Metal Ion Guest Responsive Benzoxazine Dimers and Inclusion Phenomena of Cyclic Derivatives

This study was carried out with the aim to optimize the dissolution propertiesof diclofenac (DIC) – a non-steroidal anti-inflammatory drug sparingly solublein water – through association -with gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (gif" alt="beta" align="MIDDLE" BORDER="0">CD). Theeffect of gif" alt="beta" align="MIDDLE" BORDER="0">CD on the aqueous solubility of DIC was evaluated by thephase solubility method. The amount of DIC dissolved increased linearly withthe addition of gif" alt="beta" align="MIDDLE" BORDER="0">CD according to an AL type plot and without precipitationof the complex. The apparent stability constant of the complex, calculated supposinga 1:1 stoichiometry, was 295 M^-1; this value was confirmed by circulardichroism analysis. DIC/gif" alt="beta" align="MIDDLE" BORDER="0">CD interactions were also studied in water by¹H and ¹³C NMR spectroscopy. Equimolar DIC/gif" alt="beta" align="MIDDLE" BORDER="0">CD solid systems were prepared by physical-mixing, kneading, co-evaporation andfreeze-drying, and their properties in the solid state studied by DifferentialScanning Calorimetry, X-ray powder diffractometry and Fourier-TransformInfrared analysis. For sake of comparison, the mixture of DIC and gif" alt="beta" align="MIDDLE" BORDER="0">CDseparately lyophilized was investigated too. The results demonstrated that thefreeze-dried product had the highest degree of amorphization and they were inagreement with the existence of an inclusion complex in the solid state. Thedissolution profiles of the drug from each solid system were affected by its physico-chemical properties, the freeze-dried being the most rapidly dissolvingforms.     

Synthesis and fluorination of nitro-substituted thionocarbonates

Thiocarbonylchloride reacts with gif" alt="beta" align="MIDDLE" BORDER="0">-nitroalcohols yielding symmetrical thionocarbonates. Transesterification of bis(2-fluoro-2,2-dinitroethyl)thioncarbonate affords alkyl 2-fluoro-2,2-dinitroethylthionocarbonates. Fluorination of these thionocarbonates yields the corresponding difluoroformals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 375–376, February, 1993.     

A Comparative Study of Naproxen – Beta Cyclodextrin Complexes Prepared by Conventional Methods and Using Supercritical Carbon Dioxide

Naproxen is a poorly soluble anti-inflammatorydrug, the solubility of which canbe enhanced by complexation withbeta-cyclodextrin. Besides that, the inclusioncomplex reduces the incidence of gastrointestinal side effects of the drug. The aim of this work was to compare the physicochemical characteristics of the solid complexes prepared by traditional methods (kneading, freeze-drying and spray-drying) and using a supercritical fluid technology. The unusual solvent properties of carbon dioxide above their critical temperature and pressure were exploited in order to prepare inclusion compounds. Complexes prepared using supercritical fluid technology showed similar properties to those of freeze-drying andspray-drying complexes as proved by DSC, FT-IRand UV.     

Isomerization ofn-hexane overplatinum loaded zeolites

The effect of the calcination temperature of bifunctional Pt/zeolites on the isomerization ofn-hexane has been investigated. The catalyst calcined at 350°C showed the highest metal dispersity and the best activity. The higher selectivity of dimethylbutanes over Pt/H-gif" alt="beta" align="MIDDLE" BORDER="0"> than over Pt/H-MOR might be attributed to the combined effect of acidity, channel structure and pore size of zeolites.     

Titanocen-cyandithioformiat-Komplexe

The reaction of titanocene dichloride,Cp ₂TiCl₂ (Cp=gif" alt="eegr" align="MIDDLE" BORDER="0">⁵-C₅H₅), with one or two equivalents of sodium cyanodithioformate affords the new mono- or bis(dithiocarboxylato) derivativesCp ₂TiCl(S₂CCN) (1) andCp ₂Ti(S₂CCN)₂ (2). Elimination of sulfur converts2 into the metallacyclicCp ₂TiS₂C₂(CN)₂ (3), which does not react with the diene isoprene, but can be reconverted into the appropriate titanocene dihalides by chlorine or bromine.

