Highly Efficient Asymmetric Synthesis of Chiral γ‑Alkenyl Butenolides Catalyzed by Chiral N,N′‑Dioxide–Scandium(III) Complexes

The asymmetric synthesis of γ-alkenyl butenolides was accomplished by conjugated addition of butenolides to alkynones. Both terminal alkynones and nonterminal alkynones were applicable to the N,N′-dioxide–scandium­(III) catalytic system. The corresponding products were obtained in good to excellent yields (up to 99%) with high E/Z ratios and high enantioselectivities (up to 98% ee). The novel methods of building both γ-alkenyl butenolides and continuing epoxidation products facilitated constructing core structure of biologically active natural products and synthetic intermediates. Additionally, one-pot Michael addition/epoxidation performed well with our catalytic system.本研究通过丁烯内酯与炔酮的共轭加成反应，实现了γ-烯基丁烯内酯（γ-alkenyl butenolides）的不对称合成。端基炔酮与非端基炔酮均适用于该N,N′-二氧配体-钪(III)催化体系（N,N′-dioxide–scandium(III) catalytic system）。所得目标产物具有良好至优异的收率（最高可达99%），同时具备优异的E/Z选择性与对映选择性（最高可达98% ee）。该构建γ-烯基丁烯内酯及后续环氧化产物的新型方法，可助力具有生物活性的天然产物核心结构及合成中间体的构建。此外，采用该催化体系的一锅法迈克尔加成/环氧化反应同样表现优异。