Hydrochloric Acid → 3,3-difluoro-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine-6,8-dicarboxylic acid

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Reaction Steps

953 mg (3.67 mmol) of 3,3-Difluoro-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine-6,8-dicarboxylic acid diethyl ester in 75 mL of ethanol was mixed with 1.10 g (27.5 mmol) of sodium hydroxide granules and stirred for 2 hours under nitrogen at room temperature. After acidifying the resulting mixture with 2N hydrochloric acid, the ethanol was largely evaporated off using a rotary evaporator, the solids filtered off, the filtrate washed three times with water and then dried in air. 736 g of 3,3-difluoro-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine-6,8-dicarboxylic acid was obtained corresponding to a yield of 92% yield with a melting point of 288–293° C., as characterized by:

Provenance & Evidence