20333-39-5Relevant articles and documents
Nucleophilic reactions at the sulfur of thiiranium and thiirenium ions. New insight in the electrophilic additions to alkenes and alkynes. Evidence for an episulfurane intermediate
Fachini, Marco,Lucchini, Vittorio,Modena, Giorgio,Pasi, Manuela,Pasquato, Lucia
, p. 3944 - 3950 (1999)
The thiiranium hexachloroantimonates 1a, 3, and 5a-c and the thiirenium hexachloroantimonates 6a-c and 7a with exocyclic S-R substituent (R = Me, Et, i-Pr) react at sulfur with dialkyl disulfides R″SSR″ (R″ = Me, Et and R″ ≠ R) in CD2Cl2 at 25°C to give S-R″ substituted ions. The reaction rates are affected by the steric hindrance of the substituents at sulfur and at ring carbons. t-2,t-3-Di-tert-butyl-r-1-methylthiiranium hexachloroantimonate (2) does not react, and the t-2-tert-butyl-c-3-phenyl-r-1-methylthiiranium (5a) reacts about 100 times faster than the c-2,t-3-di-tert-butyl-r-1-methylthiiranium ion (1a). The analysis of the kinetic data suggests that the sulfonium sulfur undergoes attack by the disulfide in the ring plane from a direction that is parallel to the C-C ring bond. This is also the direction which ensures the maximum overlap with the LUMO of thiiranium or thiirenium ions (determined at the RHF/3-21G*//RHF/3-21G* level). The combined consideration of the approach modality and of the maximum orbital overlap suggests that the nucleophilic substitution at sulfonium sulfur is not an SN2-like reaction but occurs via an intermediate with episulfurane-like structure. The principle of microscopic reversibility will dictate that this is also the first intermediate in the electrophilic sulfenylation of unsaturated C-C bonds.
Thiophilic addition of organolithiums to trithiocarbonate oxides (sulfines). Synthesis of β-oxoketene dithioacetals, 1,4-dicarbonyl compounds, and allyl sulfoxides
Leriverend, Catherine,Metzner, Patrick,Capperucci, Antonella,Degl'Innocenti, Alessandro
, p. 1323 - 1342 (2007/10/03)
Reaction of trithiocarbonates with meta-chloroperoxybenzoic acid in CH2Cl2 at 0°C affords the corresponding S-oxides. These sulfines are relatively stable comppounds which can be purified by chromatography. They react readily with organolithiums in THF at -78°C in a thiophilic manner to give carbanions which are stabilized by three sulfur groups. Hydrolysis affords trithioorthoester oxides. The thermal behaviour of these hindered products has been investigated and new rearrangenrent processes have been evidenced. The former carbanions are soft nucleophiles: 1,4-addition of these intermediates to α-enones was achieved selectively to lead to β-oxo ketenedithioacetals, which are easily transformed into 4-oxoalkanethioates. This 'Umpolung' route allows the formal use of the (alkylthio)carbonyl anion. A thiophilic addition was also observed with allylsilanes in the presence of n-Bu4NF furnishing allyl sulfoxides.
SCAVENGING OF RADICALS FROM THE GAS PHASE BY FREEZING WITH DIMETHYL DISULFIDE: 2. RADICALS FROM DISCHARGES AND A FLAME OF ACETYLENE.
Kubitza,Schottler,Homann
, p. 695 - 700 (2007/10/02)
The method of detecting radicals from low-pressure gas-phase systems by scavenging with dimethyl disulfide (DMD) has been applied to microwave discharges in C//2H//2/He mixtures and to a C//2H//2/O//2 flame. It was accomplished by condensing a supersonic nozzle beam from the reaction system together with a beam of DMD on a liquid-N//2 cooled surface. The scavenging products were measured by GC/MS after warming-up. Radicals measured in the discharge were C//2H, C//4H, C//6H, C//3H//2, C//2 besides H atoms. Preliminary measurements on the flame showed that C//6H//5 (phenyl), CH//2, C//3H//2, besides H and O atoms were prominent radicals at the end of the oxidation zone. The concentration of phenyl is of the same order as that of e. g. naphthalene.
