Potassium Permanganate → 2,3-Dimethoxy-6-nitrobenzoic acid

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Reaction Steps

2,3-Dimethoxy-6-nitrobenzaldehyde from Example 6 (331 g) was added to acetone (2.5 1) in a 12 1 flask. A saturated solution (approximately 60-65 g/ 1) of potassium permanganate was added until TLC showed no starting material. Approximately 7 1 was required. The reaction mixture was filtered to remove the MnO2 and was washed with 2.5N KOH and acetone (2 1 each). The combined filtrates were evaporated to dryness and acidified with concentrated HCl. The precipitated solid was collected on a filter, washed with water (250 ml) and dried overnight. The solid was dissolved in 2 1 acetone, treated with MgSO4 and charcoal, evaporated to 500 ml and cooled to 5°. The crystals were filtered, washed with acetone and hexane and dried to afford dimethoxy acid (234 g, 65.7%) mp 187°-189° C.

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