掌性磷酸催化異噁唑啉及2-甲氧基呋喃進行不對稱插烯曼尼希反應

Abstract

運用有機小分子進行不對稱催化為有效得到高光學活性產物之方法，高效率建構四級碳中心之策略，尤其含氮之雜環結構，常見於天然物分子中，且有許多的生物活性，廣泛出現應用於藥物中，故在有機合成領域中備受重視。本實驗室開發了一種不對稱有機催化Vinylogous Mannich 反應，以良好的產率和對映選擇性（最高為97% ee）得到兩個手性中心 Δ4-異噁唑啉支架，該支架帶有一個四級碳立體中心。該步驟包括在手性磷酸存在下產生異噁唑離子，然後通過不對稱陰陽離子定向催化進行去芳香化和加成反應。Asymmetric organocatalysis is a powerful tool for the construction of opticallyactive molecules. In particular, nitrogen-containing high optical pure scaffolds have been well established and provide in biologically active compounds, pharmaceuticals and drugs. For the last several years, we have been developed many organocatalytic reactions using various kind of organic molecules as catalysts for example, primary and secondary amines, thioureas, Brønsted acids like phosphoric acids, Brønsted bases like chincona derivatives.An asymmetric organocatalytic Vinylogous Mannich reaction was developed to access Δ4 -isoxazoline scaffolds having two chiral centers with a quaternary stereogenic center in good yields and excellent enantioselectivity (up to 97% ee). This protocol involves in situ generation of isoxazolium ions in the presence of a chiral phosphoric acid followed by the dearomatization and addition reaction with nucleophile (2-methoxyfuran) through asymmetric counteranion-directed catalysis.