30625-98-0Relevant academic research and scientific papers
Studies on catalytic activity of MIL-53(Al) and structure analogue DUT-5(Al) using bdc- and bpdc-ligands functionalized with L-proline in a solid-solution mixed-linker approach
Nie?ing, Sandra,Janiak, Christoph
, p. 70 - 77 (2019)
Proline-functionalized MOFs MIL-53(Al) (based on the benzene-1,4-dicarboxylate, bdc linker) and DUT-5(Al) (based on the biphenyl-4,4′-dicarboxylate, bpdc linker) were synthesized using a mixed-linker approach. The proline-functionalized bdc and bpdc ligand was mixed with both the non-functionalized ligand as well as the amino functionalized one. The influence of the length of the linker on the catalytic activity showed a counterintuitive confinement effect and advantageous increase of ee with longer linker and higher porosity, that is a change of ee values from no selectivity in the MIL-53(Al) MOFs up to 16% ee for 27-L-Pro/H2N-DUT-5(Al) and 19% ee for 26-L-Pro/H-DUT-5(Al). The conversion of 4-nitrobenzaldehyde remains over 85% after three catalytic runs for L-proline functionalized MIL-53(Al) MOFs. For the DUT-5(Al) MOFs with L-proline groups this value even increases up to 97%.
Synthesis, characterization and catalytic activity of acid-base bifunctional materials through protection of amino groups
Shao, Yanqiu,Liu, Heng,Yu, Xiaofang,Guan, Jingqi,Kan, Qiubin
, p. 768 - 773 (2012)
Acid-base bifunctional mesoporous material SO3H-SBA-15-NH 2 was successfully synthesized under low acidic medium through protection of amino groups. X-ray diffraction (XRD), N2 adsorption-desorption, transmission electron micrographs (TEM), back titration, 13C magic-angle spinning (MAS) NMR and 29Si magic-angle spinning (MAS) NMR were employed to characterize the synthesized materials. The obtained bifunctional material was tested for aldol condensation reaction between acetone and 4-nitrobenzaldehyde. Compared with monofunctional catalysts of SO3H-SBA-15 and SBA-15-NH2, the bifunctional sample of SO3H-SBA-15-NH2 containing amine and sulfonic acid groups exhibited excellent acid-basic properties, which make it possess high activity for the aldol condensation.
Facile Synthesis of Cooperative Acid-Base Catalysts by Clicking Cysteine and Cysteamine on an Ethylene-Bridged Periodic Mesoporous Organosilica
Ouwehand, Judith,Lauwaert, Jeroen,Esquivel, Dolores,Hendrickx, Kevin,Van Speybroeck, Veronique,Thybaut, Joris W.,Van Der Voort, Pascal
, p. 2144 - 2151 (2016)
A periodic mesoporous organosilica (PMO) that contains ethylene bridges was functionalized to obtain a series of cooperative acid-base catalysts. A straightforward, single-step procedure was devised to immobilize cysteine and cysteamine on the support material by means of a photoinitiated thiol-ene click reaction. Likewise, PMO materials capped with hexamethyldisilazane (HMDS) were used to support both compounds. This resulted in different materials in which the amine site was promoted by carboxylic acid groups, surface silanol groups, or both. The catalysts were tested in the aldol reaction of 4-nitrobenzaldehyde and acetone. It was found that silanol groups have a stronger promoting effect on the amine than the carboxylic acid group. The highest turnover frequency (TOF) was obtained for an amine-functionalized material that contained only silanol promoting sites. The loading of the active sites also had a significant effect on the activity of the catalysts, which was rationalized on the basis of a computational study.
Effects of amine structure and base strength on acid-base cooperative aldol condensation
Lauwaert, Jeroen,De Canck, Els,Esquivel, Dolores,Van Der Voort, Pascal,Thybaut, Joris W.,Marin, Guy B.
, p. 35 - 45 (2015)
Aminated silica materials are known to efficiently catalyse aldol condensations, especially when silanol groups are neighbouring the amine function. The effect of the amine structure and base strength has been analysed experimentally and by kinetic modelling using commercially available precursors to graft primary, secondary and tertiary amines on the silica surface. While primary amines are arranged in a clustered manner on the catalyst surface, secondary amines are arranged randomly which results in a higher percentage of promoted amines in the low silanol-to-amine ratio range. An enamine compound formed by the reaction between the amine active site and acetone has been identified as the key intermediate to explain the experimental observations. In the case of a primary amine this enamine intermediate can form an inhibiting imine with which it is in equilibrium. As a secondary amine has only one hydrogen atom bonded to the nitrogen atom, the inhibiting imine cannot be formed, resulting in a comparatively higher concentration of reactive enamines on the catalyst surface. In case of a tertiary amine the formation of the reactive intermediate is impossible due to the absence of any hydrogen atom bonded to the nitrogen atom. The activation entropies of all reaction steps occurring on the amine sites, as obtained by regression, could be correlated to the deprotonation entropies of the amine sites. As the deprotonation enthalpy does not account for steric effects, no such correlation could be found between the activation energies of these reaction steps and the deprotonation enthalpies of the amine sites.
Multifunctional heterogeneous catalysts: SBA-15-containing primary amines and sulfonic acids
Zeidan, Ryan K.,Hwang, Son-Jong,Davis, Mark E.
, p. 6332 - 6335 (2006)
(Chemical Equation Presented) Dual functions: The simultaneous immobilization of primary amines and sulfonic acids on mesoporous silica SBA-15 (SBA-15-A/B; see scheme) creates a heterogeneous catalyst that exhibits cooperative catalytic behavior in the aldol condensation reaction. The respective chemical reactivities of the acid and base groups are maintained, whereas homogeneous analogues are neutralized in solution. TEOS = tetraethoxysilane.
