[C:1]([O:5][C:6]1[CH:13]=[CH:12][C:9]([CH:10]=[O:11])=[CH:8][C:7]=1[O:14][CH3:15])([CH3:4])([CH3:3])[CH3:2].[OH-].[K+].[O-:18][Mn](=O)(=O)=O.[K+]>O1CCOCC1>[C:1]([O:5][C:6]1[CH:13]=[CH:12][C:9]([C:10]([OH:18])=[O:11])=[CH:8][C:7]=1[O:14][CH3:15])([CH3:4])([CH3:3])[CH3:2]4-tert-Butoxy-3-methoxybenzaldehyde (130 mg, 0.62 mmol) was suspended in a mixture of dioxane (520 μL) and potassium hydroxide (6.5 mL of 0.20 M, 1.3 mmol). KMnO4 (150 mg, 0.93 mmol) was added and the reaction was stirred vigorously for 16 hours. The reaction mixture was filtered and then concentrated in vacuo to 3 mL. Hydrochloric acid (1M, 4 mL) was added and the resulting precipitate was filtered and washed with 1M HCl and a small amount of water to yield 4-tert-butoxy-3-methoxy-benzoic acid (68 mg, 49%) as a white solid. ESI-MS m/z calc. 224.1. Found 225.2 (M+1)+. Retention time: 1.66 minutes (3 min run). 1H NMR (400 MHz, DMSO) δ 12.80 (s, 1H), 7.66-7.41 (m, 2H), 7.09 (d, J=8.8 Hz, 1H), 3.78 (s, 3H), 1.32 (s, 9H).
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