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Stage #1: 5,6-dichloro-3-iodo-1H-indazole With potassium <i>tert</i>-butylate In tetrahydrofuran at 0℃; for 0.5h;
Stage #2: methyl iodide In tetrahydrofuran at 0 - 20℃;
67.4 Step 45 ,6-Dichloro-3 -iodo- 1 -methyl- 1 H-indazole
Step 45 ,6-Dichloro-3 -iodo- 1 -methyl- 1 H-indazoleTo a solution of 5, 6-dichloro-3 -iodo- 1 H-indazole (820 mg, 2.62 mmol) in THF (8 ml) at 0°C was added KOt-Bu (412 mg, 3.67 mmol). The reaction mixture was stirred at 0°C for 30 min then added iodomethane (0.23 ml, 3.67 mmol). Stirred at 0°C for 30 min then warmed to room temperature and stirred for 1.5 hr. The reaction was quenched with water and extracted with EtOAc (2x). The combined organics were dried over MgS04 and concentrated. The crude residue was absorbed on silica gel and purified by chromatography with 20%> to 30%>EtOAc/hexanes to afford 585 mg (68%) of 5,6-dichloro-3-iodo-l-methyl-lH-indazole as a light yellow solid. 1H NMR (CDC13, 400 MHz): ? (ppm) 7.61 (s, 1H), 7.56 (s, 1H), 4.09 (s, 3H). The minor 5, 6-dichloro-3-iodo-2 -methyl- 1 H-indazole regioisomer was also observed but not isolated.
Stage #1: 5,6-dichloro-3-iodo-1-methyl-1H-indazole With isopropylmagnesium chloride In tetrahydrofuran at -10℃; for 0.25h;
Stage #2: tributyltin chloride In tetrahydrofuran at -10 - 20℃;
67.5 Step 55 ,6 -Dichloro - 1 -methyl-3 -tributylstannanyl- 1 H-indazo le
Step 55 ,6 -Dichloro - 1 -methyl-3 -tributylstannanyl- 1 H-indazo leTo a solution of 5, 6-dichloro-3 -iodo- 1 -methyl- 1 H-indazole (150 mg, 0.44 mmol) in THF (3 mL) at -10°C (ice/acetone) was slowly added isopropylmagnesium chloride (2.0 M in THF, 0.26 mL, 0.52 mmol). The bright yellow heterogeneous reaction mixture was stirred at -10°C for 15 min then tributylchlorostannane (0.14 mL, 0.52 mmol) was added dropwise. Stirring was continued at -10°C for 30 min then at room temperature for 1 h. The reaction mixture was quenched with water and extracted with EtOAc (2x). The combined organics were dried over MgS04 and concentrated to afford 5,6-dichloro-l-methyl-3-tributylstannanyl-lH-indazole as a pale yellow oil which was used in the next step without further purification.
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