A novel three-component reaction for the synthesis of 3-aryl-4H-benzo [1,4] oxazin-2-amine

A high yielding and fast method for the synthesis of 3-aryl-4H-benzo [1,4] oxazin-2-amine via one-pot, three component reaction of an aromatic aldehyde, isocyanide and o-aminophenol using p-toluene sulfonic acid as a catalyst is described.     

Organic synthesis in water: a green protocol for the synthesis of 2-(cyclohexylamino)-3- aryl- indeno[1,2-b]furan-4-ones

Aldehydes, 1,3-indandione and cyclohexylisocyanide undergo smooth coupling-cyclization in water to produce the corresponding 2-(cyclohexylamino)-3-aryl- indeno [1,2-b] furan-4-ones in good yields. Water was used as a solvent to avoid the use of other highly toxic and environmentally unfavorable solvents for this synthesis.

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Graphical Abstract  A simple and efficient synthesis of 2-(cyclohexylamino)-3-aryl- indeno[1,2-b]furan-4-ones was achieved via a one-pot three-component reaction of cyclohexylisocyanide, aldehydes, and 1,3-indandione in water for 5 h in good yields. zFX

     

Spatially resolved ultrasonic attenuation in resistance spot welds: implications for nondestructive testing

Spatial variation of ultrasonic attenuation and velocity has been measured in plane parallel specimens extracted from resistance spot welds. In a strong weld, attenuation is larger in the nugget than in the parent material, and the region of increased attenuation is surrounded by a ring of decreased attenuation. In the center of a stick weld, attenuation is even larger than in a strong weld, and the low-attenuation ring is absent. These spatial variations are interpreted in terms of differences in grain size and martensite formation. Measured frequency dependences indicate the presence of an additional attenuation mechanism besides grain scattering. The observed attenuations do not vary as commonly presumed with weld quality, suggesting that the common practice of using ultrasonic attenuation to indicate weld quality is not a reliable methodology.     

Mesoporous Molecular Sieve MCM‐41 as a Novel and Efficient Catalyst to Synthesis of 2‐Substituted Benzimidazoles

o‐Phenylenediamine derivatives readily react with benzoyl chloride derivatives in the presence of MCM‐41 as catalyst to yield 2‐substituted benzimidazoles in very good yields.     

Efficient Synthesis of Polyhydroquinolines via the Hantzsch Reaction Using Iron Loaded Mesoporous Materials

A simple and convenient protocol is described for the preparation of polyhydroquinolines via one‐pot, multi component reaction of an aromatic aldehyde, ethylacetoacetate, ammonium acetate and dimedone using iron loaded mesoporous materials as an efficient catalyst in good yields.     

Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples

A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100–200 nm for polyamide nanofibers with a homogeneous and porous surface structure. The extraction efficiency of new coating was investigated for headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography–mass spectrometry (GC–MS) analysis. Effect of different parameters influencing the extraction efficiency including extraction temperature, extraction time, ionic strength and polyamide amount were investigated and optimized. In order to improve the chromatographic behavior of phenolic compounds, all the analytes were derivatized prior to the extraction process using basic acetic anhydride. The detection limits of the method under optimized conditions were in the range of 2–10 ng L⁻¹. The relative standard deviations (RSD) (n = 3) at the concentration level of 1.7–6.7 ng mL⁻¹ were obtained between 1 and 7.4%. The calibration curves of chlorophenols showed linearity in the range of 27–1330 ng L⁻¹ for phenol and monochlorophenols and 7–1000 ng L⁻¹ for dichloro and trichlorophenols. Also, the proposed method was successfully applied to the extraction of phenol and chlorophenols from real water samples and relative recoveries were between 84 and 98% for all the selected analytes except for 2,4,6 tricholophenol which was between 72 and 74%.     

Algorithms for an Integer Multicommodity Network Flow Problem with Node Reliability Considerations

In this paper, we consider the problem of sending a set of multiple commodities from their origin to destination nodes via intermediate hubs. Each hub node is associated with a reliability function, which depends on the total flow that crosses that hub. The probability that each commodity is successfully relayed from its origin to its destination is given by the product of hub reliabilities on the commodity’s path. The problem we consider seeks to find minimum-cost commodity paths such that each commodity reaches its destination with a sufficiently large probability. We first formulate the problem as a nonlinear multicommodity network-flow problem and prove that it is strongly NP-hard. We then present two linearization techniques for this formulation, and propose a pair of lower- and upper-bounding formulations, which can then be used within an exact cutting-plane algorithm to solve the problem. Finally, we analyze the computational effectiveness of our proposed strategies on a set of randomly generated instances.     

Kinetics and mechanism study of aniline addition to ethyl propiolate

The kinetics of the addition reaction of aniline to ethyl propiolate in dimethylsulfoxide (DMSO) as solvent was studied. Initial rate method was used to determine the order of the reaction with respect to the reactants, and pseudo‐first‐order method was used to calculate the rate constant. This reaction was monitored by UV–Vis spectrophotometer at 399 nm by the variable time method. On the basis of the experimental results, the Arrhenius equation for this reaction was obtained as log k = 6.07 ‐ (12.96/2.303 RT). The activation parameters, E_a, ΔH^#, ΔG^#, and ΔS^# at 300 K were 12.96, 13.55, 23.31 kcal mol^?1 and ?32.76 cal mol^?1 K^?1, respectively. The results revealed a first‐order reaction with respect to both aniline and ethyl propiolate. In addition, based on the experimental results and using also density functional theory (DFT) at B3LYP/6‐31G* level, a mechanism for this reaction was proposed. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 144–151, 2006