Free radical-mediated aryl amination and its use in a convergent [3 + 2] strategy for enantioselective indoline alpha-amino acid synthesis

The scope of aryl radical additions to the nitrogen of azomethines is described. Aryl, trifluoromethyl alkyl, and alpha,beta-unsaturated ketimines engage in regioselective aryl-nitrogen bond formation via 5-exo cyclizations of an aryl radical to azomethine nitrogen. Selectivity for carbon-nitrogen over carbon-carbon bond formation is generally high (>95:5) and competes only with direct aryl radical reduction by stannane (0-10%). Alpha-ketoimines are a promising new class of carbon radical acceptors for which no competitive aryl radical reduction is observed. The reaction conditions are pH-neutral and are therefore among the mildest methods available for amination of an aromatic ring. The ketimines examined did not suffer from competitive reduction by stannane, offering an advantage over the use of diazo and azide functional groups as nitrogen sources for carbon radicals. The free radical-mediated aryl amination was sequenced with the O'Donnell phase transfer-catalyzed enantioselective alkylation strategy of glycinyl imine to provide either enantiomer of indoline alpha-amino acids with high ee. These new constrained phenyl alanine derivatives are now readily available for evaluation across a variety of applications.     

Spectrophotometric determination of the oxygen to uranium ratio in uranium oxides based on dissolution in sulphuric acid

The oxygen to uranium ratio in uranium oxides such as U(3)O(8), UO(2+x) powders and UO(2) fuel pellets has been determined by a new spectrophotometric method. The method can be used for determination of O/U ratio in UO(2) pellets and powders on a routine basis. In the described method, uranium oxides in the powder form are dissolved in 2M sulphuric acid containing a few drops of HF. The concentrations of U(IV) and U(VI) are directly determined by means of the absorbances of these species at different wavelengths. For determination of the O/U ratio in U(3)O(8) powder samples, 630 and 310 nm are the wavelengths chosen for U(IV) and U(VI), respectively. For UO(2+x) powder, where the O/U ratio lies between 2.04 to 2.15, U(IV) and U(VI) are determined at 630 and 300 nm respectively, whereas for UO(2) fuel pellets, where the O/U ratio is less than 2.01, 535 and 285 nm are used. The molar absorptivity of U(IV) at 630 and 535 nm is 21.4 and 6.8 l.mole(-1).cm(-1) and that of U(VI) at 310, 300 and 285 nm is 178.1, 278.6 and 585 l.mole(-1).cm(-1), respectively. Standard deviations of +/-0.002 O/U ratio units for pellets and +/-0.004 O/U ratio units for powders have been achieved.     

Thermal,spectroscopic and XRD studies on nitroaminoguanidine (NAG)

Nitroaminoguanidine (NAG) has been investigated as regards its thermal decomposition characteristics using simultaneous thermal analysis, infrared spectroscopy, X-ray diffraction and polarising microscopy. XRD studies show thatNAG crystal belongs to the tetragonal system. The crystal structure parameters are found to be:a=17.063±0.005Å,b=17.063±0.005Å,c=5.155±0.005Å andc/a axial ratio=0.302. Under non-isothermal conditions,NAG decomposed apparently in one stage with a loss in weight of 80%. But the thermal decomposition ofNAG in the solid phase under isothermal conditions proceeded through three stages. Both the first and the second stages obeyed theA-E (Avrami Erofee'v) equation forn=1. The 3rd stage is too slow and kinetics has not been attempted. The rate parameters for the first and second stages have been evaluated. Gaseous decomposition products detected using the IR gas cell are NH₃, NO₂, HCN, N₂O, CO and CO₂. High temperature IR studies indicate preferential deamination reaction initially indicating breaking of N?NH₂ and C?NH₂ bonds leading to NH₂ radical formation. Addition of diphenylamine, a known chain inhibitor, decelerated the thermal decomposition, supporting a radical chain reaction.     

