Annulation of 2<i>H</i>-Pyran onto 1-Oxa- or 1-Azacyclohexane-2,4-diones and Their Analogues via Sequential Condensation with α-Substituted Enals and 6π-Electrocyclization
作者:Md. Imran Hossain、Elkhabiry Shaban、Taku Ikemi、Wei Peng、Hiroyuki Kawafuchi、Tsutomu Inokuchi
DOI:10.1246/bcsj.20130069
日期:2013.7.15
2H-Pyrans are constructed on a 1-oxa- or 1-azacyclohexane-2,4-dione core via Knoevenagel condensation with enals followed by 6π-electrocyclization, which are readily catalyzed with ethylenediammonium diacetate. This formal [3 + 3] strategy constitutes C–O and C–C bond making and the diastereomer formation is circumvented using 6,6-disubstitution with the same aryl group in the 1-oxacyclohexane-2,4-diones. This facile methodology significantly advances the access to polysubstituted bicyclic 2H-pyrans with a versatile substrate choice and improved stability of the product.
通过Knoevenagel缩合反应与烯醛反应,随后进行6π-电环化反应,以1-氧杂-或1-氮杂环己烷-2,4-二酮为核心构建了2H-吡喃衍生物,这些反应易于用乙二胺二乙酸盐催化。这种形式上的[3 + 3]策略构成了C–O和C–C键的形成,并通过在1-氧杂环己烷-2,4-二酮中使用相同的芳基进行6,6-二取代来避免立体异构体的形成。这种简便的方法学极大地促进了多取代双环2H-吡喃的合成,具有多样化的底物选择和产品稳定性的提高。