Department of Chemistry, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, China.
Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, China.
Angew Chem Int Ed Engl. 2022 Aug 8;61(32):e202205919. doi: 10.1002/anie.202205919. Epub 2022 Jun 24.
1,3-Allyl and 1,2-allyl shifts through [3,3]- and [2,3]-sigmatropic rearrangements are well-established and widely used in organic synthesis. In contrast, 1,5-allyl shift through related [3,5]-sigmatropic rearrangement is unknown because [3,5]-sigmatropic rearrangement is thermally Woodward-Hoffmann forbidden. Herein, we report an unexpected discovery of a formal 1,5-allyl shift of allyl furfuryl alcohol through a 2-step sequential rearrangement. Mechanistically, this formal 1,5-allyl shift is achieved through a sequential ring expansion/contraction rearrangement: 1) Achmatowicz rearrangement (ring expansion), and 2) cascade oxonia-Cope rearrangement/retro-Achmatowicz rearrangement (ring contraction). This new 1,5-allyl shift method is demonstrated with >20 examples and expected to find applications in organic synthesis and materials chemistry.
1,3-烯丙基和 1,2-烯丙基通过 [3,3]-和 [2,3]-σ重排迁移是有机合成中常用且成熟的方法。相比之下，相关的 [3,5]-σ重排中的 1,5-烯丙基迁移是未知的，因为 [3,5]-σ重排是热伍德沃德-霍夫曼禁阻的。在此，我们报告了一个意想不到的发现，即烯丙基糠醇通过两步连续重排经历了形式上的 1,5-烯丙基迁移。从机理上讲，这种形式上的 1,5-烯丙基迁移是通过连续的环扩缩重排实现的：1）Achmatowicz 重排（环扩张），和 2）级联氧杂-科普重排/反-Achmatowicz 重排（环收缩）。这种新的 1,5-烯丙基迁移方法已通过 20 多个实例进行了验证，预计将在有机合成和材料化学中得到应用。
