[F:1][C:2]1[CH:3]=[CH:4][C:5]([SH:13])=[C:6]([CH:12]=1)[C:7]([O:9][CH2:10][CH3:11])=[O:8].F[C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][C:16]=1[N+:21]([O-:23])=[O:22].C([O-])([O-])=O.[K+].[K+]>CC(C)=O>[F:1][C:2]1[CH:3]=[CH:4][C:5]([S:13][C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][C:16]=2[N+:21]([O-:23])=[O:22])=[C:6]([CH:12]=1)[C:7]([O:9][CH2:10][CH3:11])=[O:8]To a solution of ethyl 5-fluoro-2-mercaptobenzoate (I) (25.0 g, 124.9 mmol) and 1-fluoro-2-nitrobenzene (13.2 mL, 124.9 mmol) in acetone (700 mL) was added K2CO3 (34.5 g, 249.7 mmol) at ambient temperature. The yellow suspension was heated to reflux (60° C.) for 5 hours. The reaction mixture was quenched with 1N HCl (500 mL), diluted with EtOAc (1000 mL) and filtered through a bed of diatomaceous earth. The aqueous layer was removed, the EtOAc layer was washed with 1N HCl (250 mL×2) and brine (200 mL×1), dried and the solvent removed under reduced pressure. The material was carried forward with no further purification to yield ethyl 5-fluoro-2-(2-nitrophenylthio)benzoate (II) (39.3 g, 95%) as a dark yellow solid. m/z (ES+) M+1=322.1; HPLC tR=0.88 min. 1H NMR (300 MHz, DMSO-d6): δ 1.09 (t, 3H, J=7.2 Hz), 4.16 (q, 2H, J=7.2 Hz), 7.07 (d, 1H, J=7.2 Hz), 7.40-7.75 (m, 5H), 8.20 (d, 1H, J=7.2 Hz).
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