Into a 100-mL round-bottom flask, was placed 4-(benzyloxy)-3,5-difluorobenzaldehyde and 3-(benzyloxy)-2,4-difluorobenzaldehyde (4 g, 16.11 mmol, 1.00 equiv, crude), ethyl 2-(triphenylphosphoranylidene)propanoate (8.75 g, 24.14 mmol, 1.50 equiv) and toluene (60 mL). The resulting solution was stirred for 12 h at 110° C. The resulting mixture was then concentrated under vacuum. The resulting residue was applied onto a silica gel column with ethyl acetate/petroleum ether (1:8) to yield ethyl (2E)-3-[4-(benzyloxy)-3,5-difluorophenyl]-2-methylprop-2-enoate and ethyl (2E)-3-[3-(benzyloxy)-2,4-difluorophenyl]-2-methylprop-2-enoate as yellow oil.
