Hydrochloric Acid → 6-fluoro-3-methyl-1H-indazole

Temperature

-10 °C

1-(2-Amino-4-fluorophenyl)ethanone (9.618 g, 62.9 mmol) was treated with concentrated hydrochloric acid (16 mL) and water (16 mL), and the resulting white suspension was cooled to -10° C. and treated with a solution of sodium nitrite (4.338 g, 62.9 mmol) in 10 mL H2O, maintaining the temperature below 0° C. The resulting solution was filtered directly into a rapidly stirred solution of SnCl2.2H2O (34 g in 200 mL H2O) and the resulting mixture was stirred for 1 h at 20° C., basified (32 g NaOH in 200 mL H2O) and extracted with EtOAc. The combined organic extracts were dried (MgSO4), concentrated and the residue purified by flash chromatography (25% EtOAc in hexane) to give the title compound (3.10 g, 33%) as a white solid; mp 116°-117° C. (from hexane); 1H NMR (360 MHz, CDCl3) δ12.89 (bs, 1H, NH), 7.62 (dd, J=8.8, 5.1 Hz, 1H, indazole), 7.09 (dd, J=9.1, 2.0 Hz, 1H, indazole), 6.93 (dt, J=9.1, 2.0 Hz, 1H, indazole), 2.60 (s, 3H, Me); MS (CI+) m/e 151 (M+H+); Anal. calcd for C8H7FN2 : C, 63.99; H, 4.70; N, 18.66. Found: C, 63.94: H, 4.72; N, 19.10.

1. temperaturemaintaining the temperature below 0° C
2. filtrationThe resulting solution was filtered directly into a rapidly stirred solution of SnCl2.2H2O (34 g in 200 mL H2O)
3. extractionextracted with EtOAc
4. dry with materialThe combined organic extracts were dried (MgSO4)
5. concentrationconcentrated
6. customthe residue purified by flash chromatography (25% EtOAc in hexane)

ORD record

ord-5a98f03230464cd8b989868b1bb41aa4

Source dataset

uspto-grants-1998_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05780475