Stereoselective synthesis of all stereoisomers of vicinal and distal bis(O-2-aminoethyl)-p-tert-butylthiacalix[4]arene

O,O″- and O,O′-bis(2-aminoethyl)-p-tert-butylthiacalix[4]arenes of anti conformation have been prepared by the reduction of the corresponding O,O″- and O,O′-bis(cyanomethyl) ethers. Their syn-O,O″- and O,O′-counterparts have been prepared by alternative routes via the Mitsunobu reaction of thiacalix[4]arene with N-(2-hydroxyethyl)phthalimide and the reduction of a O,O′-disiloxanediyl-bridged O″,O?-bis(cyanomethyl) ether of 1,2-alternate conformation, respectively. These products are expected to serve as useful precursors of highly elaborated synthetic receptors, including biscalixarenes.     

Thiocarboxylato Complexes of Biscyclopentadienyl and Bisindenyl Titanium (IV)

Reactions of biscyclopentadienyl (and bisindenyl) titanium (IV) dichlorides with sodium salts of various thiocarboxylic acids in tetrahydrofuran medium, yield the complexes of the general formula (D) ²Ti(SCOR) ² where D is cyclopentadienyl or indenyl group and R? H, CH₃, C₂H₅, C⁴H⁵ or p-C⁴H⁴CH³ group. The foul smelling complexes are monomeric in nature. The IR spectra, thermal stabilities and Some physical characteristics of these complexes have been studied.     

Stereoselective syntheses of 20-epi cholanic acid derivatives from 16-dehydropregnenolone acetate

A stereoselective total synthesis of naturally occurring 20-epi cholanic acid derivatives has been realized, starting from readily available 16-dehydropregnenolone acetate. The key step of these syntheses involves an ionic hydrogenation of a C-20,22-ketene dithioacetal and deoxygenation of steroidal C-20 tert-alcohols, to set up the unnatural C(20R) configuration with 100% stereoselectivity. The unnatural C-22 aldehydes with C(20R) stereocenters thus obtained were elaborated to 20-epi cholanic acid derivatives. Two derivatives of 20-epi cholanic acid were synthesized and their structures have been confirmed by single crystal X-ray analysis. Catalytic hydrogenation of 16-dehydropregnenolone acetate and 16-dehydropregnenolone in ethanol affords C-5,C-16 tetrahydro products. Crystal structure analysis of one of these products revealed C-5α and C-17α configurations of the hydrogen atoms.     

Alkoxide Derived SrBi2Ta2O9 Phase Pure Powder and Thin Films

Phase pure powder and thin films of the novel ferroelectric materials SrBi₂Ta₂O₉ (SBT) have been prepared using the organic precursors. The xero-gel formed was dried and characterized using TGA and DTA to determine the organic burn out and crystallization temperature of SBT. Powder X-ray diffraction was used systematically to check the crystallinity of SBT. Phase pure SBT powder was formed as low as 650°C and thin films at 600°C in comparison to other earlier reported work. SEM micrographs show a grain size of ≈0.1 μm and show crack free films with a film thickness of 2 μm.     

Silicon‐containing trifunctional and tetrafunctional cyanate esters: Synthesis,cure kinetics,and network properties

The synthesis and physical properties of new silicon‐containing polyfunctional cyanate ester monomers methyl[tris(4‐cyanatophenyl)]silane and tetrakis(4‐cyanatophenyl)silane, as well as polycyanurate networks formed from these monomers are reported. The higher crosslinking functionality compared to di(cyanate ester) monomers enables much higher ultimate glass transition temperatures to be obtained as a result of thermal cyclotrimerization. The ability to reach complete conversion is greatly enhanced by cocure of the new monomers with di(cyanate ester) monomers such as 1,1‐bis(4‐cyanatophenyl)ethane. The presence of silicon in these polycyanurate networks imparts improved resistance to rapid oxidation at elevated temperatures, resulting in char yields as high as 70% under nitrogen and 56% in air in the best‐performing networks. The water uptake in the silicon‐containing networks examined is 4–6 wt % after 96 h of immersion at 85 °C, considerably higher than both carbon‐containing and/or di(cyanate ester) analogs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 767–779     

Identification,Isolation, and Characterization of Unknown Degradation Products of Cefprozil Monohydrate by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The present research work was aimed to determine the stability of cefprozil monohydrate (CEFZ) as per various stress degradation...     

Integrating CuO−Fe2O3 Nanocomposites and Supramolecular Assemblies of Phenazine for Visible‐Light Photoredox Catalysis

A photoredox catalytic ensemble consisting of CuO‐Fe₂O₃ nanocomposites and oligomeric derivative of phenazine has been developed. The prepared system acts as an efficient photoredox catalyst for C?N bond formation reaction via SET mechanism under ‘green’ conditions (aerial environment, mixed aqueous media, recyclable), requiring less equivalents of base and amine substrate. The present study demonstrates the significant role of supramolecular assemblies as photooxidants and reductants upon irradiation and their important contribution towards the activation of the metallic centre through energy transfer and electron transfer pathways. The potential of oligomer 4 : CuO‐Fe₂O₃ has also been explored for C?C bond formation reactions via the Sonogashira protocol.     

Visible Colorimetric Sensor for Fluoride Ion Based on o-Phenylenediamine

A new chromogenic receptor based on 1,2-phenylene derivative containing thiourea moieties is synthesized and examined for its anion binding ability by UV–Vis and ¹H NMR studies. The results show that the receptor has selective colorimetric sensing of fluoride over all other anions like chloride, bromide, iodide, nitrate, hydrogen sulphate and acetate.