吸电子基取代苯偶姻的实用合成

Practical Synthesis of Benzoins Substituted by Electron-withdrawing Groups

将经典维生素B1法安息香缩合反应改进在惰性气体保护下进行,且在反应完成后加入硫代硫酸钠和锌粉抑制产物分解,可制备过去主要依赖KCN等剧毒催化剂合成的吸电子基团取代的苯偶姻衍生物.推测经典维生素B1法分离不到产物,可能是由于柱层析时硅胶或氧化铝与维生素B1分解产物的共同作用导致贫电子苯偶姻产物的分解,而Zn-Na2S2O3溶液可以抑制这种作用.

The Benzoins condensation reaction by the way of the classical Vitamin B1 is substituted under the protection of inert gases and adds aqueous Na2 S2 O3 and zinc dust after its completion to inhibit product disintegration to make thiamin derivate which is replaced by electron-withdrawing groups depended upon KCN hyper toxic catalyst synthesis.It is supposed that the classical way of Vitamin B1 segregated nothing and electron-deficient benzoins could not be prepared by classical Vitamin B1 -promoted ones might be owing to the synergy between silica gel /alumina and decomposed Vitamin B1 during column chromatography,which could be inhibited by Zn-Na2 S2 O3 .