对位取代苯基烯丙基醚的烷基化反应

THE ALKYLATION OF p-SUBSTITUTED PHENYL ALLYL ETHER

烯丙基醚是一个重要的β-羰基化合物的合成等价物,已有许多应用,它的应用和反应的区域选择性有密切关系.最近,Werstiuk 曾对烯丙基化合物的反应及其在合成上的应用作了综述,并讨论了立体因素对烯丙基化合物反应区域选择性的影响.Evans 等研究了烯丙基烷基醚阴离子和亲电试剂反应中位阻和区域选择性的关系.当亲电试剂是卤代烷时,烯丙基醚中烷基体积增大,γ位烷基化的比例也增大;

The influence of the electronic effect of the substituents in P-substituted phenylallyl ether on the regio-selectivity of alkylation was studied.It is found that anelectron-donating substituent favours γ-alkylation while the presence of electron-withdrawing group gives mainly α-alkylation products.A linear free energy relationshipexists in plotting log(α/γ)versus the polar nature of the substituents(Hammett's σconstants)in p-substituted phenyl allyl ether except phenyl allyl ether.An explana-tion was given for such a variation.