[OH:1][C:2]1[C:11]([CH3:12])=[C:10](O)[CH:9]=[CH:8][C:3]=1[C:4]([O:6]C)=[O:5].[C:14](=O)([O-])[O-].[Cs+].[Cs+].I[CH2:21][CH3:22].[OH-].[Na+].CN([CH:28]=[O:29])C>O1CCOCC1>[CH2:21]([O:1][C:2]1[C:11]([CH3:12])=[C:10]([O:29][CH2:28][CH3:14])[CH:9]=[CH:8][C:3]=1[C:4]([OH:6])=[O:5])[CH3:22]
Methyl 2,4-dihydroxy-3-methyl-benzoate (193 mg, 1.06 mmol) was dissolved in DMF (1 mL) containing cesium carbonate (1.03 g, 3.18 mmol). Iodoethane (847 μL, 10.6 mmol) was added and the reaction mixture was allowed to stir for 86 hours. The reaction mixture was then filtered and evaporated to dryness. The crude material was then dissolved in a mixture of dioxane (2 mL) and sodium hydroxide (1.1 mL of 1.0 M, 1.1 mmol). The reaction mixture was then heated at 80° C. for 75 minutes. The dioxane was evaporated to dryness and the reaction mixture was made acidic with 4M hydrochloric acid. The aqueous layer was extracted 3 times with ethyl acetate. The combined ethyl acetate extracts were then dried over sodium sulfate, filtered, and evaporated to dryness to yield 2,4-diethoxy-3-methyl-benzoic acid (189 mg, 80%) as a pale yellow solid which was used without further purification. 1H NMR (400 MHz, DMSO) δ 12.37 (s, 1H), 7.62 (d, J=8.7 Hz, 1H), 6.79 (d, J=8.8 Hz, 1H), 4.08 (q, J=6.9 Hz, 2H), 3.87 (q, J=7.0 Hz, 2H), 2.06 (s, 3H), 1.36 (t, J=6.9 Hz, 3H), 1.30 (t, J=7.0 Hz, 3H).
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