Electrochemical approach for synthesis of 3-substituted indole derivatives

An efficient and economical method was developed for synthesis of 3-substituted indole by using electrochemically induced condensation of various aldehyde, indole and malononitrile.     

Phase behavior, topology, and growth of neutral catanionic reverse micelles

The ternary catanionic system octylammoniumoctanoate/octane/water is studied by combined SANS, light scattering, conductivity, and phase diagram approach in the water-poor microemulsion region. The sphere-to-cylinder growth and branching depends on the concentration, the water-to-surfactant ratio, and the temperature. The unidimensional growth leads to a network of interconnected wormlike micelles. Like most studied linear nonionic surfactants, in this true catanionic system at equimolarity of anionic and cationic surfactant, the curvature toward water increases with temperature, making connections between cylinders less frequent.     

Degradation patterns of tetracycline antibiotics in reverse micelles and water

The objective of this study was to determine the chemical stability of tetracycline and oxytetracycline hydro-chlorides in reverse micelles. Their reverse micellar solutions were prepared using cetyltrimethylammonium bromide, water and ethyl formate. The aqueous solutions of the tetracycline antibiotics were also prepared for comparison. The reverse micellar and aqueous solutions were stored at 37 degrees C. Samples were analyzed by high performance liquid chromatography. When evaluation was performed on an aqueous tetracycline HCl solution, its half-life was estimated to be 329 h. Its chemical stability was not improved after being dissolved in the reverse micelles, and a similar half-life of 330 h was observed. However, there were noticeable differences between the two systems in terms of degradation kinetics and degradation byproducts. On the other hand, oxytetracycline HCl was unstable in water so that its half-life was only 34 h. Very interestingly, pronounced improvement in stability was attained with the reverse micellar system: upon dissolving in the reverse micelles, its half-life was increased to 2402 h. There were also marked differences in degradation patterns and mechanisms of oxytetracycline HCl in water and the reverse micelles. Our study indicates that the reverse micellar system has potential applications in solubilizing and stabilizing oxytetracycline HCl, thereby contributing to the development of its dosage forms.     

Volume behavior of mixed micelles of dodecyltrimethylammonium chloride and bromide

Densities of aqueous solutions of mixtures of dodecyltrimethylammonium chloride (DTAC) and dodecyltrimethylammonium bromide (DTAB) have been measured as a function of total molality at constant composition and the apparent molar volumes of the mixtures were derived from the density data. The partial molar volumes of monomeric surfactant mixtures, the molar volumes of mixed micelles, and the volumes of formation of mixed micelles were evaluated and are compared with those for decyltrimethylammonium bromide (DeTAB) and DTAB mixtures. The partial molar volumes of monomeric surfactant mixtures and the molar volumes of mixed micelles are observed to depend linearly on the monomer and micelle compositions, respectively. Although the volume of formation of mixed micelles of the DeTAB-DTAB mixture depends on the micellar composition, that of the DTAC-DTAB mixture is observed to be almost independent of the micellar composition. This suggests that the volumes of the counter ions in the micellar solutions are almost equal to those in the monomeric solutions.     

Molecular simulation study of water mobility in aerosol-OT reverse micelles

In this work, we present results from molecular dynamics simulations on the single-molecule relaxation of water within reverse micelles (RMs) of different sizes formed by the surfactant aerosol-OT (AOT, sodium bis(2-ethylhexyl)sulfosuccinate) in isooctane. Results are presented for RM water content w(0) = [H(2)O]/[AOT] in the range from 2.0 to 7.5. We show that translational diffusion of water within the RM can, to a good approximation, be decoupled from the translation of the RM through the isooctane solvent. Water translational mobility within the RM is restricted by the water pool dimensions, and thus, the water mean-squared displacements (MSDs) level off in time. Comparison with models of diffusion in confined geometries shows that a version of the Gaussian confinement model with a biexponential decay of correlations provides a good fit to the MSDs, while a model of free diffusion within a sphere agrees less well with simulation results. We find that the local diffusivity is considerably reduced in the interfacial region, especially as w(0) decreases. Molecular orientational relaxation is monitored by examining the behavior of OH and dipole vectors. For both vectors, orientational relaxation slows down close to the interface and as w(0) decreases. For the OH vector, reorientation is strongly affected by the presence of charged species at the RM interface and these effects are especially pronounced for water molecules hydrogen-bonded to surfactant sites that serve as hydrogen-bond acceptors. For the dipole vector, orientational relaxation near the interface slows down more than that for the OH vector due mainly to the influence of ion-dipole interactions with the sodium counterions. We investigate water OH and dipole reorientation mechanisms by studying the w(0) and interfacial shell dependence of orientational time correlations for different Legendre polynomial orders.     

