Catalytic Cycle during Heteropoly Acid Catalyzed Transfer Hydrogenation Reaction

Joshi, Meenal; Vaidya, Sagar D.; Pandey, Rajesh K.; Mukesh, D.

doi:10.1006/jcat.1998.2383

Cited by 6 publications

(6 citation statements)

References 12 publications

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“…[13] It is obvious that the moderate reducibility of benzimidazoline prohibits deeper reduction of the ball-shaped POM cluster, which may cause significant breakdown of the Keggin structure. [21] The mild reaction conditions and high conversion efficiency provided a rare opportunity to reveal the more detailed reaction mechanism hidden beneath the color change by 1 H NMR (Figure 5). In our design of experiment, 0.1 mol% PMA and 1.2 equiv.…”

Section: Resultsmentioning

confidence: 99%

Construction of a Clock Catalytic System: Highly Efficient and Self‐Indicating Synthesis of Benzoheterocycles at Ambient Temperature

et al. 2021

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Inspired by the mechanism of the clock reaction, we rationally constructed a novel phosphomolybdenum blue (PMB) clock catalytic system for a highly efficient synthesis of benzimidazoles and benzothiazoles simply at ambient temperature. The current PMB clock catalytic system exhibits a sharp decoloration event to announce the depletion of the intermediateconstraint, making this synthetic approach selfindicating and TLC-free. 31 P NMR and XPS analysis of PMBcatalyst showed that only two Mo 6 + atoms are reduced to Mo 5 + atoms in the Keggin structure due to the moderate reducibility of benzimidazoline and benzothiazoline intermediates. Thus,the active Keggin-type POM cluster could be well maintained in DMSO during the redox cycling of phosphomolybdic acid (PMA) and PMB. 1 H NMR tracing experiment not only confirmed the proposed reaction mechanism but also showed that PMB exerts Lewis acid catalytic activityat the early phase of the reaction other than the expected redox catalytic activity.

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Section: Resultsmentioning

confidence: 99%

Construction of a Clock Catalytic System: Highly Efficient and Self‐Indicating Synthesis of Benzoheterocycles at Ambient Temperature

et al. 2021

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“…Cu, Pd, Pt, Ni, etc. [29,30] or use of additional substances as hydrogenation agents, such as NaBH 4 or hydrasyne [31,32]. There are hardly any reports on the direct use of heteropolyacids as hydrogenation catalysts and their role in the process, despite the fact that they are widely used as a component of hydrogenation catalysts.…”

Section: Catalyst Performance In Aldol Reactionmentioning

confidence: 99%

Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

Musko

Grunwaldt

2011

Top Catal

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Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100°C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO 2 and MCM-41) and basic (hydrotalcite) materials showed interesting performance in this preliminary study under the entitled reaction conditions. Small and linear aldehydes, such as propanal, butanal, pentanal and hexanal, react more efficiently than the branched 3-methylbutanal, which is converted much slower. Whereas Amberlyst-15 showed the highest conversion based on the catalyst mass, tungstosilicic acid-based catalysts were significantly better if the rates were related to the number of acidic sites ([1000 h -1 ). The rate depends both on the dispersion and the kind of support. Strikingly, tungstosilicic acid (TSA) on MCM-41 was also an effective catalysts for the selective C=C double bond hydrogenation of 2-butenal and is therefore a potential catalyst for the ''one-pot'' synthesis of 2-ethyl-2-hexenal and 2-ethylhexanal via combined hydrogenation and aldol reaction from 2-butenal. A number of characterisation techniques, such as temperatureprogrammed desorption of ammonia (NH 3 -TPD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), etc. were used to get an insight into the catalyst structure, which support a high dispersion and strong acidity of the tungsten based species on silica and MCM-41.

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“…The introduction of vanadium(V) into the Keggin framework of [PMo 12 O 40 ] 3À is beneficial for the catalytic reaction. [13] Because the metal substitution may modify the energy and composition of the lowest unoccupied molecular orbital (LUMO) and redox properties, the energy and composition of the LUMOs have significant effects on the catalytic activity heteropoly acids with different charges. [14] Substitution of vanadium ions into the molybdenum framework stabilizes the LUMOs because these orbitals derive in part from vanadium d-orbitals, which have been assumed to be more stable than those of molybdenum and tungsten.…”

Section: General Nitrogen Heterocycle Synthesis 1709mentioning

confidence: 99%

New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst

Hekmatshoar

Sadjadi

et al. 2010

Synthetic Communications

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Catalytic Cycle during Heteropoly Acid Catalyzed Transfer Hydrogenation Reaction

Cited by 6 publications

References 12 publications

Construction of a Clock Catalytic System: Highly Efficient and Self‐Indicating Synthesis of Benzoheterocycles at Ambient Temperature

Construction of a Clock Catalytic System: Highly Efficient and Self‐Indicating Synthesis of Benzoheterocycles at Ambient Temperature

Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst

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