4413-23-4Relevant articles and documents
1,3-Dipolar cycloadditions of diphenyldiazomethane to thioketones: Rate measurements disclose thiones to be superdipolarophiles
Huisgen, Rolf,Langhals, Elke
, p. 433 - 442 (2007/10/03)
1,3-Dipolar cycloadditions of diphenyldiazomethane to thioketones afford 2,5-dihydro-1,3,4-thiadiazoles 8, which rapidly lose N2. The liberated thiocarbonyl ylides 10 furnish thiiranes 9 by electrocyclic ring closure. The rate constants, measured by spectrophotometry (DMF, 40°C) for 16 cycloaliphatic and aromatic thioketones and one cyclic trithiocarbonate, stretch over five powers of 10 with fluorene-9-thione at the top and 2,2,5,5-tetramethylcyclopentanethione at the bottom. Electron-releasing substituents decrease the cycloaddition rate of thiobenzophenone; thus, the ambiphilic diphenyldiazomethane reacts as nucleophilic partner with the electrophilic thioketone. The influence of substituents and ring size on the reactivity of cycloalkanethiones, which are sterically hindered by two gem-dimethyl groups, will be discussed. Compared with electron-deficient C=C and C≡C bonds, thiones are superdipolarophiles.
Studies on reactions of thioketones with trimethyl(trifluoromethyl)silane catalyzed by fluoride ions
Mloston, Grzegorz,Prakash, G. K. Surya,Olah, George A.,Heimgartner, Heinz
, p. 1644 - 1658 (2007/10/03)
Treatment of 2,2,4,4-tetramethylcyclobutane-1,3-dione (6) in THF with CF3SiMe3 in the presence of tetrabutylammonium fluoride (TBAF) yielded the corresponding 3-(trifluoromethyl)-3-[(trimethylsilyl)oxy]cyclobutanone 7 (Scheme 1) via nucleophilic addition of a CF3- anion at the C=O group and subsequent silylation of the alcoholate. Under similar conditions, the 'monothione' 1 reacted to give thietane derivative 8 (Scheme 2), whereas in the case of 'dithione' 2 only the dispirodithietane 9, the dimer of 2, was formed (Scheme 3). A conceivable mechanism for the formation of 8 is the ring opening of the primarily formed CF3 adduct A followed by ring closure via the S-atom (Scheme 2). In the case of thiobenzophenones 4, complex mixtures of products were obtained including diarylmethyl trifluoromethyl sulfide 10 and 1,1-diaryl-2,2-difluoroethene 11 (Scheme 4). Obviously, competing thiophilic and carbophilic addition of the CF3- anion took place. The reaction with 9H-fluorene-9-thione (5) yielded only 9,9′-bifluorenylidene (14; Scheme 6); this product was also formed when 5 was treated with TBAF alone. Treatment of 4a with TBAF in THF gave dibenzhydryl disulfide (15; Scheme 7), whereas, under similar conditions, 1 yielded the 3-oxopentanedithioate 17 (Scheme 9). The reaction of dithione 2 with TBAF led to the isomeric dithiolactone 16 (Scheme 8), and 3 was transformed into 1,2,4-trithiolane 18 (Scheme 10).
Reaction of thiobenzophenones with norbornadiene: unusual formation of a seven-membered cyclic sulfide
Okuma, Kentaro,Shiki, Kyoko,Shirokawa, Takafumi,Kojima, Kazuki,Shioji, Kosci
, p. 1281 - 1288 (2007/10/03)
Reaction of thiobenzophenone with 2,5-norbornadiene afforded an unusual seven-membered cyclic sulfide whereas 4,4′-dimethoxythiobenzophenone reacted with 2,5-norbornadiene to afford the corresponding quinone derivative via [4+2] type cycloaddition reaction. The mechanisms of these reactions are discussed.
