63702-84-1Relevant articles and documents
2,2,6,6-Tetramethylcyclohexanethione S-methylide, a highly hindered thiocarbonyl ylide: Two-step cycloadditions
Huisgen, Rolf,Giera, Henry,Polborn, Kurt
, p. 6143 - 6153 (2005)
The switching from the concerted 1,3-dipolar cycloaddition to a two-step pathway via zwitterionic intermediates requires a major energy difference between HOMO-LUMO energies of 1,3-dipole and dipolarophile, as well as sterically demanding reactants. In contrast to previously studied models, the title compound 1C, a thiocarbonyl ylide prepared by N2 extrusion from dihydrothiadiazole 7C at 80°C, combined with 2,3-bis(trifluoromethyl) fumaronitrile (11) to give a zwitterion (gauche-10); the latter failed to close the thiolane ring by 1,5-cyclization, but formed the seven-membered ketene imine 9C by 1,7-cyclization. X-ray analysis of 9C revealed an angle-deformed cumulated bond system and a transoid relation of the CF3 groups. The relatively stable 9C allowed 19F NMR recordings from -90 to +90°C; temperature-dependent line broadening resulted from equilibration with ≤1% of an unknown isomer. Among various possible angle-strained rate processes, an inversion transoid 19?cisoid 20 is preferred which involves a topomerization at the CN bond; lateral inversion and rotation are discussed. At 80°C in solution, ketene imine 9C slowly suffered fragmentation to give trans- and cis-1,2-bis(trifluoromethyl)cyclopropane-1,2-dicarbonitrile (13)+thioketone 6C by intramolecular substitution. The reaction of 1C with ethenetetracarbonitrile furnished a tetracyanothiolane 3C, whereas 1C and dimethyl 2,3-dicyanofumarate ((E)-26) afforded thiolanes of the same trans,cis-ratio as 1C with dimethyl 2,3-dicyanomaleate ((Z)-26); a preceding (E,Z)-equilibration of 26 thwarts mechanistic conclusions. When the solvent contained water or methanol, short-lived ketene imines 4C and 31 were intercepted.
Thiones as superdipolarophiles. Rates and equilibria of nitrone cycloadditions to thioketones
Huisgen, Rolf,Fisera, Lubor,Giera, Henry,Sustmann, Reiner
, p. 9671 - 9678 (2007/10/02)
1,3-Dipolar cycloadditions of N-methyl-C,C-diphenylnitrone (15) and N-methyl-C-phenylnitrone (16) with aliphatic thioketones are equilibrium reactions. The 1,4,2-oxathiazolidines were characterized and their dissociation constants measured by 1
Gas-phase Thermolysis of a Thioketen-S-Oxide
Carlsen, Lars,Egsgaard, Helge,Schaumann, Ernst
, p. 1206 - 1211 (2007/10/02)
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.
