Continuous-flow synthesis using a column reactor packed with heterogeneous catalysts: A convenient production of nitroolefins by using amino-functionalized silicagel

Ishitani, Haruro; Furiya, Yuichi; Kobayashi, Shū

doi:10.1016/j.bmc.2017.04.017

Cited by 9 publications

(5 citation statements)

References 38 publications

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“…The selective hydrogenation to oximes was then applied to the homologation of aromatic aldehyde 1c in a three-step reaction sequence (Scheme ). Aldehydes were condensed with nitromethane in the presence of amino silica, Chromatrex NH DM1020 as a base catalyst, and molecular sieves (MS4A) . After the first reaction, the catalyst was filtered off and the crude mixture was used for the next reaction directly without purification.…”

Section: Resultsmentioning

confidence: 99%

“…Aldehydes were condensed with nitromethane in the presence of amino silica, Chromatrex NH DM1020 as a base catalyst, and molecular sieves (MS4A). 16 After the first reaction, the catalyst was filtered off and the crude mixture was used for the next reaction directly without purification. The selective hydrogenation was performed under optimal conditions and, after the removal of the catalyst, the crude mixture was used directly for the next step without purification.…”

Section: Acs Catalysismentioning

confidence: 99%

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Homologation of Aryl Aldehydes Using Nitromethane as a C1 Source Enabled by Nitrogen-Doped Carbon-Supported Palladium Catalysts

et al. 2022

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Homologation of aryl aldehydes provides useful synthetic intermediates, but it requires multistep reactions and generates significant amounts of waste. We considered such reactions using nitromethane as a C1 source through nitroolefin formation, partial hydrogenation to oximes, and hydration of oximes; however, the control of selectivity in the second reaction is challenging. To achieve this pathway, nitrogen-doped carbon-incarcerated palladium nanoparticle catalysts were developed for selective hydrogenation. We found that the presence of nitrogen dopants effectively tuned the catalytic activity to show almost perfect selectivity, high activity, and reusability under ambient pressure. We then performed a three-step homologation reaction in both batch and flow systems with only one purification step. The sequential continuous-flow system worked efficiently for more than 2 days to afford the product in a high yield.

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Section: Resultsmentioning

confidence: 99%

Section: Acs Catalysismentioning

confidence: 99%

Homologation of Aryl Aldehydes Using Nitromethane as a C1 Source Enabled by Nitrogen-Doped Carbon-Supported Palladium Catalysts

et al. 2022

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“…Because of that, many different silica materials have been used as solid support for organo-catalysts, ranging from unordered silica gel to highly ordered SBA-15, and from particles to monoliths. [16][17][18][19][20] The transfer of these materials to continuous flow reactors brings several additional advantages. Continuous processing, quick and precise heat control, short reaction times, and the possibility to carry out multi-step reactions without isolating intermediate products make continuous flow setups convenient; the large surface-to-volume ratio and easy scalability by numbering-up or scaling-out can lead to greater productivity.…”

Section: Introductionmentioning

confidence: 99%

“…Its main advantage is the flexibility in the controlled variation of material properties: pore size and shape, surface area, and morphology can be tailored to fit the needs of different applications. Because of that, many different silica materials have been used as solid support for organocatalysts, ranging from unordered silica gel to highly ordered SBA‐15, and from particles to monoliths [16–20] …”

Section: Introductionmentioning

confidence: 99%

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

et al. 2022

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We report the immobilization of 4-dimethylaminopyridine (DMAP), a versatile organocatalyst for sterically demanding esterifications, on mesoporous silica particles and macromesoporous silica monoliths, both possessing optimized properties for continuous flow synthesis. An alkyne-functionalized DMAP derivative was immobilized via click chemistry; the materials were characterized by physisorption analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and elemental analysis. While silica particles were functionalized in batch and packed into a packed-bed reactor, monoliths were cladded with a polyether ether ketone (PEEK) tube after sol-gel synthesis and functionalized in a circulating flow process. Samples with three different catalyst loadings were prepared, in order to study the impact of the catalyst amount on the mesopore space as well as the catalytic performance. In continuous flow experiments, complete conversion of 1-phenylethanol to phenylethylacetate was achieved with both materials and short contact times. Monoliths exhibited far lower pressures than packed bed reactors (7 bar at a flow rate of 1 mL min À 1 ) and reached turnover rates up to 9.3x10 À 2 s À 1 , which is almost twice as high as a comparable batch experiment. The absence of diffusion limitations in monoliths made investigations on reaction kinetics with microkinetics-dominated experiments possible. This study demonstrates that all properties needed for a successful transfer of immobilized organocatalysts to sophisticated flow syntheses with complex organocatalysts can be met with functionalized meso-macroporous monoliths.

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“…In addition, its mechanical and chemical stability along with the absence of swelling in many organic solvents makes it particularly suitable to be used in flow catalysis. Commonly, bed reactors containing packed SiO 2 or polymer particles are used for continuous operations. − A prominent example is the synthesis of the anti-inflammatory drug rolipram by Tsubogo et al By connecting several packed-bed reactors with different catalysts, the final product can be obtained in good yield and high enantiomeric excess. However, because of the random packing of the sometimes simply crushed particles detrimental fluid mechanics ensue and the formation of stagnation zones and high back pressures might occur.…”

Section: Introductionmentioning

confidence: 99%

Amine-Functionalized Nanoporous Silica Monoliths for Heterogeneous Catalysis of the Knoevenagel Condensation in Flow

et al. 2020

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Porous carrier materials functionalized with organocatalysts offer substantial advantages compared to homogeneous catalysts, e.g., easy separation of the catalyst, scalability, and an improved implementation in continuous operations. Here, we report the immobilization of (3-aminopropyl)trimethoxysilane (APTMS) onto self-prepared silica monoliths and its application as a heterogeneous catalyst in the Knoevenagel condensation between cyano ethylacetate and various aromatic aldehydes under continuous-flow conditions. The meso-macroporous silica monoliths (6−7 cm in length) were optimized to be used in flow taking advantage of their hierarchical meso-and macroporosity. The monoliths were cladded with a poly(ether ether ketone) (PEEK) tube by a refined procedure to guarantee tight connection between the carrier material and PEEK. Functionalization of the bare silica monoliths consisting of APTMS can be efficiently performed in flow in ethanol and toluene. While a large grafting gradient is obtained for toluene, the grafting in ethanol proceeds homogenously throughout the monolith, as evidenced by elemental analysis and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The silica monoliths exhibit high conversion up to 95% with concurrent low back pressures, which is of importance in flow catalysis. By connecting two monoliths, high conversions can be maintained for several flow rates. Two types of monoliths were synthesized, possessing different mesopore sizes. The monolith bearing the larger mesopore size showed an enhanced turnover frequency (TOF), while the monolith with the smaller mesopores allowed for larger quantities of the product to be synthesized, due to the higher surface area. A long-term stability test showed that the functionalized monoliths were still active after 66 h of continuous usage, while the overall yield decreased over time.

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Continuous-flow synthesis using a column reactor packed with heterogeneous catalysts: A convenient production of nitroolefins by using amino-functionalized silicagel

Cited by 9 publications

References 38 publications

Homologation of Aryl Aldehydes Using Nitromethane as a C1 Source Enabled by Nitrogen-Doped Carbon-Supported Palladium Catalysts

Homologation of Aryl Aldehydes Using Nitromethane as a C1 Source Enabled by Nitrogen-Doped Carbon-Supported Palladium Catalysts

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

Amine-Functionalized Nanoporous Silica Monoliths for Heterogeneous Catalysis of the Knoevenagel Condensation in Flow

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