AbstractDefluorinative manipulation of polyfluorinated molecules has shown great promise due to its granting of synthetic versatility to inert C−F bonds. The development of chemo‐, stereo‐ and regioselective strategies to realize highly efficient formation of either the linear/branched or E/Z products from gem‐difluorocyclopropanes (gem‐F2CPs) is a challenging task. Herein, we have realized palladium/NHC‐catalyzed fluoroallylation/annulation of hydrazones with gem‐F2CPs that incorporate the hydrazone N2 moiety into the products. The thermodynamically unstable fluorinated E‐allylation products with aryl ketone hydrazones were obtained for the first time, while the di‐alkyl ketone hydrazones yielded the monofluorinated products with branched selectivity under similar reaction conditions. With aldehyde hydrazones, two kinds of pyrazoles were obtained via a defluorinative allylation/annulation cascade, in which different carbon atoms of gem‐F2CPs could be incorporated into the pyrazole rings regiospecifically. DFT calculations revealed that the divergent selectivity was kinetically controlled and the final C−C bond formation proceeded through a 7‐membered TS.
摘要 由于惰性 C-F 键具有合成多功能性,因此对多氟分子的脱氟处理已显示出巨大的前景。开发具有化学、立体和区域选择性的策略,以实现从宝石-二氟环丙烷(gem-F2CPs)高效形成线性/枝状或 E/Z 产物,是一项具有挑战性的任务。在此,我们实现了钯/NHC 催化的氟烯丙基化/烷基化肼与 gem-F2CPs 的反应,将腙的 N2 分子结合到产物中。在类似的反应条件下,芳基酮肼首次获得了热力学上不稳定的氟化 E- 烯丙基化产物,而二烷基酮肼则获得了具有支链选择性的单氟化产物。利用醛肼,通过去氟烯丙基化/annulation 级联反应获得了两种吡唑,其中 gem-F2CPs 的不同碳原子可以区域特异性地结合到吡唑环中。DFT 计算显示,发散选择性受动力学控制,最终的 C-C 键形成是通过 7 元 TS 进行的。