphical abstract: Ti 0.97Pd 0.03O 1.97 catalyst is coated on cordierite monolith honeycomb (HC) by solution combustion method and it is used in the Heck coupling reaction. Reactions are done in a specially designed flask. Catalyst is recycled for 7 times. The total turnover frequency (TOF) after 7 cycles was 3017 h - 1. [Figure not available: see fulltext.].
- Bhat, Shrikanth K,Prasad, Jagadeesh D,Hegde
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- "nok": A phytosterol-based amphiphile enabling transition-metal-catalyzed couplings in water at room temperature
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The third-generation designer amphiphile/surfactant, "Nok" (i.e., SPGS-550-M; β-sitosterol methoxypolyethyleneglycol succinate), soon to be commercially available from Aldrich, can be prepared in two steps using an abundant plant feedstock and β-sitosterol, together with succinic anhydride and PEG-550-M. Upon dissolution in water, it forms nanomicelles that serve as nanoreactors, which can be characterized by both cryo-TEM and dynamic light scattering analyses. Several transition-metal-catalyzed reactions have been run under micellar conditions to evaluate this surfactant relative to results obtained in nanoparticles composed of TPGS-750-M (i.e., a second-generation surfactant). It is shown that Nok usually affords yields that are, in general, as good or better than those typically obtained with TPGS-750-M, and yet is far less costly.
- Klumphu, Piyatida,Lipshutz, Bruce H.
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p. 888 - 900
(2014/03/21)
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- Investigation of sol-gel supported palladium catalysts for Heck coupling reactions in o/w-microemulsions
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Sol-gel supported palladium catalysts are investigated for the Heck coupling reaction between styrene and iodo-/bromobenzene to trans-stilbenes in o/w-microemulsions as alternative reaction medium. High conversions and selectivities are obtained with these catalysts and they show better catalytic performance than their commercial analogs Pd@SiO2 or Pd/C. The influence of the catalyst structure on the activity is investigated in detail showing mass transport limitations that can be optimized by the palladium loading. The catalyst is recyclable >6 times with negligible palladium leaching into the solution. Because of the good recyclability under retention of activity and selectivity, the influence of transport limitations is suppressed and the total catalyst efficiency is increased to more than 2.
- Volovych,Kasaka,Schwarze,Nairoukh,Blum,Fanun,Avnir,Schom?cker
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p. 210 - 221
(2014/07/22)
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- Interfacially cross-linked reverse micelles as soluble support for palladium nanoparticle catalysts
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Reverse micelles (RM) were formed in heptane/CHCl3 with a surfactant carrying the triallylammonium (=triprop-2-en-1-ylammonium) head group (Scheme). Photo-cross-linking with dithiothreitol (=rel-(2R,3R)-1,4- dimercaptobutane-2,3-diol; DTT) captured the RMs and afforded organic, soluble nanoparticles in a one-step reaction. Similar to dendrimers, the cross-linked reverse micelles could encapsulate palladium nanoparticles within their hydrophilic cores and protect them in catalytic reactions. Good to excellent yields were obtained in the Heck coupling of a range of alkyl acrylates (=alkyl prop-2-enoates) and iodobenzenes (Tables 1 and 2). The catalytic activity of the palladium nanoparticles was maintained in several repeated runs.
- Lee, Li-Chen,Zhao, Yan
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experimental part
p. 863 - 871
(2012/08/08)
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- Study on the Heck reaction promoted by carbene adduct of cyclopalladated ferrocenylimine and the related reaction mechanism
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Carbene adduct of cyclopalladated ferrocenylimine has been successfully applied to Heck reaction of various aryl bromides with olefins. On the basis of kinetic studies, in situ 13C NMR spectra investigations and Hg poisoning experiments, it was proposed that the Heck reaction catalyzed by carbene adduct of cyclopalladated ferrocenylimine proceeded through a classical Pd(0)/Pd(II) cycle and such palladacycle was only a reservoir of the catalytically active Pd(0) species.
- Ren, Gerui,Cui, Xiuling,Yang, Erbing,Yang, Fan,Wu, Yangjie
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scheme or table
p. 4022 - 4028
(2010/07/05)
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