[Synthesis]
Step 4: Compound C40 (3.2 g, 16.4 mmol) was suspended in dichloromethane (50 mL) at 25 °C, sulfoxide chloride (1.95 g, 16.4 mmol) was added, heated to reflux and stirred for 4 hours. Upon completion of the reaction, the mixture was cooled to 25 °C and filtered. The resulting solid was suspended in saturated sodium bicarbonate solution (10 mL) and stirred for 15 minutes. The solid was collected by filtration, washed with deionized water (50 mL) and subsequently dried under vacuum for 2 hours. The dried residue was suspended in acetonitrile (20 mL), refluxed for 1 h. The product was cooled to 25 °C, filtered and dried under reduced pressure to afford 4-chloro-3-cyano-1H-pyrrolo[2,3-b]pyridine (C41) as a light brown solid in 70% yield (2 g). The product was confirmed by infrared spectroscopy (KBr press) with major absorption peaks located at 3136, 2857, 2228, 1609, 1573, 1511, 1455, 1398, 1336, and 1312 cm^-1. NMR hydrogen spectra (CDCl3) showed δ: 13.1-13.3 (broad peaks, 1H), 8.6 (single peak, 1H), 8.3- 8.4 (double peak, 1H), 7.4-7.5 (double peak, 1H). Mass spectrometry analysis showed a molecular ion peak (M+H) of 178.2, which is consistent with the theoretically calculated value of C8H4ClN3. |