Cycloadditionsreaktionen von Heterocumulenen, XXV. Cycloaddukte und Umlagerungsprodukte aus der Umsetzung von Isothiocyanaten mit Keten‐acetalen

Abstract

Aus Isothiocyanaten 1 und Keten-acetalen 2 entstehen Cycloaddukte, die ausgehend von den Sulfonylisothiocyanaten 1 a -d als 2-Iminothietane 5, ausgehend von Arylisothiocyanaten l e -h als 2-Azetidinthione 6 zu formulieren sind. In Folge-und Nebenreaktionen findet Umlagerung zu Malonsaure-Derivaten 4 und zu Thioacrylamiden 7 statt; aunerdem entstehen 3-Imino-3H-l,2-dithiole 10. Umsetzungen von 2b,c rnit iiberschussigem Phenylisothiocyanat (le) in der Warme ergeben 2-Thiouracile 12,15 und 16. Die Konstitutionen von 10b und 12a konnten durch Rdntgenstrukturanalysen bewiesen werden. Cycloaddition Reactions of Heterocumulenes, XXV l) Cycloadducts and Rearrangement Products from the Reaction of Isothiocyanates with Ketene AcetalsIsothiocyanates 1 and ketene acetals 2 yield cycloadducts, which starting from sulfonylisothiocyanates l a -d have to be formulated as 2-iminothietanes 5, starting from arylisothiocyanates l e -h as 2-azetidinethiones 6. In subsequent or side reactions, rearrangements lead to malonic acid derivatives 4 and thioacrylamides 7; furthermore, 3-imino-3H-l,2-dithiols 10 are generated. Reactions of 2b,c with excess phenylisothiocyanate (le) on heating afford 2-thiouracils 12, 15, and 16. The constitutions of 10b and 12a could be proven by X-ray structural analyses.

From Carbodiimides to Carbon Dioxide: Quantification of the Electrophilic Reactivities of Heteroallenes

“…Harsh reaction conditions were needed for the reactions of ketene acetals ( N ≈ 10) with 1c . Thus, the [2+2] cycloaddition of 1,1-dimethoxy-2-methylprop-1-ene across the CN bond of 1c was reported to take place when equimolar amounts of the two reactants were heated without a solvent for 3 days at 100 °C …”

“…Thus, 1-(N-morpholino)cyclopentene (N = 13.41) reacted with 1c in chloroform under reflux, 26c and the weakly nucleophilic α-(N-morpholino)styrene (N = 10.30) reacted with 1c in EtOAc under reflux for 1 h. 22b Harsh reaction conditions were needed for the reactions of ketene acetals (N ≈ 10) with 1c. 29 Thus, the [2+2] cycloaddition of 1,1-dimethoxy-2-methylprop-1-ene across the CN bond of 1c was reported to take place when equimolar amounts of the two reactants were heated without a solvent for 3 days at 100 °C. 29 As expected from their low nucleophilicities, toluene (N = −4.36), furan (N = 1.33), and pyrrole (N = 4.63) do not undergo uncatalyzed reactions with 1c.…”

“…29 Thus, the [2+2] cycloaddition of 1,1-dimethoxy-2-methylprop-1-ene across the CN bond of 1c was reported to take place when equimolar amounts of the two reactants were heated without a solvent for 3 days at 100 °C. 29 As expected from their low nucleophilicities, toluene (N = −4.36), furan (N = 1.33), and pyrrole (N = 4.63) do not undergo uncatalyzed reactions with 1c. 30 These arenes can be converted into the corresponding aromatic thioamides, however, by heating them with phenyl isothiocyanate (1c) in cyclohexane solution with stoichiometric amounts of AlCl 3 .…”

Adsorption of Phenyl Isothiocyanate on Si(001): A 1,2-Dipolar Surface Addition Reaction

“…We therefore conclude that the most plausible adsorption configuration is one in which the NdC bond of the isothiocyanate group undergoes a 1,2-dipolar cycloaddition reaction with the Si dimer to form Structure E. This cycloaddition product is also consistent with the known solution-phase reaction of PITC with an alkene to form a four-member ring. 33 We note that this structure will produce a high density of benzene rings on the surface. The underlying order of the dimers does not translate into exact ordering of the overlayer, but the benzene rings are held in position with respect to the dimer axis.…”

3-Methyl-2-thioxo-6-trifluoromethyl-2,3-dihydro-4(1H)-pyrimidinone

“…Fig. 1 is a stereoscopic 4-amino-2-thioxo-6-pyrimidinone monohydrate (Raper, Oughtred & Nowell, 1985), 4-benzyl-2-thiouracil ), 6-methyl-2-thiouracil (Delage, H'Naifi, Goursolle & Carpy, 1986) and 6-ethylthio-1,3-diphenyl-2-thiouracil (Schaumann, Bauch, Sieveking & Adiwidjaja, 1982).…”