1) Preparation of [1,1'-biphenyl]-2-amine (1a-1):
To an ethanol solution (500 ml) of phenylboronic acid (12.36 g, 109.58 mmol), o-iodoaniline (20.00 g, 91.31 mmol), K3PO4 (48.46 g, 228.29 mmol), and Pd(PPh3)4 (1.06 g, 0.91 mmol) were added. The reaction solution was reacted under argon protection for 6 hours, and then the ethanol was removed under reduced pressure.
The residue was dissolved in ethyl acetate, washed once with water and once with saturated brine, dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The residue was then subjected to silica gel column chromatography (elution buffer volume ratio, petroleum ether:ethyl acetate = 20:1-10:1) to give a yellow solid 1a-1 (14.68 g, 95% yield).
2) Preparation of 2-iodobiphenyl (1a-2):
Add 221.7 ml of 4 M hydrochloric acid aqueous solution to a tetrahydrofuran solution (280 ml) of 1a-1. After stirring for 20 minutes, add dropwise 20 ml of an aqueous solution of sodium nitrite (9.17 g, 132.96 mmol) under an ice-water bath. After stirring for 30 minutes, add dropwise 20 ml of an aqueous solution of potassium iodide (36.79 g, 221.16 mmol) under an ice-water bath. After stirring for 30 minutes, slowly raise the solution to room temperature and stir for another hour.
Finally, add 1M sodium thiosulfate solution dropwise until the reaction solution remains colorless. Separate the layers, extract the aqueous phase with ethyl acetate (100 mL × 3). Combine the organic phases, wash successively with water (50 mL × 2) and saturated brine (50 mL × 1), dry with anhydrous sodium sulfate, filter, and remove the solvent under reduced pressure.
