[CH3:1][O:2][C:3]1[CH:4]=[C:5]([CH:10]=[C:11]([O:14][CH3:15])[C:12]=1[OH:13])[C:6]([O:8][CH3:9])=[O:7].CN(C)C=O.[H-].[Na+].I[CH2:24][CH3:25]>C(OCC)(=O)C.C(OCC)(=O)C.CCCCCC>[CH3:15][O:14][C:11]1[CH:10]=[C:5]([CH:4]=[C:3]([O:2][CH3:1])[C:12]=1[O:13][CH2:24][CH3:25])[C:6]([O:8][CH3:9])=[O:7]Combine methyl 3,5-dimethoxy-4-hydroxy-benzoate (2.12 g, 10 mmol) and dimethylformamide (50 mL). Cool in an ice bath. Add portionwise, sodium hydride (0.4 g, 16.7 mmol). after 2 hours, add iodoethane (4 mL, 50 mmol). Warm to ambient temperature. After 18 hours, dilute the reaction mixture with ethyl acetate and extract with water, 1M hydrochloric acid solution, a saturated sodium bicarbonate solution, and then brine. Dry the organic layer over MgSO4, filtered and evaporated in vacuo to give a residue. chromatograph the residue on silica gel eluting with 5% ethyl acetate/hexane to give methyl 3,5-dimethoxy-4-ethoxy-benzoate.
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