[Cl:1][C:2]1[CH:9]=[C:8]([C:10]([F:13])([F:12])[F:11])[CH:7]=[CH:6][C:3]=1[C:4]#N.[H-].C([Al+]CC(C)C)C(C)C.C(O)(=[O:26])C.ClCCl>C1(C)C=CC=CC=1>[Cl:1][C:2]1[CH:9]=[C:8]([C:10]([F:13])([F:12])[F:11])[CH:7]=[CH:6][C:3]=1[CH:4]=[O:26]Dissolve 2-chloro-4-trifluoromethylbenzonitrile (405 mg, 1.97 mmol) in anhydrous toluene (7 mL) and cool in a dry ice/ethanol bath. Add diisobutylaluminum hydride (DIBAL) (3.94 mL, 3.94 mmol, 1.0 M in toluene) slowly. Stir 30 min. Warm to room temperature, add acetic acid (2 mL) and wafer (10 mL) and stir for 2 hours. Extract the aqueous layer with ethyl acetate twice. Wash the organic layer with potassium sodium tartrate solution (Rochelle salt) twice. Dry (magnesium sulfate), filter, and concentrate to give a residue. Chromatograph the residue on silica gel eluting with a gradient of 100:0 to 1:1 hexanes:dichloromethane to give 2-chloro-4-trifluoromethylbenzaldehyde (123 mg, 30%). 1H NMR (400 MHz, CDCl3) δ 10.52 (s, 1H), 8.05 (d, 1H, J=8.0 Hz), 7.75 (s, 1H), 7.66 (d, 1H, J=8.0 Hz).
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