30649-18-4Relevant articles and documents
Enolization of aldehydes and ketones: Structural effects on concerted acid-base catalysis
Hegarty, Anthony F.,Dowling, Joseph P.,Eustace, Stephen J.,McGarraghy, Michelle
, p. 2290 - 2296 (1998)
The third-order term (k(AB)) for the concerted acid-base catalyzed enolization of a selection of simple aldehydes and ketones has been measured in a series of substituted acetic acids at 25°C at constant ionic strength 2.0 (NaNO3). While there is no direct correlation of the magnitude of the third-order term with either the rate constants for acid (k(A)) or base (k(B)) catalysis, a simple log-log relationship exists between the product of the consecutive rate constants (k(A)·k(B)) and the concerted (third order) rate constants (k(AB)). This implies that the concerted pathway is important only when both the general acid and the general base terms are significant; this will be useful in designing other systems which might show such concerted catalysis. In the case of aldehydes, a slope of 0.97 was found for this plot, which compares to the result for 4-substituted cyclohexanones (0.51) and other ketones (0.59), as measured in acetic acid buffers. The resultant Bronsted β(AB) value of 0.20 found for propanal (2) is consistent with the overall observation that concerted catalysis is largely independent of the buffering species, and that process is overall base catalyzed. The solvent isotope effect on the concerted acid-base catalyzed enolization rate term, k(AB)(H2O)/k(AB)(D2O) = 1.33, indicates that the transition state for proton transfer to the carbonyl is more advanced than in the case of ketones. In general we have found that carbonyl compounds with large measured (or estimated) enol contents show significant third-order terms.
Isolation and synthesis of analgesic and anti-inflammatory compounds from Ochna squarrosa L.
Anuradha,Srinivas, Pullela V.,Ranga Rao,Manjulatha,Purohit, Muralidhar G.,Madhusudana Rao
, p. 6820 - 6826 (2007/10/03)
Two new furanoflavonoids (1, 2), one new chalcone dimer (3) along with six known compounds, chrysophanol, 5-O-methyl squarrosin, 5-methoxy furano[4″,5″,6,7]flavone, calodenone, lophirone A and lophirone H were isolated from the ethyl acetate-soluble fraction of methanol extract of root bark of Ochna squarrosa. Chrysophanol, calodenone, lophirone A and lophirone H were isolated from this plant for the first time. The structures of all the isolated compounds were confirmed by 1D and 2D spectroscopic data. These compounds were tested for analgesic and anti-inflammatory activity. All the new compounds showed good analgesic and anti-inflammatory activity. A simple and facile method for the cleavage of benzyl ethers using I2 in trigol is also reported.
Oxidative deprotection of silylethers, acetals and ketals by oxygen or air in presence of manganese and cobalt salts of 4-aminobenzoic acid supported on silica gel as catalyst
Hashemi, Mohammed M.,Kalantari, Fariba
, p. 1857 - 1863 (2007/10/03)
Oxidative deprotection of silylethers, acetals and ketals, to their corresponding alcohols, aldehydes and ketones have been achieved using oxygen or air in the presence of cobalt and manganese salts of 4-aminobenzoic acid supported an silica gel as catalysts. Reactions are clean and catalysts can be recovered easily and reused repeatedly.
