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

The asymmetric synthesis of gamma-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(111) 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 y-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.