NFSI and Its Analogs’ Fluorination for Preparing Alkenyl Fluorides

Excerpt

The preparation of various N-fluorosulfonamides was first reported by Barton (Scheme 1) [1]. These compounds provided important precedent toward developing N-fluorobenzenesulfonimide (NFSI), due to their stability and synthesis from readily available precursors. Nevertheless, the potential to fluorinate carbanions was not explored until seminal work by Barnette that demonstrated the applicability of the reagents toward preparing fluorinated alkanes (Scheme 1b) [2]. Subsequently, Schwartz et al. pioneered an analogous transformation providing fluorinated alkenes (Scheme 1c) [3]. At that time, the reactions of alkenyl-metal (Hg, Al, B, and Zr) species with electrophilic halogen reagents were used to prepare vinyl halides, but the reactions had not been extended to fluorinated alkenes. To expand the scope of these transformations, Schwartz and coworkers used vinyl iodides as precursors to organolithium intermediates and demonstrated the stereospecific synthesis of fluorinated alkenes in excellent yields using N-fluoro(tert-butyl)benzenesulfonamide. Later, Differding and Ofner communicated the preparation of NFSI and included a single example of alkene fluorination using Schwartz’s conditions, showcasing the potential of NFSI to prepare fluorinated alkenes (Scheme 1d) [4].

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