Under a nitrogen atmosphere, heptyl 4-iodobenzoate (2a) (3.64 g, 10.5 mmol) was dissolved in anhydrous triethylamine (8.6 mL), and anhydrous tetrahydrofuran (4.0 mL), triphenylphosphine (39.3 mg, 0.150 mmol), copper (I) iodide (43.8 mg, 0.230 mmol), and Pd(PPh3)2Cl2 (27.9 mg, 0.0397 mmol) were added. Thereafter, a solution of heptyl 4-ethynylbenzoate (4a) (2.64 g, 10.8 mmol) in anhydrous tetrahydrofuran (2.0 mL) was slowly added dropwise, and the mixture was stirred at room temperature for 3 hr. The reaction solution was filtered through celite and, after removal under reduced pressure, diluted with ethyl acetate, washed with water and saturated brine, and the organic layer was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was purified by column chromatography (ethyl acetate:hexane=1:10). Subsequent recrystallization from methanol/ethanol (5:1, v/v) gave bis[4-(heptyloxycarbonyl)phenyl]acetylene (5a) (4.64 g, yield 95%) as a white solid.
