The reaction regioselectivity of gem-difluoroalkenes is dependent on the intrinsic polarity. Thus, the reversal of the regiose-lectivity of the addition reaction of gem-difluoroalkenes remains a formidable challenge. Herein, we described an unprecedented reversal of regioselectivity of hydrogen atom transfer (HAT) to gem-difluoroalkenes triggered by Fe–H species for the formation of difluoroalkyl radicals. Hydrogenation of the in-situ generated radicals gave difluoromethylated products. Mechanism experiments and theoretical studies revealed that the kinetic effect of the irreversible HAT process resulted in the reversal of the regioselectivity of this scenario, leading to the formation of a less stable α-difluoroalkyl radical regioisomer. On basis of this new reaction of gem-difluoroalkene, the iron-promoted hydrohalogenation of gem-difluoroalkenes for the efficient synthesis of aliphatic chlorodifluoromethyl-, bromodifluoromethyl- and iododifluoromethyl-containing compounds was developed. Particularly, this novel hydrohalogenation of gem-difluoroalkenes provided an effect and large-scale access to various iododifluoromethylated compounds of high value for synthetic application.

中文翻译：

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铁促进的偕二氟烯烃氢化和氢卤化反应区域选择性的逆转

偕二氟烯烃的反应区域选择性取决于其固有极性。因此，偕二氟烯烃加成反应的区域选择性的逆转仍然是一个艰巨的挑战。在此，我们描述了由 Fe-H 物质引发的氢原子转移（HAT）到偕二氟烯烃的区域选择性前所未有的逆转，以形成二氟烷基自由基。原位产生的自由基的氢化得到二氟甲基化产物。机理实验和理论研究表明，不可逆HAT过程的动力学效应导致了这种情况的区域选择性逆转，导致形成不太稳定的α-二氟烷基自由基区域异构体。在偕二氟烯烃的这一新反应的基础上，开发了铁促进偕二氟烯烃的氢卤化反应，用于有效合成脂肪族氯二氟甲基、溴二氟甲基和碘二氟甲基化合物。特别是，这种新型的偕二氟烯烃的氢卤化反应为合成应用具有高价值的各种碘二氟甲基化化合物提供了有效和大规模的途径。