Modular Synthesis of Tetrahydrofluorenones from 5-Alkylidene Meldrum's Acids

The one-pot synthesis of tetrahydrofluorenones, the core
6-5-6 tricyclic structural motif found in norditerpenoid natural
products, from alkylidene Meldrum's acids via thermal
Diels−Alder/BF3·OEt2-catalyzed Friedel−Crafts acylation
reactions is described. A series of tetrahydrofluorenones was
assembled in good yields, and the Diels−Alder/Friedel−Crafts acylation protocol allowed modification of the substitution within the rings.

本研究报道了四氢芴酮类化合物（tetrahydrofluorenones）的一锅法合成策略：该类化合物的核心结构为存在于去甲二萜类天然产物中的6-5-6三环结构基元，合成以亚烷基麦氏酸（alkylidene Meldrum's acids）为起始原料，经由热诱导狄尔斯-阿尔德（Diels−Alder）/三氟化硼乙醚络合物（BF3·OEt2）催化傅克酰基化（Friedel−Crafts acylation）串联反应实现。系列四氢芴酮类化合物均以良好收率被成功合成，且该狄尔斯-阿尔德/傅克酰基化反应体系可实现环上取代模式的多样化修饰。