electropholes allow Stille couplings to very hindered stannanes, not possible under common conditions. In contrast, the usage of triflates and elevated temperatures yields exclusively the product of a Cine substitution. In this was, by the choice of the reaction conditions, two alternative stereoisomers can be obtained from the same stannane.
配体与
钯的比率非常低,尤其是弱的
配体和
碘化物,因为它们的电离子使Stille偶联至受阻的
锡烷,这在通常条件下是不可能的。相比之下,
三氟甲磺酸酯的使用和升高的温度仅产生Cine取代的产物。在这种情况下,通过选择反应条件,可以从相同的
锡烷获得两种替代的立体异构体。