Studies in spiroheterocycles,Part XV. Investigation of the reaction of 3-(2-oxocycloalkylidene)-indol-2-ones with thiourea and urea derivatives

The reaction of 3-(2-oxocycloalkylidene)indol-2-one 1 with thiourea and urea derivatives has been investigated. Reaction of 1 with thiourea and urea in ethanolic potassium hydroxide media leads to the formation of spiro-2-indolinones 2a-f in 40–50% yield and a novel tetracyclic ring system 4,5-cycloalkyl-1,3-diazepino-[4,5-b]indole-2-thione/one 3a-f in 30–35% yield. 3-(2-Oxocyclopentylidene)indol-2-one afforded 5′,6′-cyclopenta-2′-thioxo/ oxospiro[3H-indole-3,4′(3′H)pyrimidin]-2(1H)-ones 2a,b and 3-(2-oxocyclohexylidene)indol-2-one gave 2′,4′a,5′,6′,7′,8′- hexahydro-2′-thioxo/oxospiro[3H-indole-3,4′ (3′H)-quinazolin]-2(1H)-ones 2c-f . Under exactly similar conditions, reaction of 1 with fluorinated phenylthiourea/cyclohexylthiourea/phenylurea gave exclusively spiro products 2g-1 in 60–75% yield. The products have been characterized by elemental analyses, ir pmr. ¹⁹F nmr and mass spectral studies.     

Quantum effects in a homogeneous dust cloud collapse

The status of a classical space-time singularity, when quantum effects are taken into account, has remained a matter of intense interest ever since the epochmaking paper of DeWitt [1] on quantum gravity. We examine here the evolution of quantum fluctuations in the vicinity of the singularity arising out of the classical collapse of a homogeneous dust cloud. As opposed to the pathintegral method used to quantize the conformal degree of freedom (see, e.g., [3] or [4]), we use here the traditional operator approach to the quantum theory which is much more direct and appealing while achieving an additional generalization that the wave function of the system is assumed to have a completely general form. It is shown that the quantum uncertainty diverges in the limit of approach to the classically singular epoch and that nonsingular, nonclassical states can occur with finite probability.     

Ply-by-Ply Failure Analysis of Laminates Under Dynamic Loading

Ply-by-ply failure analysis of symmetric and anti-symmetric laminates under uniform sinusoidal transverse dynamic loading is performed for a specified duration. The study investigates the first ply failure load, followed by the detection of successive ply failures along with their failure modes using various failure theories. Some of the well-established failure theories, mostly used by the researchers, are considered for the failure prediction in laminates. The finite element computational model based on higher order shear deformation displacement field is used for the failure analysis and the complete methodology is computer coded using FORTRAN. The ply-discount stiffness reduction scheme is employed to modify the material properties of the failed lamina. The failure theories used in the analysis are compared according to their ability to predict failure load, failed ply, failure mode and progression of failure. The failure analysis is performed for both the cross-ply and angle-ply laminates with all edges simply supported and clamped. The significance of fibre orientation and stacking sequence in terms of the strength of a laminate and failure progression is also highlighted.     

First direct kinetic measurement of i-C4H5 (CH2CHCCH2) + O2 reaction: Toward quantitative understanding of aromatic ring formation chemistry

The kinetics of the i-C₄H₅ (buta-1,3-dien-2-yl) radical reaction with molecular oxygen has been measured over a wide temperature range (275–852 K) at low pressures (0.8–3 Torr) in direct, time-resolved experiments. The measurements were performed using a laminar flow reactor coupled to photoionization mass spectrometer (PIMS), and laser photolysis of either chloroprene (2-chlorobuta-1,3-diene) or isoprene was used to produce the resonantly stabilized i-C₄H₅ radical. Under the experimental conditions, the measured bimolecular rate coefficient of i-C₄H₅ + O₂ reaction is independent of bath gas density and exhibits weak, negative temperature dependency, and can be described by the expression k₃ = (1.45 ± 0.05) × 10^?12 × (T/298 K)^{?(0.13±0.05)} cm³ s^?1. The measured bimolecular rate coefficient is surprisingly fast for a resonantly stabilized radical. Under combustion conditions, the reactions of i-C₄H₅ radical with ethylene and acetylene are believed to play an important role in forming the first aromatic ring. However, the current measurements show that i-C₄H₅ + O₂ reaction is significantly faster under combustion conditions than previous estimations suggest and, consequently, inhibits the soot forming propensity of i-C₄H₅ radicals. The bimolecular rate coefficient estimates used for the i-C₄H₅ + O₂ reaction in recent combustion simulations show significant variation and are up to two orders of magnitude slower than the current, measured value. All estimates, in contrast to our measurements, predict a positive temperature dependency. The observed products for the i-C₄H₅ + O₂ reaction were formaldehyde and ketene. This is in agreement with the one theoretical study available for i-C₄H₅ + O₂ reaction, which predicts the main bimolecular product channels to be H₂CO + C₂H₃ + CO and H₂CCO + CH₂CHO.     

