Sodium Carbonate → 1-phenyl-5-pyridin-4-yl-1H-benzoimidazole

Participants

Reaction Steps

5-Bromo-1-phenyl-1H-benzoimidazole (11) (13.4 g, 49.1 mmol), 4-pyridylboronic acid (6.63 g, 54.0 mmol), palladium(II) acetate (551 mg, 2.45 mmol) and triphenylphosphine (1.93 g, 7.36 mmol) were stirred in 80 mL of n-PrOH in a flask equipped with a reflux condenser, under Ar. Sodium carbonate (6.24 g, 58.9 mmol) was dissolved in 30 mL of water and the resulting solution was added to the nPrOH mixture. The resulting mixture was degassed three times by alternating vacuum and argon atmoshphere. The reaction was then heated to reflux. After 18 h the reaction as cooled, diluted with water and extracted three times with EtOAc. The combined extracts were washed with sat. NaCl (aq), dried over sodium sulfate, filtered and concentrated. Purification by flash column chromatography (95:5 CH2Cl2 /MeOH) afforded 8.82 g of 1-phenyl-5-pyridin-4-yl-1H-benzoimidazole (66% yield). 1H NMR (CDCl3) δ8.68 (d, J=6.0 Hz, 2H), 8.18 (s, 1H), 8.17 (s, 1H), 7.63-7.59 (m, 6H), 7.56-7.51 (m, 3H). Mass Spectrometry (for C18H13N3): [M+H]+272.1182, theoretical 272.1182. ##STR22## 1-Phenyl-5-pyridin-4-yl-1H-benzoimidazole (12) (8.82 g, 32.5 mmol) was dissolved in 120 mL of CH2Cl2. The resulting solution was cooled to 0° C. and to it was added mCPBA (11.2 g, 65.0 mmol). After stirring for 2.5 days an additional portion of mCPBA (3.0 g, 17 mmol) was added. After an additional 24 h the reaction solution was loaded directly onto a column (8×20 cm) pre-wetted with CH2Cl2. The resulting flash column chromatography, eluting with 9:1 CH2Cl2 /MeOH, afforded 7.40 g of 5-(1-oxy-pyridin-4-yl)-1-phenyl-1H-benzoimidazole (13) (79% yield). 1H NMR (CDC13) 6 8.40 (d, J=6.0 Hz, 2H), 8.18 (s, 1H), 8.11 (d, J=1.5 Hz, 1H), 7.66-7.47 (m, 9H). Mass Spectrometry (for C18H13N3): [M+H]+288.1131, theoretical 288.1131.

Provenance & Evidence