487-26-3Relevant articles and documents
Effect of Li on the catalytic activity of MgO for the synthesis of flavanone
Cortes-Concepcion, Jose A.,Patcas, Florian,Amiridis, Michael D.
, p. 1 - 8 (2010)
We have investigated the effects of Li on the structure, surface basicity and catalytic activity of MgO for the synthesis of flavanone. Introduction of low amounts of Li (i.e., ≤0.1 wt.%) was found to promote the rate of the Claisen-Schmidt condensation reaction, which is the first step in this process. However, at Li loadings above 0.1 wt.% a detrimental effect was observed, due to a concomitant decrease in surface area and increase in MgO crystallite size. A strong correlation was observed between surface-normalized basicity and catalytic activity. The increase in activity at higher levels of surface basicity can be attributed to the increased ability of Li-O- pairs to abstract a proton from the 2′-hydroxyacetophenone reactant, thus facilitating the adsorption and subsequent surface reactions of this molecule.
Mechano-chemical versus co-precipitation for the preparation of Y-modified LDHs for cyclohexene oxidation and Claisen-Schmidt condensations
Angelescu, Emilian,B?rjega, Ruxandra,Bucur, Ioana Cristina,Parvulescu, Vasile I.,Pavel, Octavian Dumitru,Stamate, Alexandra-Elisabeta,Z?voianu, Rodica
, (2020)
Y-modified LDHs with atomic Mg2+/(Al3++Y3+) of 3 and Al3+/Y3+ ratios of 0.5, 1 and 1.5 were prepared following two preparation methods, i.e. the co-precipitation and mechano-chemical one. The substitution of Al by Y in the brucite-type layer was less effective for the samples prepared by co-precipitation compared to those prepared via mechano-chemical route. In spite the fact yttrium has a larger ionic radius (0.9?) the structural characterizations of these solids confirmed that the layered structure incorporates part of it in the octahedral positions. Further, the reconstruction of the layered structure after an exposure to water for 1 h was more effective for the solid prepared by co-precipitation. The yttrium modified LDHs showed better catalytic activities for cyclohexene oxidation to the corresponding epoxide than the un-modified LDH sample. Then, mixed oxides derived from yttrium-LDH showed very high conversions and selectivities for the synthesis of chalcone.
The effect of solvents on the heterogeneous synthesis of flavanone over MgO
Drexler, Michele T.,Amiridis, Michael D.
, p. 136 - 146 (2003)
The effect of several solvents on the heterogeneous synthesis of flavanone from benzaldehyde and 2-hydroxyaceophenone over a solid MgO catalyst was studied experimentally through kinetic and FTIR spectroscopic studies. High boiling point solvents considered were dimethyl sulfoxide, tetralin, mesitylene, benzonitrile, and nitrobenzene. Dimethyl sulfoxide (DMSO) significantly promoted the rates of both steps used in this synthesis, i.e., the Claisen-Schmidt condensation reaction of benzaldehyde with 2-hydroxyacetophenone and the subsequent isomerization of the 2′-hydroxychalcone intermediate to flavanone. The effect was more pronounced for the second reaction. Even the presence of small amounts of DMSO in other solvents, e.g., benzonitrile and nitrobenzene, resulted in strong promotion of the flavanone synthesis scheme. The results of FTIR studies indicated the formation of strongly held surface sulfate species following the interaction of DMSO with the MgO surface. The presence of these sulfate species affected the adsorption behavior of benzaldehyde and 2-hydroxyacetophenone on the surface of the MgO catalyst and led to the formation of surface benzoate species. These differences might be responsible for the observed change in the catalytic behavior of MgO during the synthesis of flavanone in the presence on DMSO.
Stereoselective reduction of flavanones by marine-derived fungi
Birolli, Willian G.,Nitschke, Marcia,Porto, André Luiz M.,Santos, Darlisson de A.,de Matos, Iara L.
, (2021/08/13)
Biotransformation is an alternative with great potential to modify the structures of natural and synthetic flavonoids. Therefore, the bioreduction of synthetic halogenated flavanones employing marine-derived fungi was described, aiming the synthesis of flavan-4-ols 3a-g with high enantiomeric excesses (ee) of both cis- and trans-diastereoisomers (up to >99% ee). Ten strains were screened for reduction of flavanone 2a in liquid medium and in phosphate buffer solution. The most selective strains Cladosporium sp. CBMAI 1237 and Acremonium sp. CBMAI1676 were employed for reduction of flavanones 2a-g. The fungus Cladosporium sp. CBMAI 1237 presented yields of 72–87% with 0–64% ee cis and 0–30% ee trans with diastereoisomeric ratio (dr) from 52:48 to 64:36 (cis:trans). Whereas Acremonium sp. CBMAI 1676 resulted in 31% yield with 77–99% ee of the cis and 95–99% ee of the trans-diastereoisomers 3a-g with a dr from 54:46 to 96:4 (cis:trans). To our knowledge, this is the first report of the brominated flavon-4-ols 3e and 3f. The use of fungi, with emphasis for these marine-derived strains, is an interesting approach for enantioselective reduction of halogenated flavanones. Therefore, this strategy can be explored to obtain enantioenriched compounds with biological activities.
Preparation of a novel bridged bis(β-cyclodextrin) chiral stationary phase by thiol-ene click chemistry for enhanced enantioseparation in HPLC
Gong, Bolin,Guo, Siyu,Zhang, Ning
, p. 35754 - 35764 (2021/12/02)
A bridged bis(β-cyclodextrin) ligand was firstly synthesized via a thiol-ene click chemistry reaction between allyl-ureido-β-cyclodextrin and 4-4′-thiobisthiophenol, which was then bonded onto a 5 μm spherical silica gel to obtain a novel bridged bis(β-cyclodextrin) chiral stationary phase (HTCDP). The structures of HTCDP and the bridged bis(β-cyclodextrin) ligand were characterized by the 1H nuclear magnetic resonance (1H NMR), solid state 13C nuclear magnetic resonance (13C NMR) spectra spectrum, scanning electron microscope, elemental analysis, mass spectrometry, infrared spectrometry and thermogravimetric analysis. The performance of HTCDP in enantioseparation was systematically examined by separating 21 chiral compounds, including 8 flavanones, 8 triazole pesticides and 5 other common chiral drugs (benzoin, praziquantel, 1-1′-bi-2-naphthol, Tr?ger's base and bicalutamide) in the reversed-phase chromatographic mode. By optimizing the chromatographic conditions such as formic acid content, mobile phase composition, pH values and column temperature, 19 analytes were completely separated with high resolution (1.50-4.48), in which the enantiomeric resolution of silymarin, 4-hydroxyflavanone, 2-hydroxyflavanone and flavanone were up to 4.34, 4.48, 3.89 and 3.06 within 35 min, respectively. Compared to the native β-CD chiral stationary phase (CDCSP), HTCDP had superior enantiomer separation and chiral recognition abilities. For example, HTCDP completely separated 5 other common chiral drugs, 2 flavanones and 3 triazole pesticides that CDCSP failed to separate. Unlike CDCSP, which has a small cavity (0.65 nm), the two cavities in HTCDP joined by the aryl connector could synergistically accommodate relatively bulky chiral analytes. Thus, HTCDP may have a broader prospect in enantiomeric separation, analysis and detection. This journal is
