It was found that (E)-vinylic sulfones preferentially afford (Z)-allylic sulfones as kinetically-controlled products by treatment with a base under mild conditions, while (Z)-vinylic sulfones give (E)-allylic sulfones. Such stereochemical relationship was rationalized by “syn-effect”, and its relative degree for various substituents was determined by observation of E/Z ratios of the allylic sulfones resulted from the corresponding γ-mono- or γ,γ-disubstituted vinylic sulfones as follows: RO– (R = CH3, C2H5) ArO– (Ar = p-CH3OC6H4, p-CH3C6H4, C6H5, p-NO2C6H4) ≥ AcO– > Cl– ≥ Br– > CH3– > CH3S– ≥ –CH2– (cyclic and acyclic) > (CH3)2CH– >> (CH3)3C–, C6H5–. X-Ray crystallography was performed for some vinylic sulfones to reveal the origin of the “syn-effect”.
研究发现,在温和条件下通过碱性处理,(E)-
乙烯基砜类化合物倾向于优先形成动力学控制的(Z)-烯丙基砜类产物,而(Z)-
乙烯基砜则生成(E)-烯丙基砜。这种立体
化学关系可通过“邻位效应”来解释,并且通过观察相应的γ-单取代或γ,γ-双取代
乙烯基砜所生成的烯丙基砜的E/Z比率,确定了不同取代基的相对程度如下:RO–(R=
CH3,
C2H5)> ArO–(Ar=p- OC6H4, p- C6H4,
C6H5, p-NO2C6H4)≥ AcO–> Cl– ≥ Br–> –> S– ≥ –
CH2–(环状和非环状)>( )2CH–>>( )3C–, –。对一些
乙烯基砜进行了X射线晶体学分析,以揭示“邻位效应”的起源。