645-62-5Relevant articles and documents
Two sides of the same amino acid - Development of a tandem aldol condensation/epoxidation by using the synergy of different catalytic centres in amino acids
Ostrowski, Karoline A.,Lichte, Dominik,Terhorst, Michael,Vorholt, Andreas J.
, p. 1 - 7 (2016)
A new tandem catalysis was set up after intensive investigations regarding the amino catalysed aldol condensation and epoxidation. 20 proteinogenic amino acids were investigated as organocatalysts in the epoxidation of an α-branched α,β-unsaturated aldehyde. The most active amino acids were chosen for the optimization of the reaction conditions obtaining excellent yields in the epoxidation. With these insights the first tandem aldol condensation/epoxidation was developed gaining very good yields of the epoxy aldehyde, which was obtained directly from butanal without any purification or isolation of the intermediate. Applying butanal as substrate, which is produced on a large industrial scale, opens up new horizons for novel useful and reactive products. Furthermore, the beneficial influence of lysine and arginine was proven and it was revealed that these amino acids bear two different catalytic centres, which have impact on the synergy in this new tandem catalysis being active within two different reaction mechanisms. The α-amino function catalyses the aldol condensation and the corresponding side chain group is responsible for the catalytically conversion in the epoxidation.
Butanal Condensation Chemistry Catalyzed by Br?nsted Acid Sites on Polyoxometalate Clusters
Yang, Yifei,Lin, Fan,Tran, Honghi,Chin, Ya-Huei Cathy
, p. 287 - 299 (2017)
The connection of active site structures and their catalytic chemistry during butanal deoxygenation on polyoxometalate clusters with varying H+ site densities and identity of central atoms [HxNa4?xSiW12O40 (x=0–4) and HyNa3?yPW12O40 (y=0–3)] was established with rate assessment, IR spectroscopic, and chemical titration methods. Butanal adsorbs on the H+ or Na+ ions on polyoxometalate clusters and forms RC=O???H+ or RC=O???Na+ complexes at 348 K. A portion of the adsorbed butanals on the H+ sites converts to surface acetates through their reactions with vicinal framework oxygen atoms, as confirmed from the detection of νas(OCO) band at approximately 1580 cm?1, and remains as the spectator species. Bimolecular reactions of butanals on the remaining H+ sites lead to 2-ethyl-2-hexenal as the predominant products, within which a small fraction undergoes sequential cyclization–dehydration to produce aromatics. A trace amount of butanal converts through minor, competitive pathways that form light olefins and dienes. These findings on the connection between active sites and their catalytic chemistry provide mechanistic insights useful for tuning the rates of the various concomitant paths and thus yields towards the different products during deoxygenation reactions.
Tailoring the cooperative acid-base effects in silica-supported amine catalysts: Applications in the continuous gas-phase self-condensation of n-butanal
Shylesh, Sankaranarayanapillai,Hanna, David,Gomes, Joseph,Krishna, Siddarth,Canlas, Christian G.,Head-Gordon, Martin,Bell, Alexis T.
, p. 1283 - 1290 (2014)
A highly efficient solid-base organocatalyst for the gas-phase aldol self-condensation of n-butanal to 2-ethylhexenal was developed by grafting site-isolated amines on tailored silica surfaces. The catalytic activity depends largely on the nature of amine species, the surface concentration of amine and silanol groups, and the spatial separation between the silanol and amine groups. In situ FTIR measurements demonstrated that the formation of nucleophilic enamines leads to the enhanced catalytic activity of secondary amine catalysts, whereas the formation of imines (stable up to 473 K) leads to the low activity observed for silica-supported primary amines. Blocking the silanol groups on the silica support by silylation or cofeeding water into the reaction stream drastically decreased the reaction rates, demonstrating that weaker acidic silanol groups participate cooperatively with the amine groups to catalyze the condensation reaction. This work demonstrates that the spatial separation of the weakly acidic silanols and amines can be tuned by the controlled dehydration of the supporting silica and by varying the linker length of the amine organosilane precursor used to graft the amine to the support surface. A mechanism for aldol condensation was proposed and then analyzed by DFT calculations. DFT analysis of the reaction pathway suggested that the rate-limiting step in aldol condensation is carbon-carbon bond formation, which is consistent with the observed kinetics. The calculated apparent activation barrier agrees reasonably with that measured experimentally. Secondary amines come first: A solid-base organocatalyst achieved by grafting amines onto silica surfaces is applied to the gas-phase aldol self-condensation of n-butanal to 2-ethylhexenal. Silica-supported secondary amine catalysts demonstrate a much higher catalytic activity than the primary amine analogues, owing to the respective formation of enamines as shown by in situ FTIR analysis. The reaction pathway is analyzed by DFT calculations.