Selective extraction of U(VI), Th(IV), and La(III) from acidic matrix solutions and environmental samples using chemically modified Amberlite XAD-16 resin

A new grafted polymer has been developed by the chemical modification of Amberlite XAD-16 (AXAD-16) polymeric matrix with [(2-dihydroxyarsinoylphenylamino)methyl]phosphonic acid (AXAD-16-AsP). The modified polymer was characterized by a combination of ¹³C CPMAS and ³¹P solid-state NMR, Fourier transform-NIR-FIR-Raman spectroscopy, CHNPS elemental analysis, and thermogravimetric analysis (TGA). The distribution studies for the extraction of U(VI), Th(IV), and La(III) from acidic solutions were performed using an AXAD-16-AsP-packed chromatographic column. The influences of various physiochemical parameters on analyte recovery were optimized by both static and dynamic methods. Accordingly, even under high acidities (>4 M), good distribution ratio (D) values (10²–10⁴) were achieved for all the analytes. Metal ion desorption was effective using 1 mol L^–1 (NH₄)₂CO₃. From kinetic studies, a time duration of <15 min was sufficient for complete metal ion saturation of the resin phase. The maximum metal sorption capacities were found to be 0.25, 0.13, and 1.49 mmol g^–1 for U(VI); 0.47, 0.39, and 1.40 mmol g^–1 for Th(IV); and 1.44, 1.48, and 1.12 mmol g^–1 for La(III), in the presence of 2 mol L^–1 HNO₃, 2 mol L^–1 HCl, and under pH conditions, respectively. The analyte selectivity of the grafted polymer was tested in terms of interfering species tolerance studies. The system showed an enrichment factor of 365, 300, and 270 for U(VI), Th(IV), and La(III), and the limit of analyte detection was in the range of 18–23 ng mL^–1. The practical applicability of the polymer was tested with synthetic nuclear spent fuel and seawater mixtures, natural water, and geological samples. The RSD of the total analytical procedure was within 4.9%, thus confirming the reliability of the developed method.     

A new chelating sorbent for metal ion extraction under high saline conditions

A new chelating polymeric sorbent was developed by functionalizing Amberlite XAD-16 with 1,3-dimethyl-3-aminopropan-1-ol via a simple condensation mechanism. The newly developed chelating matrix offered a high resin capacity and faster sorption kinetics for the metal ions such as Mn(II), Pb(II), Ni(II), Co(II), Cu(II), Cd(II) and Zn(II). Various physio-chemical parameters like pH-effect, kinetics, eluant volume and flow rate, sample breakthrough volume, matrix interference effect on the metal ion sorption have been studied. The optimum pH range for the sorption of the above mentioned metal ions were 6.0–7.5, 6.0–7.0, 8.0–8.5, 7.0–7.5, 6.5–7.5, 7.5–8.5 and 6.5–7.0, respectively. The resin capacities for Mn(II), Pb(II), Ni(II), Co(II), Cu(II), Cd(II) and Zn(II) were found to be 0.62, 0.23, 0.55, 0.27, 0.46, 0.21 and 0.25 mmol g⁻¹ of the resin, respectively. The lower limit of detection was 10 ng ml⁻¹ for Cd(II), 40 ng ml⁻¹ for Mn(II) and Zn(II), 32 ng ml⁻¹ for Ni(II), 25 ng ml⁻¹ for Cu(II) and Co(II) and 20 ng ml⁻¹ for Pb(II). A high preconcentration value of 300 in the case of Mn(II), Co(II), Ni(II), Cu(II),Cd(II) and a value of 500 and 250 for Pb(II) and Zn(II), respectively, were achieved. A recovery of >98% was obtained for all the metal ions with 4 M HCl as eluting agent except in the case of Cu(II) where in 6 M HCl was necessary. The chelating polymer showed low sorption behavior to alkali and alkaline earth metals and also to various inorganic anionic species present in saline matrix. The method was applied for metal ion determination from water samples like seawater, well water and tap water and also from green leafy vegetable, from certified multivitamin tablets and steel samples.     

Rotational dynamics of UVITEX-OB in alkanes, alcohols and binary mixtures

Steady-state and time resolved fluorescence anisotropy measurements were carried out to study the rotational diffusion dynamics of UVITEX-OB (U-OB) in series of alcohols, alkanes and binary mixtures of toluene and butanol at room temperature. The experimentally measured rotational reorientation times were compared with those estimated by the hydrodynamic and molecular models developed for microscopic friction. The experimental results are in good agreement with theoretical slip hydrodynamics and a deviation towards subslip behavior is noted. Also a faster rotation of the probe in binary mixture of toluene and butanol is noted as compared to that in alcohols and alkanes.     

