Bacteriostatic activities of N-substituted tris-thioureas bearing amino acid and aniline substituents

A series of tri-substituted thiourea derivatives were synthesized by the reaction of 1,3,5-triacetylbenzoyl isothiocyanate with aminoacids and aniline derivatives. All thiourea derivatives were characterized by FT-IR, ¹H and ¹³C NMR spectroscopy. Antibacterial activities against wild-type Escherichia coli American Type Culture Collection 8739 were determined by use of the turbidimetric methodto evaluate the effect of varying amino groups on the synthesized thioureas. Tris-thiourea derivatives bearing ortho-chloroaryl substituents showed excellent antibacterial activity against E. coli with minimal inhibitory concentration (MIC) of 96 ppm. The optimum inhibition was dependent on the type of amines and the position of the halogen in aniline.     

A spectroscopic investigation of aggregations in chlorophyll solutions

Abstract— Absorption and emission spectra are reported for polar and non-polar solutions of chlorophyll a and chlorophyll b. These spectra can be interpreted in terms of the formation of chlorophyll dimers and more highly aggregated forms. The phosphorescence spectra of polar and non-polar solutions of chlorophyll a are identical and are associated with emission from a π-π-* triplet state.     

A spectroscopic investigation of the structure of alcohol-water solutions

The v₂ + v₃ combination band of water has been recorded for nine alcohol-water solutions in which the volume fraction of water is less than 2% and for three alcohol-water solutions over the entire range of composition. In dilute solutions it was found that the fraction of symmetrically bonded water was, in general, smaller than in aprotic solvent-water systems. The fraction of nonbonded water protons was greater in alcohols of higher molecular weight and was also greater in tertiary alcohols than in primary ones. The 2v_OH overtone band was recorded for three alcohols in alcohol-rich solutions. Water appears to break up the polymeric alcohol structure, and there appears to be a slight preference for water-water bonds over water-alcohol bonding. Raman spectra of the alcohol C–O stretching mode indicate that water-alcohol bonding is stronger than alcohol-alcohol bonding. The fraction of free alcohol and water OH groups appears to be smaller in solutions of intermediate composition than in the pure liquids. This increased structure of the solutions is consistent with the maxima occurring in the viscosity of alcohol-water solutions.     

Luminescent compounds diphenylboron analogs of Alq3 and its methyl substituents: A theoretical investigation of their electronic and spectroscopic properties

The absorption and emission energies for diphenylboron analogs of Alq₃ (Ph₂Bq) and its methyl substituents (Ph₂Bmq) were systematically investigated at the Zerner's intermediate neglect of differential overlap (ZINDO), configuration interaction singles (CIS), and time‐dependent density functional theory (TD‐DFT) levels of theory. The lowest excited‐state geometries were optimized at the ab initio CIS level. The TD‐DFT method provides the most reliable results for the absorption and emission transition energies, compared with other methods. Moreover, the TD‐DFT calculations reliably estimate the changes of absorption and emission λ_max values upon methyl substitution, with errors of 1.2% and 1.8%, respectively. The Stokes shifts are well reproduced by TD‐DFT calculations. Various density functional theory methods have been tested and the B3LYP functional clearly seems to be the best choice for this class of compounds. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

A spectroscopic investigation of the phenolcarboxylic acids ofCynara scolymus

Summary Tigogenin and gitogenin have been isolated from the leaves and flowers, and digitogenin (0.283%) and tigogenin (0.062%) from the seeds ofD. ciliata Trautv. The presence of gitogenin in the seeds has also been established by paper chromatography.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 5, pp. 315–318, 1965     

Effects of substituents in reactions of sulfenyl chlorides with derivatives of phosphonallenic acids

Conclusions In the reaction of sulfenyl chlorides with derivatives of allenylphosphonic acid, the structure of the products formed is determined by the effect of substituents at the P atom and the terminal C atom of the cumulene, and also by the nature of the organyl group attached to the S atom in sulfenyl chloride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1851–1859, August, 1933.     

Mass spectrometric investigation of phenylthiovinyl chlorides

Three isomeric phenylthiovinyl chlorides (β-, E and Z, and α-) have been examined under EI and FI conditions with particular attention paid to the fragmentation leading to [C₈H₇S]⁺ ions via loss of Cl˙. Kinetic energy release data, MIKE and CAD MIKE spectra obtained with these precursors, as well as with model compounds, suggest the thioacylium ion PhCH₂CS⁺ as the predominant structure observed for the [C₈H₇S]⁺ species in all cases examined. A comparison is made with the solution behaviour of incipient β-thiovinyl carbenium ions, which are known to rearrange to the S-bridged thiirenium structure.     

Theoretical investigation on the spectroscopic properties of furylfulgide with different substituents and design of novel bis‐furylfulgimide photochromes

Density functional theory and time‐dependent density functional theory were employed to theoretically analyze the effect of different substituents on the spectroscopic properties of furylfulgide. The result shows that the absorption spectra of ring‐closed isomer which substituted by an electron‐donating group (NH₂) at the R₃‐position of furylfulgide has an evident bathochromic shift compared with the others. Due to the steric hindrance effect, the difference of absorption wavelength was evidently enlarged by introducing several representative electron‐withdrawing groups at the R₆‐position of furylfulgide. In addition, we also designed a series of novel dimers which combined two furylfulgimide monomers into one new molecule. The relevant frontier molecular orbitals, energy levels and absorption properties were analyzed in detail by the calculation of low‐lying excited states. Finally, taking BFF‐6 (bis‐furylfulgimide) for an example, we discussed the transformation mechanism of four stable isomers in the toluene solution. Our conclusions manifest that the asymmetrical BFF‐6 can act as a potential multifunctional molecular switch in consideration of its distinguishable absorption bands and reversible conversion process. We hope that this research will be beneficial to design more practical and efficient molecular switch for further applications.     

