Sulfuric Acid → 1H-Isoindol-3-amine, 5,6-diethoxy-4-fluoro-, sulfate (1:1)

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Reaction Conditions

Reaction Steps

A mixture of 4,5-diethoxy-3-fluorophthalonitrile (2.34 g, 10 mol) prepared in Preparation Example 1, sulfuric acid (0.56 mL, 10 mol), 20% palladium hydroxide-carbon (0.59 g, 50% hydrate) (20% palladium-carbon powder, palladium hydroxide type (hydrate), N.E. Chemical Corporation) and 1,2-dimethoxyethane (23 mL) was stirred at −23° C. under hydrogen atmosphere (atmospheric pressure) for 29 hours. After insoluble matter in the reaction mixture was filtered off, the residue was washed with methanol (23 mL), and the combined filtrate was divided into five equal portions. To one of them, triethylamine (0.14 mL, 1 mol) was added, and the mixture was stirred at 60° C. for three hours and concentrated at 40° C. under reduced pressure. Methanol (2.3 mL) and 1,2-dimethoxyethane (6.9 mL) were added to the residue, then sulfuric acid (0.11 mL, 2 mol) was added on ice, and the mixture was stirred. Precipitated crystals were filtered, washed with a 5% methanol-1,2-dimethoxyethane solution, and dried at room temperature under reduced pressure to give 0.45 g of the title compound (yield: 72%) as grayish white crystals.

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