L-proline modulated zirconium metal organic frameworks: Simple chiral catalysts for the aldol addition reaction
Feng, Xiao,Jena, Himanshu Sekhar,Leus, Karen,Wang, Guangbo,Ouwehand, Judith,Van Der Voort, Pascal
, p. 36 - 42 (2018)
Three L-proline modulated zirconium based MOFs denoted as UiO-66, Zr-NDC (NDC = 2,6-Naphthalenedicarboxylate) and UiO-67 were synthesized, characterized and explored as heterogeneous catalyst in diastereoselective aldol addition reactions between 4-nitrobenzaldehyde and linear/cyclic ketones. Upon L-proline modulation, chirality was introduced into these Zr-MOFs which were consequently explored as chiral catalysts for asymmetric reactions. A systematic study was conducted to look into the effect of the synthesis temperature on the modulation in each Zr-MOF. The modulated UiO-66 material synthesized at 120 °C exhibited full conversion and a good diastereoselectivity whereas the homogeneous L-proline catalyst showed only 61% conversion and a reversed diastereoselectivity. The catalyst exhibited no leaching of the catalytically active species and was reused for at least three additional cycles. The observed high catalytic activity is a result of the electron withdrawing nature of the Zr-node coordinated to L-proline.
Exploration of acid-base geometric influence on cooperative activation for aldol reaction
Liu, Bo,Liu, Heng,Wang, Chunhua,Liu, Lulu,Wu, Shujie,Guan, Jingqi,Kan, Qiubin
, p. 1 - 7 (2012)
Bifunctionalized material with organized pairs of carboxylic acid and primary amine structurally similar to β3-amino acid derivatives has been prepared through post-grafted approach. Then the organized acid-base bifunctionalized material and the base monofunctionalized material were used as catalysts in aldol reaction to study the influence of the acid-base geometry on acid-base cooperativity. The catalytic result using acid-base bifunctionalized material towards aldol reaction was almost as same as the result obtained with the monofunctional amino catalyst, indicating that cooperative activation is not able to act efficiently unless the acid and the base active centers are positioned with appropriate geometry for the aldol reaction (e.g. about 2.6 ).
Comparison of deep eutectic solvents and solvent-free reaction conditions for aldol production
Milker,P?tzold,Bloh,Holtmann
, p. 70 - 74 (2019)
In this work, we investigated the catalytic aldolase activity of the porcine pancreas lipase (PPL) for 4-nitrobenzaldehyde (4-NBA) and acetone in different deep eutectic solvent (DES) compared with bovine serum albumin (BSA)-catalyzed aldol reaction. The PPL catalyzed the aldol addition specifically towards the desired aldol product, especially in hydrophobic DES. In contrast to this result, BSA-catalyzed aldol additions did not exhibit specificity for neither aldol nor olefin formation. For the PPL-catalyzed reactions, the product composition could be directly correlated with the choice of DES, differing in their hydrophobicity. The initial reaction velocity of the aldol addition was higher in the hydrophilic DES ChCl:Gly. However, this DES was limited by the solubility for the 4-NBA substrate. The 4-NBA containing DES exhibited the highest solubility for 4-NBA. However, the fastest reaction with a final yield of 1296.5 mM, which corresponds to 71% yield and 82% conversion after 32 h, was achieved in the co-solvent acetone, making this reaction solvent-less and improving the productivity up to 40.5 mM h?1 compared to reactions performed in DES.
Lipase CAL-B does not catalyze a promiscuous decarboxylative aldol addition or Knoevenagel reaction
Evitt, Andrew S.,Bornscheuer, Uwe T.
, p. 1141 - 1142 (2011)
Recently it was reported that lipase B from Candida antarctica (CAL-B) shows catalytic promiscuity in the decarboxylative aldol addition and Knoevenagel reaction between 4-nitrobenzaldehyde (4-NBA) and ethyl acetoacetate. We here provide experimental evidence that CAL-B simply catalyzed hydrolysis of the ester yielding the free acetoacetic acid, which under the reaction conditions readily reacts with 4-NBA to the described products.
Silanol-assisted aldol condensation on aminated silica: Understanding the arrangement of functional groups
Lauwaert, Jeroen,De Canck, Els,Esquivel, Dolores,Thybaut, Joris W.,Van Der Voort, Pascal,Marin, Guy B.
, p. 255 - 264 (2014)
Free silanol groups are known to promote the activity of aminated silica. In this work the effect of the silanol-to-amine ratio on the aldol condensation of 4-nitrobenzaldehyde and acetone is investigated in a range from 0 to 2.4. Irrespective of the amine density, identical, moderate turnover frequencies are obtained if the silica exclusively has amines on its surface. The turnover frequency increases with increasing silanol-to-amine ratio until an upper limit is reached at a silanol-to-amine ratio of 1.7. At this upper limit the turnover frequency is a factor 5 higher than the turnover frequencies obtained with the monofunctional amine-based catalysts. This increase is ascribed to hydrogen-bridge interactions between the silanols and the carbonyl moiety of the reactants that provoke a more easy interaction between the carbonyl moiety and the amine as required for the aldol condensation. The observation that higher values than one for the silanol-to-amine ratio are required is rationalized by computer simulations. It was found that amine groups were grafted on the silica surface in a clustered manner, originating from positive deviations from ideality in the synthesis mixture, that is, from clustering of the amine precursor in the liquid phase. Copyright
