The first palladium-catalyzed protocol for the denitrated coupling reaction of nitroarenes with phenols has been developed, achieving unsymmetrical diaryl ethers in moderate to excellent yields. The cyclopalladated ferrocenylimine (catalyst Ic) exhibited highly catalytic activity for this transformation with low catalyst loading (0.75 mol%) and short reaction time (2 h). The efficiency of this reaction was demonstrated by its compatibility with a range of groups. Moreover, the rigorous exclusion of air or moisture was not required in these transformations.
A new stationary phase for high-performance liquid chromatography was prepared by covalently bonding N-ferrocenyl(benzoyl)amino-acid esters (L(1)) onto silica gel using 3-aminopropyltriethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic behavior of the phase was illustrated in reversed-phase (RP) and normal-phase (NP) modes using polycyclic aromatic hydrocarbons (PAHs), aromatics positional isomers, amines, 5-nitroimidazoles, organophosphorus pesticides and phenols as probes. Multiple mechanisms including hydrophobic, hydrogen bonding, π-π, dipole-dipole, charge-transfer and acid-base equilibrium interactions are involved. Thus, multi-interaction mechanisms and mixed-mode separation of the new phase can very likely guarantee its excellent chromatographic performance for the analysis of complex samples. The L(1) AminoSil column was successfully employed for the analysis of organophosphorus pesticides in vegetable.
Based on the unique molecular structure of ferrocene and its potential as a new liquid chromatography separation medium, a new silica-bonded (4-cyclopentadienyl benzoic acid-iron-toluene) hexafluorophosphoric acid stationary phase was prepared. The structure of this new material was characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis et al. The chromatographic performance and retention mechanism of this new stationary phase were evaluated using different solute probes, including polycyclic aromatic hydrocarbons (PAHs), positional isomers of naphthylamine, positional isomers of nitro-aniline, nitroimidazoles, organic phosphorus et al. It could provide various action sites for different solutes in normal-phase chromatography such as π electron transfer, π-π electron interactions, dipole-dipole interactions, and electrostatic interactions with the substrates. And the possible separation mechanisms are discussed.
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