Palladium(II)-Catalyzed Substituted Pyridine Synthesis from α,β-Unsaturated Oxime Ethers via a C–H Alkenylation/Aza-6π-Electrocyclization Approach,Organic Letters

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Palladium(II)-Catalyzed Substituted Pyridine Synthesis from α,β-Unsaturated Oxime Ethers via a C–H Alkenylation/Aza-6π-Electrocyclization Approach
Organic Letters ( IF 4.9 ) Pub Date : 2021-02-10 , DOI: 10.1021/acs.orglett.1c00061
Takahiro Yamada ₁ , Yoshimitsu Hashimoto ₁ , Kosaku Tanaka ₁ , Nobuyoshi Morita ₁ , Osamu Tamura ₁

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An efficient synthetic method for multisubstituted pyridines from β-aryl-substituted α,β-unsaturated oxime ethers and alkenes via Pd-catalyzed C–H activation has been developed. Systematic optimization of catalyst ligands revealed that sterically hindered pyridines increased the reactivity. Mechanistic studies suggested that the products are formed by Pd-catalyzed β-alkenylation of α,β-unsaturated oxime followed by aza-6π-electrocyclization. Various oximes and alkenes could be utilized to afford multisubstituted pyridines with complete regioselectivity. The usefulness of this methodology was showcased by the synthesis of 4-aryl-substituted pyridine derivatives, which are difficult to access with previously reported Rh-catalyzed approaches with alkenes.

中文翻译：

α–β-不饱和肟醚通过C–H烯基化/Aza-6π-电环化方法催化钯（II）取代的吡啶合成

已经开发了一种有效的合成方法，可通过Pd催化的CH活化从β-芳基取代的α，β-不饱和肟醚和烯烃中合成多取代的吡啶。催化剂配体的系统优化表明，位阻吡啶可提高反应活性。机理研究表明，产物是由Pd催化α，β-不饱和肟的β-烯基化，然后进行aza-6π-电环化而形成的。可以使用各种肟和烯烃来提供具有完全区域选择性的多取代吡啶。该方法的有用性通过4-芳基取代的吡啶衍生物的合成得到了证明，这是以前报道的用烯烃进行的Rh催化方法难以获得的。

更新日期：2021-03-05

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