343869-25-0Relevant articles and documents
Structure and mechanism of hydrolysis of diaryl(acylamino)(chloro)-λ4-sulfanes and diaryl(acylamino)sulfonium salts
Nagy, Peter,Csampai, Antal,Szabo, Denes,Varga, Jeno,Harmat, Veronika,Ruff, Ferenc,Kucsman, Arpad
, p. 339 - 349 (2007/10/03)
Aryl (methylaminocarbonylaryl) sulfides were converted by t-BuOCl to diaryl(acylamino)(chloro)-λ4-sulfanes or the corresponding diaryl(acylamino)sulfonium chlorides depending on the substituent of the S-aryl group. 1H NMR data showed that chloro-λ4-sulfanes exist only in CDCl3 and DMSO-d6 solvents, whereas in CD3OD complete ionic dissociation takes place, leading to sulfonium chlorides. Both the chemical shifts of 1H NMR signals and NOE data suggest that chloro-λ4-sulfanes and sulfonium salts having an o-MeO, o-Cl or o-Me substituent on the phenyl ring assume a skew conformation, whereas the aryl ring in compounds without an ortho-substituent can rotate practically free about the S-C(1') axis. In o-MeO-substituted derivatives there exists an equatorial 1,4 type S...O close contact. Sulfonium salts with axial 1,5 type S...O close contacts involving neighbouring COOMe, CONHMe, COMe or NO2 groups occur in butterfly conformation, like spiro-λ4-sulfanes. There is a correlation between the 15N chemical shift of the amide-nitrogen and the elongation of the S-N covalent bond, by which the interdepending S-N, S-Cl and S...O bonds can be characterized. Effective intermolecular S...O interaction was detected between the sulfonium centre and solvent molecules having a negatively polarized oxygen atom. The hydrolysis of sulfonium salts yielding sulfoxides was investigated by a kinetic method in 98:2 (v/v) dioxane-water mixture and in water. On the basis of medium, substituent (ρ + 1.03), steric, salt and kinetic isotope effects detailed mechanisms involving a hydroxy-λ4-sulfane intrmediate are proposed. The more reactive sulfonium salts with a five-membered hetero ring are hydrolyzed by water, whereas the sulfonium centre of the less reactive analogues with a six-membered ring is attacked only by OH- ions.
