Ammonium Chloride → 6-(3-Amino-phenyl)-7-pyridin-4-yl-pyrazolo[5,1-b]thiazole-3-carboxylic acid ethyl ester

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6-(3-Nitrophenyl)-7-pyridin-4-yl-pyrazolo[5,1-b]thiazole-3-carboxylic acid ethyl ester (200 mg, 0.508 mmol) was dissolved in a 5:1 dioxane/water mixture (3 mL). Zinc powder (133 mg, 2.03 mmol, 4 eq) and ammonium chloride (271 mg, 5.08 mmol, 10 eq) were added and the mixture was stirred at 100° C. After 4 hours an addition of Zinc powder was made (37 mg) and heating was continued for 1.5 more hours. It was then diluted with water, made basic by addition of saturated aqueous NaHCO3 and extracted with ethyl acetate (3×20 mL). Combined organic layers were washed with sat. aq. NaHCO3 and brine, dried over Na2SO4 and concentrated under reduced pressure. 82 mg of 6-(3-amino-phenyl)-7-pyridin-4-yl-pyrazolo[5,1-b]thiazole-3-carboxylic acid ethyl ester were obtained as off-white solid, which was used without purification in the following step.

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