Cesium fluoride and tetra-n-butylammonium fluoride mediated 1,4-N-->O shift of disubstituted phenyl ring of a bicalutamide derivative

A novel 1,4-N→O migration of a disubstituted phenyl ring was observed during N-methylation of a bicalutamide derivative, (2S)-2-(tert-butyldimethylsilanyloxy)-N-(4-cyano-3-trifluoromethylphenyl)-3-(4-fluorophenoxy)-2-methylpropionamide, in the presence of CsF-Celite/acetonitrile and desilylation of (2S)-2-(tert-butyldimethylsilanyloxy)-N-(4-cyano-3-trifluoromethylphenyl)-3-(4-fluorophenoxy)-2,N-dimethylpropionamide in tetra-n-butylammonium fluoride/THF. Both NMR and X-ray analysis confirmed the structure of the 1,4-N→O disubstituted phenyl ring migrated product.     

Chickpea leaf exudates (CLE) mediated Knoevenagel–Michael reactions for the synthesis of diketodiols and biscoumarins

A green, highly efficient, and eco-friendly protocol for Knoevenagel–Michael addition reaction is reported in Chickpea leaf exudates (CLE) as a naturally sourced biosurfactant. The reactions between dimedone/4-hydroxycoumarins and a variety of aryl aldehydes were carried out in presence of CLE to afford diketodiols/biscoumarins. The synthetic pathway complies with several key requirements of green chemistry principles such as the employment of natural feedstock as green reaction media, ambient temperature, atom economy along with natural biosurfactant type Bronsted acids, and recyclable and biodegradable catalyst which led to a 28-fold increase in molar efficiency versus industrial standard protocols. Its dynamic phase is confirmed by the optical microscopy technique and critical micelle concentration measurement. The notable advantages of the present protocol were simple work-up procedure, high yield within short reaction time, easy separation of products, avoiding tedious column chromatography thus making the protocol environmentally friendly, sustainable, and economical.

Graphical abstract

     

Equilibrium Constant Studies for Complexation between Ammonium Ions and 18-Crown-6 in Aqueous Solutions at 298.15 K

Osmotic vapor pressure and density measurements have been carried out for binary aqueous and ternary aqueous solutions containing a fixed concentration of 18-crown-6 (0.2 mol⋅kg⁻¹) and ammonium chloride or ammonium bromide at 298.15 K. The concentration of the ammonium salts was varied between 0.02 to 0.5 mol⋅kg⁻¹. The measured water activities were used to obtain the activity coefficient of water and the mean molal activity coefficient of the ions in binary as well as ternary solutions. Using the method developed by Patil and Dagade reported earlier in this journal and the McMillan-Meyer pair and triplet Gibbs energy interaction parameters, the thermodynamic equilibrium constant (K) for the 18-crown-6:NH₄ ⁺ complexes were determined. It is observed that the nature and polarizability of anions play important roles in imparting stability to the complexed species. The log₁₀ K values for the 18-crown-6:NH₄ ⁺ complexed species are lower than for the complexes involving alkali metal ions such as K⁺. The volume of complexation for the studied systems obtained from the apparent molar volumes of ammonium halides in ternary solutions are positive and of smaller magnitude than those reported for complexation with alkali ions. The results are further discussed in terms of water structural effects, complex formation, the role of counter anions and hydrophobic interactions.     

Determination of neptunium using controlled potential coulometry

A method for controlled potential coulometric determination of neptunium by titration with internally electrolytically generated iron(II) has been developed. The method involves oxidation of Np to Np(VI) by Ce(IV), destruction of excess of Ce(IV) by NaNO₂ followed by determination of neptunium by reduction of Np(VI) to Np(IV) by internal generation of Fe(II). The method was employed for various neptunium solution samples and a precision of ±0.25% at 2–5 mg level of neptunium was obtained.     

Catalytic decomposition of hydrogen peroxide on fine particle ferrites and cobaltites

The kinetics of heterogeneous decomposition of hydrogen peroxide on fine particle ferrites, MFe₂O₄ and cobaltites, MCo₂O₄, where M=Mn, Fe, Co, Ni, Zn and Mg, have been investigated. The decomposition of H₂O₂ was found to be first order at low concentration (0·3%) and zero order at high concentration (30%) of H₂O₂. The catalytic activity of cobaltites on the decomposition of H₂O₂ is found to be better than ferrites. The observed catalytic behaviour of ferrites and cobaltites has been attributed to their fine particle nature, large surface area and electronic structure.     

