171919-36-1

b) Synthesis of 1-methyl-1H-pyrrolo[2,3-b]pyridine-3-carboxaldehyde: Phosphorus trichloride (1.2 g, 7.9 mmol) was slowly added dropwise to 10 mL of N,N-dimethylformamide at 0 °C with stirring. After the dropwise addition, stirring was continued for 10 minutes. Subsequently, a solution of 1-methyl-7-azaindole (0.95 g, 7.2 mmol) dissolved in 5 mL of N,N-dimethylformamide was added over 1 min. The reaction mixture was stirred at 0°C for 1 hour, followed by warming to 60°C and continued stirring for 30 minutes. Upon completion of the reaction, the mixture was poured into water, adjusted to alkaline with aqueous sodium bicarbonate and extracted three times with ethyl acetate. The organic layers were combined, washed with water, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was obtained as 0.85 g in 74% yield, and the purity met the requirements of the subsequent reaction.1H NMR (300MHz, CDCl3) δ: 9.99 (s, 1H), 8.55 (m, 1H), 8.44 (m, 1H), 7.84 (s, 1H), 7.27 (m, 1H), 3.97 (s, 3H).

[1] Chemical and pharmaceutical bulletin, 1995, vol. 43, # 8, p. 1351 - 1357
[2] Patent: WO2005/66132, 2005, A1. Location in patent: Page/Page column 66
[3] Heteroatom Chemistry, 2011, vol. 22, # 2, p. 148 - 157
[4] Patent: WO2009/3003, 2008, A2. Location in patent: Page/Page column 61-62
[5] Bioorganic and Medicinal Chemistry, 2012, vol. 20, # 3, p. 1201 - 1212