Showing papers by "Ernst Schaumann published in 1980"

Cycloadditionsreaktionen von Heterocumulenen, XX. Umsetzung von Allyl(trimethylsilyl)thioketenen mit Azomethinen

Abstract: Die Thio-Claisen-Umlagerung von Allyl(silylethinyl)sulfiden 4 fuhrt zu Allyl(silyl)thioketenen 5. Mit Aminen 6 entstehen aus 5 2-Silylthioamide 7 oder desilylierte Produkte 8. Bei Cycloadditionen von 5 mit den Azomethinen 11 bieten die β-Thiolactame 12a–c die einzigen Beispiele fur silylhaltige Cycloaddukte. Hauptprodukte sind die formal von Allylthioketenen abgeleiteten β-Thiolactame 12d–k, die Hexahydro-4-pyrimidinthione 13 und die 2-Allylzimtsaurethioamide 17. Zimtsaurethioamide 21 sind ebenfalls Endprodukt der Cycloaddition des Alkinyl(silyl)sulfids 18 mit den Azomethinen 11b–d. Cycloaddition Reactions of Heterocumulenes, XX. Reaction of Allyl(trimethylsilyl)thioketenes with Azomethines Thio-Claisen rearrangement of allyl silylethynyl sulfides 4 leads to allyl(silyl)thioketenes 5. With amines 6 2-silylthioamides 7 or desilylated products 8 are formed from 5. In cycloadditions of 5 with azomethines 11, the β-thiolactams 12a–c represent the only examples of silicon-containing cycloadducts. The main products are the β-thiolactams 12d–k, the hexahydro-4-pyrimidinethio 13, and the 2-allylthiocinnamides 17, which are formally derived from allylthioketenes. Thiocinnamides 21 are also the final result of cycloadditions between the alkynyl silyl sulfide 18 and the azomethines 11b–d.

Cycloadditionsreaktionen von Heterocumulenen, XIX. 1:1‐, 2:1‐ und 1:2‐Cycloaddukte aus der Umsetzung von Thioketenen mit Azomethinen

Abstract: Die Umsetzung der Thioketene 1a–e mit den Azomethinen 2a, b fuhrt zu 1: 1-, 2: 1- und 1 : 2-Cycloaddukten (2-Azetidinthione 3, Dihydro-4H-1,3,5-dithiazine 5 bzw. Hexahydro-4-pyrimidinthione 9). Aus den Allylthioketenen 15 und 2a – d, 19 entstehen die entsprechenden Cycloaddukte 16, 17 und 18. Bei der Pyrolyse der 4-Alkylthiadiazole 13 im Azomethin 2d werden die freigesetzten Aldothioketene 1f, gin situ durch 2d zu den β-Thiolactamen 3e, f abgefangen. Die 1:1-Addukte 3, 16 fallen in der sterisch gunstigeren Konfiguration A (fur 16a: B) an, wenn nicht von sterisch besonders gehinderten Thioketenen ausgegangen wird (16f, g) oder die sterischen Wechselwirkungen der Substituenten an C-3, C-4 ahnlich (3b, 16h) bzw. gering (3e) sind. Bei den Heterocyclen 5a, b last sich geometrische Isomerie an der exocyclischen CC-Bindung an C-2 nachweisen. Die Bildung der Produkte 5, 9, 17, 18 und die Stereochemie von 3, 16 last sich durch die Annahme einer dipolaren Zwischenstufe 20 verstehen. Cycloaddition Reactions of Heterocumulenes, XIX. 1:1-, 2:1-, and 1:2-Cycloadducts from the Reaction of Thioketenes with Azomethines The reaction of the thioketenes 1a–e with the azomethines 2a, b affords 1:1-, 2:1-, and 1:2-cycloadducts (2-azetidinethiones 3, dihydro-4H-1,3,5-dithiazines 5, and hexahydro-4-pyrimidinethiones-thiones 9). From allylthioketenes 15 and 2a – d, 19 the corresponding cycloadducts 16, 17, and 18 are isolated. On pyrolysis of the 4-alkylthiadiazoles 13 in the azomethine 2d the liberated aldothioketenes 1f, g are trapped by 2d to give the β-thiolactams 3e, f. The 1:1-adducts 3, 16 are formed in the sterically favoured configuration A (for 16a: B), unless sterically extremely hindered thioketenes are the starting materials (16f, g) or steric interactions of the substituents on C-3, C-4 are comparable (3b, 16h) or negligible (3e). For the heterocycles 5a, b geometrical isomerism at the exocyclic CC bond on C-2 is detected. Formation of products 5, 9, 17, 18 and the stereochemistry of 3, 16 can be understood in terms of the dipolar intermediate 20.

