189503-05-7Relevant articles and documents
The fluoride anion-catalyzed sulfurization of thioketones with elemental sulfur leading to sulfur-rich heterocycles: First sulfurization of thiochalcones ?
Bielinski, Dariusz M.,Heimgartner, Heinz,Mloston, Grzegorz,Urbaniak, Katarzyna,Wreczycki, Jakub
, (2021/06/12)
Fluoride anion was demonstrated as a superior activator of elemental sulfur (S8) to perform sulfurization of thioketones leading to diverse sulfur-rich heterocycles. Due to solubility problems, reactions must be carried out either in THF using tetrabutylammonium fluoride (TBAF) or in DMF using cesium fluoride (CsF), respectively. The reactive sulfurizing reagents are in situ generated, nucleophilic fluoropolysulfide anions FS(8?x)?, which react with the C=S bond according to the carbophilic addition mode. Dithiiranes formed thereby, existing in an equilibrium with the ring-opened form (diradicals/zwitterions) are key-intermediates, which undergo either a step-wise dimerization to afford 1,2,4,5-tetrathianes or an intramolecular insertion, leading in the case of thioxo derivatives of 2,2,4,4-tetramethylcyclobutane-1,3-dione to ring enlarged products. In reactions catalyzed by TBAF, water bounded to fluoride anion via H-bridges and forming thereby its stable hydrates is involved in secondary reactions leading, e.g., in the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone to the formation of some unexpected products such as the ring enlarged dithiolactone and ring-opened dithiocarboxylate. In contrast to thioketones, the fluoride anion catalyzed sulfurization of their α,β-unsaturated analogues, i.e., thiochalcones is slow and inefficient. However, an alternative protocol with triphenylphosphine (PPh3) applied as a catalyst, offers an attractive approach to the synthesis of 3H-1,2-dithioles via 1,5-dipolar electrocyclization of the in situ-generated α,β-unsaturated thiocabonyl S-sulfides. All reactions occur under mild conditions and can be considered as attractive methods for the preparation of sulfur rich heterocycles with diverse ring-size.
The conversion of thioketones to 1,2,4,5-tetrathianes and its mechanism
Huisgen, Rolf,Rapp, Jochen
, p. 507 - 525 (2007/10/03)
Thiobenzophenone and adamantanethione react with sulfur (1:1) under catalysis by sodium thiophenoxide in acetone at rt furnishing 1,2,4,5-tetrathianes (9 and 43) in high yields. An attack of the oligothiolate (R-SX-) on the C-atom of C = S is proposed as initiating step. Thione S-sulfides (R2C = S+ - S-, thiosulfines) cannot be intermediates, since they combine fast with thiones affording 1,2,4-trithiolanes. With more sulfur, adamantanethione produces the 1,2,3,5,6-pentathiepane-bis(spiroadamantane) (44) which interconverts with the tetrathiane, but not with the 1,2,4-trithiolane, in an equilibrium catalyzed by R-SX-. According to 13C NMR evidence, the tetrathiane-bis(spiroadamantane) occurs in a twist conformation which inverts with ΔG≠ 16.0 kcal mol-1.
FROM THIIRANES TO THIOCARBONYL S-SULFIDES; RECENT RESULTS
Huisgen, Rolf
, p. 63 - 94 (2007/10/02)
A novel nucleophilic catalysis for the desulfurization of thiiranes is described.Triphenylthiirane is quantitatively converted to triphenylethylene by some molpercent sodium thiophenoxide or other thiolates in DMSO at 35 deg C.A rapid initial reaction is retarded by the eliminated sulfur leading to a pseudo-first-order reaction under quasi-stationary conditions.The suggested mechanism is based on structure-rate relationships. - The thiolate-catalyzed reaction of cis-2,3-diphenylthiirane is exceptional in furnishing equimolar quantities of cis-stilbene and 3,4,6,7-tetraphenyl-1,2,5-trithiepane (2 diastereoisomers with bilateral symmetry); mechanistic implications - thiolate attack on sulfur or C-atom of thiirane - are discussed. - Desulfurization of 2,2-diphenylthiirane by thiobenzophenone or other thioketones gives access to thiocarbonyl S-sulfides ("thiosulfines") which are intercepted by 1,3-cycloadditions to activated acetylenes or to thiones.
