[S:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6](Cl)=[O:7].C(N(CC)CC)C.[C:16]([O:24][CH2:25][C:26]#[CH:27])(=[O:23])[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1>O1CCOCC1.Cl[Pd](Cl)([P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.[Cu](I)I>[C:16]([O:24][CH2:25][C:26]#[C:27][C:6](=[O:7])[C:2]1[S:1][CH:5]=[CH:4][CH:3]=1)(=[O:23])[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1A solution of 2-thiophenecarbonyl chloride (549 mg, 3.75 mmol) in anhydrous dioxane (15 mL) was bubbled with argon for 10 minutes. Triethylamine (1.31 mL, 9.36 mmol) was added and the bubbling was maintained for 5 minutes. Bis(triphenylphosphine)palladium(II) dichloride (88 mg, 0.12 mmol), copper iodide (48 mg, 0.25 mmol) and propargyl benzoate (0.45 mL, 3.12 mmol) were added, and the reaction mixture was stirred for 1 hour at room temperature, under argon atmosphere. The solution was filtered and water (20 mL) was added to the filtrate. Layers were separated, and the aqueous layer was extracted with dichloromethane (2×20 mL). The combined organic layers were washed with a saturated solution of sodium hydrogenocarbonate (20 mL), dried over sodium sulfate and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate 100/0 to 95/5) to provide 4-oxo-4-(thiophen-2-yl)but-2-yn-1-yl benzoate (3a) (333 mg, 1.23 mmol, 39%).
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