Synthesis and Antimicrobial Activities of Some 1-[(N,N-Disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines

The increasing clinical importance of drug-resistant fungal and bacterial pathogens has lent additional urgency to microbiological research and new antimicrobial compound development. For this purpose, new pyrazoline derivatives were synthesized and evaluated for antimicrobial activity.

Some 1-[(N, N-disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines derivatives were synthesized by reacting 1-(chloroacetyl)-3,5-diaryl-2-pyrazolines with appropriate potassium salts of secondary amine dithiocarbamic acids. The chemical structures of the compounds were elucidated by IR, ¹ H-NMR, and FAB⁺-MS spectral data. Their antimicrobial activities against Staphylococcus aureus (B-767), Escherichia coli (B-3704), Pseudomonas aeruginosa (ATCC 27853), Proteus vulgaris (NRLL B-123), and Candida albicans (NRRL-27077) were investigated. The results showed that some of the compounds have notable activity against S. aureus and C. albicans.     

Synthesis,Electrical Conductivity,Spectral and Thermal Stability Studies on Poly(aniline-co-o-nitroaniline)

o-Nitroaniline units were incorporated in the polyaniline backbone through copolymerization with aniline. The copolymers were synthesized for 1:3 and 1:1 molar ratios of aniline and o-nitroaniline in acidic medium using potassium persulphate as oxidant and their properties were compared with that of polyaniline. The polymers showed less electrical conductivity than polyaniline. Unlike polyaniline, the presence of nitro group caused higher frequency dependence of electrical conductivity. Electronic spectra showed a blue shift in both the band of the copolymers due to the decrease in the extent of conjugation leading to lower conductivity, which could also be explained in terms of a decrease of delocalization of electron as evinced from electron para magnetic resonance (EPR) data. Thermo gravimetric analysis (TGA) revealed that copolymer derived from 1:1 molar ratio showed comparable thermal stability with polyaniline and the one derived from 1:3 molar ratios is thermally less stable than polyaniline. Activation energies for thermal degradation were estimated using Broido equation. The temperature dependence of electrical conductivity suggested charge transport is mainly through variable range hopping.     

Synthesis and Characterization of New Unsaturated Polyesters Containing 4‐Phenylcyclohexanone Moiety in the Main Chain

Two series of new unsaturated polyesters were prepared from 2,6‐bis(p‐hydroxidebenzylidene)‐4‐phenylcyclohexanone (I) and 2,6‐divanillyidene‐4‐phenylcyclohexanone (II) with adipoyl, isophthaloyl, sebacoyl and terephthaloyl dichlorides utilizing the interfacial polycondensation technique at ambient temperature. In addition to that, the model compounds were synthesized by reacting (I) and (II) with benzoyl chloride. The model compound and polyester samples have been characterized by elemental and spectral analyses. The unsaturated polyesters have inherent viscosities of 0.96–1.63 dl/g. All the polyesters are amorphous and most of them are partially soluble in most common organic solvents, but easily soluble in concentrated sulfuric acid. Their glass transition temperatures (T_g) range from190.15 to 245.28°C, and the temperatures of 10% weight loss as high as 180 to 220°C in air, indicating that these aromatic polyesters have high T_g and excellent thermal stability.     

Synthesis,Electrical, Electronic and Charge Transport Properties of Poly(aniline‐co‐p‐toluidine)

Copolymers of aniline with p‐toluidine were synthesized for different molar ratios of the respective monomers in acid medium. The electrical conductivity, charge transport and spectral characteristics upon incorporation of p‐toluidine units into the polyaniline backbone were investigated. The electrical conductivity of the copolymers showed frequency dependence which became more prominent with an increase in the number of p‐toluidine units in the polyaniline backbone. A direct relationship between the frequency dependence and electron localization was observed in the copolymers. Electronic spectra showed blue shifts in the π→π*and benzenoid→quinoid transitions revealing a decrease in the extent of conjugation in the copolymers. The protonated forms of the copolymers were soluble in DMSO giving polaron band around 400 nm. The decrease in electrical conductivity was attributed to the greater electron localizations as revealed from the broader ESR signals. Temperature dependence of electrical conductivity showed that charge transport was mainly through variable range hopping though a mixed conduction behavior was observed at higher temperature range.     

In vitro study of the interaction of cysteine with a thiazide diuretic (hydrochlorothiazide) at different ph by voltammetric and spectroscopic techniques

The interaction of cysteine (RSH) with a thiazide diuretic, hydrochlorothiazide (HCTZ) was characterized by UV-Vis absorption spectroscopy and square-wave voltammetry in Britton-Robinson (B-R) buffer solution (with pH 5, 7 and 9). On the square-wave voltamogram of cysteine, the reduction peak current of mercurous cysteine thiolate (Hg₂(RS)₂) decreased and its peak potential shifted to more positive values with the addition of HCTZ. This results showed that the RSH interacted with HCTZ. The stoichiometry of HCTZ-RSH molecular complex was determined by voltammetric data with the result of 1: 1. By using linear regression analysis of the voltammetric data at pH 5, 7 and 9, the apparent formation constants of HCTZ-RSH complex were calculated to be 9.54 × 10³, 2.80 × 10⁴ and 2.55 × 10⁴ M^?1, respectively. At the same time, this interaction was also supported by UV-Vis spectroscopic measurements. According to the voltammetric and spectroscopic results, it was suggested that the interaction mode between RSH and HCTZ molecules might be a combination of hydrophobic interactions and hydrogen bonds.     

Synthesis and characterization of new 4,5-dihydropyrazol-1-yl derivatives

In this study, first, a series of chalcone compounds S1–S6 were synthesized from various acetophenone derivatives (acetophenone, p-methyl acetophenone, and p-methoxy acetophenone) and aromatic aldehyde derivatives (benzaldehyde, p-methyl benzaldehyde, and p-methoxy benzaldehyde) by the Claisen–Schmidt condensation reaction. These S1–S6 compounds were then used in the preparation of 4,5-dihydropyrazol-1-yl derivatives S7–S15. Finally, four new compounds S16–S19 were synthesized from compound (S7, S8, S9, and S12) and 2,4-dinitrophenylhydrazine. Therefore, three known and ten new heterocyclic compounds were synthesized and completely characterized using ¹H NMR, ¹³C NMR, IR, and elemental analysis.     

Synthesis of Novel Bithiophene-Substituted Heterocycles Bearing Carbonitrile Groups

Symmetrical and unsymmetrical bithiophene-substituted heterocycles bearing carbonitriles including imidazo[1,2-a]pyridine, benzimidazole, and pyridine derivatives have been synthesized via different synthetic protocols. The bithiophene bis-imidazo[1,2-a]pyridine derivatives 3a,b were achieved in three steps starting from 2-acetyl-5-bromothiophene. Suzuki coupling reaction of 2a with 5-formylthiophen-2-ylboronic acid forms the formyl derivative 5, which by condensation with 3,4-diaminobenzonitrile in the presence of sodium bisulfite furnishes the unsymmetrical bithiophene derivative6. The bis-benzimidazole derivative 8 was obtained via hexabutylditin-mediated homocoupling of 5-bromothiophene-2-carboxaldehyde, while the benzimidazole derivatives 12a,b were prepared via the formyl derivatives 11a,b, a product of Velsmier formylation reaction of 10a,b. Two synthetic protocols for the aryl/hetaryl-2,2′-bithiophene derivative 14 have also been presented. In addition, the guanyl hydrazones of bithiophenes, 16 and 17, were prepared from bis(tri-n-butylstannyl)-2,2′-bithiophene through a Stille coupling reaction followed by a condensation step.