Enantioselective Palladium-Catalyzed Hydrofluorination of Alkenylarenes

Hydrofluorination of simple alkenes is an attractive strategy to prepare fluorine-containing molecules. However, the catalytic asymmetric hydrofluorination remains an ongoing challenge. Here, we describe a palladium(II)-catalyzed enantioselective hydrofluorination of alkenylarenes, by employing sulfoxide phosphine (SOP) as a chiral ligand, triarylphosphine as a secondary ligand, Selectfluor as a fluorine source, and trihexylsilane as a hydride source. Under the optimal reaction conditions, a range of chiral benzyl fluorides bearing different functional groups are obtained in good yields (up to 80%) with high enantiopurity (having an enantiomeric ratio of up to 94:6). Some mechanistic insight of this reaction is obtained using in situ one-and two-dimensional H-1-P-31 HMBC nuclear magnetic resonance spectroscopy and a catalytic cycle is proposed.