Hydrochloric Acid → 5-Iodo-1H-indazole

Temperature

-5 °C

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.

1. temperaturehad been cooled to 0° C
2. customa black, tarry gum formed
3. additionAfter the addition
4. temperaturethe mixture was heated to 90° C. for 1 hour
5. dissolutionThe tarry precipitate dissolved
6. temperatureduring heating
7. temperatureThe reaction was then cooled to room temperature
8. customto form
9. filtrationThis precipitate was collected by suction filtration
10. customdried under vacuum

ORD record

ord-1301bc2658464ba898bbd910275a5c1c

Source dataset

uspto-grants-2005_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06919461B2