Kinetics and mechanism of the Pudovik reaction in the azomethine series: III. Acid-catalyzed hydrophosphorylation of imines

A complex spectral (UV, IR, and ³¹P NMR), preparative, and kinetic investigation of the mechanism of the noncatalytic variant of the Pudovik reaction in the series of imines was carried out. The reaction proceeds through a four-center cyclic transition state. The transition state is highly labile, which determines its high sensitivity to the structure of the reagents, the nature of the solvent and catalyst, and some other factors. The necessary condition for the hydrophosphorylation of imines to occur is the participation of proton-donor reagents and acidic admixtures, specifically hydrolysis products of dialkyl hydrogen phosphites, such as monoalkyl dihydrogen phosphates and phosphorous acid, which act as acid catalysts. When the starting reagents are thoroughly purified and no such catalysts are present, the Pudovik reaction fails to occur in the imine series.     

Superacid mediated hydroxyalkylation reaction of 1,2,3‐indanetrione: a theoretical study

Energies of mono‐ and multiprotonation for 1,2,3‐indanetrione and ninhydrin in triflic acid (TFSA) media were estimated at PBE0/aug‐cc‐pvtz//6‐31+G** level of theory. The reactivity of formed intermediates in the reaction of aromatic electrophilic substitution has been studied at the same level of theory. It appears that the basicity of carbonyl groups in 1,2,3‐indanetrione is extremely low due to mutual influences of carbonyl groups. Carbonyl 2 is the least basic but the most reactive in accordance with experiment. Calculations demonstrated that monoprotonated intermediates are the principal reactive species in the reaction of hydroxyalkylation of 1,2,3‐indanetrione in TFSA. A new isomerization mechanism of 2,2‐diaryl‐1,3‐indanediones to 3‐(diarylmethylene)isobenzofuranones in TFSA media has been proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Redox Isomerism in <Emphasis Type="Italic">o</Emphasis>-Semiquinonato Cobalt Complexes in the Crystalline Phase

The key regularities of redox isomerism of six-coordinate bis-semiquinonato cobalt complexes in the crystalline phase are considered. The factors determining the temperature of transition between the redox isomers of various cobalt complexes (mononuclear and binuclear complexes, coordination polymers) were described. The transition parameters were shown to depend not only on the electronic and spatial structure of the ligands in a particular complex, but also on the crystal structure of the complex and intermolecular interactions in the lattice.     

3, 6-Di(tert-butyl)-o-benzoquinone fluoroalkylated derivatives

Russian Chemical Bulletin - A reaction of perfluoroalkyltrimethylsilanes with 3, 6-di(tert-butyl)-o-benzoquinone was used to obtain new perfluoroalkyl-substituted sterically hindered...     

Conductor destruction in electrical explosion

Conductor damage has been examined when the current is switched off at various stages in electrical explosion. If the switching is fairly rapid, kink instability growth is accompanied by formation of vapor bubbles at the kinks within the volume of the liquid metal. Later switching results in vapor bubbles uniformly distributed along the conductor. Cumulative ejection occurs under certain conditions. A qualitative interpretation is given.     

Relation of electron concentration to physical properties of electrodes and discharge parameters for low-voltage condensed discharges

It is found that the electron concentration is dependent on the pressure, the electrical conditions, and the thermophysical properties of the electrode material.     

Synthesis of novel polyaryl(ether–ketones) with tert-butyl pendent groups

Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether–ketones). The current polyaryl(ether–ketones) showed glass transition temperatures in the range 170–240°C and decomposition temperatures, as measured by TGA, of about 500°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1251–1256, 1998     

Superelectrophilic Activation of N‐Substituted Isatins: Implications for Polymer Synthesis,a Theoretical Study

The stability and reactivity of mono‐ and multi‐protonatred N‐substituted isatin derivatives were studied at PBE0/aug‐cc‐pvtz//PBE0/6‐31+G** level of theory in triflic acid (TFSA) solution. Calculations showed that the monocationic intermediates are the principal reactive species in the reaction of hydroxyalkylation of isatin derivatives in TFSA media. Electron‐withdrawing substituents on the nitrogen atom increase the reactivity of isatin‐containing electrophiles towards aromatic hydrocarbons, in accordance with their expected electronic influence. Steric factors also play an important role in the reactivity of isatin‐containing electrophiles, especially in the second reaction step, due to their more sterically hindered reactive center.