posted on 2021-09-03, 20:06authored byVirginie Carreras, Thierry Ollevier
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.