Porphyrins with exocyclic rings. Part 23: Synthesis of porphyrins with large exocyclic rings—cyclohexadeca[b]pyrroles and porphyrins therefrom

Knorr-type condensation of cyclododecanone, cyclopentadecanone, and cyclohexadecanone with phenylhydrazones derived from acetoacetate esters in the presence of zinc dust at elevated temperatures gave the corresponding large ring cycloalka[b]pyrroles in excellent yields. A cyclohexadeca[b]pyrrole was reacted with lead tetraacetate to give an acetate derivative, and this condensed with α-unsubstituted pyrroles in the presence of p-toluenesulfonic acid in acetic acid to give a series of related dipyrrolic structures. Hydrogenolysis of the benzyl ester protective groups, followed by ‘2+2’ condensations with dipyrrylmethane dialdehydes, gave unusual cycloalkanoporphyrins with 16-membered exocyclic rings. When an alkyl group is situated next to the carbocyclic ring, proton NMR spectroscopy indicates that the conformational mobility of the carbocyclic unit is severely restricted.     

New biodegradable hydrogels based on a photo-cross-linkable polyaspartamide and poly(ethylene glycol) derivatives. Release studies of an anticancer drug

 The functionalization of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) with glycidyl methacrylate (GMA) gives rise to a water-soluble photosensitive copolymer PHEA-GMA (PHG). Aqueous solutions of PHG alone or in combination with various concentrations of poly(ethylene glycol) dimethacrylate or poly(ethylene glycol) diacrylate (PEGDA) have been exposed to a source of UV rays at 313 nm in order to obtain polymeric networks. All samples have been prepared both as water-swellable microparticles and as gel systems. Microparticles have been characterised by Fourier transform IR spectrophotometry, dimensional analysis and swelling measurements in aqueous media mimicking biological fluids. In vitro chemical and enzymatic hydrolysis studies showed that all the prepared samples undergo a partial degradation at pH 1, 7.4 and 10 as well as after incubation with enzymes such as esterase. The effect of the cross-linking density on the rheological behavior of gel systems has also been investigated. PHG/PEGDA hydrogel is able to incorporate, during UV-irradiation, 5-fluorouracil (5-FU), chosen as a model drug, and to release it in simulated biological fluids, as confirmed by in vitro drug release studies at pH 1 and 7.4. PHG/PEGDA gel containing 5-FU is able to release this drug in a prolonged way, more slowly than a commercial ointment, as confirmed by in vitro studies at pH 5.5 and 7.4 using a Franz diffusion cell system and a synthetic membrane. Received: 3 October 2000 Accepted: 13 December 2000     

Neutral Pentacoordinate Halogeno‐ and Pseudohalogenosilicon(IV) Complexes with an SiSONCX Skeleton (X=F,Cl, Br,I, N,C): Synthesis and Structural Characterization in the Solid State and in Solution

A series of neutral pentacoordinate silicon(IV) complexes with an SiSONCX skeleton (X=F, Cl, Br, I, N, or C) was synthesized and structurally characterized by multinuclear solution‐state and solid‐state NMR spectroscopy and single‐crystal X‐ray diffraction. These compounds contain an identical tridentate dianionic S,N,O ligand, a monodentate (pseudo)halogeno ligand (F, Cl, Br, I, NCS, N₃, or CN), and a monodentate organyl ligand (methyl, phenyl, 4‐(trifluoromethyl)phenyl, or pentafluorophenyl). For most of these compounds, a dynamic equilibrium between the pentacoordinate silicon(IV) complex and two isomeric tetracoordinate silicon species in solution was observed. Most surprisingly, comparison of two series of analogous compounds containing fluoro, chloro, bromo, or iodo ligands demonstrated that pentacoordination in these series of silicon(IV) complexes is favored in the rank order I≈Br>Cl>F; i.e., increasing the softness of the halogeno ligand favors pentacoordination.     

Simulation of the chipping behavior of coated abrasives by cooperating cellular automata

During the production of high-grade wooden components often the conditioning with coated abrasives composes the end of the process train. The chipping process and the resulting wood surface are depending of the scatter pattern parameters (particle size and distribution, …) and their time depending variations. Till now, no models exist concerning the interaction of the scatter pattern with the grinding process, the work piece surface and the clogging. The developed model is based on cooperating cellular automata. One is describing the sandpaper, the other one the work piece. These two automata interacts witch each other. Update rules are designed by physical laws and measurements. The paper shows surprising results with respect of surface structures which are the result of self-organization effects in the boundary layer of wood and sandpaper. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)