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Alkynyl silyl sulfides 2 reacted with ynamines 3 to give 1:1 adducts. The structure of 4-silylcyclobut-2-enethiones 4 was confirmed by X-ray analysis of 4a. A cyclobutadiene intermediate is probably not involved in this reaction; we think that it is initiated by a silyl transfer from 2 to 3, and that this is followed by a combination of the resulting ions to give the unsaturated thioketene 7, which undergoes an electrocyclization to give products 4. In the reaction of thiones 4 with trimethyloxonium tetrafluoroborate (Meerwein salt) selective methylation at sulfur was observed to give cyclobutenethionium ions 16. Ions 16 underwent fluoride-induced desilylation with various fluoride sources to give cyclobutadienes 17, which could not be isolated, but trapping of 17 a-c was possible with dimethyl acetylenedicarboxylate yielding regioisomeric benzene derivatives 20–23. Similarly, 17 a and bis(methylthio)methylene malononitrile (24) led to hexatriene derivative 27 by a sequence of cycloaddition and two ring-opening reactions. In contrast, silyl-substituted cyclobutadienes 17d,e dimerized even in the presence of trapping agents to anti-tricyclo-[4.2.0.02,5]octadienes 29; this suggests that a two-step cycloaddition is taking place, rather than a concerted Diels-Alder reaction. Attempts to intercept 17d, e, generated from 16d,e with cyclopentadiene (30), gave deprotonation of 30 leading to substitution of the methylthio group in 16 and finally to formation of cyclobutenes 33 through a hydrogen shift.

Thioketenes or thioketene equivalents give β-thiolactams in the reaction with C=N systems, but problems arise in the synthesis of highly functionalized derivatives. Therefore to obtain the thione analog of a bactam a thionation approach was chosen.

Uber die Reaktion des Alkinids 2 mit Schwefel lassen sich in einfacher Weise (Aminoethinyl)sulfide 5 mit verschiedenen Zweitsubstituenten am Sulfid-Schwefel erhalten. In der Hydrolyse und in Cycloadditionen mit Diphenylketen, Phenylisocyanat oder Tosylisothiocyanat erweisen sich die S-Alkyl-Derivate 5a, b als typische Inamine, wahrend die Amin-Addition an die Silylthio-Verbindung 5c einen abweichenden Verlauf nimmt. A Novel Synthesis and Reactions of Aminoethynyl Sulfides Reaction of the alkynide 2 with sulfur provides ready access to aminoethynyl sulfides 5 with different second substituents on the sulfide sulfur atom. Hydrolysis and cycloadditions with diphenylketene, phenyl isocyanate, or tosyl isothiocyanate prove the S-alkyl derivatives 5a, b to be typical ynamines, whereas amine addition to the silylthio compound 5c takes a different course.

Bei der Thermolyse der stellungsisomeren Thiadiazole 1a oder 1b in feuchtem 2,2′-Oxydiethanol (3) entstehen das Keton 6, das Thiophen 7, das Alkin 8 und das durch eine Rontgenstrukturanalyse eindeutig aufgeklarte dimere Disulfid 11. In Gegenwart von Diphenylacetylen (15) bilden sich aus 1a und 1b die Thiophene 16a und 16b im selben Verhaltnis. Die bei der Thermolyse zunachst entstehenden 1,3-Diradikale 13 konnen demnach durch Alkine abgefangen werden. Die Bildung identischer Thiophene aus isomeren Thiadiazolen 1 las sich durch ein Gleichgewicht der Primarfragmente 13 verstehen, das sich uber das Thiiren 14 einstellt. Auch das Keton 6 scheint nicht aus 8, sondern aus 14 zu entstehen. Thiirenes as Intermediates in the Thermolysis of 1,2,3-Thiadiazoles Thermolysis of the isomeric thiadiazoles 1a or 1b in moist 2,2′-oxydiethanol (3) yields the ketone 6, the thiophene 7, the alkyne 8, and the disulfide 11, the structure of which was determined by an X-ray analysis. In the presence of diphenylacetylene (15) 1a and 1b react to give the thiophenes 16a and 16b in the same ratio. This implies that the primary products of thermolysis, the 1,3-diradicals 13, can be trapped by alkynes. The formation of identical thiophenes from isomeric thiadiazoles 1 can be understood in terms of an equilibrium between the primary fragments 13via the thiirene 14. Similarly, the ketone 6 seems not to result from 8 but from 14.