“<i>Syn-Effect</i>” in the Desulfonylation Reaction of<i>α</i>,<i>α</i>-Dialkylated (<i>E</i>)-Allylic Sulfones
作者:Atsushi Shibayama、Tetsuya Nakamura、Takahiro Asada、Takehiko Shintani、Yutaka Ukaji、Hideki Kinoshita、Katsuhiko Inomata
DOI:10.1246/bcsj.70.381
日期:1997.2
It was found that the desulfonylation reaction of α,α-dialkylated (E)-allylic sulfones with a base preferentially affords the sterically unfavorable (Z)-alkadienes. The relative degree of the “syn-effect”, which is herein defined as an effect which stabilizes the syn-conformation, leading to (Z)-products, in the transition state against the steric hindrance, was revealed for various substituents at the δ-position of the (E)-allylic sulfones to be as follows: RO– >> CH3– > RS– > –CH2– > (CH3)2CH– >> (CH3)3C– > C6H5–. This finding is in accord with a previously found tendency in the conversion of (E)-vinylic sulfones to the corresponding allylic sulfones under basic conditions.
研究发现,α,α-二烷基化(E)-烯丙基砜与碱的脱磺化反应优先产生立体上不利的(Z)-烷二烯。(E)-烯丙基砜的 δ 位上的不同取代基所产生的 "合成效应 "的相对程度如下:RO- >> CH3- >> CH4- >> CH5- >> CH6- >> CH7- >> CH8-RO->>CH3->RS->-CH2->(CH3)2CH->>(CH3)3C->C6H5-。这一发现与之前发现的(E)-乙烯砜在碱性条件下转化为相应的烯丙基砜的趋势一致。