Synthesis
![Synthetic route of 7-bromo-5H-pyrido[4,3-B]indole](https://img.chemicalbook.com/NewsImg/2020-10-24/2020102477889914354.png)
Step 1: Preparation of 3-(4-bromobenzene)-4-nitropyridine
2.02 g (10.0 mmol) 3-bromo-4-nitropyridine, 2.20 g (11.0 mmol) 4-bromophenylboronic acid, 0.46 g (0.4 mmol) tetrakis(triphenylphosphine)palladium, and 1.33 g (25 mmol) NaCO3 were dissolved in 60 mL of dioxane and 10 mL of water. The mixture was refluxed at 110 °C for 12 h, cooled, poured into 80 mL of water, and then extracted three times with 100 mL of ethyl acetate. The mixture was dried over anhydrous magnesium sulfate.
The solvent was removed under vacuum, and the solid was separated by column chromatography to obtain 2.1 g of yellow solid product (yield: 75%). Step 2: Preparation of 7-bromo-5H-pyrido[4,3-B]indole
1.68 g of 3-(4-bromobenzene)-4-nitropyridine was dissolved in 60 mL of triethyl phosphite, heated at 110 °C for 3 h under nitrogen protection, cooled, and the triethyl phosphite was removed under reduced pressure. The resulting solid was separated by column chromatography to obtain 1.05 g of brownish-yellow solid product (yield: 71%).
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