Lewis acid-promoted hydrofluorination of alkynyl sulfides to generate α-fluorovinyl thioethers

A new method for the preparation of α-fluorovinyl thioethers is reported which involves the hydrofluorination of alkynyl sulfides with 3HF·Et(3)N, a process that requires Lewis acid activation using BF(3)·Et(2)O and TiF(4). The method gives access to a range of α-fluorovinyl thioethers, some in high stereoselectivity with the Z-isomer predominating over the E-isomer. The α-fluorovinyl thioether motif has prospects as a steric and electronic mimetic of thioester enols and enolates, important intermediates in enzymatic C–C bond forming reactions. The method opens access to appropriate analogues for investigations in this direction.