Catalytic Enantioselective Cyclization and C3-Fluorination of Polyenes
摘要:
(Xylyl-phanephos)Pt2+ in combination with XeF2 mediates the consecutive diastereoselective cation-olefin cyclization/fluorination of polyene substrates. Isolated yields were typically in the 60-69% range while enantioselectivities reached as high as 87%. The data are consistent with a stereoretentive fluorination of a P2Pt-alkyl cation intermediate.
多烯环化反应是高效且独特的仿生转化,可从其无环前体产生复杂的多环分子。近年来,随着可见光的使用,已经开发了各种阳离子介导和自由基介导的合成方法来获得高度非对映选择性环化。在本文中,我们报道了在酚环不同位置含有溴基和氯基的香叶基酚的可见光介导、无催化剂级联环化。在不使用任何光催化剂的六氟-2-丙醇中,使用蓝色 LED 灯以高立体选择性获得所需的环化产物。卤素(特别是氯或溴)的存在对于这种环化的成功至关重要,使用蓝色 LED 灯代替绿色 LED 灯也是如此。尽管这一成功的确切原因尚不清楚,但讨论了一些可能的解释,并且光反应的进一步控制研究应该成为该领域任何努力的一部分。
Organic Photocatalytic Cyclization of Polyenes: A Visible-Light-Mediated Radical Cascade Approach
作者:Zhongbo Yang、Han Li、Long Zhang、Ming-Tian Zhang、Jin-Pei Cheng、Sanzhong Luo
DOI:10.1002/chem.201503118
日期:2015.10.12
A visible‐light‐mediated, organic photocatalytic stereoselective radical cascade cyclization of polyprenoids is described. The desired cascade cyclization products are achieved in good yields and high stereoselectivities with eosin Y as photocatalyst in hexafluoro‐2‐propanol. The catalyst system is also suitable for 1,3‐dicarbonyl compounds, which require only catalytic amounts of LiBr to promote the