The general procedure for the synthesis of 3-formylindazole from 3-hydroxymethylindazole is as follows:
1. (1H-indazol-3-yl)-methanol (200 mg, 1.35 mmol) was dissolved in dichloromethane (10 mL).
2. manganese dioxide (MnO?, 1.3 g, 13.46 mmol) was added to the above solution.
3. The reaction mixture was stirred at room temperature for 16 hours. 4.
4. Upon completion of the reaction, the mixture was filtered to remove the solid catalyst.
5. The filtrate was concentrated to give 1H-indazole-3-carbaldehyde (150 mg, 76% yield).
Product characterization data:
- Mass spectrum (MS): m/z = 145.0 (API-).
- 1H-NMR (400 MHz, DMSO-d6): δ (ppm) = 7.37 (t, 1H), 7.51 (t, 1H), 7.71 (d, 1H), 8.14 (d, 1H), 10.20 (s, 1H, aldehydic hydrogen), 14.17 (br, 1H, indazole NH).