Beryllium-Induced Conversion of Aldehydes
Müller, Matthias,Buchner, Magnus R.
, p. 11147 - 11156 (2019)
Aldehydes play a key role in the human metabolism. Therefore, it is essential to know their reactivity with beryllium compounds in order to assess its effects in the body. The reactivity of simple aldehydes towards beryllium halides (F, Cl, Br, I) was studied through solution and solid-state techniques and revealed distinctively different reactivities of the beryllium halides, with BeF2 being the least and BeI2 the most reactive. Rearrangement and aldol condensation reactions were observed and monitored by in situ NMR spectroscopy. Crystal structures of various compounds obtained by Be2+-catalyzed cyclization, rearrangement, and aldol addition reactions or ligation of beryllium halides have been determined, including unprecedented one-dimensional BeCl2 chains and the first structurally characterized example of an 1-iodo-alkoxide. Long-term studies showed that only aldehydes without a β-H can form stable beryllium complexes, whereas other aldehydes are oligo- and polymerized or decomposed by beryllium halides.
Vapor-phase self-aldol condensation of butanal over Ag-modified TiO2
Sun, Daolai,Moriya, Shizuka,Yamada, Yasuhiro,Sato, Satoshi
, p. 8 - 16 (2016)
Vapor-phase self-aldol condensation of butanal was performed over various solid catalysts. Among the tested catalysts, SiO2-Al2O3, Nb2O5 and TiO2 showed relatively high catalytic activity for the formation of aldol condensation product, 2-ethyl-2-hexenal, whereas all the catalysts deactivated rapidly. In order to stabilize the catalytic activity, metal-modified catalysts were investigated in hydrogen flow, and it was found that Ag-modified TiO2 showed the best catalytic performance. Characterizations such as XRD, TPD, TPR, TG-DTA, and DRIFT were performed for investigating the effect of the additive Ag and analyzing the coke component. The loaded Ag metal inhibited the formation of carbon accumulated on catalyst surface, and H2 carrier gas was indispensable in the inhibition. Ag would work as a remover of the products on the catalyst surface together with H2 to prevent dehydrogenation followed by coke formation. Self-aldol condensation of butanal was stabilized over Ag-modified TiO2 at Ag2O loadings higher than 3 wt.% at 220 °C in H2 flow. TiO2 with Ag2O of 5 wt.% showed the best catalytic performance and gave a 72.2% selectivity to 2-ethyl-2-hexenal at 72.1% conversion in H2 flow at 220 °C.
Structured hydroxyapatite composites as efficient solid base catalysts for condensation reactions
Bruijnincx, Pieter C. A.,Ftouni, Jamal,Jose, Tharun
, p. 3428 - 3436 (2021)
Herein, we report the use of structured hydroxyapatite composite (SHCs) as highly efficient and recyclable solid base catalysts for various condensation reactions. Catalyst performance as function of catalyst loading, reaction time and reaction temperature were studied in the solventless self-aldol condensation reaction of butyraldehyde to 2-ethylhexenal under mild reaction conditions. SHC catalysts were found to outperform benchmark solid base catalysts such as MgO, TiO2, calcium carbonate and hydroxyapatites. Characterization of the synthesized SHC catalysts by a range of surface analysis, spectroscopic and electron microscopy techniques, showed that a moderate acid/base ratio and high BET surface area to be key to their high efficiency. Furthermore, recycling experiments showed the catalyst to be stable over multiple runs. Moreover, the most active SHC catalyst was investigated in other prototypical condensation reactions such as the Knoevenagel condensation, Claisen-Schmidt condensation and Henry reaction, again showing excellent performance. These results highlight the versatility of these SHC materials and their potential for industrial employment as solid base catalysts.