Thermal behavior of n-alcohols, benzene, and toluene in water urea and water ethyleneglycol systems

Relations are suggested for calculating the heat characteristics of alcohols, benzene, and toluene in aqueous solutions of urea and ethylene glycol. The solution heat of an alcohol shows greater dependence on the glycol concentration, while the heat capacity of solution, on the urea concentration. For n-butanol in aqueous glycol, the characteristic temperature at which the solution heat of the alcohol is zero decreases as the glycol concentration increases. The dependence of the characteristic temperature of 1-butanol on the urea concentration has a maximum.     

Study of reverse micelles of di-isobutyl-phenoxy-ethoxy-ethyl-dimethyl-benzyl ammonium methacrylate in benzene by nuclear magnetic resonance spectroscopy

(1)H NMR spectroscopy was used to investigate the aggregation of the surfactant di-isobutyl-phenoxy-ethoxy-ethyl-dimethyl-benzyl ammonium methacrylate (Hyamine-M) in benzene. Adding water makes swollen reverse micelles (microemulsion droplets). The droplets also contain cadmium ions and the sodium salt of the methacrylic acid. The critical micelle concentration of Hyamine-M was determined by NMR to be 3.95 mM under the current conditions. Two-dimensional NMR NOESY spectra were used to study the conformation of the surfactant in the micelle and the spatial localization of water and counterions. We found that the surfactant molecules are folded with both phenyl fragments oriented toward the micelle exterior and the oxyethylene and NCH(3) groups in the micelle core. The water molecules and counterions are distributed around the surfactant polar groups in the micelle interior and penetrate up to both aromatic rings. The investigated system can be further utilized as a microemulsion matrix for the synthesis of cadmium-containing semiconductor nanocrystals, eventually capped with a polymer shell, or of polymer nanoparticles.     

Mechanism of YF3 nanoparticle formation in reverse micelles

This article reports an investigation of the mechanism of YF(3) nanoparticle formation in two variants of the reverse microemulsion precipitation method. These two variants involve the addition of F(-), either as a microemulsion or directly as an aqueous solution, to Y(3+) dispersed in nonionic reverse micelles. The two methods yield amorphous and single-crystal nanoparticles, respectively. The kinetics of reagent mixing are studied by (19)F NMR and colorimetric model reactions, and the particle growth is monitored by TEM. Mixing and nucleation are shown to occur within seconds to minutes whereas particle growth continues for 4 to 48 h, depending on the particle type. Moreover, the growth rate remains constant during most of the growth period, indicating that Ostwald ripening is the most probable growth mechanism. The single-emulsion method also produces a minority amorphous population that exhibits significantly different growth kinetics, attributed to a coagulation mechanism. Secondary growth experiments, involving the addition of precursor ions to mature particles, have been conducted to evaluate the relative importance of nucleation and the competitive growth of existing particle populations. The key differences between the two methods reside in the nucleation step. In the case of the classical method, nucleation occurs upon intermicellar collisions and under conditions of comparable concentrations of Y(3+) and F(-). This method generates more numerous stable nuclei and smaller particles. In the single-microemulsion method, nucleation occurs in the presence of excess F(-) through the interaction of Y(3+)-containing micelles with microdroplets of aqueous F(-). These conditions lead to the formation of crystalline particles and a wider size distribution of unstable nuclei.     

Construction,molecular docking,antimicrobial and antioxidant activity of some novel 3-substitued indole derivatives using 3-Acetyl indole

This dissertation presents a method for the synthesis of substituted indoles bearing heterocyclic substituent in the 3- position. The route for the synthesis of the heterocyclic substituents indoles starts from the 3-acetyl indole nucleus. The reaction of 3-acetyl indole 1 with hydrazide compounds such as phenylhydrazine, hydrazine hydrate, and thio-semicarbazide, yields 3-(1-(2-phenylhydrazono) ethyl)-1H-indole 2, 3-(1-hydrazonoethyl)-1H-indole 6, and thiosemicarbazone 10, respectively. Thiophene-2-carboxaldeyde, isatine and 3-acetyl indole reacted with 3-(1-Hydrazonoethyl)-1H-indole 6. In the same way, 3-(1-(2-phenylhydrazono) ethyl)-1H-indole 2 reacted with thioglycollic acid, glycine and benzaldehyde. Thiosemicarbazone 10 reacted smoothly with acetic anhydride, piperidine, concentration of hydrochloric acid and thiophene-2-carboxaldeyde to provide the corresponding heterocycles. The reaction of 3-acetyl indole 1 with amine compounds such as p-nitroaniline formed Schiff base 15, which reacted with thioglycollic acid to give compound 16. 3-Acetyl indole 1 reacted with ethylene diamine to afford bis imine indole 17. The reports of the docking study revealed that the new compounds exhibit good antibacterial activity. The synthesized compounds screened in vitro for their antibacterial activity revealed remarkable inhibitory effects on the selected microorganisms. Besides, the antioxidant activity of some newly designed compounds has been investigated. The structures of the newly synthesized compounds are examined by spectral data (IR, ¹HNMR, ¹³C NMR and mass spectra).     

