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Δ16‐20‐Ketosteroids by C2‐Elongation from Δ16‐17‐Substituted Steroids Reactions of corticoid precursor steroids with a Δ16‐double bond and iodine, trimethylsilyl, tributylstannyl or trifluoromethanesulfonyloxy groups in 17‐position were studied with the aim of introducing an acyl substituent in 17‐position. Starting with the 17‐trimethylsilyl compounds, using acyl chlorides and AlCl3 as a catalyst, a mixture of chlorinated compounds were obtained, among others. Better results gave palladium‐catalyzed reactions, such as the cross‐coupling of 17‐tributylstannyl compounds with acyl chlorides or the substitution of the 17‐iodides or the 17‐triflates by vinyl ethers. In the reaction of the 17‐iodides, different protecting groups are tolerated; thus this method is of general use. No Δ16‐17‐triflates were obtained by the reaction of androsta‐4‐ene‐3, 17‐dione or androsta‐1,4‐diene‐3, 17‐dione with trifluoromethanesulfonyl anhydride. This is a limitation of the triflate method, which in the other cases gives the best yields (>80%).

Over the last decade enormous efforts and progress have been made in the investigation of metallocene-type catalysts of group IV: The discovery that methylalumoxanes (MAO) promote the formation of highly active cationic species, the design of "single site" catalysts for the polymerization of 1-olefines, the isolation of cationic species involving [Cp 2 M-R] + cations, which are responsible for the catalytic reactivity, the tuning of the catalytic reactivity by adjusting the ligands, and the development of industrial processes are some examples for this rapidly growing field [1 -5].Most recently group IV metal complexes that contain inorganic donor sets have been to focus attention as potential catalysts [2, 6 -34]. However, the coordination chemistry and organometallic chemistry of these compounds is more complicated and much less developed than the metallocene chemistry. Especially, the understanding of the controlling effects of ligands containing an inorganic donor set in group IV metal catalysts is not well understood. This might be the most important problem in the development of new highly active and selective group IV catalysts containing anionic ancillary ligands having for example N or O donor atoms. Salicylidene-imine-Zirconium(IV) Complexes in Combination with Dedicated to Professor Egon Uhlig on the Occasion of his 70th BirthdayKeywords: Cyclizations, Schiff bases, Zirconium, Catalysis Abstract. A variety of substituted Schiff base complexes of the composition ("salen")ZrCl 2 (thf) (1 -21) were synthesized, with methylalumoxane ("MAO") activated and used for a systematic study of their catalytic activity towards hexa-1,5-diene ("salen": substituted salicylidene-ethylene-iminato ligands). Main product of the catalytic cycle is methylenecyclopentane. Dimers are only formed in minor amounts. The catalytic activity and selectivity of the Ziegler-Natta systems strongly depend on the nature and the position of the peripheric substituents in the Schiff base ligands. Electron-withdrawing substituents in para-position to the phenolato oxygen (5-position) decrease the catalytic activity. Improved activity andIn this paper we report on the catalytic conversion of hexa-1,5-diene by a number of MAO-activated (salicylidene-ethylene-imine)Zr(IV)(thf) complexes in which a N 2 -O 2 donor set is coordinated as four-dentate chelate ligand opening the possibility to study the electronic and steric influence of peripheric groups on the catalytic reactivity.Our aim was to get a deeper insight into the possibility to control the catalytic reactivity of the metal center depending on the coordinative environment. Since the catalytic conversion of hexa-1,5-diene was a slow reaction it was also possible to indicate the starting steps of the catalysis. Catalytic Reactions of (Salen)ZrCl 2 (thf)/MAO with Hexa-1,5-dieneFor the preparation of the Zr(IV) complexes 1 -21 the quadridentate Schiff base N,N'-ethylene-bis(salicylideneimine) ("salen") ligands were treated with two equivalents n-butyl-lithium to form the lithium salts. Re...

Bacteria in acidophilic biofilm communities, i.e. acid streamers and snottites, obtained from a subsurface mine in Königstein were visualized by fluorescence microscopy using four new fluorescent dyes (DY-601XL, V07-04118, V07-04146, DY-613). The pH of the bulk solution in which these bacteria thrive was pH 2.6 to 2.9. The new fluorescent dyes were all able to clearly stain and microscopically visualize in-situ the bacteria within the biofilm community without changing pH or background ion concentration. The commonly used fluorescent dyes DAPI and SYTO 59 were also applied for comparison. Both dyes, however, were not able to visualize any bacteria in-situ, since they were not stable under the very acid conditions. In addition, dye V07-04118 and dye DY-613 also possess the ability to stain larger cells which were presumably eukaryotic origin and may be attributed to yeast cells or amoeba-like cells. PCR analyses have shown that the dominant bacterial species in these acidophilic biofilm communities was a gram negative bacterium of the species Ferrovum myxofaciens. The presented four new dyes are ideal for in-situ investigations of microorganisms occurring in very acid conditions, e.g. in acidophilic biofilm communities when in parallel information on pH sensitive incorporated fluorescent heavy metals should be acquired.