Solution properties of polyurethane

Polyurethane was fractionated and the fractions were characterized by gel permeation chromatography (GPC) and viscometry. The intrinsic viscosities of polyurethane in ten solvents varying in their polarity were determined and are in the order of mineral spirit < acetone < cyclohexane < cyclohexanone < xylene < ethyl benzene < toluene < benzene < methyl ethyl ketone < tetrahydrofuran. The Mark-Houwink relations suggested that solvent blend MEK: n-heptane (1:3) is a poor solvent with an a value of 0·52 and tetrahydrofuran is a good solvent with an a value of 0·78. The weight average molecular weight has been estimated by an extrapolation technique based on a linear relationship between the viscosity average molecular weight _v and the Mark-Houwink constant. The weight average molecular weights obtained from viscosity studies were used to evaluate the unpertureb dimension of the chain.     

On the homology of lattice vibrations of alkali metals

Investigations of the dependence of lattice vibrations of alkali metals on their interatomic distance,r reveal that they satisfy an empirical relation,Mv ² r =(q), a constant which depends on, with q=2·48 ± 0·19 at all wave vectors and hence are homologous. It is shown that the observed crossover of [00] branches of lithium is not an anomalous property, but only manifests itself in alkali metals with smaller interatomic distance due to small variations of . The role played by interatomic distance which is closely related to that of the electron gas constantC in producing a crossover and a possible reason for the observed homology are discussed.The authors are grateful to Professor B. Sharan and Mr. S. B. Rajendraprasad for many valuable and stimulating discussions. One of the authors (M. S.) is greatly indebted to Professor D. M. Sen, principal, and Professor L. V. Sud of Regional Engineering College, Kurukshetra, for granting him study leave.     

Synthesis,spectral, structural characterization and biological activity of new palladium(II) complexes containing 3‐acetyl‐8‐methoxy‐2H‐chromen‐2‐one derived Schiff bases

Four different mononuclear palladium(II) complexes of 3‐acetyl‐8‐methoxycoumarin Schiff bases were synthesized and characterized by spectrochemical techniques. Further analysis through X‐ray crystallography confirmed the structures of the complexes. Their interactive ability with Calf Thymus DNA and protein (Bovine Serum Albumin and Human Serum Albumin) were investigated by means of absorption and emission methods. The intercalative mode of binding with DNA was supported by EB displacement studies and viscosity measurements. Configurational changes that occurred in the proteins have been analysed with the help of 3D fluorescence studies. The complexes were shown to have good antimicrobial activity against the tested bacterial and fungal pathogens. In addition, antiproliferative activity of the complexes was evaluated on A549 and MCF‐7 cell lines and the complexes were comparatively more active than the standard drug cisplatin. Among the compounds, complex 3 was the most effective against MCF‐7 (IC₅₀ value of 5.20 ± 0.15 μM) and A549 (5.09 ± 0.13 μM) compared with the other complexes 1 (6.48 ± 0.17 μM; 5.98 ± 0.09 μM), 2 (5.53 ± 0.12 μM; 5.85 ± 0.11 μM), 4 (6.73 ± 0.19 μM; 6.63 ± 0.16 μM) and cisplatin (16.79 ± 0.08 μM; 15.10 ± 0.05 μM) respectively. LDH and NO release assays confirmed the cytotoxic potential of the synthesized complexes.     

Synthesis,spectral, electrochemical and catalytic studies of new Ru(III) tetradentate Schiff base complexes

The synthesis and characterization of several hexa‐coordinated ruthenium(III) Schiff base complexes of the type [RuX(EPh₃)(L)] (X = Cl or Br; E = P or As; L = dianion of the tetradentate Schiff base) are reported. IR, EPR, electronic spectra and cyclic voltammetric data of the complexes are discussed. An octahedral geometry has been tentatively proposed for all of these complexes. The new complexes have been subjected to catalytic activity in the reaction of oxidation of alcohols in the presence of N‐methylmorpholine‐N‐oxide. Copyright © 2007 John Wiley & Sons, Ltd.