Hierarchical Beta zeolites as catalysts in a one-pot three-component cascade Prins-Friedel-Crafts reaction
?ejka, Ji?í,Barakov, Roman,Bezverkhyy, Igor,Opanasenko, Maksym,Shcherban, Nataliya,Yaremov, Pavel
, p. 6992 - 7002 (2020)
Hierarchical Beta zeolites obtained from concentrated reaction mixtures (H2O/Si = 2.5-7.0) in the presence of CTAB and their conventional and nanosponge analogues were investigated in a one-pot cascade environmentally friendly Prins-Friedel-Crafts reaction of butyraldehyde with 3-buten-1-ol and anisole under mild conditions (60 °C). The highest yields of the desired products with 4-aryltetrahydropyran structure were achieved when using hierarchical zeolites characterised by well-developed mesoporosity (facilitating the formation of bulky intermediates and products) and by an increased fraction of highly accessible (evaluated by TTBPy method) medium-strength Br?nsted acid sites. Acid sites with higher strength promote strong adsorption of bulk O-containing intermediates or products and the formation of byproducts (tetrahydropyranyl ether and 2-propyloxan-4-ol). Therefore, this is an inexpensive and simple synthesis method for preparing hierarchical zeolites with catalytic activity comparable to that of nanosponge Beta, which is however prepared using complex and expensive multi-quaternary ammonium surfactants. Moreover, this synthetic protocol for 4-aryltetrahydropyrans replaces the carcinogenic and toxic chemicals, which have been previously used for Prins-Friedel-Crafts reactions, with green and non-toxic substances. This journal is
Cobalt-catalyzed direct α-hydroxymethylation of amides with methanol as a C1 source
Ma, Ben,Sun, Rongxia,Yang, Jingya
supporting information, p. 1382 - 1385 (2022/02/05)
Herein, we report a cobalt-catalyzed α-hydroxymethylation of amides with methanol under mild conditions. Using CoCl2·6H2O as an inexpensive and efficient catalyst, some important bioactive β-hydroxyamides were obtained in moderate to excellent yields. The
Preparation and catalytic performance of NiO-MnO2/Nb2O5-TiO2 for one-step synthesis of 2-ethylhexanol from n-butyraldehyde
An, Hualiang,Li, Sibo,Wang, Yanji,Zhang, Jiaxun,Zhao, Xinqiang
, (2020/12/02)
One-pot synthesis of 2-ethylhexanol(2EHO) from n-butyraldehyde is of commercialimportance. The promotion of 2EHO selectivity requires suppressing direct hydrogenation of n-butyraldehyde. In this work, a series of NiO-MOx/Nb2O5-TiO2 catalysts were prepared and utilized by means of reduction-in-reaction technique, aiming at delaying the formation of metal sites and suppressing the direct hydrogenation. NiO-MnO2/Nb2O5-TiO2 with a Ni/Mn mass ratio of 10 and NiO-MnO2 loading of 14.3 wt% shows the best catalytic performance; 2-EHO selectivity could reach 90.0% at a complete conversion of n-butyraldehyde. Furthermore the catalyst could be used for four times without a substantial change in its catalytic performance.
READILY BIODEGRADABLE ALKOXYLATE MIXTURES
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Paragraph 0037-0039; 0043, (2021/05/14)
A mixture of octanols, nonanols and decanols is useful for the preparation of alkoxylates, which alkoxylates may be used as surfactants, which surfactants have surprisingly good biodegradability.
