I[C:2]1[C:3]([CH3:12])=[CH:4][C:5]([CH3:11])=[C:6]([CH:10]=1)[C:7]([OH:9])=[O:8].[C:13]1(P(C2C=CC=CC=2)C2C=CC=CC=2)[CH:18]=CC=C[CH:14]=1.[Cl-].C([Al+]CC)C.[C]=[O:39]>COCCOC.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>[CH3:11][C:5]1[CH:4]=[C:3]([CH3:12])[C:2]([C:14](=[O:39])[CH2:13][CH3:18])=[CH:10][C:6]=1[C:7]([OH:9])=[O:8]Into a 100-mL autoclave (30 atm), was placed a solution of 5-iodo-2,4-dimethylbenzoic acid (compound 1.3, 2.00 g, 7.24 mmol) in ethylene glycol dimethyl ether (20 mL). Triphenylphosphine (190 mg, 0.73 mmol), Pd(PPh3)2Cl2 (500 mg, 0.71 mmol) and diethylaluminum chloride (2M, 10.8 mL, 21.6 mmol) were added to the reaction mixture. The resulting mixture was stirred under pressure with carbon monoxide (gas, 30 atm) at 80° C. for 15 h. (CAUTION: Highly toxic gas at high pressure. All necessary safety precautions were performed). After cooling to room temperature, the mixture was carefully purged, then quenched with 20 mL of water. Aqueous HCl (2M) was added carefully to adjust the pH to 5-6 and the aqueous layer was extracted with ethyl acetate (100 mL). The combined organic layers were washed with brine (2×100 mL), dried (Na2SO4), filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography with ethyl acetate/petroleum ether (1:40-1:20) as the eluent to yield the title compound as a light yellow solid (1.2 g, 80%).
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