Citric Acid → 3-Methoxy-2-naphthoic acid

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A solution of methyl 3-methoxy-2-naphthoate (6.28 g, 29.10 mmol) and water (10 mL) in MeOH (100 mL) at room temp. was treated with a 1 N NaOH solution (33.4 mL, 33.4 mmol). The mixture was heated at the reflux temp. for 3 h, cooled to room temp., and made acidic with a 10% citric acid solution. The resulting solution was extracted with EtOAc (2×100 mL). The combined organic layers were washed with a saturated NaCl solution, dried (MgSO4) and concentrated under reduced pressure. The residue was triturated with hexane then washed several times with hexane to give 3-methoxy-2-naphthoic acid as a white solid (5.40 g, 92%): 1H-NMR (DMSO-d6) δ 3.88 (s, 3H), 7.34-7.41 (m, 2H), 7.49-7.54 (m, 1H), 7.83 (d, J=8.09 Hz, 1H), 7.91 (d, J=8.09 Hz, 1H), 8.19 (s, 1H), 12.83 (br s, 1H).

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