The cleavage of heterocyclic compounds in organic synthesis II Use of 5‐nitroisatine for synthesis of various nitrogenous heterocycles

The reactions of 5‐nitroisatine were studied with nucleophiles like heterocyclic amines and alkaline hydroxide. With the use of alkaline hydroxide it was converted into 2‐amino‐5‐nitrophenylglyoxylic acid 2 , with piperidine, morpholine and carbethoxypiperazine to its amides 4a‐4c or by oxidation to 5‐nitroanthranilic acid 7. This acid was used for synthesis of 3‐hydroxy‐6‐nitro‐2‐phenyl‐1H‐quinolin‐4‐one 10. Semicarbazone of 5‐nitroisatine 11 was converted to 5‐(2‐amino‐5‐nitrophenyl)‐2,3,4,5‐tetrahydro‐1,2,4‐triazine‐3,5‐dione 12. Cyclocondensation of this compound to afford 8‐nitro‐2,3‐dihydro‐5H‐[1,2,4]triazino‐[5,6‐b]indol‐3‐one 13 was unsuccessful.     

Volume Chemistry of Nitrogen in Binary Metal Nitrides and Subnitrides

A comparison of the concept of volume increments created by W. Biltz with that based on quantum mechanical calculations by R.F.W. Bader was performed for crystal structures of binary metal nitrides and ‐subnitrides. The mutual comparison of both concepts permits insights into the bonding relationships of these compounds and reveals the considerable range of volume demand of a strongly polarisable bonding partner, such as the nitride ion. Finally it becomes clear that the Biltz volume increments show a quantum‐chemical relevance in the chemistry of solids.     

Air/polymer distribution coefficients for polycyclic aromatic hydrocarbons by solid-phase microextraction sampling

Two methods to estimate distribution coefficients (K) between air and poly(dimethylsiloxane) (PDMS) coating of solid-phase microextraction (SPME) fibers for eight low molecular polycyclic aromatic hydrocarbons (PAHs) there are presented. The PDMS phases were used for determination of the coefficients according to equilibrium theory with help of a developed static calibration system (SCS). Another way to estimate the coefficients is based on the use of a linear relationship between the logarithm of the coefficients (log K) and linear temperature-programmed retention indexes (LTPRI) of the compounds without necessity to calibrate. The log K values for both of methods ranged from 5.2 (naphthalene) to 8.9 (pyrene) at 22 degrees C. Relative standard deviation (R.S.D.) of log K for each compound determined by static calibration was no more than 5.3%. R.S.D. of retention times for LTPRI indices did not exceed 0.28% for repeated injection. All experiments were implemented on a GC-MS system.     

Wetting films of lipids in the development of sensitive interfaces. An electrochemical approach

Solid-supported thin liquid films of lipids, contacting an electrolyte phase, turned out to be a dependable system in the field of bosensors. The investigations of these objects during the past decade reveal some of their intriguing features enabling the application in constructions of receptor part with 'two-dimensional' arrangement. As a model system, complementary to the other artificial analogs of biomembranes, the wetting films of lipids offer certain advantages concerning the compromise between the stability and flexibility of the molecular structures involved in sensing. The basic principles underlaying the techniques of formation, as well as the conditions of the films stability are emphasized in the present consized review. While no limitations are imposed by the way of preparation, the films seem especially profitable in conjunction with methods for electrochemical signal transduction. In this regard some prominent examples are discussed.     

Crystal habit modifications of imatinib mesylate under various precipitation conditions

Abstract  

Crystals of the α-form of imatinib mesylate with various habits (e.g., polyhedral-like and plate-like) were prepared from various organic solvents (e.g., butyl lactate, 4-methyl-2-pentanone, 2-methyl-2-butanol, 2-isopropoxyethanol, propyl ether) by several precipitation methods. The methods provide imatinib mesylate in a non-needle-shaped crystalline α-form. The crystal modification was identified by hot-stage microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The analyses by DSC, IR, and XRPD indicate that imatinib mesylate crystals with various habits have the same crystal structure. The plate-like habit has been also observed in the system where the organic solvent acts as a precipitant.     

Syntheses and PE-Spectroscopic Investigations of 2,6- and 3,5-Bridged 1,4-Dimethylidenecyclohexanes

Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 .     

Magnesium azaphthalocyanines: an emerging family of excellent red-emitting fluorophores

Magnesium(II), zinc(II), and metal-free phthalocyanines (Pcs) and azaphthalocyanines (AzaPcs) containing alkylsulfanyl, aryloxy, and dialkylamino peripheral substituents have been synthesized. The complexation of magnesium(II) by metal-free Pcs and AzaPcs has been studied in detail to determine the optimal reaction conditions necessary to ensure a complete conversion. Photophysical and photochemical measurements in tetrahydrofuran showed that magnesium(II) AzaPcs with aryloxy and alkylsulfanyl substituents have excellent fluorescent properties (Φ(F) up to 0.73) and that the corresponding zinc(II) Pcs are efficient singlet oxygen producers (Φ(Δ) up to 0.68). The presence of dialkylamino substituents causes intramolecular charge transfer within the molecule that competes with fluorescence and singlet oxygen formation. Alkylsulfanyl MgAzaPc and ZnAzaPc were the most photostable compounds among the series of studied derivatives. In addition, high molar absorption coefficients (ε ～ 300,000 M(-1) cm(-1)), absorption (λ(max) ～ 650 nm), and emission (λ(em) ～ 660 nm, high Φ(F)) in the red region suggest that these molecules are potential fluorescent probes that are superior to the commercial red cyanine dye Cy5. MgAzaPc, when incorporated into lipidic bilayers of liposomes, maintains excellent fluorescence properties (Φ(F) = 0.64). Water-soluble MgAzaPc with quaternary ammonium peripheral substituents retained a high fluorescence quantum yield even in water (Φ(F) = 0.25). The described properties show that magnesium(II) AzaPcs are excellent red-emitting fluorophores with potential applications as fluorescent probes in sensing or in vitro imaging applications.     

Benzofurazane as a New Redox Label for Electrochemical Detection of DNA: Towards Multipotential Redox Coding of DNA Bases

Benzofurazane has been attached to nucleosides and dNTPs, either directly or through an acetylene linker, as a new redox label for electrochemical analysis of nucleotide sequences. Primer extension incorporation of the benzofurazane‐modified dNTPs by polymerases has been developed for the construction of labeled oligonucleotide probes. In combination with nitrophenyl and aminophenyl labels, we have successfully developed a three‐potential coding of DNA bases and have explored the relevant electrochemical potentials. The combination of benzofurazane and nitrophenyl reducible labels has proved to be excellent for ratiometric analysis of nucleotide sequences and is suitable for bioanalytical applications.     

The B2–B7 phase transition in symmetrical bent‐shaped mesogens with methoxy substitution

New mesogens composed of achiral bent molecules with thermally stable ester linkages, and laterally substituted by a methoxy group symmetrically near the central benzene ring, were synthesized. Texture, calorimetric, electro‐optical, X‐ray and dielectric measurements were performed. In most of studied compounds the antiferroelectric B₂ phase was found on cooling from the isotropic phase, followed by the B₇ phase at lower temperatures. Undulation of layers in the B₇ phase was confirmed by precise synchrotron studies.