Spectrophotometric studies on the formation of adducts involved in synergistic extraction of uranium(IV) by mixtures of HTTA and neutral donors

Formation of adducts between U(TTA)₄ and several neutral donors was studied by spectrophotometry and it was shown that each of the neutral donors forms only 1∶1 adduct with U(TTA)₄. The adduct formation constants with some neutral donors were determined for benzene and chloroform media. As these adducts are involved in the synergistic extraction of U(IV) from aqueous media by mixtures of HTTA and neutral donors dissolved in organic solvents, the extraction equilibrium constants were estimated, The adduct formation was found to result in an increase of the co-ordination number of U(IV) from 8 in U(TTA)₄ to 9 in the adducts it forms with the neutral donors. Similar absorption spectral studies with U(DBM)₄ revealed that it forms much weaker adducts than the corresponding ones with U(TTA)₄.     

Concise and practical synthesis of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6-iminosugars

The syntheses of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6 iminosugars 1a and 1b, respectively, from d-glucose are described. The key transformations in this reaction sequence include regio-selective epoxide ring opening with N-benzylamine followed by intramolecular reductive amination of amino-aldehyde.     

Synthesis, characterisation and biological evaluation of lanthanide(III) complexes with 3-acetylcoumarin-o-aminobenzoylhydrazone (ACAB)

Lanthanide(III) complexes of the general formula [Ln(ACAB)(2)(NO(3))(2)(H(2)O)(2)].NO(3).H(2)O where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III), ACAB=3-acetylcoumarin-o-aminobenzoylhydrazone have been isolated and characterised based on elemental analyses, molar conductance, IR, (1)H- and (13)C-NMR, UV, TG/DTA and EPR spectral studies. The ligand behaves in bidentate fashion coordinating through hydrazide >C=O and nitrogen of >C=N. A coordination number of ten is assigned to the complexes. Antibacterial and Antifungal studies indicate an enhancement of activity of the ligand on complexation.     

Some studies on synergic extraction of mixed ligand species of uranium(VI)

The extraction of U(VI) by mixtures of HTTA and TBP from aqueous thiocyanate medium has been studied. From the data obtained it was observed that the predominant uranium species extracted, causing synergic enhancement in the extraction of U(VI), is UO₂(SCN)TTA · 2TBP when benzene and cyclohexane are used as diluents, and that at a very low concentration of TBP the contribution of additional species, viz. UO₂(TTA)₂ · TBP becomes significant. With chloroform as diluent, however, both of these species are contributing to the synergic enhancement. The extraction of a quaternary uranium species, UO₂(SCN)TTA · 2TBP, involving the participation of the aqueous anion is thus established. Equilibrium constants for the various extraction equilibria involved are calculated.     

Encapsulation of uncharged water-insoluble organic substance in polymeric membrane capsules via layer-by-layer approach

We report a general and versatile method for the encapsulation of electrically uncharged organic substance in polymeric capsules by using a layer-by-layer (LbL) approach. Electrical charge was induced on the surface of pyrene (uncharged organic substance) with an amphiphilic surfactant (sodium dodecyl sulfate, SDS) by micellar solubilization. The SDS micellar solution of pyrene in water was then deposited on a flat substrate as well as colloidal particles with chitosan as an oppositely charged polyelectrolyte. Pyrene was used as a model drug because it displayed intrinsic fluorescence that allowed us to monitor LbL growth by fluorescence and under confocal laser scanning microscopy (CLSM). To examine the proof of concept, multilayers were coated on the planar support by the LbL method. UV-vis spectroscopy showed regular growth of each layer deposited. Thin film formation was evidenced by scanning electron microscopy. The LbL method was extended to particles where fluorescence spectroscopy revealed LbL growth and transmission electron microscopy (TEM) provided evidence of particle coating. The quantification of dye in each deposited layer further proved LbL growth. The removal of sacrificial core provided thin capsules. The capsules were characterized by TEM and CLSM. The capsules showed potential as a drug delivery system, which is suggested by the slow release of entrapped dye by concentration-dependent diffusion in isotonic saline solution. The kinetics of desorption of pyrene from this thin film was modeled by a pseudo-second-order model.