Yield:518990-35-7 46%

Reaction Conditions:

with potassium carbonate in N,N-dimethyl-formamide at 20; for 24 h;Inert atmosphere;

Steps:

105.1 Step 1: preparation of 5-ethoxy-1H-indazole

5-hydroxy-1H-indazole (2.68 g, 20 mmol) was dissolved in DMF (50 mL), and then ethyl iodide (3.28 g, 21 mmol) and potassium carbonate (4.16 g, 30 mmol) were added. The mixture was stirred at room temperature for 24 hours, extracted with ethyl acetate and purified by column chromatography to obtain 5-ethoxy-1H-indazole (1.5 g, 46%). ¹H NMR (400 MHz, CDCl₃) δ 8.73-8.18 (m, 1H), 8.03 (d, J = 0.9 Hz, 1H), 7.42 (d, J = 8.6 Hz, 1H), 7.15-7.06 (m, 2H), 4.10 (q, J = 7.0 Hz, 2H), 1.48 (t, J = 7.0 Hz, 3H); MS m/z (ESI): 163 [M+H]⁺.

References:

EP3205650,2017,A1 Location in patent:Paragraph 0106; 0545; 0546