     

Cyclic Conjugation Energy Effects in Polycyclic π-Electron Systems

Summary. The fact that cyclic arrangements of double bonds have a dramatic effect on the behavior of conjugated organic molecules is known since the 19th century. The fact that in monocyclic conjugated systems the size of the cycle and the number of gif" alt="pgr" align="BASELINE" BORDER="0">-electrons involved is decisive for their stability (gif" alt="ldquo" align="MIDDLE" BORDER="0">aromaticitygif" alt="rdquo" align="MIDDLE" BORDER="0">) or lack of stability (gif" alt="ldquo" align="MIDDLE" BORDER="0">antiaromaticitygif" alt="rdquo" align="MIDDLE" BORDER="0">) is known since the 1930s. In polycyclic gif" alt="pgr" align="BASELINE" BORDER="0">-electron systems several cyclic effects are present simultaneously and their separation became possible only recently. A molecular orbital method has been elaborated, by means of which the energy effects of individual cycles in polycyclic gif" alt="pgr" align="BASELINE" BORDER="0">-electron systems can be estimated. This method is briefly outlined and illustrated by pertinent examples. An exhaustive bibliography of the topic considered is given.     

Linear silver clusters in aqueous solution (clusterites): radiation-induced chemical synthesis and properties

The formation and properties of the products of the radiation-induced chemical reduction of silver ions in aqueous solutions containing sodium polyacrylate were investigated. The absorption spectra of these species exhibit a band at 290 mn and a band in the visible region. The latter shifts from 470 nm to -800 nm with time or after the addition of silver ions. The species obtained (clusterites) arc linear silver clusters bound to the carboxyl groups of the ion exchanger. The red shift of the visible band is due to the increase in their size. The mechanism of the formation and the structure of the clusterites are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1429–1435, June, 1996.     

peri-Naphthylenediamines. 36. 5,6-Bis(dimethylamino)acenaphthylene in [4+2] cycloaddition reactions. Synthesis and characteristic features of protonation of “proton sponges” with the 8,9-diazafluoranthene structure

5,6-Bis(dimethylamino)acenaphthylene is readily involved in [4+2] cycloaddition reactions with symm-tetrazine derivatives to form new gif" alt="ldquo" align="MIDDLE" BORDER="0">proton spongesgif" alt="rdquo" align="MIDDLE" BORDER="0"> with the diazafluoranthene skeleton. Under analogous condition, 1,8-bis(dimethylamino)-4-vinylnaphthalene gave 4-pyridazinyl derivatives. The relative reactivities of 5,6-bis(dimethylamino)acenaphthylene, 1,8-bis(dimethylamino)-4-vinylnaphthalene, 5-dimethylaminoacenaphthylene, and acenaphthylene in the reactions with 3,6-diphenyl-symm-tetrazine are in a ratio of 32 : 17 : 14 : 1. The site of protonation of 3,4-bis(dimethylamino)-7,10-diphenyl-8,9-diazafluoranthene is controlled by the basicity of the solvent. The reaction in acetonitrile afforded the cation stabilized by an intramolecular hydrogen bond, whereas the reaction in dimethyl sulfoxide gave rise to the resonance-stabilized cation. 6,7-Bis(dimethylamino)phenalen-1-one was protonated only at the carbonyl group.     

Synthesis and Cytotoxic Activity of 4-Substituted 3-Cyano-6,6-dimethyl-5,6-dihydro-2-pyranones

The respective 4-(arylvinyl)lactones and compounds of the Michael adduct type were synthesized by the condensation of substituted benzaldehydes with 3-cyano-4,6,6-trimethyl-5,6-dihydro-2-pyranone in the presence of catalytic amounts of sodium hydroxide. It was shown by the semiempirical AM1 method that the indicated products can be formed through one and the same intermediate compound. Some of the synthesized phenylvinyl-5,6-dihydro-2-pyranones have a cytotoxic effect, and this corresponds to the prognosis of the OREX expert system.     

Localization of Iα and Iβ phases in algal cellulose revealed by acid treatments

Highly crystalline I_{gif" alt="agr" align="BASELINE" BORDER="0">}-rich type Cladophora cellulose, which had been kept in never-dried condition, was treated in 60wt% sulfuric acid at 100°C, for 1–48h. The cellulose microcrystals thus obtained were analysed by X-ray diffractometry, FT-IR, and transmission electron microscopy. The I_{gif" alt="agr" align="BASELINE" BORDER="0">} component was found to be more degraded than the I_{gif" alt="beta" align="MIDDLE" BORDER="0">} component. The cellulose I_{gif" alt="agr" align="BASELINE" BORDER="0">}/I_{gif" alt="beta" align="MIDDLE" BORDER="0">} ratios of the samples acid-treated for 0, 24, and 48 h were about 8:2, 6:4, and 4:6, respectively. After the acid treatment, the microcrystals became narrower in width, and very sharp at their ends. These results indicate that the I_{gif" alt="agr" align="BASELINE" BORDER="0">} phase is mostly located at the surface of the microcrystals, which is morphologically more susceptible to the acid treatment.