Percolative phenomena in lecithin reverse micelles: the role of water

 The role played by the solvation water molecules on the macroscopically observed sol–gel transition in lecithin/cyclohexane/water reverse micelles is investigated by quasielastic neutron scattering, dielectric relaxation and conductivity measurements. The experimental results are juxtaposed to those from spherical Aerosol OT reverse micelles. It is shown how the results from lecithin-based system can be interpreted only assuming that, in contrast to Aerosol OT systems, the water molecules are entrapped at the interfaces without coalescing into an inner water pool. It is suggested that, in the case of lecithin, the solvation water can induce a change in the surface curvature, in such a way promoting the formation of branch points. Such a hypothesis is supported by the temperature dependence of the conductivity which agrees with the hypothesis of an intermicellar bond percolation. The investigation of the structures imposed by an external electric field is also studied. The observed electrorheological behaviour seems to confirm the existence of a percolated transient network in the gel phase. Received: 21 March 2001 Accepted: 24 August 2001     

Insertion of isoprene units into indole and 3-substituted indoles in aqueous systems

Indole (1) and 3- methylbut - 2 - enyl bromide (2) were reacted in aqueous solution over a wide range of pH, in absence of Lewis catalysts, leading to 3-(3'-methylbut-2'-enyl) indole (3), 2,3-di-(3'-methylbut-2-enyl) indole (4) and to 2 - (3 - indolyl) - 3,3 - di - (3' - methylbut - 2' - enyl) - 2,3 - dihydroindote (6) in acidic buffer, whereas compound 6 was not formed at basic pH. Both the reactivity and the selectivity of the reaction appear to be influenced by the acidity of the medium. The reaction extended to biologically significant 3-substituted indoles gave a series of new products. 3-Substituted indoles bearing a basic group at their β-position (7, 11, 12 and 13) in acetic buffer (pH = 3) gave mainly cyclization to dihydrofurano or dihydropyrrolo [2.3-b] indoles (15,16, 20, 21 and 23), whereas those with the basic group at the γ-position (9,10) gave the 2 - (3 - methylbut - 2 - enyl) indole derivatives (18,19) only.     

A facile, mild and efficient one-pot synthesis of 2-substituted indole derivatives catalyzed by Pd(PPh3)2Cl2

2-Phenylindoles were prepared by heteroannulation of 2-haloaniline derivatives and phenylacetylene under mild conditions in a one-pot reaction catalyzed by Pd(PPh3)2Cl2.     

Modulation of dynamics and reactivity of water in reverse micelles of mixed surfactants

In this contribution, we attempt to correlate the change in water dynamics in a reverse micellar (RM) core caused by the modification of the interface by mixing an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and a nonionic surfactant, tetraethylene glycol monododecyl ether (Brij-30), at different proportions, and its consequent effect on the reactivity of water, measured by monitoring the solvolysis reaction of benzoyl chloride (BzCl). The dimension of the RM droplets at different mixing ratios of AOT and Brij-30 (X(Brij-30)) has been measured using dynamic light scattering (DLS) technique. The physical properties of the RM water have been determined using Fourier transform infrared spectroscopy (FTIR) and compressibility studies, which show that with increasing X(Brij-30), the water properties tend toward that of bulk-like water. The solvation dynamics, probed by coumarin 500 dye, gets faster with X(Brij-30). The rotational anisotropy studies along with a wobbling-in-cone analysis show that the probe experiences less restriction at higher X(Brij-30). The kinetics of the water-mediated solvolysis also gets faster with X(Brij-30). The increased rate of solvolysis has been correlated with the accelerated solvation dynamics, which is another consequence of surfactant headgroup-water interaction.     

Ultrafast dynamics in reverse micelles,microemulsions, and vesicles

Recently techniques of solvation dynamics have been applied to reverse micelles, microemulsions and vesicular systems. The dynamical data obtained provides a complement to steady-state experiments and builds an understanding of the details of these systems. Recent molecular dynamics simulations show the power of combined experiments and simulations.     

Electrochemical behavior of uranyl in ionic liquid 1-butyl-3-methylimidazolium chloride mixture with water

Electrochemical behaviors of U(VI) in 1-butyl-3-methylimidazolium chloride (C₄MimCl) with various water contents investigated by chronopotentiometry and cyclic voltammetry. The electrochemical reduction of U(VI) was identified to follow two processes: a lower valence intermediate U(V) was initially formed at the potential of ca. ?0.2 V(vs. Ag wire). Then, further deposition of UO₂ was followed at around ?0.8 V. Little amount of water (1–4 wt%) in C₄MimCl, however, has an effect on the U(VI) reduction by changing the current density of the redox reaction and the diffusion coefficient of U(VI) in C₄MimCl. The deposited product by potentiostatic electrolysis on the surface of stainless steel electrode was characterized by the scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) methods. Although the electrodeposited black film was amorphous, the electrochemical reduced product of U(VI) can be still confirmed to be UO₂ by XRD after the crystallization of the amorphous deposits at 1,073 K in nitrogen atmosphere.