Bulky alkylphosphines with neopentyl substituents as ligands in the amination of aryl bromides and chlorides

Di(tert-butyl)neopentylphosphine (DTBNpP) in combination with palladium sources provided catalysts with comparable or better activity for the Hartwig-Buchwald amination of aryl bromides than tri(tert-butyl)phosphine (TTBP) under mild conditions. DTBNpP also provided effective catalysts for amination reactions of aryl chlorides at elevated temperatures. Further replacement of tert-butyl groups with neopentyl substituents resulted in less effective ligands for amination reactions. Computationally derived cone angles showed that replacement of a tert-butyl group with a neopentyl group significantly increased the cone angle of the phosphine. The larger cone angle of DTBNpP than TTBP appears to correlate with the higher activity of catalysts derived from DTBNpP in the amination of aryl bromides. TTBP is a stronger electron donor than DTBNpP, which may explain the higher activity for TTBP-derived catalysts toward aryl chlorides.     

O- and N-substituted products from the treatment of 3,5-dichioro-2-pyridone with benzenesulfonyl chlorides

Treatment of 3,5-dichloro-2-pyridone with various benzenesulfonyl chlorides in the presence of triethylamine at 25° yielded both O- and N-sulfonylated products. These isomers were isolable, relatively stable compounds which were distinguished by their ir and uv spectra.     

A study on applications of N-substituted main-chain NHC-palladium polymers as recyclable self-supported catalysts for the Suzuki-Miyaura coupling of aryl chlorides in water

The preparation and characterization of a number of main-chain organometallic polymers (NHC-Pd MCOP) with different N-alkyl substituted groups such as benzyl (3a), n-hexyl (3b), and n-dodecyl (3c) are described. Among these polymers, 3c bearing the more lipophilic group n-dodecyl was found to be a more reactive and recoverable catalytic system in the Suzuki-Miyaura cross-coupling reaction of chloroarenes, including both deactivated and hindered aryl chlorides with different types of arylboronic acids under aqueous conditions. While the catalysts seem to be highly recyclable, on the contrary, we have provided much compelling evidence, such as kinetic monitoring, poisoning experiments, and average molecular weight determination before and after catalysis, that shows that the described organometallic polymers might be indeed the source of production of active soluble Pd species in the form of either Pd nanoparticles or fragmented NHC-Pd complexes. Our studies showed that in order to assess whether the catalysts are functioning in a heterogeneous pathway or they are simply a source of production of active Pd species, it is crucial to devise a suitable and highly efficient poison that could capture essentially soluble catalytic species. In this regard, we interestingly found that among a variety of well-known catalyst poisons such as Hg(0), SBA-15-PrSH, and cross-linked poly(4-vinylpyridine) (PVP), only PVP could efficiently quench catalysis, thus providing clear evidence of the formation soluble Pd species in our protocol. In addition, several experiments such as bright-field microscopy, dynamic light scattering (DLS) of the reaction mixture, and kinetic monitoring of the reaction at an early stage confirm not only that the described organometallic polymers could be a source of production of trace amounts of Pd nanoparticles but the capsular structures of these lipophilic polymers in water provides a means of entrapment of nanoclusters in a hydrophobic region, thus accelerating the reaction in pure water in the absence of any co-organic solvent.     

Electronic effect of substituents in dimethylethynylalkoxysilanes

Russian Chemical Bulletin -     

Synthesis of 2-aryl-4-cyano-1,3-oxazole-5-sulfonyl chlorides and N-substituted sulfonamides

Oxidative chlorination of 2-aryl-5-benzylsulfanyl-1,3-oxazole-4-carbonitrile results in the previously unknown 4-cyano-1,3-oxazole-5-sulfonyl chlorides and N-substituted sulfonamides.     

A spectroscopic investigation into the reaction of sodium tetrathionate with cysteine

A spectroscopic investigation into the reaction of sodium tetrathionate with cysteine at pH 5 both at the boil and at room temperature has been carried out. The Raman and infrared spectra of the model compounds cysteine, cysteine-S-sulfonate, cysteine-S-thiosulfonate, sodium thiosulfate and sodium sulfite were also obtained and vibrations involving the sulfur atoms were analyzed in detail. These results were utilized in the interpretation of the spectra obtained from tetrathionate-cysteine reaction mixtures. The reaction supernatants were analyzed by high performance thin layer chromatography while the precipitates were analyzed gravimetrically. It was found that during the reaction, the thiol groups of cysteine are oxidised to give predominantly cysteine-S-sulfonate. Cystine was also detected but was determined gravimetrically to be a minor reaction product. No significant amounts of cysteine-S-thiosulfonate were detected. The reaction is accompanied by the formation of elemental sulfur and a small amount of sulfite. Major reaction pathways are put forth that are consistent with the experimental data.