Organocatalytic Friedel-Crafts Alkylation/Lactonization Reaction of Naphthols with 3-Trifluoroethylidene Oxindoles: The Asymmetric Synthesis of Dihydrocoumarins
作者:Yun-Long Zhao、Qin-Xin Lou、Long-Sheng Wang、Wen-Hui Hu、Jun-Ling Zhao
DOI:10.1002/anie.201609390
日期:2017.1.2
Naphthols and 3‐trifluoroethylidene oxindoles were found to undergo an asymmetric Friedel–Crafts alkylation/lactonization reaction, catalyzed by only 2.5 mol % of a quinine‐derived squaramide catalyst, to afford the corresponding α‐aryl‐β‐trifluoromethyl dihydrocoumarin derivatives in high yields (up to 99 %) with excellent enantio‐ and diastereoselectivities (up to 98 % ee, >20:1 d.r.). Importantly
发现萘酚和3-三氟乙叉基吲哚会发生不对称的Friedel-Crafts烷基化/内酯化反应,仅需2.5摩尔%奎宁衍生的方酰胺催化剂即可催化,从而以高收率提供相应的α-芳基-β-三氟甲基二氢香豆素衍生物(高达99%)具有优异的对映异构和非对映异构选择性(高达98%ee,> 20:1 dr)。重要的是,在温和的反应条件下,内酯化是通过在羟吲哚的酰胺基序处萘酚羟基的亲核攻击而进行的。该方案代表了通过有效的分子内酰胺CN键断裂和酯化过程形成二氢香豆素的新策略。