Sulfuric Acid → 5-Iodo-1H-indazole-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

5-Iodoisatin (5 g, 18.3 mmol) is heated in the presence of sodium hydroxide (0.77 g, 19.2 mmol in 12 ml of H2O) until it is dissolved, and the reaction mixture is then cooled to 0° C. A solution of sodium nitrite precooled to 0° C. (1.26 g, 18.3 mmol in 5.5 ml of H2O) is added. The paste obtained is added portionwise, with vigorous stirring, to a solution of sulphuric acid (3.40 g, 34.8 mmol in 37 ml of H2O) precooled to 0° C. such that the temperature does not exceed 4° C. The stirring is maintained for 15 min and then a tin chloride solution (SnCl2.2H2O, 9.91 g, 43.9 mmol in 15 ml of concentrated HCl) is added slowly such that the temperature does not exceed 4° C. The mixture is left to react for several hours. The reaction mixture is filtered. The solid is washed with boiling water and then taken up with ethanol under hot conditions. The insoluble impurities are eliminated by filtration. 2 g of product are obtained.

Provenance & Evidence