[CH2:1]([SH:3])[CH3:2].[H-].[Na+].[CH2:6]([O:8][C:9](=[O:19])[C:10]1[CH:15]=[C:14]([F:16])[C:13](Cl)=[N:12][C:11]=1[Cl:18])[CH3:7].O>C1COCC1>[CH2:6]([O:8][C:9](=[O:19])[C:10]1[CH:15]=[C:14]([F:16])[C:13]([S:3][CH2:1][CH3:2])=[N:12][C:11]=1[Cl:18])[CH3:7]
Ethanethiol (15.08 mL, 204 mmol) was added slowly to a stirred suspension of NaH (60% in Mineral oil, 8.15 g, 204 mmol) in THF and stirred for 30 min at room temperature to yield a white thick suspension. This suspension was diluted by cold THF, cooled to 0° C. and transferred to an already cooled solution of 2,6-dichloro-5-fluoro-nicotinic acid ethyl ester (65) (48.5 g, 204 mmol) in THF at −20° C. under argon by maintaining the temperature below −10° C. The solution was stirred at −20° C. for 15 min and allowed to come at room temperature slowly. The solution was poured into water and extracted by ethyl acetate. The organic layer was dried over MgSO4 and concentrated under reduced pressure to yield 53 g (98%) of 2-chloro-6-ethylsulfanyl-5-fluoro-nicotinic acid ethyl ester (66) as brown liquid. 1H-NMR (DMSO-d6): δ 1.33 (m, 6H), 3.19 (q, J=7.2 Hz, 2H), 4.33 (q, J=7.2 Hz, 2H), 8.10 (d, J=9.6 Hz, 1H); EIMS m/z 264 (M+1).
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