C(NC(C)C)(C)C.C([Li])CCC.[CH2:13]1[O:23][C:16]2([CH2:21][CH2:20][C:19](=[O:22])[CH2:18][CH2:17]2)[O:15][CH2:14]1.C1C=CC(N[S:31]([C:34]([F:37])([F:36])[F:35])(=[O:33])=[O:32])=CC=1>C1COCC1>[F:35][C:34]([F:37])([F:36])[S:31]([O:22][C:19]1[CH2:18][CH2:17][C:16]2([O:15][CH2:14][CH2:13][O:23]2)[CH2:21][CH:20]=1)(=[O:33])=[O:32]To a solution of diisopropylamine, (6.24 mL, 44.2 mmol) in THF (60 mL) at −78° C. under argon was slowly added n-butyllithium (17.7 mL, 44.2 mmol, 2.5 M in hexanes). The mixture was stirred for 30 min at that temperature before 1,4-cyclohexanedione mono-ethylene ketal (6.00 g, 38.4 mmol) was added slowly as a solution in THF (20 mL). The mixture was stirred for an additional 30 min at −78° C. and then n-phenyltriflamide (13.7 g, 38.4 mmol) was slowly added as a suspension in THF (50 mL). This mixture was stirred overnight with gradual warming to room temperature. The solvent was removed in vacuo and the remaining oil was partitioned between 3:1 ethyl acetate/hexane and water. The layers were separated and the organic layer was washed with water (3×), dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo to give 1,4-dioxaspiro[4.5]dec-7-en-8-yl trifluoromethanesulfonate.
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