14680-00-3Relevant articles and documents
Effects of adjacent acceptors and donors on the stabilities of carbon-centered radicals
Bordwell,Zhang, Xian-Man,Alnajjar, Mikhail S.
, p. 7623 - 7629 (1992)
The radical stabilization energies (RSEs) for 21 radicals, GCH2*, where G is an electron donor or acceptor group, were estimated from differences in homolytic C-H bond dissociation energies (ABDEs relative to that of methane). These RSEs were found to agree reasonably well in order with theoretically calculated RSEs that have been reported and with those obtained by averaging RSEs from nine different methods (a literature RRSx scale). But the RSEs estimated from ΔBDEs were almost without exception larger because the theoretical calculations and RRSx method greatly underestimate the size of most RSEs. The RSEs for GCH2* radicals were found to be enhanced to the extent that G is able to delocalize an odd electron on an adjacent carbon atom and were diminished by the presence of electron-withdrawing properties in G. Most groups stabilize the radical, but when the electron-withdrawing effect of the group is large, as in F3C? and Me3N+CH2? radicals, the net effect is to destabilize the radical relative to the methyl radical. The RSEs of 12 radicals of the type RSC?HG or PhSC?HG, relative to that of the GCH2? radical, were found to increase progressively as the acceptor group G was changed along the series Ph, fluorenyl (Fl), CO2Et, CN, COMe, and COPh. The RSEs of these donor-acceptor radicals were all smaller than the sum of the RSEs of the singly-substituted radicals, GCH2? and PhSCH2? (or RSCH2?). The effects of a second PhS or like donor and of a second acceptor on the RSEs were also determined. Examination of the RSEs of GC?(Ph)CN radicals indicates that the interactions of G and CN in the GC?CN moieties, with G = MeO, EtS, or c-C5H10N, are not synergistic as has been claimed from ESR studies.
Catalyst-Free Insertion of Sulfoxonium Ylides into Aryl Thiols. A Direct Preparation of β-Keto Thioethers
Dias, Rafael M. P.,Burtoloso, Antonio C. B.
, p. 3034 - 3037 (2016/07/06)
Insertion of sulfoxonium ylides into the S-H bond of aryl thiols without the need for a catalyst is demonstrated, furnishing β-keto thioethers in excellent yield in most cases. The method overcomes traditional syntheses that employ metal catalysts in combination with diazo compounds or toxic and hard-prepared haloketones. The experimental setup consists of mixing the reagents in acetonitrile at room temperature. Additional experimental as well as kinetic isotopic effect studies give some insight into the mechanism of this reaction.
