Knoevenagel and aldol condensations catalysed by a new diamino-functionalised mesoporous material

Choudary, B. M.; Kantam, M. Lakshmi; Sreekanth, Pavani M.; Bandopadhyay, Tania; Figuéras, F.; Tuel, A.

doi:10.1016/s1381-1169(98)00301-x

Cited by 152 publications

(85 citation statements)

References 22 publications

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“…This technique was also used as an additional tool to evaluate the loading of the functional groups on the MSN surface by means of 29 Si spectra, measured using direct polarization (DP) under magic angle spinning (MAS)…”

Section: Solid-state Nmrmentioning

confidence: 99%

“…with Carr-Purcell-Meiboom-Gill (CPMG) refocusing of 29 Si magnetization, [37] as previously described (Table S1). [38] Experimental parameters are given below using the following symbols: νR denotes the MAS rate, νRF(X) the magnitude of radiofrequency magnetic field (RF) applied to X spins, τCP the mixing time during cross polarization, NCPMG the number of CPMG echoes, τRD the recycle delay, NS the number of scans, and AT the total acquisition time.…”

Section: Solid-state Nmrmentioning

confidence: 99%

“…7 29 Si DPMAS with CPMG: νR = 10 kHz, νRF( The chemical shifts of 29 Si, 13 C and 1 H are reported using the  scale and are referenced to tetramethylsilane (TMS) at 0 ppm.…”

Section: Solid-state Nmrmentioning

confidence: 99%

“…[25,26] Solin and collaborators, as well as Thiel and co-workers, obtained similar results, using different combinations of alkylamines and acidic groups in mesoporous silica supports. [23,27] However, the poor catalytic activity of monofunctional amine on silica, which remains commonly used for the aldol and similar types of condensation, [20,22,24,[29][30][31][32] is still not well understood.…”

Section: Introductionmentioning

confidence: 99%

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Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

137

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In this study, we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support. Disciplines Materials Chemistry | Other Chemistry | Physical ChemistryComments NOTICE: this is the author's version of a work that was accepted for publication in Journal of Catalysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Catalysis, [291, (2012) AbstractIn this study we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support.

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Section: Solid-state Nmrmentioning

confidence: 99%

Section: Solid-state Nmrmentioning

confidence: 99%

“…7 29 Si DPMAS with CPMG: νR = 10 kHz, νRF( The chemical shifts of 29 Si, 13 C and 1 H are reported using the  scale and are referenced to tetramethylsilane (TMS) at 0 ppm.…”

Section: Solid-state Nmrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

137

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“…This reaction is catalyzed by alkali and acid compounds such as potassium hydroxide (1), hydrotalcites (2) and natural phosphates/KF (3). So depending on the molar ratio of substrates, temperature, catalyst and reaction condition, β-hydroxyketones or α, β-unsaturated carbonyl compounds are formed as major product (1,4,5). Recently, using natural substrates derived from animal sources such as bone powder and other marine resources (6) have been reported.…”

Section: Introductionmentioning

confidence: 99%

The Persian Gulf Calcined Coral, Acropora Species: An Efficient Catalyst for Aldol Condensation

Bigdeli

Shushizadeh

Mohandespur

2015

Jundishapur J Nat Pharm Prod

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Background: Coral, a marine organism, is known for its unique solid, natural, and efficient catalyst in organic reactions. Calcium carbonate (CaCO 3 ), the main component of marine coral, is an efficient, basic, and natural solid for catalytic aldol condensation reaction of aldehydes and ketones having α-hydrogens to produce β-hydroxy carbonyl compounds with good yields at room temperature. Objectives: The purpose of this research was to study using calcined coral as an efficient catalyst for aldol reaction at room temperature. Materials and Methods: Marine coral (Acropora sp.) was washed several times using methanol-ethyl acetate and deionized water and then dried in an oven at 80°C for 48 hours. The dried coral was ground to get fine powder. For preparation of calcined coral, its powder was put in an oven at 800°C for 2 hours. Calcined coral and sodium nitrate (1:1) were well stirred in sufficient water for about 5 hours. Then, the mixture was calcined in an oven at 800°C for 2 hours. In general experiment, the reaction was carried out by mixing aldehyde (150 mmol), ketone (50 mmol), 0.1 g of calcined coral/sodium nitrate, 5 mL water-ethanol (1:1) as a solvent. Finally, the mixture was stirred at room temperature for the appropriate time. Results: The best conditions for condensation reaction are using the calcined coral/sodium nitrate, as a catalyst in the presence of ethanol/water at room temperature. Aldol condensation reaction of nitro-substituted benzaldehydes with ketones has greater yields than benzaldehydes. Electron-withdrawing groups such as NO 2 on benzaldehyde ring activate aldol condensation reaction. In comparison, 4-methoxybenzaldehyde reacts more slowly with ketones and decreases the yield of products. Conclusions: Calcined coral/sodium nitrate as a new, efficient, and natural heterogeneous catalyst used in aldol condensation reaction of ketones and aldehydes led to β-hydroxyketones in good to high yields in appropriate condition.

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Bases and Base Catalysis—Heterogeneous

Ono¹

2010

Encyclopedia of Catalysis

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Although catalysis by solid bases has received much attention due to its importance in petroleum refining and petrochemical processes, relatively few studies have focused on catalysis by solid bases. Base catalysts, however, play a decisive role in a number of organic reactions essential for fine‐chemical synthesis. Solid‐base catalysis has many advantages over liquid bases in many respects from environmental aspects. This article offer general accounts of solid‐base catalysis and consists of three parts. The first part, gives the definition and concepts of solid bases and the methods for characterizing basic sites on solid surfaces. In the second part the typical solid‐base catalysts are surveyed. The solid bases include alkaline earth oxides, hydrotalcites and related materials, oxynitrides, zeolites, and modified zeolites alkaline metals and alkaline compounds such as KF/Al 2 O 3 and KNH 2 /Al 2 O 3 and amines anchored on mesoporous silica. The third part will show that a great variety of organic reactions is catalyzed by solid bases. The reactions described include the isomerization of alkenes and alkyns, aldol condensation, nitroaldol condensation, Knoevenagel condensation, Michael addition, substitution reactions, reactions of silicon compounds, and alkylation reactions.

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Knoevenagel and aldol condensations catalysed by a new diamino-functionalised mesoporous material

Cited by 152 publications

References 22 publications

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

The Persian Gulf Calcined Coral, Acropora Species: An Efficient Catalyst for Aldol Condensation

Bases and Base Catalysis—Heterogeneous

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