Lithium Hydroxide → 6-(Benzo[d]thiazol-6-ylamino)-4-(isopropylamino)nicotinic acid

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Ethyl 6-(benzo[d]thiazol-6-ylamino)-4-(isopropylamino)nicotinate (3) (1 g, 2.8 mmol) in ethanol (20 mL) and water (5 mL) was stirred at rt then added LiOH (14 mmol, 5 equiv.). The reaction mixture was stirred at room temperature for 4 h, the then heated at 70° C. for 1 h. The solvent was concentrated under reduced pressure, diluted with EtOAc and added water. The aqueous layer was collected and acidified to pH 3-4 using solid citric acid. Solid material precipitated out. Filtered the solid material and dried under vacuum to furnish the title compound (4). LC/MS: Acquity BEH C18 2.1×50 mm, 1.8 micron; Solvent A=0.1% TFA in water; Solvent B=0.1% TFA in ACN; gradient 0-100% B over 2 min; retention time: 0.65 min; LCMS (ES-API), m/z 329.8 (M+H).

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