1.β-Keto esters from ketones and ethyl chloroformate: a rapid, general, efficient synthesis of pyrazolones and their antimicrobial, in silico and in vitro cytotoxicity studies.
Ragavan RV1, Kumar KM, Vijayakumar V, Sarveswari S, Ramaiah S, Anbarasu A, Karthikeyan S, Giridharan P, Kumari NS. Org Med Chem Lett. 2013 Jul 19;3(1):6. doi: 10.1186/2191-2858-3-6.
BACKGROUND: Pyrazolones are traditionally synthesized by the reaction of β-keto esters with hydrazine and its derivatives. There are methods to synthesize β-keto esters from esters and aldehydes, but these methods have main limitation in varying the substituents. Often, there are a number of methods such as acylation of enolates in which a chelating effect has been employed to lock the enolate anion using lithium and magnesium salts; however, these methods suffer from inconsistent yields in the case of aliphatic acylation. There are methods to synthesize β-keto esters from ketones like caboxylation of ketone enolates using carbon dioxide and carbon monoxide sources in the presence of palladium or transition metal catalysts. Currently, the most general and simple method to synthesize β-keto ester is the reaction of dimethyl or ethyl carbonate with ketone in the presence of strong bases which also requires long reaction time, use of excessive amount of reagent and inconsistent yield.
2.Comparative analysis of antibacterial properties and chemical composition of Glycyrrhiza glabra L. from Astrakhan region (Russia) and Calabria region (Italy).
Astaf'eva OV1, Sukhenko LT. Bull Exp Biol Med. 2014 Apr;156(6):829-32. doi: 10.1007/s10517-014-2462-8. Epub 2014 May 3.
We compared antibacterial activity of various extracts of two licorice subspecies against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. Diethyl carbonate extracts of Glycyrrhiza glabra root from Astrakhan region (Russia) exhibited maximum activity against the test microbial strains; activity of Astrakhan licorice was superior among 50% ethanol extracts from Astrakhan (Russia) and Calabria (Italy). Antibacterial activity is directly proportional to the content of glycyrrhizin and 18β-glycyrrhetinic acid in the extracts. According to preliminary data, the content of these chemical components in Glycyrrhiza glabra root from Astrakhan region is higher than in licorice growing in Italy, which is presumably related to climate and geographic characteristics of Astrakhan region.
3.Picosecond pulse radiolysis of the liquid diethyl carbonate.
Torche F1, El Omar AK, Babilotte P, Sorgues S, Schmidhammer U, Marignier JL, Mostafavi M, Belloni J. J Phys Chem A. 2013 Oct 24;117(42):10801-10. doi: 10.1021/jp406856u. Epub 2013 Oct 16.
The diethyl carbonate, DEC, is an ester that is used as a solvent in Li-ion batteries, but its behavior under ionizing radiation was unknown. The transient optical absorption spectra, the decay kinetics, and the influence of various scavengers have been studied by using the picosecond laser-triggered electron accelerator ELYSE. In neat DEC, the intense near-IR (NIR) absorption spectrum is assigned to the solvated electron. It is overlapped in the visible range by another transient but longer-lived and less intense band that is assigned to the oxidized radical DEC(-H). The solvated electron molar absorption coefficients and radiolytic yield evolution from 25 ps, the geminate recombination kinetics, and the rate constants of electron transfer reactions to scavengers are determined. The radiolytic mechanism, indicating a certain radioresistance of DEC, is compared with that for other solvents.
4.Palladium nanoparticles bonded to two-dimensional iron oxide graphene nanosheets: a synergistic and highly reusable catalyst for the Tsuji-Trost reaction in water and air.
Liu J1, Huo X, Li T, Yang Z, Xi P, Wang Z, Wang B. Chemistry. 2014 Sep 1;20(36):11549-55. doi: 10.1002/chem.201402545. Epub 2014 Jul 22.
Low cost, high activity and selectivity, convenient separation, and increased reusability are the main requirements for noble-metal-nanocatalyst-catalyzed reactions. Despite tremendous efforts, developing noble-metal nanocatalysts to meet the above requirements remains a significant challenge. Here we present a general strategy for the preparation of strongly coupled Fe(3)O(4) and palladium nanoparticles (PdNPs) to graphene sheets by employing polyethyleneimine as the coupling linker. Transmission electron microscopic images show that Pd and Fe(3)O(4) nanoparticles are highly dispersed on the graphene surface, and the mean particle size of Pd is around 3 nm. This nanocatalyst exhibits synergistic catalysis by Pd nanoparticles supported on reduced graphene oxide (rGO) and a tertiary amine of polyethyleneimine (Pd/Fe(3)O(4)/PEI/rGO) for the Tsuji-Trost reaction in water and air. For example, the reaction of ethyl acetoacetate with allyl ethyl carbonate afforded the allylated product in more than 99 % isolated yield, and the turnover frequency reached 2200 h(-1).