Asymmetric cycloaddition reactions represent a powerful strategy for building up complex molecular architectures, especially those with medium-sized rings. Herein, we disclose a highly diastereo- and enantioselective cycloaddition strategy that involves the palladium-catalyzed [4 + 4] cycloaddition between ortho-quinone methides and γ-methylene-δ-valerolactones. This method provided a straightforward and applicable approach to access various functionalized benzo[b]oxocines bearing adjacent all-carbon quaternary and tertiary stereocenters (38 examples, up to 95% yield, 20 : 1 dr, 98% ee). The process was efficient and scalable, and the products could be further transformed to various chiral eight-membered molecules. In addition, DFT calculations were performed to shed light on the mechanism of good stereoselectivities.

中文翻译：

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钯催化的 [4 + 4] 环加成用于高度非对映和对映选择性合成官能化苯并 [b] 氧杂辛

不对称环加成反应代表了构建复杂分子结构的强大策略，特别是那些具有中等大小环的分子结构。在此，我们公开了一种高度非对映和对映选择性的环加成策略，该策略涉及邻苯醌甲基化物和 γ-亚甲基-δ-戊内酯之间的钯催化的 [4 + 4] 环加成反应。该方法提供了一种直接且适用的方法来获取各种功能化苯并[ b]oxocines 具有相邻的全碳四级和三级立体中心（38 个示例，产率高达 95%，20:1 dr，98% ee）。该过程高效且可扩展，产品可以进一步转化为各种手性八元分子。此外，还进行了 DFT 计算以阐明良好立体选择性的机制。