Fluoride-Triggered Synthesis of 1‑Aryl-2,2-difluoroalkenes via Desilylative Defluorination of (1-Aryl)-2,2,2-trifluoroethyl-silanes

An efficient route for the synthesis of 1-aryl-2,2-difluoroalkenes via 1,2-desilylative defluorination is disclosed. Only a catalytic amount of fluoride source is required to initiate the desilylation and afford gem-difluoroalkenes in very good to quantitative yields, using mild reaction conditions in dimethyl carbonate as a green solvent. This reaction uses (1-aryl)-2,2,2-trifluoroethyl-silanes, which are easily prepared via the insertion reaction of trifluoro­ethyl diazo alkanes into the Si–H bond of tertiary organosilanes. (1-Aryl)-per­fluoro­alkyl-silanes cleanly afford the corresponding (Z)-1-benzylidene­perfluoro­alkanes, which upon hydro­de­fluorin­ation furnish the (E)-β­(per­fluoro­alkyl)­styrene derivatives with excellent yield and complete stereoselectivity. A one-pot system involving sequential insertion and desilylative–defluorination is also suitable for this transformation. This method demonstrates the usefulness of organosilanes toward the preparation of fluorinated alkenes as synthetically useful targets.