Faber-Theorie für Riemannsche Flächen

Ohne ZusammenfassungHerrnHermann Schmidt zum 60. Geburtstag     

Zur Biosynthese pflanzlicher Stilbene, 4. Mitt.: Die Bildung von Ring A des Oxyresveratrols

Ohne Zusammenfassung     

Enough Regular Cauchy Filters for Asymmetric Uniform and Nearness Structures

Quasi-nearness biframes provide an asymmetric setting for the study of nearness; in Frith and Schauerte (Quaest Math 33:507–530, 2010) a completion (called a quasi-completion) was constructed for such structures and in Frith and Schauerte (Quaest Math, 2012) completeness was characterized in terms of the convergence of regular Cauchy bifilters. In this paper questions of functoriality for this quasi-completion are considered and one sees that having enough regular Cauchy bifilters plays an important rôle. The quasi-complete strong quasi-nearness biframes with enough regular Cauchy bifilters are seen to form a coreflective subcategory of the strong quasi-nearness biframes with enough regular Cauchy bifilters. Here a significant difference between the symmetric and asymmetric cases emerges: a strong (even quasi-uniform) quasi-nearness biframe need not have enough regular Cauchy bifilters. The Cauchy filter quotient leads to further characterizations of those quasi-nearness biframes having enough regular Cauchy bifilters. The fact that the Cauchy filter quotient of a totally bounded quasi-nearness biframe is compact shows that any totally bounded quasi-nearness biframe with enough regular Cauchy bifilters is in fact quasi-uniform. The paper concludes with various examples and counterexamples illustrating the similarities and differences between the symmetric and asymmetric cases.     

The Samuel compactification for quasi-uniform biframes

The paircover approach is used to explore the links between quasi-uniform and proximal biframes. The Samuel compactification for quasi-uniform biframes is constructed and its universal property discussed.     

Michael additions with an enaminoester: Reaction of phenyl 4-chromone-3-sulfonate with methyl 3-amino-2-pentenoate

The novel benzoxathiinopyridines 5 and 8 and the hitherto unknown oxathiinobenzopyran 17 were synthesized by ring transformations of phenyl 4-chromone-3-sulfonate ( 1 ) with methyl 3-amino-2-pentenoate ( 2 ). The structures of 5, 8 and 17 were determined by spectroscopic methods and the reaction pathways for the formation of these compounds are discussed.     

Die Umsetzung von Vinylbromid und substituierten Vinylbromiden mit Lithium in Tetrahydrofuran zu Lithiumacetyliden

Zusammenfassung Bei der Umsetzung mit metallischem Li in sied. Tetrahydrofuran (THF) entstehen aus 2-Brom-propen und 2-Brom-buten-(1) an Stelle der erwarteten Lithiumalkenyle die Acetylide R-CCLi, wobei allerdings ein größerer Teil des Ausgangsbromids in das entsprechende Alken übergeht. Außerdem wird neben LiBr auch noch eine geringe Menge LiH gebildet, das bei, der analogen, zu C₂Li₂ führenden Umsetzung des Vinylbromids in wesentlich größerer Menge entsteht. Die Bildung von Lithiumvinyl konnte nicht beobachtet werden. Auchcis-1-Brom-buten-(1), geht inTHF in das entsprechende Lithiumacetylid über.InTHF, das die zu Acetylid führenden Reaktionen offenbar begünstigt, wird schon bei—65° Acetylidbildung aus 2-Brompropen beobachtet, in Äther aber nur dann, wenn bei Siedetemp. und in höherer Konzentration als bei der Darstellung der Lithiumalkenyle bisher üblich gearbeitet wird.Die Acetylide, deren Bildungsmechanismus diskutiert wird, werden mit verschiedenen Ketonen umgesetzt.Phenylacetylen und Octin-(1) geben mit metall. Li in sied.THF die entsprechenden Acetylide. Der dabei verfügbar werdende Wasserstoff führt einen Teil der Ausgangsverbindungen in Äthylbenzol bzw. Octen-(1) über; LiH oder Wasserstoff entsteht dabei nicht. Acetylen selbst greift unter diesen Bedingungen Li nur oberflächlich an.Reaction of metallic lithium with 2-bromo-propene and 2-bromo-but-1-ene in boiling tetrahydrofurane yields acetylides of the structure R–CC-Li instead of the expected lithium alkenes. To a larger extent, however, the starting material is converted to the corresponding alkene. Besides LiBr a small amount of LiH is formed. In the analogous reaction with vinyl bromide leading to C₂Li₂ an essentially larger amount of LiH is formed, whereas the formation of lithium vinyl was not observed.cis-1-Bromo-but-1-ene inTHF similarily gives the corresponding lithium acetylide.THF obviously favours the reactions leading to acetylides, e.g. at—65°C formation of the acetylide from 2-bromo-propene can be observed. In diethyl ether however formation of acetylides requires, reflux temperature and concentrations higher as usual for the preparation of lithium-alkenyles.The mechanism of the acetylide formation as well as the reaction of the acetylides with certain ketones are described. On treatment of phenylacetylene and octine-1 with metallic lithium in boilingTHF the corresponding acetylides are obtained. Some of the starting material is converted into ethylbenzene and octene-1 respectivly. LiH or H₂ are not formed. Under the same conditions lithium is only slightly affected by acetylene.Dem verehrten Kollegen Professor Dr. Dr. h. c.F. Wessely zum 70. Geburtstag in Freundschaft gewidmet.     

Untersuchung von Fruchterzeugnissen

Ohne Zusammenfassung