Reaction of 5-hydroxyindole derivatives with o-nitrobenzenesulfenyl chloride

In the reaction of o-nitrobenzenesulfenyl chloride with 5-hydroxyindole derivatives, electrophilic substitution occurs in the 3 position. When there is a carbethoxy group in the 3 position, the o-nitrobenzenesulfenyl residue enters the 6 position. The corresponding 5-hydroxy derivatives, the aminomethylation of which leads to 4-dimethylaminomethyl derivatives, were obtained by hydrolysis of the 5-acetoxy derivatives of o-nitrophenyl 3-indolyl sulfides.     

Synthesis of aldehydes and nitriles in the 5-hydroxyindole series

A preparative method for the synthesis of previously inaccessible 3-formyl-5-hydroxyindole derivatives by Vilsmeier formylation of 5-acetoxyindoles is proposed. 5-Hydroxyindole-3-carboxylic acid nitriles and their 4-dimethylamino-methyl derivatives were obtained from 3-formyl-5-hydroxyindoles through their oximes.     

Synthesis of aminoalkyl derivatives of 2-benzyl-5-hydroxyindole

Derivatives of 2-benzyl-5-methoxyindole-3-carboxylic acid are decarboxylated on heating and are converted to the corresponding 2-benzyl-5-methoxyindoles. 2-Benzyl-5-methoxygramine hydrochlorides were obtained from the latter and used to obtain (2-benzyl-5-methoxy-3-indolyl)acetonitriles. The nitriles were converted to 2-benzyl-5-methoxytryptamines by hydrogenation. A number of Mannich bases were obtained by aminomethylation of 2-benzyl-3-carbomethoxy-5-hydroxyindole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 208–212, February, 1971.     

Synthesis of alkylamine derivatives of 1-aryl-5-hydroxyindole

Condensing substituted l-aryl-5-hydroxyindoles with bisdimethylaminomethane, or sodium-alcohol reduction of l-aryl-2-methyl-3-acetyl-5-methoxyindoles gives 4-dimethylaminomethyl and 3-alkylamino derivatives of 1-aryl-5-hydroxy (methoxy) indole, isolated as the hydrochlorides.     

Photophysical properties of 5-hydroxyindole (5HI): Laser flash photolysis study

Steady state fluorescence emission and transient absorption spectra of 9-fluorenone (9FL) were measured in the presence of 5-hydroxyindole (5HI) in highly polar acetonitrile (ACN) environment at ambient temperature. Cyclic voltammetry measurements demonstrate that ground state 5HI as a donor could take part in highly exothermic electron transfer (ET) reactions with excited 9FL, which should serve as electron acceptor. From the transient absorption measurements it is inferred that in geminate ion-pair (GIP) (or contact ion pair), formed initially due to photoinduced ET, the decay of this contact ion-pair occurs not only through ion recombination (back electron transfer to ground state of reactants), but through the other processes also such as proton-transfer (hydrogen abstraction) from radical cation to anion and separation of ion-pair producing the free ions. From the computed reorganisation energy parameter (λ) and experimentally observed -‡ _ET ⁰ values it is hinted that there is a possibility that highly exothermic forward electron transfer reactions in the singlet stateS ₁ occur, within present reacting systems, in Marcus inverted region. Back transfer seems to follow the same path. Investigations with similar other reacting systems are underway.     

Photophysics of melatonin in different environments

Melatonin (N-acetyl-5-methoxytryptamine) is a naturally occurring hormone with a structural resemblance to tryptophan. Its fluorescence is solvent dependent and strongly quenched in the presence of oxygen. Fluorescence quenching in aqueous and organic solutions have been studied in the presence of different quenchers. A 1: 1 inclusion complex formation between melatonin and different cyclodextrins in aqueous solution has been observed. The effects of microheterogeneous media provided by cyclodextrins, micelles and reverse micelles on the fluorescence characteristics of melatonin have been investigated. The water-soluble inorganic quenchers like KBr and KI were unable to quench the fluorescence of melatonin dissolved in a microemulsion consisting of surfactant + cyclohexane + 1-propanol + water, whereas the organic quenchers like CCl4 and CHCl3 were able to quench the fluorescence with a rate constant (on the order of 10(8) dm3 mol-1 s-1) quite similar to that in neat organic solvents.     

