Ligand-controlled regioselective and chemodivergent defluorinative functionalization of gem-difluorocyclopropanes with simple ketones,Chemical Science

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Ligand-controlled regioselective and chemodivergent defluorinative functionalization of gem-difluorocyclopropanes with simple ketones
Chemical Science ( IF 7.6 ) Pub Date : 2021-11-08 , DOI: 10.1039/d1sc05451a
Leiyang Lv ₁ , Huijun Qian ₁ , Yangyang Ma ₁ , Shiqing Huang ₁ , Xiaoyu Yan ₁ , Zhiping Li ₁

Affiliation

Modulating the reaction selectivity is highly attractive and pivotal to the rational design of synthetic regimes. The defluorinative functionalization of gem-difluorocyclopropanes constitutes a promising route to construct β-vinyl fluorine scaffolds, whereas chemo- and regioselective access to α-substitution patterns remains a formidable challenge. Presented herein is a robust Pd/NHC ligand synergistic strategy that could enable the C–F bond functionalization with exclusive α-regioselectivity with simple ketones. The key design adopted enolates as π-conjugated ambident nucleophiles that undergo inner-sphere 3,3′-reductive elimination warranted by the sterically hindered-yet-flexible Pd-PEPPSI complex. The excellent branched mono-defluorinative alkylation was achieved with a sterically highly demanding IHept ligand, while subtly less bulky SIPr acted as a bifunctional ligand that not only facilitated α-selective C(sp³)–F cleavage, but also rendered the newly-formed C(sp²)–F bond as the linchpin for subsequent C–O bond formation. These examples represented an unprecedented ligand-controlled regioselective and chemodivergent approach to various mono-fluorinated terminal alkenes and/or furans from the same readily available starting materials.

中文翻译：

偕二氟环丙烷与简单酮的配体控制区域选择性和化学发散脱氟官能化

调节反应选择性非常有吸引力，并且对于合成方案的合理设计至关重要。偕二氟环丙烷的脱氟官能化构成了构建β-乙烯基氟支架的有前途的途径，而化学和区域选择性获得α-取代模式仍然是一个艰巨的挑战。本文提出了一种强大的 Pd/NHC 配体协同策略，可以使用简单的酮实现具有独特 α-区域选择性的 C-F 键功能化。关键设计采用烯醇化物作为 π 共轭环境亲核试剂，通过空间位阻但灵活的 Pd-PEPPSI 络合物进行内球 3,3'-还原消除。优异的支链单脱氟烷基化是通过空间要求高的 IHept 配体实现的，而体积稍小的 SIPr 作为双功能配体，不仅促进 α-选择性 C(sp ³ )–F 裂解，而且还使新形成的C(sp ² )–F 键作为后续 C–O 键形成的关键。这些例子代表了从相同的容易获得的起始材料中制备各种单氟化末端烯烃和/或呋喃的前所未有的配体控制的区域选择性和化学发散方法。

更新日期：2021-11-24

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