Methodology studies on in situ generated Fischer carbene complexes of Group VI transition metals, on the chromium-Reformatsky reaction of nitrogen-based compounds, and analytical studies of the Vogel collection.

摘要

The synthesis and reactivity of alkoxy vinyl Fischer carbene complexes of chromium, molybdenum and tungsten were investigated. The synthesis involved the addition of an alkynyl lithium reagent to the corresponding metal hexacarbonyl. followed by alkylation of the resulting metal acylate complex. Subsequent Michael addition of an alcohol afforded the desired beta-alkoxy vinyl carbene complexes of chromium and tungsten in good yields. The corresponding molybdenum complexes were labile and underwent fast decomposition or polymerization.;Synthetic routes to various dienynes were designed and developed. Their reactivity with molybdenum carbene complexes was analyzed. Systematic variations in the position of substituents on the carbon tether clarified the impact of coordination and steric and electronic effects on this reaction. Experimental results suggest that coordination of the oxygenated substituent on the tether to the vinylcarbene complex intermediate prevent cyclopropanation pathways.;The reactions between nitrogen based Reformatsky substrates and aldehydes with chromium(II) reagents were investigated. The results of reactivity studies of symmetric and asymmetric alpha-bromonitriles, -amides and -imines are presented herein. The reaction of alpha-bromonitriles with aldehydes proceeded in good to excellent yields. The diastereoselectivity of asymmetric alpha-bromonitriles was dependent on the bulkiness of the aldehyde and of the alpha-substituent on the corresponding nitrile. Amides showed moderate to good yields but asymmetric amides resulted in minimal diastereoselectivity upon product formation. Imines resulted in very low yields of the corresponding products. Mechanistic models explaining the results have been proposed. Aldehyde competition studies with achiral brominated nitriles and esters were analyzed.;The sixty pigments of organic and inorganic basis constituting the Vogel collection of the Doerner Institute in Munich were identified and characterized by chemical and physical analytical methods. All samples were submitted to qualitative and quantitative analyses including optical microscopy, thin layer chromatography, scanning electron microscopy, energy-dispersive X-ray spectrometry and X-ray powder diffraction. Characterization results based on these studies included main composition of the pigments as well as mineral residues, contaminants or fillers present in the samples. After defining the chemical composition of the samples, primary documentary sources in German and English were researched. Analytical results were brought into historical context and related to original 18th and 19th century European records.