Organocatalytic Asymmetric One-Pot Sequential Conjugate Addition/Dearomative Fluorination: Synthesis of Chiral Fluorinated Isoxazol-5(4H)-ones

A facile one-pot sequential conjugate addition/dearomative fluorination transformation of isoxazol-5(4H)ones with nitroolefins and N-fluorobenzenesulfonimide (NFSI) has been developed. By using a bifunctional chiral tertiary amino-thiourea catalyst, a series of chiral fluorinated isoxazol-S(4H)-ones containing one fluorine-substituted quarternary stereocenter were obtained in high yields with high enantio- and diastereoselectivities. Further transformation of adducts could afford isoxazolidin-5-one derivatives with three contiguous stereocenters.