Diazomethane → 1-Methyl 2,6-dimethyl-1,4-benzenedicarboxylate

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Reaction Steps

A solution of 4-(methoxycarbonyl)-2,6-dimethylbenzoic acid (2.08 g: 10 mmol) in methanol (25 mL) is treated with ethereal diazomethane until the yellow color persists and the solution is left at room temperature overnight. The solution is concentrated in vacuo to remove the remaining diethyl ether, then tetrahydrofuran (25 mL) is added. The solution is stirred in an ice-water bath as a solution of lithium hydroxide monohydrate (0.462 g, 11 mmol) in water (25 mL) is added. After the cooling bath is removed, the reaction is allowed to proceed at room temperature overnight. The volatiles are removed under reduced pressure on a rotary evaporator (bath temperature <30° C.), then the concentrate is diluted with brine and extracted with dichloromethane to remove residual 2,6-dimethylterephthalic acid dimethyl ester. The aqueous phase is acidified to pH 2 using 3N hydrochloric acid (4 mL), then is extracted with dichloromethane (2×25 mL). The combined organic extracts are washed with brine, then are dried (MgSO4), filtered and evaporated in vacuo to yield 3,5-dimethyl-4-(methoxycarbonyl)benzoic acid.

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