Zeng Yaxin, Gao Han, Jiang Zhong-Tao, Zhu Yulei, Chen Jinqi, Zhang Han, Lu Gang, Xia Ying
West China School of Public Health and West China Fourth Hospital, West China-PUMC C.C. Chen Institute of Health, and State Key Laboratory of Biotherapy, Sichuan University, Chengdu, 610041, China.
School of Chemistry and Chemical Engineering, Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University, Jinan, 250100, China.
Nat Commun. 2024 May 21;15(1):4317. doi: 10.1038/s41467-024-48541-5.
Transition-metal catalyzed allylic substitution reactions of alkenes are among the most efficient methods for synthesizing diene compounds, driven by the inherent preference for an inner-sphere mechanism. Here, we present a demonstration of an outer-sphere mechanism in Rh-catalyzed allylic substitution reaction of simple alkenes using gem-difluorinated cyclopropanes as allyl surrogates. This unconventional mechanism offers an opportunity for the fluorine recycling of gem-difluorinated cyclopropanes via C - F bond cleavage/reformation, ultimately delivering allylic carbofluorination products. The developed method tolerates a wide range of simple alkenes, providing access to secondary, tertiary fluorides and gem-difluorides with 100% atom economy. DFT calculations reveal that the C - C bond formation goes through an unusual outer-sphere nucleophilic substitution of the alkenes to the allyl-Rh species instead of migration insertion, and the generated carbon cation then forms the C - F bond with tetrafluoroborate as a fluoride shuttle.
由内球机制的固有偏好驱动，过渡金属催化的烯烃烯丙基取代反应是合成二烯化合物最有效的方法之一。在此，我们展示了一种外球机制，该机制存在于使用偕二氟环丙烷作为烯丙基替代物的简单烯烃的铑催化烯丙基取代反应中。这种非常规机制为偕二氟环丙烷通过C−F键断裂/重排实现氟循环提供了机会，最终得到烯丙基碳氟化合物产物。所开发的方法可耐受多种简单烯烃，能以100%的原子经济性获得仲氟化物、叔氟化物和偕二氟化物。密度泛函理论计算表明，C−C键的形成经历了烯烃对烯丙基-铑物种的异常外球亲核取代，而非迁移插入，生成的碳阳离子随后与作为氟化物载体的四氟硼酸盐形成C−F键。
