Synthesis of 5,12-diazadibenz[a,h]anthracene

5, 12-Diazadibenz[a,h]anthracene ( 20 ) was synthesized in 21% overall yield for seven steps. Salient features of the synthesis include the initial, one-step conversion of trans, trans-1,4-bis-(β-nitrovinyl)benzene into 2,2″-dinitro-p-terphenyl by Diels-Alder condensation plus elimination, monocyclization of the derived 2,2″-diformylamino-p-terphenyl to give 8-(2-amino-1-phenyl)-phenanthridine ( 10 ) in the presence of fortified polyphosphoric acid, and accomplishment of a second cyclization step only after reduction of the heteroring in 10 (by means of diisobutyl-aluminum hydride) plus formylation. The 6-methyl and 6,13-dimethyl derivatives of 20 were prepared similarly.     

Addition reactions of a phosphorus triamide to nitrosoarenes and acylpyridines

Abstract

Tricoordinate phosphorus compounds react with a wide variety of double bonds through addition reactions. The dipolar and cyclic products formed are important intermediates in organophosphorus chemistry. We investigated the reactivity between phosphorus triamide 1 and nitrosoarenes and 2-acylpyridines. For sterically congested substrates, the formation of σ⁵ Aroyan, C. E.; Dermenci, A.; Miller, S. J. The Rauhut–Currier Reaction: A History and Its Synthetic Application. Tetrahedron 2009, 65, 4069–4084. DOI: 10.1016/j.tet.2009.02.066.[Crossref], [Web of Science ®] , [Google Scholar],λ⁵-phosphorus products is observed. DFT calculations indicate this product is formed through a concerted [4?+?1] mechanism. For less sterically congested substrates, products are observed arising from cleavage of the N?=?O or C?=?O bond with formation of a terminal P?=?O bond and aryl nitrene or carbene migration into a P–N bond of the phosphorus triamide core. DFT calculations are consistent with an initial [2?+?1] addition to phosphorus followed by formal carbene/nitrene migration in these cases.     

Synthesis and psychotropic properties of furyl- and thienyl-germatranes

Trihalogermyl-furans and -thiophenes were prepared by inserting germanium dibromide (GeBr₂) generated from the dibromogermane(II) dioxanate complex into the carbon-halogen bond of halo-furans and -thiophenes. Their ethanolysis and transesterification by triethanolamine yielded the germatranes which were subjected to psychotropic activity assays. The psychotropic properties of germatranes were found to depend on the type of the heterocycle and on the position of the germatrane moiety.     

Changes of the solution pH due to exposure by high-voltage electric pulses

The change of the pH of a NaCl solution (139-149 mM NaCl) buffered with 5-15 mM sodium phosphates (pH 7.4) during electromanipulation was studied. It has been determined that an increase in the pH value of electroporation solution of a whole chamber volume, caused by the application of electric field pulses, commonly used in cell electromanipulation procedures, can exceed 1-2 pH units. Several materials for the cathode were tested. In all cases a stainless steel anode was utilized. The aluminum cathode gave a two-fold greater DeltapH in comparison with platinum, copper or stainless steel cathodes. In addition, a substantial release of aluminum (up to 1 mg/l) from the cathode was observed. It has also been found that the shift in pH depended on the medium conductivity: DeltapH of the solution, in which sucrose was substituted for NaCl, was about 5 times less. On the basis of the results obtained here, to avoid the plausible undesirable consequences of the cathodic electrolysis processes, in particular under the conditions of strong electric treatment, it could be recommended that chambers with aluminum electrodes not be utilized and one should use strongly buffered solutions of low conductivity and alternating current (sine or square wave) bipolar electric pulses.     

Conductivities and silver electrode polarization resistance of solid electrolyte ceramics from ZrO2-Y2O3 powder synthesized in air plasma

Ceramic specimens have been obtained from the powder of ZrO₂-7.5 mol% Y₂O₃ having a specific surface area of 30 m²/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties. The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm³. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the temperature range 200–850 °C in heating and cooling cycles. The intragrain, the grain boundary and the total bulk conductivities, the electrode polarization resistance and their activation energies were determined. The thermal stability of the studied system was proved in three measurement series up to 600–850 °C in heating and cooling cycles. The results obtained have shown that the conductivity of ZrO₂-7.5 mol% Y₂O₃ ceramics is not solely a function of temperature, but also depends on the previous thermal state of the ceramics. Received: 16 October 1997 / Accepted: 19 January 1998     

The Film Formation of Polymer Particles in Drying Thin Films of Aqueous Acrylic Latices

The aim of this study is to determine the factors that contribute to the process of film formation of binder particles in drying aqueous dispersion coatings, based on acrylic polymers. It is known that concentrated latices of uniform size show iridescent, colored light patterns. These colors are caused by interparticle interference, and they are only present when the latex particles are ordered in a regular structure. The interparticle interference can be characterized by measuring the transmission as a function of wavelength of the incident light. It appeared that the changes of the interparticle interference of a drying latex film can be related to changes in the interparticle distance and displacement. It was also found that the interparticle distance becomes "negative" upon coalescence of the latex particles. This means that from this point on, the change in interparticle interference is directly related to the indentation or deformation of the latex particles. It became clear that the coalescence process differs from deformation mechanisms accepted in the literature. It seems that the deformation of the particles follows a biaxial mechanism. This means that the particles deform only in one direction, perpendicular to the film surface. Copyright 2000 Academic Press.     

Chiralization in mesogenic 1,3-diacylaminobenzenes

The effect of molecular chirality in thermotropic mesomorphic H-bonded polymeric systems has not really been investigated so far. Therefore, five new chiral mesogenic diamides have been prepared and described. Besides more ordered mesophases, the enantiomers exhibit a chiral nematic polymorphism detected by microcalorimetry and probably corresponding to different modes of chiral coiling to give these singular twisted nematic phases.     

Reactivity of B‐Xanthyl N‐Heterocyclic Carbene‐Boranes

The synthesis and reactivity of mono‐ and bis‐S‐xanthyl NHC‐boranes is reported. The new NHC‐boranes are prepared through nucleophilic exchange at boron from either mono‐ or bis‐triflyl NHC‐boranes, themselves obtained by protolysis of the NHC‐BH₃ starting compounds. The B?H bond of the S‐xanthyl NHC‐boranes can be cleaved both homolytically and heterolytically, albeit the latter is more synthetically useful. The S‐xanthyl NHC‐boranes can reduce both aldehydes and imines. The B?S bond can also be cleaved homolytically. Under UV irradiation, the S‐xanthyl NHC‐boranes generate NHC‐boryl radicals that can initiate radical polymerizations of acrylates.