Stille coupling versus cine substitution. Electronic effects also influence coupling sterically hindered stannanes
作者:Alexander Flohr
DOI:10.1016/s0040-4039(98)01058-2
日期:1998.7
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。