C([N-]C(C)C)(C)C.[Li+].[C:9]([C@@H:13]1[O:17][C:16](=[O:18])[C@H:15]([CH3:19])[O:14]1)([CH3:12])([CH3:11])[CH3:10].[F:20][C:21]([F:25])([F:24])[CH2:22]I.[NH4+].[Cl-]>>[C:9]([C@@H:13]1[O:17][C:16](=[O:18])[C@@:15]([CH3:19])([CH2:22][C:21]([F:25])([F:24])[F:20])[O:14]1)([CH3:12])([CH3:10])[CH3:11]To a solution of lithium diisopropylamide (prepared from 13 ml of diisopropylamine and 54 ml of 1.6 M n-BuLi in hexanes in 200 ml of anhydrous THF at 0° C.) at −72° C. was added slowly 2-(s)-t-butyl-5-(s)-methyl-1,3-dioxolan-4-one (12.95 g, 81.9 mmol, Tetrahedron, 1984, 40, 1313) at such a rate as to maintain the internal temperature below −60° C. and the mixture was aged at −72° C. for an hour. 1,1,1-Trifluoro-2-iodoethane (25 g, 119 mmol) was added quickly, the reaction temperature increased to −45° C. and the mixture was aged at −72° C. for 45 min. and then allowed to warm up to −20° C. over 20 min. Saturated aq. NH4Cl was then added and the product was extracted in i-PrOAc, dried over Na2SO4, concentrated and distilled under reduced pressure to afford 7.51 g of a brown oil BP 90° C./20 mm Hg.
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