[Cl:1][C:2]1[CH:9]=[CH:8][C:7]([C:10]([F:13])([F:12])[F:11])=[CH:6][C:3]=1[CH:4]=O.C1C[O:17][CH2:16][CH2:15]1>C(OCC)C.O.[Zn+2].[Br-].[Br-].[Cl-].[Cl-].[Zn+2]>[Cl:1][C:2]1[CH:9]=[CH:8][C:7]([C:10]([F:13])([F:12])[F:11])=[CH:6][C:3]=1[CH:4]=[CH:15][CH:16]=[O:17]To a solution of 2-chloro-5-trifluoromethylbenzaldehyde (300 mg) in 5 mL THF was added 40 mg of ZnBr2. With stirring, 360 mg of α,α-bis(trimethylsilyl)-t-butylacetaldimine (7) was added, and stirring was continued overnight. The solution was cooled to 10° C., then hydrolyzed by the addition of a solution of ZnCl2 (40 mg) in diethyl ether/water (3 mL each), followed by stirring at room temperature for 1 h. The solids were removed by filtration through Celite and the filtrate extracted with diethyl ether (2×). The combined ether extracts were washed with water and brine, dried over magnesium sulfate, filtered and concentrated to provide the title compound as a light brown oil (220 mg): 1H NMR (CDCl3) δ 6.09 (s, 2H), 6.14 (s, 1H), 6.86-6.98 (m, 4H), 7.43 (d, 1H, J=9.6 Hz), 9.69 (d, 1H, J=4.5 Hz).
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