Gold(I) ethylene complexes supported by electron-rich scorpionates

Ethylene complexes of gold(I) have been stabilized by electron-rich, κ2-bound tris(pyrazolyl)borate ligands. Large up-field shifts of olefinic carbon NMR resonances and relatively long C=C distances of gold bound ethylene are...

Design, Synthesis, and Antibacterial and Antifungal Activities of Novel Trifluoromethyl and Trifluoromethoxy Substituted Chalcone Derivatives

Despite the availability of many drugs to treat infectious diseases, the problems like narrow antimicrobial spectrum, drug resistance, hypersensitivities and systemic toxicities are hampering their clinical utility. Based on the above facts, in the present study, we designed, synthesized and evaluated the antibacterial and antifungal activity of novel fluorinated compounds comprising of chalcones bearing trifluoromethyl (A1–A10) and trifluoromethoxy (B1–B10) substituents. The compounds were characterized by spectroscopic techniques and evaluated for their antimicrobial activity against four pathogenic Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Bacillus subtilis) bacterial and fungal (Candida albicans and Aspergillus niger) strains. In this study, the compounds with trifluoromethoxy group were more effective than those with trifluoromethyl group. Among the 20 fluorinated chalcones, compound A3/B3 bearing an indole ring attached to the olefinic carbon have been proved to possess the most antimicrobial activity compared to the standard drugs without showing cytotoxicity on human normal liver cell line (L02). Further, the minimum inhibitory concentration (MIC) for A3/B3 was determined by serial tube dilution method and showed potential activity. These results would provide promising access to future study about the development of novel agents against bacterial and fungal infections.

N-Heterocyclic carbene-catalyzed stereoselective construction of olefinic carbon–sulfur bonds via cross-coupling reaction of gem-difluoroalkenes and thiols

A novel organocatalytic olefinic carbon–sulfur bond forming reaction was developed.

The chemical behavior of terminally tert-butylated polyolefins

The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition to 3 and 7 yielded the dibromides 17 and 18, respectively, i.e., the oligoene system has been attacked at its terminal olefinic carbon atoms. Analogously, the higher vinylogs 19 and 20 yielded the 1,8- and 1,10-bromine adduts 23 and 24, respectively, when less than 1 equivalent of bromine was employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it yielded the symmetrical epoxide 32 with DMDO. Analogously, 19 was converted to mono-epoxide 33 with MCPBA and to 34 with DMDO. Diels–Alder addition of 7 with N-phenyltriazolinedione (PTAD) did not take place. Extension of the conjugated π-system to the next higher vinylog, 19, caused NPTD-addition to the symmetrical adduct 37 in good yield. Comparable results were observed on adding NPTD (equivalent amount) to pentaene 20 and hexaene 21. Using 36 in excess provided the 2:1-adduct 40 from 21 and led to a complex mixture of adducts from heptaene 22. With tetracyanoethylene (TCNE) as the dienophile, tetraolefin 19 yielded the symmetrical adduct 43, although the reaction temperature had to be increased. Pentaene 20 and hexaene 21 led to corresponding results, adducts 44 and 45 being produced in acceptable yields. With nonaene 42 and TCNE the 2:1-adduct 48 was generated according to its spectroscopic data. Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52.

Changes of humic acids structure on selected key monitoring localities of arable soils

Soil fertility is largely determined by the content and quality of soil organic matter. SlovakRepublic monitoring system includes evaluation of soil humus content, basic humic parameters and also chemical structure of humic acids (HA). Changes in humic acids structure on five selected key localities during monitoring period (1994–2000) are presented in this study. Among soil types, essentially between Chernozem and Planosol, in elemental analysis, optical parameter and 13C NMR parameters significant differences determined by Student’s test were observed (Tables 2 and 3). During monitoring period small oxidation trend mainly on Calcaric Fluvisol and Planosol HA expressed by increase of oxygen content and O/C, O/H ratio was observed. Oxidation trends during monitoring period confirm also position of Calcaric Fluvisol and Planosol HA on van Krevelen diagram. Changes in optical parameter E^1%₆and content of carboxylic groups for the period of monitoring were negligible. Some changes throughout monitoring in ¹³C NMR parameters were recorded. On all observed HA considerable decrease of carbon in region 106–143 ppm, characteristic for aromatic and olefinic carbon with C–C, C–H bond, was observed. Spectroscopic parameters are in good agreement with elemental analysis and carboxylic groups. Joint relationships between changes in determined parameters are expressed by significant linear correlations. Predominantly between parameters calculated from ¹³C NMR spectra and data of elemental analysis and optical parameter E^1%₆highly significant linear correlations (R > 0.93) are found (Table 4).