ChemInform Abstract: “Syn‐Effect” in the Conversion of (E)‐Vinylic Sulfones to the Corresponding Allylic Sulfones.

Abstract

Syn-Effect" in the Conversion of (E)-Vinylic Sulfones to the Corresponding Allylic Sulfones.-Various γ-mono-and γ,γ-disubstituted (E)-vinylic sulfones are reacted under mild basic conditions to afford preferentially the isomeric (Z)-allylic sulfones as the kinetically controlled products. This outcome is rationalized by the "syn" effect and its relative degree for various substituents is evaluated by 1H NMR spectroscopic determination of the E/Z ratios of the resulting allylic sulfones. Thus, the following series are obtained: R-O (R: Me, Et) .simeq. Ar-O (Ar: p-anisyl, p-tolyl, phenyl, p-nitrophenyl) . gtoreq. Ac-O ¿ Cl ≥ Br ¿ Me ¿ MeS ≥ -CH2-(cyclic and acyclic) ¿ iPr tBu, phenyl. Some vinylic sulfones are submitted to X-ray crystal analyses in order to reveal the origin of the "syn" effect. -(HIRATA, T.; SASADA, Y.; OHTANI, T.; ASADA, T.; KINOSHITA, H.; SENDA, H.; INOMATA, K.; Bull. Chem. Soc. Jpn. 65 (1992) 1, 75-96; Dep. Chem., Fac. Sci., Kanazawa Univ., Kanazawa 920, Japan; EN)