2,3-Dihydroxybenzoic Acid → Methyl 2,3-Dihydroxybenzoate

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Reaction Steps

50 g of 2,3-dihydroxybenzoic acid in 450 ml of methanol is mixed at room temperature drop by drop with 50 ml of thionyl chloride. Then, the solution is heated for 5 hours to 60° C. and stirred overnight at room temperature. The solvent is completely removed in a vacuum, and the remaining oil is taken up in diethyl ether and extracted with saturated bicarbonate solution. After washing with brine, drying with sodium sulfate and removal of the solvent in a vacuum, 46 g of 2,3-dihydroxybenzoic acid methyl ester is obtained. The latter is mixed in 575 ml of DMF and 20.2 ml of dibromomethane with 56.7 g of potassium carbonate, and it is heated for 5 hours under argon to 100° C. Then, it is stirred overnight at room temperature. It is then mixed with water and extracted three times with ethyl acetate. The organic phase is washed several times with water and dried on sodium sulfate. The solvent is removed in a vacuum, and 50.2 g of 1,3-benzodioxole-4-carboxylic acid-methyl ester is obtained as a brown solid. Flash point: 55-57° C.

Provenance & Evidence