Synthesis of azetidines via visible-light-mediated intermolecular [2+2] photocycloadditions
Synthesis of azetidines via visible-light-mediated intermolecular [2+2] photocycloadditions
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DOI：
10.1038/s41557-020-0541-1
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发表时间：
2020-09-23
期刊：
影响因子：
21.8
通讯作者：
Schindler, Corinna S.
中科院分区：
文献类型：
--
作者：
Becker, Marc R.;Wearing, Emily R.;Schindler, Corinna S.
分子间 [2+2] 光环加成是合成高张力四元环的有效方法。尽管这种方法通常用于合成氧杂环丁烷和环丁烷，但通过分子间氮杂Paterno-Buchi反应合成氮杂环丁烷仍然非常不发达。在这里，我们报道了可见光介导的分子间氮杂Paterno-Buchi反应，该反应利用肟（特别是2-异恶唑啉-3-羧酸盐）独特的三重态反应性。此类肟的反应性可以通过市售铱光催化剂的三重态能量转移来利用，并允许与多种烯烃进行[2+2]环加成。该方法的特点是操作简单、条件温和、范围广泛，并且允许从容易获得的前体合成高度官能化的氮杂环丁烷。重要的是，可获取的氮杂环丁烷产物可以很容易地转化为游离的、未受保护的氮杂环丁烷，这代表了获取这些非常理想的合成目标的新方法。
Intermolecular [2+2] photocycloadditions represent a powerful method for the synthesis of highly strained, four-membered rings. Although this approach is commonly employed for the synthesis of oxetanes and cyclobutanes, the synthesis of azetidines via intermolecular aza Paterno-Buchi reactions remains highly underdeveloped. Here we report a visible-light-mediated intermolecular aza Paterno-Buchi reaction that utilizes the unique triplet state reactivity of oximes, specifically 2-isoxazoline-3-carboxylates. The reactivity of this class of oximes can be harnessed via the triplet energy transfer from a commercially available iridium photocatalyst and allows for [2+2] cycloaddition with a wide range of alkenes. This approach is characterized by its operational simplicity, mild conditions and broad scope, and allows for the synthesis of highly functionalized azetidines from readily available precursors. Importantly, the accessible azetidine products can be readily converted into free, unprotected azetidines, which represents a new approach to access these highly desirable synthetic targets.