[Synthesis]
General procedure for the synthesis of 2-phenyl-4-azaindole from the compound (CAS: 945607-88-5): Phosphorus trichloride (0.02 mL, density 1.57, 0.22 mmol) was added slowly and dropwise to a solution of pyridine N-oxide (12 mg, 0.038 mmol) in chloroform (1 mL) under stirring conditions. The reaction mixture was heated to 80 °C and maintained at this temperature for 7 hours. Upon completion of the reaction, ice was added to the mixture and the pH was subsequently adjusted to 10 with saturated aqueous sodium bicarbonate solution to neutralize the reaction system. After continued stirring for 30 minutes, extraction was carried out with chloroform (3 x 15 mL). The organic layers were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by column chromatography with a gradient elution of 100% ethyl acetate to 10% methanol/ethyl acetate as eluent to afford the target product 2-phenyl-4-azaindole as a white solid (6 mg, 0.03 mmol, 80% yield). The melting point of the product was 250-252 °C. IR spectrum (neat, cm^-1): 3439, 1642. nMR hydrogen spectrum (400 MHz, MeOD) δ 7.23 (1H, s), 6.58 (1H, d, J = 5.7 Hz), 6.29 (2H, d, J = 7.7 Hz), 5.93 (2H, t, J = 7.5 Hz), 5.89 (1H, d, J = 5.9 Hz), 5.82 (1H, t, J = 7.3 Hz), 5.45 (1H, s). NMR carbon spectrum (100 MHz, MeOD) δ 143.5, 142.8, 141.9, 140.5, 133.2, 130.3, 129.5, 127.9, 126.8, 108.1, 99.1. high-resolution mass spectrometry (ESI): C13H10N2 ([M]+) calculated value 194.0844, measured value 194.0852. |