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

A new method for the preparation of alpha-fluorovinyl thioethers is reported which involves the hydrofluorination of alkynyl sulfides with 3HF center dot Et3N, a process that requires Lewis acid activation using BF3 center dot Et2O and TiF4. The method gives access to a range of alpha-fluorovinyl thioethers, some in high stereoselectivity with the Z-isomer predominating over the E-isomer. The alpha-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.