[F:1][C:2]([F:17])([F:16])[C:3]1[CH:4]=[C:5]([CH:11]=[C:12]([CH:14]=C)[CH:13]=1)[C:6]([O:8][CH2:9][CH3:10])=[O:7].C[OH:19]>>[CH:14]([C:12]1[CH:11]=[C:5]([CH:4]=[C:3]([C:2]([F:17])([F:16])[F:1])[CH:13]=1)[C:6]([O:8][CH2:9][CH3:10])=[O:7])=[O:19]25.39 g (103.96 mmol) of ethyl 3-(trifluoromethyl)-5-vinylbenzoate 33 is dissolved in dry MeOH (200 mL) and reaction vessel Is cooled down to −78° C. Then O3 is bubbled through for 1.5 hours until the reaction mixture turned dark blue. Then ozone is turned off and nitrogen is bubbled through the reaction mixture to remove extra ozone from the solution. 9.6 g of dimethyl sufide (155.95 mmol, 1.5 eq) is added and the reaction mixture is stirred at −78° C. for 2 hours followed by at room temperature for another hour. All the solvents are removed and ethyl 3-formyl-5-(trifluoromethyl)benzoate 34 is isolated via flash column chromatography (5-10% EtOAc/Hex). MS: m/z [M+H+]) 247.18, 1H NMR 10.16 (s, 1H), 8.73 (s, 1H), 8.56, (s, 1H), 8.35 (s, 1H), 4.46-4.51 (q, 2H, J=7.21 Hz), 1.45-1.49 (t, 3H, J=7.21 Hz).
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