[Cl:1]C1C=C(C=CC=1)CP(=O)([O-])[O-].[Li][CH2:14][CH2:15][CH2:16][CH3:17].[CH3:18][CH2:19][CH2:20][CH2:21][CH2:22][CH3:23].[CH:24](=O)[CH2:25][CH2:26]CC#C>C1COCC1>[Cl:1][C:20]1[CH:19]=[CH:18][CH:23]=[CH:22][C:21]=1[CH:17]=[CH:16][CH2:15][CH2:14][CH2:24][C:25]#[CH:26]An oven-dried 250 mL three-necked round-bottomed flask under a nitrogen atmosphere was charged with 3-chlorobenzylphosphonate (3.9 g, 15 mmol) and THF (60 mL). The solution was cooled to 0° C. in an ice bath for 15 min, then n-BuLi (12 mL of a 1.6 M n-hexane solution, 19 mmol) was added dropwise over 10 min via syringe. The mixture was stirred at 0° C. for 30 min, then aldehyde 4 (1.0 g, 10 mmol) in THF (40 mL) was added. The solution was warmed to rt and was stirred for 3 h. The consumption of the starting material was monitored by TLC (AcOEt/n-hexane 0.5:9.5). The reaction was quenched by adding sat'd aq ammonium chloride solution (70 mL). The layers were separated and the aqueous phase was extracted with ether (3×50 mL). The combined organic layers were washed with brine (2×50 mL), dried over Na2SO4, gravity filtered, and concentrated under reduced pressure. The reaction residue was purified by silica gel flash chromatography, eluting with AcOEt/n-hexane 0.5:9.5, to provide 1.11 g of the title compound as a colorless oil in a 54% yield.
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