Base-catalyzed cross coupling of secondary alcohols and aryl-aldehydes with concomitant oxidation of alcohols to ketones: An alternative route for synthesis of the Claisen-Schmidt condensation products

Base-catalyzed C–C cross coupling of secondary alcohols and aryl-aldehydes was achieved, when an alcoholic solution of an aryl-aldehyde was stirred under reflux for 45 h in the presence of a catalytic (20 mol%) amount of K₂CO₃. The consistent formation of α,α′-bis-(benzylidene) alkanones was obtained in moderate to good yields using various secondary alcohols and substituted aryl-aldehydes. Herein, α,α′-bis-(benzylidene)alkanones, which are the classical products of Claisen-Schmidt (cross aldol) condensation, have been synthesized via an alternative strategy using secondary alcohols. Bis-(benzylidene) alkanones are an integral part of various drug regimes and the production of bis-(benzylidene) alkanones without using any precious metal is a major outcome of the present reaction.     

Preparation of electrodeless discharge lamps for emission studies of uranium isotopes at trace level

A simplified method for preparation of electrodeless discharge lamp for uranium isotopes with specific concerns for ²³²U is described. Micro-gram quantities of solid uranium oxides and aqueous solution of uranium nitrate have been used as a starting material for in situ synthesis of uranium tetraiodide. High temperature iodination reaction is carried out in the presence of inert gas neon. By careful design, the preparation time and surface area of quartz reaction tubes have been reduced considerably. The latter decreases the level of contamination which has a direct bearing on the operational lifetime of the lamps. Incorporation of steps to purify the product from an unwanted material improved the stability of the lamps. The procedure provides a safe and convenient way of handling ²³²U in particular but can be extended in general to any actinides having radioactivity similar to that of freshly separated ²³²U. Characteristic emission of uranium isotopes have been recorded by Fourier Transform Spectrometer to show the satisfactory operation of the lamps as well as their usage for studying emission spectra of the specific isotope.     

Towards the catalytic formation of α,β-vinylesters and alkoxy substituted γ-lactones

A facile, one pot, high yield synthesis of α,β-vinylester (1-14) and alkoxy substituted γ-lactones (15-28) has been achieved by the photochemical reaction of terminal acetylene (ferrocenyl phenyl trimethylsillyl, hexyl and cyclohexyl) with alcohol (methanol, ethanol and isopropanol) and carbon monoxide in presence of iron pentacarbonyl as a catalyst. The selectivity of the compounds depends on the time of photolysis of the reaction as well as the solvent used. A stable reaction intermediate ferrole was isolated, and further photolysis with alcohols, resulted in the formation of α,β-vinylester. All the compounds were fully characterised by spectroscopic methods and the molecular structures of compounds 1, 16, 17 and 20 were established crystallographically.     

KHSO4: a highly efficient and reusable heterogeneous catalyst for hydroarylation of styrenes

Abstract  

Hydroarylation of styrenes with arenes/heteroarenes using KHSO₄ (10 mol%) as an efficient heterogeneous catalyst is described. High conversion and selectivity (>99%) were observed for hydroarylation of styrenes with 2-naphthol at reflux temperature of 1,2-dichloroethane. Yields were quantitative with all styrenes. Moderate to good conversions and selectivities were achieved with other aromatics and heteroaromatics under the same conditions. Regeneration and reusability of KHSO₄ were demonstrated. Addition of a trace amount of water could help to reactivate the KHSO₄ through dispersion and to facilitate the hydroarylation reaction.     

Growth and characterization of L‐alanine doped KDP crystals

Potassium Dihydrogen Phosphate (KDP) is an excellent inorganic nonlinear optical (NLO) material with different device applications. Most of amino acids possess NLO property; therefore, it is of interest to dope them in KDP crystals. In the present study, amino acid L‐alanine doped KDP crystals were grown by slow aqueous solvent evaporation technique. The doping of L‐alanine was confirmed by the paper chromatography, the CHN analysis and the FT‐IR spectroscopy. The powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was studied by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. As the amount of doping increased the thermal stability of crystals decreased. However, the second harmonic generation (SHG) efficiency and the UV‐Vis spectroscopy studies indicated that as the L‐alanine doping increased the SHG efficiency and optical transmission percentage increased. The dielectric behavior of the samples has been studied. The variation of dielectric constant, dielectric loss (tanδ), a.c.resistivity and a.c.conductivity with frequency of applied field in the range from 100 Hz to 100 kHz was studied. The dielectric constant and dielectric loss decreased with increase the value of frequency of applied field. The dielectric constant and the dielectric loss values of L‐alanine doped KDP crystals were lower than the pure KDP crystals. The results are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)