Hydrochloric Acid → 5-Iodo-1H-indazole

Participants

Reaction Conditions

Reaction Steps

5-Amino-1H-indazole (10.21 g, 76.7 mmol) was suspended in a mixture of water (100 mL), ice (100 mL), and concentrated HCl (35 mL). The mixture was cooled in an ice-salt bath to an internal temperature of −5° C. To this mixture was added a solution of sodium nitrite (5.82 g, 84.4 mmol) in water (30 mL), which had been cooled to 0° C. The resulting diazonium solution was stirred for 10 minutes at −5° C., then a solution of potassium iodide (15.3 g, 92 mmol) in water (50 mL) was added slowly dropwise. Significant foaming occurred with the first few drops of KI solution, and then a black, tarry gum formed. After the addition was completed, the mixture was heated to 90° C. for 1 hour. The tarry precipitate dissolved and purple vapor was evolved during heating. The reaction was then cooled to room temperature, causing a fine brown precipitate to form. This precipitate was collected by suction filtration, and dried under vacuum to give 5-iodoindazole 2a (14.12 g, 75%) as a brown powder: Rf=0.28 (50% ethyl acetate/hexanes); 1H NMR (DMSO-d6) δ 7.40 (d, 1H, J=9.0 Hz), 7.56 (dd, 1H, J=8.5, 1.5 Hz), 8.01 (s, 1H) 8.16 (s, 1H), 13.23 (s, 1H). Anal. (C7H5IN2) C, H, I, N.

Provenance & Evidence