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Hydroxy chalcones

Hydroxy-propiophenon 2 -Hydroxy-chalcon 5-Chlor-2-hydroxy-benzophenon 2-Hydroxy-1 -formyl-naphthalin... [Pg.289]

Matsushima, R., Miyakawa, K., Nishihata, M. Photochromic properties of 2-hydroxy-chalcones. Chem. Lett. 1988, 1915-1916. [Pg.31]

The condensation of 2-hydroxyacetophenone with benzaldehyde yielded exclusively 2 -hydroxy-chalcone, and the cyclization to flavanone was not observed. An investigation of the species adsorbed on the catalyst (289) suggested that CS condensation on the Ba(OH)2 surface occurs via a very rigid transition state, whereby the OH group of 2-hydroxyacetophenone is bonded to the catalyst surface and placed at great distance from the carbonyl carbon atom of the aldehyde, making the cyclization of 2 -hydroxy-chalcone to flavanone difficult. Deactivation of the catalyst was not observed in the presence of moderate amounts of organic acids, such as benzoic, acrylic, or trichloroacetic acid. [Pg.289]

Total syntheses of chrysin (93) and luteolin (94), which are non-toxic potent inhibitors of reverse transcriptases from Rauscher murine leukemia (RLV) and the human immunodeficiency virus (HIV), were accomplished by Antus and coworkers via cyclodehydrogenation of the appropriately substituted 2 -hydroxy-chalcone (179) in the presence of PIDA/KOH in MeOH [136] (Scheme 45). [Pg.242]

Reaction between 2 -hydroxyacetophenone and benzaldehyde (Claisen-Schmidt condensation) in the absence of a solvent at 423 K giving 2 -hydroxy chalcones and flavanones has been successfully performed with MgO as a solid base catalyst/581 A conversion of 40 % after 1 h with 67 % selectivity to chalcone was achieved. The influence of the solvent and the effects of a substituent on the aromatic ring were investigated by Amiridis et a//59,6"1 The reaction was carried out on MgO at 433 K. Dimethyl sulfoxide (DMSO) showed a strong promoting effect on the reaction, which was attributed to the ability of this dipolar aprotic solvent to weakly solvate anions and stabilize cations so that both become available for reaction. In this case, a conversion of 2-hydroxyacetophenone of 47 % with a selectivity to flavanone of 78 % was achieved after 30 min in a batch reactor. Further investigations1611 showed that DMSO significantly increases the rate of the subsequent isomerization of the 2 -hydroxychalcone intermediate to flavanone. [Pg.178]

BrF is an effective reagent in aromatic brominations of deactivated systems 567,568. IC1 is a selective reagent for the nuclear iodination of hydroxy chalcones without affecting the double bond. This reagent is the active species in the a-iodination of carboxylic acids with I2/SOCl2570. [Pg.564]

Salicylaldehydes can be condensed, by base or acid catalysis, with ketones that have an a-methylene. When base catalysis is used, the intermediate hydroxy-chalcones can be isolated, but overall yields are often better when the whole sequence is carried out in one step, using acid. It is important to note that because this route does not rely upon an electrophilic cychsation onto the benzene ring, 1-benzopyryliums free from benzene ring (activating) substituents can be produced. [Pg.238]

Farkas et al., [123] synthesised different natural isoflavanones (255) and isoflavans (256) by oxidative rearrangement of 2-hydroxy chalcones (254) with thallium nitrate in methanol followed by acid-catalyzed cyclization as shown in Fig. (11). [Pg.946]

Phenols have been condensed with alkenoylesters to give chromans by an oxa-Michael addition/electrophilic aromatic addition sequence with magnesium(II)- or copper(II)-bis-oxazoline complexes as chiral Lewis acid catalysts (Scheme 17b) [97]. This reaction may be initiated by an oxa-Michael reaction, followed by a hydroarylation of a carbonyl group. The authors suggest that the initial stereodetermining oxa-Michael addition is followed by a fast diastereoselective aromatic substimtion [97]. A nickel Lewis acid, derived from Ni(hfacac)2 (hfacac = 1,LL5,5,5-hexafluoro-3,5-dioxopentane enolate) and chiral Al-oxide ligands, catalyzes the enantioselective oxa-Michael cyclization of 2-tert-butyloxycarbonyl-2 -hydroxy-chalcones to 3-ferf-butoxycarbonyl flavanones, which can be decarboxylated to flavanons in a separate step (Scheme 17c) [98]. A Lewis acid activation of the unsaturated p-ketoester unit can be assumed. [Pg.140]

The cyclization of 2 -amino- and 2 -hydroxy-chalcones (12a,b) (Scheme 1.9) using silica-supported sodium hydrogen sulfate (NaHS04-Si02) was accomplished by Kumar and Perumal (2006). Preparation of tetrahydroquinolones and flavonones is a matter of great interest as these compounds display various pharmacological... [Pg.8]

Kumar, K.H., Perumal, P.T. 2006. A simple and facile solventless procedure for the cycfiza-tion of 2 -amino- and 2 -hydroxy-chalcones using silica-supported sodium hydrogen sulphate as heterogenous catalyst Canadian Journal of Chemistry 84 1079-1086. [Pg.41]

However, in the absence of iodine, the reaction did not proceed even after a long time. It indicates that the oxidation of 2-hydroxy chalcone into flavones is only due to molecular iodine and not because of air O2. The reaction proceeded smoothly at 400 W and no undesirable side products were formed. At higher power level, decrease in yield was observed due to product decomposition. [Pg.306]

Similar studies have also been carried out by them with o-hydroxy chalcones in dry media in silical gel. [Pg.126]


See other pages where Hydroxy chalcones is mentioned: [Pg.224]    [Pg.200]    [Pg.259]    [Pg.1084]    [Pg.139]    [Pg.589]    [Pg.327]    [Pg.163]    [Pg.96]    [Pg.66]    [Pg.398]   
See also in sourсe #XX -- [ Pg.99 , Pg.474 ]




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Chalcone

Hydroxy chalcones cyclization

Hydroxy chalcones rearrangement

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