Oxidations of Allylic and Benzylic Alcohols under Inductively‐Heated Flow Conditions with Gold‐Doped Superparamagnetic Nanostructured Particles as Catalyst and Oxygen as Oxidant

Chaudhuri, Sangeeta Roy; Hartwig, Jan; Kupracz, Lukas; Kodanek, Torben; Wegner, Jens; Kirschning, Andreas

doi:10.1002/adsc.201400261

Cited by 46 publications

(33 citation statements)

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“…Moreover, when heat is transferred from the walls, the temperature gradient through the cross section may lead to lower temperature in the central part, resulting in low reaction rates. Recently, the RF-heated continuous flow reactor where heat is generated by the magnetic particles in the alternating magnetic field has been applied in the organic synthesis [29][30][31][32] . As heat is uniformly generated over the entire catalyst volume, it provides much a smaller radial temperature gradient and reduced heat loss to the environment.…”

Section: Introductionmentioning

confidence: 99%

Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor

et al. 2016

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A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. AbstractCore-shell composite magnetic catalysts TiO2@NiFe2O4 with a titania loading of 9-32 wt. % have been synthesised by sol-gel method for direct amide synthesis in a radiofrequency (RF)-heated continuous flow reactor. The catalyst calcination temperature was optimised in the range of 350-500 ºC and the highest activity was observed for the catalyst calcined at 500 ºC due to conversion of titania into catalytically active anatase phase. No reaction between the magnetic core and the titania shell was observed up to the calcination temperature of 1000 ºC and no sintering of titania shell was observed after calcination at 500 ºC. The comparison of direct amide synthesis in a continuous flow fixed bed reactor under conventional and RF heating demonstrated that the RF heating mode increased the apparent reaction rate by 60 % and decreased the deactivation rate due to a better temperature uniformity. The titania weight normalised reaction rate in the RF-heated reactor was constant for titania loadings above 17 wt. %, while it decreased by a factor of 3 at lower titania loadings because of interactions between the ferrite core on the thin layer of the catalyst. The catalyst deactivation study showed that the deactivation rate could be accurately described by a first order kinetics and that the main reason of deactivation was coking. The catalyst regeneration via calcination at 400 ºC resulted in the catalyst sintering, while a treatment with a hydrogen peroxide solution at 90 ºC fully recovered catalytic activity.

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Section: Introductionmentioning

confidence: 99%

Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor

et al. 2016

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“…Aerobic oxidation of allylic and benzylic alcohols under inductively-heated flow conditions with gold-doped superparamagnetic nanostructured particles. 156 Recently, Uozumi et al developed a highly practical, fast and clean continuous-flow procedure for the aqueous aerobic flow oxidation of primary and secondary alcohols to their corresponding carboxylic acids and ketones. 157 Platinum nanoparticles dispersed on an amphilic polystyrenepoly(ethylene glycol) resin (APR-Pt) were used as an active heterogeneous catalyst.…”

Section: Transition Metal-catalyzed Aerobic Oxidation Processes In Comentioning

confidence: 99%

“…156 The magnetic particles were packed into a mesofluidic PEEK (polyether ether ketone) reactor (3 mL) and diluted with MAGSILICA® to facilitate inductive heating. A medium frequency (25 kHz) external inductor was used to rapidly heat the magnetic particles.…”

Section: Transition Metal-catalyzed Aerobic Oxidation Processes In Comentioning

confidence: 99%

Liquid phase oxidation chemistry in continuous-flow microreactors

et al. 2016

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Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described.

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“…Gold-catalyzed oxidation procedures are currently gaining a considerable amount of interest in the continuous flow community [69][70][71][72][73][74][75][76][77][78]. Among those, an extremely efficient protocol was communicated by Kobayashi and coworkers (Scheme 8a) [69].…”

mentioning

confidence: 98%

“…Another strategy was communicated by Kirschning and coworkers in 2014 using an unconventional heating methodology (Scheme 8b) [78]. Catalytically active gold(0) nanocrystals were immobilized on nanostructured particles with a superparamagnetic iron oxide core and a silica shell (MAGSILICA ® ).…”

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confidence: 99%

Aerobic Oxidations in Continuous Flow

Pieber

Kappe

2015

Organometallic Flow Chemistry

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In recent years, the high demand for sustainable processes resulted in the development of highly attractive oxidation protocols utilizing molecular oxygen or even air instead of more uneconomic and often toxic reagents. The application of these sustainable, gaseous oxidants in conventional batch reactors is often associated with severe safety risks and process challenges especially on larger scales. Continuous flow technology offers the possibility to minimize these safety hazards and concurrently allows working in high-temperature/high-pressure regimes to access highly efficient oxidation protocols. This review article critically discusses recent literature examples of flow methodologies for selective aerobic oxidations of organic compounds. Several technologies and reactor designs for biphasic gas/liquid as well as supercritical reaction media are presented in detail.

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Oxidations of Allylic and Benzylic Alcohols under Inductively‐Heated Flow Conditions with Gold‐Doped Superparamagnetic Nanostructured Particles as Catalyst and Oxygen as Oxidant

Cited by 46 publications

References 100 publications

Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor

Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor

Liquid phase oxidation chemistry in continuous-flow microreactors

Aerobic Oxidations in Continuous Flow

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Oxidations of Allylic and Benzylic Alcohols under Inductively‐Heated Flow Conditions with Gold‐Doped Superparamagnetic Nanostructured Particles as Catalyst and Oxygen as Oxidant

Cited by 46 publications

References 100 publications

Direct amide synthesis over core–shell TiO2@NiFe2O4 catalysts in a continuous flow radiofrequency-heated reactor

Direct amide synthesis over core–shell TiO2@NiFe2O4 catalysts in a continuous flow radiofrequency-heated reactor

Liquid phase oxidation chemistry in continuous-flow microreactors

Aerobic Oxidations in Continuous Flow

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Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor

Direct amide synthesis over core–shell TiO₂@NiFe₂O₄ catalysts in a continuous flow radiofrequency-heated reactor