[CH2:1]([O:3][CH:4]([O:7][CH2:8][CH3:9])[C:5]#[CH:6])[CH3:2].C([Li])CCC.CCCCCC.[F:21][C:22]([F:29])([F:28])[C:23](OCC)=[O:24]>C1COCC1>[CH2:1]([O:3][CH:4]([O:7][CH2:8][CH3:9])[C:5]#[C:6][C:23](=[O:24])[C:22]([F:29])([F:28])[F:21])[CH3:2]3,3-Diethoxy-1-propyne (10 mL, 70 mmol) was dissolved under argon in THF (200 mL) and cooled to −70° C. Then a 1.6 M solution of n-butyllithium in hexane (48 mL, 77 mmol) was added slowly at −70° C., then allowed to warm to −30° C. and stirred at −30° C. for 30 min, then cooled again to −70° C. Ethyl trifluoroacetate (9.2 mL, 77 mmol) was added in one portion at −70° C. (the temperature rose to −50°) then stirred without cooling until −30° C. was reached, then quenched with sat. NH4Cl solution (20 mL). Extraction: 2×AcOEt, 1× sat. NH4Cl sat., 1× sat. NaCl. Chromatography on silica gel in heptane/ethyl acetate 5:1 afforded 4.94 g (31%) of an orange oil. GC/MS: m/z=223 (M−H).
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