Sodium Hydroxide → 6-Amino-7-chloro-benzo[1,2,5]thiadiazole-5-carboxylic acid

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Reaction Steps

To a solution of 0.37 g (1.50 mmol) of 6-amino-7-chloro-benzo[1,2,5]thiadiazole-5-carboxylic acid methyl ester in 7.32 mL of dioxane and 0.92 mL of MeOH, is added 2.25 mL (2.25 mmol) of an aqueous solution of NaOH 1 N. The mixture is stirred at ambient temperature during 2 hours and then the solvents were evaporated. The residue is suspended in H2O and the mixture is acidified to pH 2-3 with an aqueous 1 N HCl solution. The reddish-violet precipitate obtained is filtrated and washed with a minimum of H2O. 291 mg (1.27 mmol) of the expected product can be isolated. The aqueous phase is extracted with EtOAc (2 times) and then the organic layer is washed once with brine, dried on Na2SO4, filtrated and concentrated under reduced pressure. 10 mg (43.54 ?mol) of the acid is obtained more giving a total amount of 301 mg (1.31 mmol, 87%) of a dark violet solid. LC/MS: 230/232 (M+1)+.

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