An Efficient Difluorohydroxylation of Indoles Using Selectfluor as a Fluorinating Reagent

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-5(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.

Direct conversion of indoles to 3,3-difluoro-2-oxindoles via electrophilic fluorination

3,3-Difluoro-2-oxindoles can be obtained directly from indoles in moderate yields via electrophilic fluorination using N-fluorobenzenesulfonimide as a mild fluorinating reagent. The presence of tert-butyl hydroperoxide during the reaction, together with additional heating after quenching the reaction with triethylamine, is beneficial to the formation of the desired product.