Divergent reactivities in fluoronation of allylic alcohols: synthesis of Z-fluoroalkenes via carbon–carbon bond cleavage† †Electronic supplementary information (ESI) available: Full data for the optimization of reaction conditions, detailed experimental procedures, and full characterization of substrates and products. See DOI: 10.1039/c7sc00483d Click here for additional data file.

The incorporation of uorine in pharmaceuticals and agrochemicals has become common practice due to the attractive properties that uorine can provide. Accordingly, uorination chemistry has been extensively explored in the last few decades to deliver uorinated compounds with various substitution patterns. Despite the great progress achieved for catalytic Csp3– F bond formation as well as aryl uoride synthesis, signicant limitations still exist in the preparation of certain structures such as uoroalkenes that are highly valuable as peptide isosteres and building blocks. The preparation of uoroalkenes through direct C–F formation requires the use of sensitive organometallic reagents or intermediates (such as alkenyl lithium) and is thus limited in substrate scope. Alternatively, classical olenation reactions using uorine-containing reagents have been extensively explored; the control of olen geometry in thesemethods, however, has remained an unsolved challenge. Only very recently the synthesis of 1,2-disubstituted Z-uoroalkenes was achieved through catalytic cross metathesis. We present here a highly efficient and operationally simple method that can deliver functionalized trisubstituted Zuoroalkenes from readily available allylic alcohols with excellent stereoselectivity. Electrophilic uorination of enolate intermediates and alkenes has proven to be a highly successful strategy for C–F bond formation. By utilizing allylic alcohols as the substrate, a tandem metal-catalyzed isomerization to the enolate followed by uorination has been reported to prepare a-uoroketones. Alternatively, uorination of an alkene moiety followed by semipinacol rearrangement was realized to prepare b-uoroketones