Heterocyclic ring‐closure reactions. 6. preparation and further cyclization reactions of 5‐imino‐1,3‐diphenyl‐4‐thioxo‐2‐imidazolidinone and 5‐imino‐1,3‐diphenyl‐2,4‐imidazolidinedithione

Abstract: Phenylisothiocyanat (I) bildet mit Blausaure ein Addukt (II), das mit weiterem Isothiocyanat (I) zu den Cyclisierungsprodukten (III) bzw. den Acylierungsprodukten (IV) fuhrt.

Gas-phase thermolyses. Part 3. Gas-phase thermolysis of silylated thionocarboxylic acid derivatives: a route to thioketens?

Abstract: The unimolecular gas-phase thermolytic decomposition of three silylated thionocarboxylic acid derivatives (2b), (3), and (8) have been studied by the flash vacuum thermolysis–field ionization mass spectrometry technique in the temperature range from 783 to 1 404 K in order to elucidate its possible applicability as a route to thioketens. Only very minor amounts of the expected thioketens were found, whereas the corresponding ketens were obtained as the major products. A possible mechanism for keten formation is discussed.

Umlagerung von α‐Isocyanato‐N2‐(arylsulfonyl)amidinen in 1‐Arylsulfonyl‐3‐imidazolin‐2‐one

Abstract: Die Reaktion der Azirine 1 mit den Isocyanaten 2 fuhrt zu den α-Isocyanato-N2-(arylsulfonyl)-amidinen 6. Ausgehend von 1b werden auch betrachtliche Mengen 7b und 8b als Folge einer Retro-En-Reaktion von 6b gebildet. Die Heterocumulene 6 lagern sich unter Wanderung der Sulfonyl-Gruppe leicht in die Heterocyclen 10 um. Die Beweglichkeit des Sulfonyl-Rests wird auch in der Reaktion von 6a mit Chlorwasserstoff zu Tosylchlorid und 8a sowie in der Umsetzung mit Aminen deutlich, die neben Tosylamiden 15 allerdings auch Harnstoffe 13 und deren Folgeprodukte 14 liefert. Rearrangement of α-Isocyanato-N2-(arylsulfonyl)amidines to 1-Arylsulfonyl-3-imidazolin-2-ones The reaction of the azirines 1 with the isocyanates 2 leads to the α-isocyanato-N2-(arylsulfonyl)-amidines 6. Starting from 1b, also considerable amounts of 7b and 8b are formed as a result of a retro-ene reaction of 6b. The heterocumulenes 6 readily rearrange with a shift of the sulfonyl group to give the heterocycles 10. The mobility of the sulfonyl residue is also obvious from the reaction of 6a with hydrogen chloride to afford tosyl chloride and 8a as well as from the reaction with amines, which, however, does not only yield the tosylamides 15, but also the ureas 13 and their secondary products 14.

Gas-phase thermolysis of a thioketen-S-oxide

Abstract: The unimolecular gas-phase thermolytic decomposition of 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane S-oxide (3) has been studied as a function of temperature by a flash vacuum thermolysis (f.v.t.) technique. The products detected are the carbenes (4) and (5), the ketone (6), the keten (7), the thioketone (8), and the thioketen (9). The product ratio is highly dependent on the thermolysis temperature. The thermolysis of (3) is mechanistically rationalized by assuming the existence of only two concurrent primary processes, which are (a) extrusion of atomic oxygen, leading to the thioketen (9), and (b) electrocyclic ring closure into the corresponding three-membered oxathiiran (10). The latter is dominant at lower temperatures, whereas higher thermolysis temperatures favour atomic oxygen extrusion. At further elevated temperatures additional concurrent primary reactions, i.e. extrusions of SO and CSO leading to the carbenes (5) and (4), respectively, are observed. Owing to an apparently very short half-life of the oxathiiran (10), only the decomposition products of the three-membered ring compound have been detected. These are the thioketone (8), formed by rearrangement of (10) into the α-thiololactone (11) followed by loss of CO, minor amounts of the ketone (6), formed analogously, and the keten (7), as a result of simple sulphur extrusion.

Photolysis of thioketene s-oxides

Abstract: In contrast to the photolytically-induced ring closure of diarylthioketone S-oxides into oxathi-iranes, thioketene S-oxides are found to undergo photo-deoxygenation in a reaction between the excited thioketene S-oxide molecule and the solvent. The relative quantum yield was studied as a function of the solvent and the sterical hindrance of the thioketene S-oxide and correlated with available p.e.s. data. The mechanism is discussed.