The reaction of o-[1-(alkylthio)alkyl]phenols with silver(I) oxide at room temperature generated o-quinonemethides in good yields along with silver alkanethiolate. This mechanism, based upon one-electron oxidation, is excluded in view of several experimental facts. The resulting o-quinonemethides reacted efficiently with ethyl vinyl ether to afford cis-chromans as the result of endo cycloaddition between (E)-o-quinonemethides and the ether. Similarly, o-[1-(alkylthio)allyl]phenols were converted to cis-chromans via the corresponding (E)-o-quinonemethides (6-allylidenecyclohexadienone). In the absence of dienophiles, some chromenes were obtained from the allylphenols.
室温下,o-[1-(烷
硫基)烷基]
苯酚与
氧化银反应,能以良好产率生成邻醒
甲叉中间体和
银的烷
硫醇盐。根据几个实验事实,基于单电子氧化的机制被排除。生成的邻醒
甲叉中间体能高效地与乙基
乙烯基醚反应,通过邻醒
甲叉中间体与醚的endo环加成反应,生成顺式色满。类似地,o-[1-(烷
硫基)烯丙基]
苯酚通过相应的邻醒
甲叉中间体(6-烯丙叉环
己二烯酮)转化为顺式色满。在没有双烯亲和物存在时,从烯丙基
苯酚获得了一些色烯。