C([Li])CCC.[CH3:6][O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[C:11]([O:18][CH3:19])=[CH:10][C:9]=1[CH2:20][OH:21].[Br:22]C(F)(F)C(F)(F)Br.O>C1COCC1>[CH3:6][O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[C:11]([O:18][CH3:19])=[C:10]([Br:22])[C:9]=1[CH2:20][OH:21]n-Butyllithium (2.9 mL, 7.33 mmol, 2.5 M in hexanes) was added dropwise to a solution of 23a (400 mg, 1.83 mmol) in THF (25 mL) at −78° C. under argon. The reaction mixture was slowly warmed to room temperature and stirred for 1 h. 1,2-dibromotetrafluoroethane (0.26 mL, 2.20 mmol) was added dropwise and the solution was stirred for 1 h. Water (10 mL) was added and the mixture was extracted with EtOAc (3×). The combined organic layers were dried (MgSO4), filtered and evaporated. Column chromatography of the crude product (35:65 EtOAc:hexanes) afforded 23d (273 mg, 50%, 63% based on recovered 23a, 84 mg) as a yellow solid; Rf=0.62 (35:65 EtOAc:hexanes); mp=115-117° C.; 1H NMR (CDCl3): δ 8.11 (m, 2H), 7.57 (m, 2H), 5.03 (s, 2H), 4.02 (s, 3H), 3.99 (s, 3H), 2.36 (bs, 1H).
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