Sodium hydride (60% dispersed in mineral oil, 154 mg, 3.85 mmol) was added batchwise to an anhydrous tetrahydrofuran solution of methyl 1H-indazole-6-carboxylate (566 mg, 3.21 mmol) under cooling conditions in an ice bath. The reaction mixture was stirred at room temperature for 30 min. Subsequently, iodomethane (547 mg, 3.85 mmol) was slowly added dropwise and the reaction was continued with stirring at room temperature overnight. Upon completion of the reaction, the mixture was cooled to 0 °C, the reaction was quenched by careful addition of water and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. Purification by silica gel column chromatography afforded methyl 1-methyl-1H-indazole-6-carboxylate (130 mg) and methyl 2-methyl-2H-indazole-6-carboxylate (230 mg) in 59% overall yield. The structures of the products were confirmed by 1H NMR: 1-methyl-1H-indazole-6-carboxylic acid methyl ester: 1H NMR (400 MHz, CDCl3) δ 3.97 (3H, s), 4.14 (3H, s), 7.74-7.82 (2H, m), 8.02 (1H, s), 8.17 (1H, d, J = 0.8 Hz). 2-methyl-2H-indazole- 6-carboxylic acid methyl ester: 1H NMR (400 MHz, CDCl3) δ 3.94 (3H, s), 4.25 (3H, s), 7.65-7.72 (2H, m), 7.92 (1H, s), 8.47 (1H, d, J = 1.2 Hz). Mass spectral analysis: [M + H]+ m/z 191.0815 (calculated value C10H11N2O2, 191.0816).