The behaviour of micro-bitumen drops in aqueous clay environments

This study summarises the rheological behaviour of emulsion bitumen drops in the presence of aqueous solutions of de-ionised or process water (DIW or PW) containing montmorillonite clays (M) and/or calcium ions (Ca++). The presence of calcium ions and montmorillonite clays resulted in the plastic behaviour of bitumen drops. In a DIW+M+Ca++ system, increasing temperature and calcium ion concentration resulted in an increase in the number and degree of plastic bitumen drops. In the presence of considerable amounts of Ca++ ions and/or at higher experimental temperature, bitumen drops in a PW+M system exhibited no significant overall plasticity of their surfaces. Both calcium and sodium ions contained in process water compete with each other to occupy the montmorillonite clay surface. At the pH value of process water (pH congruent with8), increasing the temperature did not change the value of bitumen droplet zeta potential. Stability of bitumen-in-water emulsions at 22 degrees C showed that bitumen droplets coalesced upon contact in the DIW+M system. The addition of calcium ions (Ca++) led to the inhibition of coagulation and coalescence of bitumen droplets, which may indicate the formation of CaM aggregates at the bitumen-water interface.     

Convenient synthesis of 7-hydroxyindole

7-Hydroxyindole, the key building block for the synthesis of AJ-9677 1, was prepared from indoline in six steps in 36% overall yield. AJ-9677 1 is a potent and selective adrenaline β3-agonist being considered as a clinical candidate to treat obesity in those who are suffering from diabetes.     

Shedding light upon macromolecular behaviour: Luminescence studies of polymers

In this paper the use of two time-resolved luminescence techniques in the study of polymer behaviour is illustrated. Time-resolved anisotropy measurements, TRAMS, have been used to study macromolecular mobilities both in solution and bulk phases. The first use of TRAMS involving phosphorescent labels in the study of synthetic polymers is reported and the potential of the technique for future applications in polymer science is discussed. Time-resolved energy transfer has been used to study polymer compatibility and interdiffusion in blends of PS-PMMA. The data offer clear evidence of the fact that the local concentration of chain termini in phase-separated systems is enriched in the interphase regions compared to that in the two bulk phases of the blend.     

Synthetic route to 4-(2-aminoethyl)-5-hydroxyindole derivatives

In synthetic studies leading to the title compounds, application of the Claisen rearrangement of 5-allyloxyindole was investigated. Almost quantitative yields of Claisen rearrangement product were realized, and a strategy for oxidative cleavage of the allyl double bond to an indole-4-acetaldehyde derivative was developed. A new method for conversion of 2,3-dihydroindoles into indoles was utilized: air oxidation in a strongly basic environment. The Claisen rearrangement of allyloxyindoles is presented as a method having considerable potential utility in synthesis of a variety of polysubstituted indoles.     

Luminescence studies of the conformational behaviour of hydrophobically-modified,water-soluble polymers

A range of hydrophobically-modified water-soluble polymers, based upon acrylic acid and methacrylic acid as hydrophilic components, has been studied using various luminescence techniques. Time-resolved anisotropy measurements, on fluorescently labelled macromolecules, have been used to quantify the extent to which the conformational behaviour of a given polyelectrolyte affects its segmental mobility, and to gauge how such behaviour can be controlled by hydrophobic modification. Room-temperature stabilized phosphorescence from the labels and/or occluded guests and energy transfer experiments have been used to investigate the nature of the hydrophobic domains formed in these polymers. Hydrophobic modification of polyelectrolytes can be used to enhance the scope of water-soluble macromolecules as solubilizing media for photochemical and spectroscopic applications.     

