Progress of Catalytic Asymmetric Diels-Alder Reactions of 2-Pyrones

2-Pyrone is a type of heterocycles with a conjugated diene motif.It can react as a privileged diene in Diels-Alder reactions.In the past several decades, 2-pyrone-based Diels-Alder reactions have been widely used in the total synthesis of complex natural products.Therefore, the catalytic asymmetric Diels-Alder reactions of 2-pyrones have attracted increasing attention from the synthetic community in recent years.The research progress of catalytic asymmetric normal-electron-demand Diels-Alder reactions and inverse-electron-demand Diels-Alder reactions, and their applications in total synthesis of natural products are summarized.Keywords 2-pyrone; Diels-Alder reactions; asymmetric catalysis; total synthesis of natural products Diels-Alder 反应 [1] 是有机合成中最重要的反应之 一, 有关它的合成方法、应用及机理的研究在有机化学 中占据重要的地位 [2] .2-吡喃酮是一种具有部分芳香性 的杂环化合物, 其结构中含有共轭二烯和内酯官能团.它作为一种特殊的双烯体参与 Diels-Alder 反应有很长 的历史.1931 年, 也就是 Diels-Alder 反应被发现三年之 后, Diels 和 Alder 又报道了香豆灵酸甲酯与马来酸酐在 甲苯回流的条件下发生[4＋2]反应, 然后发生逆[4＋2] 反应脱除二氧化碳, 再与过量的马来酸酐发生第二次 [4 ＋ 2] 反 应 (Scheme 1) [3] .这 是 首 个 2-吡 喃 酮 参 与 Diels-Alder 反应的例子.2-吡喃酮的 Diels