Synthesis of Isoxazol-5(2H)-one Derivatives via (tBuO)2Mg Promoted [3 + 2] Annulations of δ-Acetoxy Allenoates with Hydroxylamine.

Herein, an efficient (tBuO)2Mg promoted [3 + 2] annulation of δ-acetoxy allenoates with N-benzylhydroxylamine has been developed. This method provides a concise and facile protocol to synthesize vinylated isoxazol-5(2H)-one derivatives stereospecifically in a broad substrate scope with high efficiency (31 examples, up to 87% yield).