Phosphorylation of Acetylaminophenols with Secondary Phosphine Chalcogenides: Synthesis of O-(Acetylamino)phenyl Chalcogenophosphinates

Russian Journal of General Chemistry - Oxidative cross-coupling of 4-acetylaminophenol (paracetamol) and its structural isomers (2- and 3-acetylaminophenols) with secondary phosphine chalcogenides...     

Alkylation of 4-methoxyphenol with styrene in the presence of alumoxane compounds

The catalytic properties of alumoxane compounds in the alkylation of 4-methoxyphenol with styrene were studied. Structures and yields of aikylation products depend on the amount of catalyst, the phenol: olefin ratio, and the reaction time. Phenoxyalumoxanes are effectiveortho-directing catalysts with respect to the hydroxy group. Under optimum conditions, 2-(-methylbenzyl)-4-methoxyphenol and 2,5-di-(-methylbenzyl)-4-methoxyphenol were obtained in 94 % and 84–86 % yields, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 992–994, May, 1993.     

Chemoselective cross-coupling of terminal propargylamines with (het)aroyl chlorides: synthesis of β-aminoacetylenic ketones bearing aromatic and heteroaromatic substituents

Russian Chemical Bulletin - Terminal secondary 4-chlorophenyl propargylamines, synthesized by addition of acetylene to N-(4-chlorophenyl)ketimines (ButOK, DMSO, 20–25 °C) in 76–93%...     

Interrelation between the Inhibiting Properties and the Activity of Phenoxy Radicals of Antioxidants Different in Structure

Efficiency of the inhibiting action of phenol-based antioxidants (AO) was studied in initiated oxidation of methyl oleate (MO). The following AO were examined: hydroxybenzene (I), tyrosol (4-2-hydroxyethylphenol) (II), 2-tert-butyltyrosol (III), 2,6-di-tert-butyltyrosol (IV), 4-3-hydroxypropylphenol (V), 2,6-di-tert-butylphenol (VI), dibunol (2,6-di-tert-butyl-4-methylphenol) (VII), and -tocopherol (VIII). The rate constants k ₇ determining the activity of AO in the reaction with peroxide radicals were equal to (0.94, 0.97, 0.93, 0.75, 0.92, 1.30, and 360.00) × 10⁴ M^-1 s^-1 for compounds II, III, IV, V, VI, VII, VIII, respectively. For inhibitors II-VI, VIII, the dependence of the induction period on the AO concentration was of an extreme character, and the most efficient concentrations of AO (C _max) were equal to (0.7, 1.0, 1.6, 1.0, 1.1, and 2.5) × 10^-3 M, respectively. The efficiency of inhibitors (_max and C _max) was demonstrated to rise with increasing extent of shielding of the OH group and shortening of the chain of a substituent in the para position. Using the stationary photolysis method, the rate constants of disproportionation (k ₉) of phenoxy radicals of inhibitors I, III, VII, and VIII were evaluated and equal to (0.52, 2.38, 3.40, and 0.94) × 10³ M^-1 s^-1, respectively, at 20°C. It was shown that the k ₉ value depended on the extent of shielding of phenoxy radicals. The rate constants (k _{10, eff}) were determined for the reaction of phenoxy radicals with lipids with various extents of unsaturation: MO, linoleic and arachidonic acids. The values of k _{10, eff} for the reaction of phenoxy radicals of I, III, VII, and VIII with linoleic acid (20°C) were equal to (0.69, 0.48, 0.09, and 0.49) × 10² M^-1 s^-1, respectively. It was found that in MO oxidation, the k _{10, eff} values decreased in proportion to the number of ortho-tert-butyl substituents in an AO molecule. For the reactions of phenoxy radicals of inhibitor VII with MO, linoleic and arachidonic acids, the values of k _{10, eff} increased with the number of double bonds in a substrate and were equal to (0.09 ± 0.01, 0.09 ± 0.01, and 0.64 ± 0.04) × 10² M^-1 s^-1, respectively. The k _{10, eff} rate constants for the reaction of phenoxy radicals of compound VIII with the same lipids were equal to (0.20 ± 0.04, 0.49 ± 0.01, and 0.74 ± 0.12) × 10² M^-1 s^-1, respectively.     

Surface Tension and Shear Strain Contributions to the Mechanical Behavior of Individual Mg-Ni-Phyllosilicate Nanoscrolls

Some phyllosilicate compounds have the ability of spontaneous scrolling because of the size mismatch between the covalently bounded metal oxide and silica sheets. Their unique structure and high theoretically predicted Young's modulus (around 210–230 GPa) induce phyllosilicates’ application as reinforcing fillers. However, previous nanomechanical experiments with individual phyllosilicate nanoscrolls are in poor agreement with theory. The main reason for this is the low accuracy of experiments, which leads to large measurement errors compared to measured average values. Here, the study of the mechanical properties of synthetic (Mg_1–xNi_x)₃Si₂O₅(OH)₄ phyllosilicates is reported by testing a suspended nanoobject (a nanobridge) with an atomic force microscope (AFM). The Young's modulus of corresponding phyllosilicate model layers is also calculated by means of the density functional theory (DFT). The original AFM approach makes it possible to account for the probe slipping off the nanobridge and determine its boundary conditions. The measured Young's modulus values are considered within the models of surface tension and shear strain contributions. The shear strain appears to have a decisive impact on the measured Young's modulus (from 150 ± 70 GPa to 200 ± 210 GPa) and its spread.     

Cation Redistribution along the Spiral of Ni-Doped Phyllosilicate Nanoscrolls: Energy Modelling and STEM/EDS Study

Here, we study the stress-induced self-organization of Mg²⁺ and Ni²⁺ cations in the crystal structure of multiwalled (Mg_1–x,Ni_x)₃Si₂O₅(OH)₄ phyllosilicate nanoscrolls. The phyllosilicate layer strives to compensate size and surface energy difference between the metal oxide and silica sheets by curling. But as soon as the layer grows, the scrolling mechanism becomes a spent force. An energy model proposes secondary compensation of strain: two cations distribute along the nanoscroll spiral in accordance with preferable radii of curvature. To reveal this, we study synthetic (Mg_1–x,Ni_x)₃Si₂O₅(OH)₄ nanoscrolls by the scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDS) technique. For a number of scrolls, we have found indeed a change of Ni concentration with increase in distance from the nanoscroll central axis. The concentration gradient, according to our estimates, can reach 50 at.% over 25 nm of the wall thickness.     

First Examples of the Atherton–Todd‐Like Reaction in the Absence of Bases

Oxidative cross‐coupling between secondary phosphine chalcogenides and alcohols or phenols proceeds in CCl₄ medium at 80–82°C to afford phosphinoсhalcogenоic O‐esters in up to 92% yield. These couplings represent first examples of the Atherton–Todd‐like reaction occurring in the absence of bases.     

Chemoselective Synthesis of Alkylphosphinic Acids from Red Phosphorus and Alkyl Bromides in the System KOH/H2O/Toluene/Micellar Catalyst

Russian Journal of Organic Chemistry - Alkylphosphinic acids, including long-chain ones, were synthesized in up to 76% yields from red phosphorus and n-AlkBr (Alk = C4–C14) under micellar...