Visible light-mediated photocatalyzed synthesis of oxazole via intermolecular C?N and C?O bond formation

An efficient visible light-mediated, eosin Y-catalyzed synthesis of oxazole has been developed from benzil with primary amines, that providing a straightforward, green, and environmentally benign access to a wide variety of substituted oxazole-2-amines under mild reaction conditions.     

Synthesis and characterization of hydroxyapatite-poly-(vinyl alcohol) based nanocomposites for their perspective use as bone substitutes

The present work adds to the continuing efforts of designing a natural bone like structure. In these studies the hydroxyapatite (HA) impregnated polymeric composites of polyacrylamide (PAm) and poly-(vinyl alcohol) (PVA) have been synthesized by free radical polymerization for the purpose of studying their blood compatibility, water sorption behavior mechanical properties, and porosity. The prepared PAm-PVA-HA composites were characterized using techniques like fourier transform spectroscopy, X-ray diffraction studies, thermogravimetric analysis and scanning electron microscopy. The composites were also evaluated for mechanical properties like compressive strength and modulus.     

Growth and thermal kinetics of pure and cadmium doped barium phosphate single crystal

Non-isothermal kinetic parameter of pure and cadmium-doped barium phosphate single crystal grown by room temperature solution technique have been investigated. Single crystal X-ray diffraction establishes grown crystal to be orthorhombic in nature. Scanning electron microscopy supplemented with energy dispersive X-ray analysis was used to study the surface features and to find the exact stoichiometric composition of the grown crystal. Fourier transform infrared spectroscopy studies confirm the presence of various functional groups. The effect of cadmium doping on pure barium phosphate single crystal was studied using thermogravimetry analysis. Thermogravimetry studies shows that the pure crystal was stable up to a temperature of 330 °C whereas doped crystal was stable up to a temperature of 240 °C, i.e., pure crystals were more stable than doped ones. Various solid-state reaction kinetics, i.e., activation energy (E _a), frequency factor (Z), and entropy (ΔS*) was calculated out to find the mechanism of thermal decomposition at different stages for pure and cadmium doped barium phosphate.     

Assessment of natural radioactivity in soil samples and comparison of direct and indirect measurement of environmental air kerma rate

This study presents the high purity germanium (HPGe) gamma spectrometric measurement of natural radioactivity mainly due to ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples collected in Ferozepur and Faridkot district of Punjab, India. ²²⁶Ra activity varied from 28.6 to 51.1 Bq kg⁻¹ with the mean of 39.7 Bq kg⁻¹. The range and mean activity of ²³²Th were 42.9–73.2 and 58.2 Bq kg⁻¹, respectively. ⁴⁰K activity was in the range of 470.9–754.9 Bq kg⁻¹ with the mean of 595.2 Bq kg⁻¹. The air kerma rate (AKR) at 1 m height from the ground was also measured using gamma survey meter in all the sampling locations, which was ranging from 92.1 to 122.8 nGy h⁻¹ with the mean of 110.6 nGy h⁻¹. The radiological parameters such as Ra_eq and activity index of the soil samples were also evaluated, which are the tools to assess the external radiation hazard due to building materials. The mean and range of the Ra_eq values were 168.7 and 132.9–210.4 Bq kg⁻¹, respectively, whereas the activity index varied from 0.5 to 0.8 with the mean value of 0.62. These indices show that the indoor external dose due to natural radioactivity in the soil used for the construction will not exceed the dose criteria. The AKR was also evaluated from soil activity concentration and altitude correction of cosmic radiation contribution. The statistical tests such as Pearson correlation, spearman rank correlation, box and whisker plot, the Wilcoxon/Mann–Whitney test and chi-square test, were used to compare the measured AKR with evaluated AKR, which indicates good correlation.     

Ring-closing metathesis of sulfoximine-substituted N-tethered trienes: modular asymmetric synthesis of medium-ring nitrogen heterocycles

A synthesis of sulfoximine-substituted medium-ring nitrogen heterocycles (MRNHs) having a high degree of substitution has been developed. Its key steps are the modular asymmetric synthesis of sulfoximine-substituted N-tethered trienes and their Ru-catalyzed ring-closing metathesis (RCM) reaction. The highly substituted N-tethered trienes were obtained enantio- and diastereopure through 1) the diastereoselective aminoalkylation of sulfoximine-substituted allyltitanium complexes with N-tert-butylsulfonyliminoester, 2) N-allylation of homoallylic N-sulfonyl amines, 3) allylation, hydroxylalkylation, and formylation of α-lithioalkenylsulfoximines, and 4) allylation of α-formylalkenylsulfoximines. The Ru-catalyzed RCM reaction of the sulfoximine-substituted 1,7,10- and 1,7,12-trienes stereoselectively afforded the corresponding nine-, ten-, and eleven-membered MRNHs in good yields. An interesting difference in reactivity was noted in the case of a sulfoximine-substituted 1,7,10-triene and its corresponding 1,10-diene. While the triene readily underwent a RCM reaction, the diene reacted only in the presence of Ti(OiPr)(4) under formation of the corresponding MRNH. The feasibility of a removal of the sulfoximine auxiliary and the N-sulfonyl protecting group from the MRNHs were demonstrated through reduction and cleavage, respectively, of a nine-membered heterocycle, both of which proceeded readily and gave the corresponding cyclic alkene and amine, respectively.     

Phosphane-free green protocol for selective nitro reduction with an iron-based catalyst

Iron phthalocyanine with iron sulfate has been successfully applied for high chemo- and regioselective reduction of aromatic nitro compounds to give the corresponding amines in a green solvent system without using any toxic ligand. The catalytic systems were also compatible with a large range of other reducible functional groups, such as keto, acid, amide, ester, halogen, lactone, nitrile, N-benzyl, O-benzyl, hydroxy, and heterocycles. In the present study, dinitro compounds have been regioselectively reduced to the corresponding amines with high yield. In most of the cases the conversion and selectivity was greater than 99% as determined by GC-MS analysis.     

Dating of hot springs at Attri,Tarabalo and Athmalik sites in Odisha,India using radiocarbon technique

Journal of Radioanalytical and Nuclear Chemistry - In this study environmental radioisotopes of water (3H and 14C) were used to determine the residence time of thermal waters. The temperature of...