Organophosphorus chemistry. Part 21 [1]. Insertion of olefins into P  CF3 bonds

Tris(trifluoromethyl)phosphine and ethylene reacted efficiently under u.v. irradiation to give 3,3,3-trifluoropropylbis(trifuomothyl) phosphine in good yield. With vinyl fluoride, vinylidene fluoride, and propene the reaction was regioselective rather than regiospecific, and the yield of 1:1 adduct was low. In these reactions, and in those with vinyl chloride, but-1-ene, and hexafluoropropene, in which only traces of 1:1-adduct could be detected, the bulk of the olefin and of the phosphine was recovered, and numerous by-products consistent with radical intermediates were identified. With propyne, 1,1,1-trifluoro-3-bis(trifluoromethyl)phosphino-cis-but-2-ene was obtained in moderate yield, but no reaction occurred between the phosphine and either but-2-yne or hexafluorcbut-2-yne. Tris(trifluoromethyl)phosphine oxide did not form an adduct with ethylene, tetrafluoroethylene, or propyne.Bis(trifluoromethyl)phosphine and dimethylphosphine both reacted readily under u.v. irradiation with 3,3,3-trifluoropropene, the phosphinyl radical attacking the terminal carbon in each case.     

Effective sorbents for solid-phase extraction in the analysis of quinolones in animal tissues by capillary electrophoresis

In this work, several commercial sorbents (Zorbax C18, Bond Elut C18, Isolute ENV+, Oasis HLB, Oasis MAX, SDB-RPS, and MPC-SD) were compared for the solid-phase extraction of the series of quinolones regulated by the European Community in chicken tissues in order to establish a method for the determination of this series of quinolones by capillary electrophoresis and diode array detection. Sorbents were chosen in order to achieve maximum recoveries and optimal clean-up efficiency. Better results were obtained using SDB-RPS and Oasis MAX which would provide suitable limits of detection, below of the maximum residue limits (MRLs) regulated.     

Efficient non-gated remote filament-induced breakdown spectroscopy of metallic sample

Remote filament-induced breakdown spectroscopy (R-FIBS) is a novel technique that could be applied at long distance up to a few kilometers. Our work demonstrates that by creating short and strong filaments in the atmosphere with a telescopic beam delivering system, continuum background in R-FIBS spectrum will be significantly reduced. This allows for a non-gated R-FIBS configuration for identifying solid targets. As an example, we used an aluminum plate located 50 m away from our detection system. The obtained fingerprint spectrum is so strong that the detection limit could reach 1.9 km in distance and ppm level in terms of minor element concentration.     

Nickel(II), copper(II) and zinc(II) binding properties and cytotoxicity of tripodal, hexadentate tris(ethylenediamine)--analogue chelators

Three tripodal hexamine chelators based on cis,cis-1,3,5-triaminocyclohexane (tach) have been synthesized and their aqueous coordination chemistry with Ni(II), Cu(II) and Zn(II) is reported. The chelators have a 2-aminoethyl pendant arm attached to each nitrogen of tach, specifically 'tachen'(N,N',N'-tris(2-aminoethyl)cyclohexane-cis,cis-1,3,5-triamine), and two with S,S,S-chiral pendant arms, 'tachpn'(N,N',N'-tris(2-aminopropyl)cyclohexane-cis,cis-1,3,5-triamine) and 'tachbn'(N,N',N'-tris(2-amino-3-phenylpropyl)cyclohexane-cis,cis-1,3,5-triamine. These chelators complex Ni(II), Cu(II) and Zn(II) in aqueous or aqueous/methanolic medium. The crystalline products [M(II)L](X)2 are isolated, where M = Ni(II), Cu(II) or Zn(II), L = tachen, tachpn or tachbn, and X = ClO4-. Crystallographic study of selected tachpn and tachbn complexes shows the chelate arms are constrained in a Lambda(deltadeltadelta) configuration about M(II), which is attributed to their chirality. Solution UV-vis spectroscopy of the Ni(II) and Cu(II) complexes indicates six-coordination and little effect of the pendant arm substitution on ligand-field strength. The single exception is [Cu(tachbn)]2+, whose spectrum is consistent with five-coordination in solution. The cytotoxicities of tachen, tachpn and tachbn toward cultured cancer cells is in the order tachen < tachpn < tachbn < tachpyr, where tachpyr is the aminopyridyl chelator N,N',N'-tris(2-pyridylmethyl)cyclohexane-cis,cis-1,3,5-triamine. The cytotoxicity difference is attributed to an order of increasing lipophilicity, tachen < tachpn < tachbn.     

Synthesis of persialylated beta-cyclodextrins

The synthesis of homogeneous hepta-antennated C-6 branched sialosyl cyclomaltoheptose derivatives (persialylated beta-cyclodextrins) has been performed in good to excellent yields, and the compounds have been fully characterized. The thioacetate N-acetylneuraminic acid derivative 6 was selectively de-S-acetylated and coupled by nucleophilic displacement in a one-pot reaction to the heptakis(chloroacetamido) beta-CDs 2 and 5, yielding multivalent sialosides 8 and 9, respectively. The thiourea-linked sialyl-CD 10 was obtained by reaction of the 4-isothiocyanatophenyl N-acetylneuraminic acid derivative 7 with the per-tert-butoxycarbonylamino beta-CD derivative 2 after suitable deprotection of the amino function.     

A convenient synthesis of 2-nitroindoles

The reaction of 2-iodo- and 2-bromoindoles with silver nitrite in aqueous acetone affords the corresponding 2-nitroindoles in modest to good yields.     

Revision and confirmation of the regiochemistry of isoxazoles derived from methyl oleanonate and lanost-8-en-3-one. Synthesis of a new lanostane triterpenoid with a cyano-enone functionality in ring A

It was previously reported that methyl oleanonate (5) and lanost-8-en-3-one (10) give predominantly [3,2-c]isoxazoles. On the contrary, we have confirmed that both compounds 5 and 10 do not give [3,2-c]isoxazoles but rather afford regioselectively [2,3-d]isoxazoles in good yields. Consequently, a new lanostane triterpenoid with a cyano-enone functionality in ring A was synthesized in two steps from the corresponding [2,3-d]isoxazole, which is interesting from the perspective of biological activity because lanosterol is the biogenetic precursor of steroids.     

Use of oxide minerals to abate fluoride from water

The removal of fluoride from aqueous solutions has been investigated using various oxide ores such as refractory grade bauxite, feed bauxite, manganese ore, and hydrated oxides of manganese ores (WAD). The refractory grade bauxite showed promising results. The studies were carried out as functions of contact time, pH, concentration of adsorbents, concentration of adsorbate, and temperature. The adsorption was rapid during the initial 5 min but equilibrium was attained within 120 min. The adsorption followed first-order kinetics. The present system followed the Langmuir adsorption isotherm model. Various thermodynamic parameters such as free energy, enthalpy, entropy, and equilibrium constants were calculated. The isosteric heat calculations showed that the adsorption process followed a heterogeneous model.