Water → 3-iodo-1H-thieno[3,2-c]pyrazole-5-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of 3-iodo-1H-thieno[3,2-c]pyrazole-5-carboxylic acid methyl ester [4.5 g, 14.60 mmol, Intermediate (26)] in tetrahydrofuran (90 mL) is added potassium hydroxide (2.83 g, 50.44 mmol) and water (20 mL). The resulting reaction mixture is heated at 60° C. oil bath under for 2 hours. The solvent is removed in vacuo and dissolved crude in water (20 mL). The water layer is acidified using 2N hydrochloric acid till pH is 5. White solid precipitated are collected and rinsed with water. The filtrate is extracted three times with ethyl acetate (50 mL). The combined ethyl acetate phases are washed with brine and dried over magnesium sulfate and filtered. Combined solids and stirred in heptane and filtered to obtain 3-iodo-1H-thieno[3,2-c]pyrazole-5-carboxylic acid [2.15 g, 50%, Intermediate (29)] as white solid; 1H NMR [(CD3)2SO)]: δ 13.711 (1H, s), 7.832 (1H, s); LC/MS: 294 (M+H).

Provenance & Evidence