Pyridazines. LIX. Synthesis of c-annelated pyridazines from 3-amino-4-pyridazinecarbonitrile

The utility of the aminonitrile 1 as an educt for the preparation of several new examples of heterocyclefused pyridazines (the [1,2,4]triazolo[1′,5′:1,6]pyrimido[4,5-c]pyridazine 7 , the pyrimido[4,5-c]pyridazines 8, 10a,b , and the pyrido[2,3-c]pyridazine 11 ) is demonstrated.     

Influence of the transport direction on gas permeation in two-layer ceramic membranes

Experimental and theoretical results of studying gas permeation through porous membranes are presented. In order to mimic an asymmetric membrane two porous ceramic disks with different pore radii were arranged in series. Besides the possibility to perform conventional permeation measurements, the applied experimental setup permits the determination of the pressure at the interface between the two discs. To predict the performance of the asymmetric structure, in preliminary experiments structure parameters were determined for both membranes separately. For the same total pressure difference across the two-disk arrangement, different interlayer pressures and fluxes were predicted and detected experimentally depending on the flow direction.     

Silica–gelatin hybrids for tissue regeneration: inter-relationships between the process variables

Owing to their diverse range of highly tailorable material properties, inorganic/organic hybrids have the potential to meet the needs of biodegradable porous scaffolds across a range of tissue engineering applications. One such hybrid platform, the silica–gelatin sol–gel system, was examined and developed in this study. These hybrid scaffolds exhibit covalently linked interpenetrating networks of organic and inorganic components, which allows for independent control over their mechanical and degradation properties. A combination of the sol–gel foaming process and freeze drying was used to create an interconnected pore network. The synthesis and processing of the scaffolds has many variables that affect their structure and properties. The focus of this study was to develop a matrix tool that shows the inter-relationship between process variables by correlating the key hybrid material properties with the synthesis parameters that govern them. This was achieved by investigating the effect of the organic (gelatin) molecular weight and collating previously reported data. Control of molecular weight of the polymer is as an avenue that allows the modification of hybrid material properties without changing the surface chemistry of the material, which is a factor that governs the cell and tissue interaction with the scaffold. This presents a significant step forward in understanding the complete potential of the silica–gelatin hybrid system as a medical device.     

Axial Ligand Effects on the Redox Reactions of Manganese Porphyrins

A systematic study for the effect of axially coordinated monovalent anions on the electrode reactions of several manganese porphyrins in acetonitrile is presented. Potential shifts of the metal-centered reduction with changes in counterion were related to the degree of Mn(III)-counterion interaction. In the electrochemically induced ligand exchange, perchlorate anion replaces the other anions as axial ligand coordinated to Mn(III) at oxidation potential less than the first oxidation of manganese porphyrins. Formation constants for axial ligation of OH^? are calculated. One-electron oxidation of dihydroxide coordinated manganese porphyrins generate oxomanganese(IV) porphyrin complexes electrochemically. O=Mn^IVOEP(OH) is more thermodynamically stable than O=Mn^IVTPP(OH), while O=Mn^IVTpFPP(OH) cannot be generated electrochemically. In the presence of styrene or cyclohexene, the absorption spectra of oxomanganese(IV) porphyrins are changed to form manganese(III) porphyrins gradually, which indicates the oxygen atom transfer from oxomanganese(IV) porphyrins to the substrates.     

Synthesen und Reaktionen von Pyridazinderivaten, 11. Mitt.: 5-Acyl-4-pyridazincarbonsäurrester als „key intermediates” für 4-Acylpyridazine und 4-Alkyl-bzw. 4-Arylpyridazino[4,5-d]pyridazin-1 (2H) one

A convenient general method of preparing 4-acylpyridazines (4) is reported. It involves homolytic acylation of ethyl-4-pyridazinecarboxylate yielding ethyl-5-acyl-4-pyridazinecarboxylates (2) which easily can be converted to4 by alkaline hydrolysis followed by decarboxylation. The hitherto unknown pyridazino[4,5-d]pyridazine-1 (2H) ones bearing an alkyl- or arylsubstituent on C-4 (5a-g) were prepared in quantitative yields by reaction of2 with hydrazine.

10. Mitt.:G. Heinisch, A. Jentzsch undI. Kirchner, Tetrahedron Lett.1978, 619.     

The electron impact fragmentation of 3- and 4-styrylpyridazine

The electron impact mass spectrometric fragmentation of trans-3- and trans-4-styrylpyridazine is reported in detail, including a comparison with other aza-stilbenes. With regard to a distinction between the two isomeric styrylpyridazines, the intensity ratio of the M⁺ and [M-1]⁺ ions, the general degree of fragmentation and the elimination pathways of nitrogen proved to be most characteristic.     

Studies on main group metal-transition-metal bonded compounds 7. A 199Hg NMR study of home group of some group VI trasition-metal mercury compounds

A ¹⁹⁹Hg Fourier Tranformation NMR study has been carried out on Hg[M(CO)₃C₅H₅]₂ (M = Cr, Mo, W), [C₅H₅(CO)₃M]HgCl, and [C₅H₅(CO)₃W]HgX (X = Cl, Br, I, SCN). The ¹⁹⁹Hg chemical shifts are ?80, +115 and ?348 ppm respectively for the symmetrical compounds, ?542, ?617, and ?997 ppm for the chloride and ?1200, ?1529 and ?924 ppm for the Br, I, SCN-tungsten derivatives respectively. The ₁₉₉Hg chemical shifts for several other mercury derivatives are reported for comparison. All chemical shifts are relative to 90% HgMe₂/10% internal lock C₆F₆ with positive values indicating decreasing shielding. The J_199Hg-183W values are 151, 706, 690, 630 and 684 Hz for the symmetrical compound and the Cl, Br, I and SCN derivatives respectively. The factors which may influence these parameters are discussed briefley.