[F:1][CH:2]([F:8])[C:3]([O:5]CC)=O.C[O-].[Na+].[C:12]([C:15]1[S:16][C:17]([Br:20])=[CH:18][CH:19]=1)(=[O:14])[CH3:13].Cl>CCOCC.C1COCC1>[F:8][CH:2]([F:1])[C:3](=[O:5])[CH2:13][C:12]([C:15]1[S:16][C:17]([Br:20])=[CH:18][CH:19]=1)=[O:14]
Ethyl difluoroacetate (2.43 g, 19.6 mmol) was placed in a 100 mL round bottom flask, and dissolved in ether (15 mL). To the stirred solution was added 25 weight % sodium methoxide (4.23 g, 19.5 mmol) followed by 2-acetyl-5-bromothiophene (3.59 g, 17.5 mmol). After two hours a precipitate formed and THF (15 mL) was added to allow stirring to continue. The reaction was stirred at room temperature 6.2 hours, then treated with 3N HCl (20 mL). The organic layer was collected and washed with brine, dried over MgSO4, and concentrated in vacuo to give a yellow oil which was crystallized from methylene chloride/isooctane to give yellow needles (3.63 g, mp 83.5°-85° C., 73% ). 1H NMR (CDCl3) 300 MHz 14.60 (br s, 1H), 7.53 (d, J=4.0 Hz, 1H), 7.15 (d, J=4.0 Hz, 1H), 7.19 (m, 1H), 6.32 (s, 1H), 6.04 (t, J=54.2 Hz, 1H); 19F NMR (CDCl3) 300 MHz: -127.00 (d) ; M+282.
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