Regioselective Friedel-Crafts acetylation of 5-hydroxyindole derivatives: synthesis of 4H-pyranoindol-4-one derivatives

The Friedel-Crafts acetylation of 5-hydroxyindole derivativesla-c regioselectively produced 6-acetyl-5-hydroxy-indole derivatives2a-c which were condensed with cinnamic acid using POC1₃ and dry pyridine to afford 5-cinnamoyloxy-6-acetyl-indoles3a-c. These upon Baker-Venkataraman transformation furnished 6-cinnamoylacetyl-5-hydroxyindoles4a-c which were cyclised separately with AcOH/HCl and Ac₂O/AcONa to 4H-pyrano-(2,3-f)indol-4-one derivatives5a-c and6a-c respectively.     

Sampling and characterization of nanoaerosols in different environments

Efficient sampling and characterization of nanoparticles have been challenging tasks in environmental research due to the limitations of regular analytical techniques (e.g., dynamic light scattering, and nuclear magnetic resonance and UV-Vis spectroscopies) - especially the difficulties in their application to in situ and real-time monitoring, which are intrinsically related to the nanometer-size range.This critical overview aims at characterizing recent instrumental techniques (e.g., hygroscopic tandem-differential mobility analysis, thermal desorption-gas chromatography-mass spectrometry, and time-of-flight secondary ion mass spectrometry) for sampling and characterization of individual nanoaerosols in terms of their general operation principles, analytical parameters, advantages and limitations. We also discuss classification of this instrumentation based on off-line and/or in situ methods, and on physical and chemical characterization of nanoaerosols. Further, we summarize recent air-quality studies aimed at understanding the physical and chemical behavior of aerosols in different environments.     

Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy

Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright (1)L(a) and (1)L(b) electronic states of (1)ππ? character and spectroscopically dark and dissociative (1)πσ? states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited (1)L(a) state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived (1)L(b) state or the (1)πσ? state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the (1)πσ? state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied.     

A Convenient and Efficient Process to 5-(2-Di-n-Propylaminoethyl)-6-hydroxyindole

An intermolecular trapping of the Pummerer intermediate, generated from 9 with TFAA, by 4 at position 5 under mild Lewis acid conditions gave 5. Sequential treatment of 5 with Ra-Ni, LiAlH₄ and again Ra-Ni, afforded 8 in high overall yield.     

Thermal behaviour of cephalexin in different mixtures

The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate, starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min⁻¹. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min⁻¹. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears. These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates: 5, 7, 10 and 12 °C min⁻¹. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C).     

On the vibronic structure of all-trans-retinal in different environments

The great sensitivity of the electronic structure of a polyene in different environments is visualized through the all-trans-retinal molecule in solvents with different polarity. A vibronic structure in the ¹B_u⁺ ← ¹A_g⁻ transition of all-trans-retinal is detected in the second-derivative spectrum of the ordinary band-shape function. It consists mainly of a 1480 cm⁻¹ progression. Attempts to simulate this are presented. A correlation between the resolution in the vibronic structure and the polarity of the environment of retinal is found. A second excited state of all-trans-retinal may be responsible for the changes in the vibronic structure in the different solvents.     

Compositional changes in lime-based mortars exposed to different environments

Specimens of aerial and hydraulic lime-based mortars to be used in restoration works were prepared, hardened and subjected to different environments to study their compositional changes during setting, hardening and exposure to environment. Outside exposure, weathering cycles in a climatic chamber, SO₂-rich environment and indoor exposure (as control group) were selected to expose the mortars. XRD, FT-IR and TG-DTA analyses were performed at 7, 14, 21 and 28 days to determine the chemical and mineralogical composition, as well as the formation of the degradation products. Outside and SO₂-chamber exposures and increasing the relative humidity allowed faster carbonation (enhancing CO_2(g) dissolution) and hydration of hydraulic compounds. In SO₂-chamber, sulfate attack appears as a surface phenomenon, giving: gypsum in aerial specimens and gypsum and syngenite in hydraulic specimens.