[H-].[Na+].[CH3:3][S:4]([CH:7]([CH3:13])[C:8]([O:10][CH2:11][CH3:12])=[O:9])(=[O:6])=[O:5].[I-].[K+].Br[CH2:17][CH2:18][C:19]#[CH:20]>CN(C)C=O>[CH3:13][C:7]([S:4]([CH3:3])(=[O:5])=[O:6])([CH2:20][CH2:19][C:18]#[CH:17])[C:8]([O:10][CH2:11][CH3:12])=[O:9]
Sodium hydride (60% dispersion in mineral oil, 3.9 g, 17.2 mmol, 1.2 equiv) was added to a solution of ethyl 2-(methylsulfonyl)propanoate (14.8 g, 82.0 mmol, 1.0 equiv) in N,N-dimethylformamide (180 mL) at room temperature. After the evolution of gas subsided (approx. 30 min), a stirred mixture of potassium iodide (2.89 g, 17.2 mmol, 0.2 equiv) and 4-bromobut-1-yne (10.9 g, 82.0 mmol, 1.0 equiv) in N,N-dimethylformamide (20 mL) was added dropwise via cannula (approx. 2 h). After 3 h, the reaction was quenched with water (200 mL), and the resulting solution was extracted with 1:1 ethyl acetate-hexanes (2×200 mL). The combined organic phases were washed with water (2×50 mL), brine (50 mL), dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude material was purified by flash chromatography (340 g silica gel column, 0-25% gradient ethyl acetate in hexanes) to provide the title compound as a clear colorless oil (6.63 g, 35%). MS (GCMS) m/z 233 (M+1). 1H NMR (400 MHz, CHLOROFORM-d) δ1.33 (t, J=7.12 Hz, 3H) 1.64 (s, 3H) 2.00 (t, J=2.63 Hz, 1H) 2.11-2.22 (m, 1H) 2.22-2.32 (m, 1H) 2.33-2.45 (m, 1H) 2.46-2.58 (m, 1H) 3.05 (s, 3H) 4.28 (q, J=7.16 Hz, 2H).
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