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.
B regioselective and chemoselective biotransformation of 2′-hydroxychalcone derivatives by marine-derived fungi
Nitschke, Marcia,Porto, André Luiz Meleiro,de Matos, Iara Lisboa
, (2021/08/06)
Eight fungal strains (Penicillium raistrickii CBMAI 931, Cladosporium sp. CBMAI 1237, Aspergillus sydowii CBMAI 935, Penicillium oxalicum CBMAI 1996, Penicillium citrinum CBMAI 1186, Mucor racemosus CBMAI 847, Westerdykella sp. CBMAI 1679, and Aspergillus sclerotiorum CBMAI 849) mediated the biotransformation of the 2′-hydroxychalcone 1a. The main products obtained were from hydrogenation, hydroxylation, and cyclization reactions. Penicillium raistrickii CBMAI 931 catalyzed the chemoselective reduction of 1a to produce 2′-hydroxydihydrochalcone 2a (72%) in 7 days of incubation in phosphate buffer (pH 7). Aspergillus sydowii CBMAI 935 promoted the hydroxylation of 1a to yield 2′,4-dihydroxy-dihydrochalcone 5a (c = 42%) in 7 days of incubation in phosphate buffer (pH 8). The reaction using P. citrinum CBMAI 1186 and M. racemosus CBMAI 847 presented main cyclization products in phosphate buffer (pH 8), but the reactions with these fungi did not present enantioselectivity. Marine-derived fungi were effective and versatile biocatalysts for biotransformation of the 2′-hydroxychalcones yielding different products according to the conditions and microorganism used.
