Background and overview[1]
4-Methylbiphenylboronic acid is a boronic acid derivative that can be used as a pharmaceutical synthesis intermediate. If 4-methylbiphenylboric acid is inhaled, move the patient to fresh air; if skin contact occurs, take off contaminated clothing, rinse the skin thoroughly with soap and water, and seek medical attention if you feel unwell.
Structure
Preparation method[1]
The preparation of 4-methylbiphenylboronic acid is as follows:
Step 1: 4-bromo-4′-methyl-1,1′-biphenyl (7)
A mixture of 5 (2.83g, 10mmol), 6 (1.63g, 12mmol), Pd(PPh3)4 (0.35g, 0.3) will be dissolved in 200mL toluene/ethanol/water (8/1/1v Potassium carbonate (2.76g, 20mmol) in /v/v) was heated to reflux for 12 hours. The reaction mixture was cooled to room temperature, poured into water, and extracted twice with dichloromethane. The combined organic layers were washed with saturated brine solution and water, and dried over anhydrous magnesium sulfate. After filtration and evaporation of the solvent, the residue was purified by silica gel column chromatography using hexane/dichloromethane as eluent. A white solid was obtained with a yield of 82% (2.02g). LC-MS (APCI): m/z 246.1 (C13H11Br, calculated 246.0044). The product can be used in the next step without further characterization
Step 2: 4-methylbiphenylboronic acid (8)
Cool 7 (2.5g, 10mmol) in 80mL THF under N2 to -78°C, add 4.4mL (11mmol) n-BuLi (2.5M) dropwise and stir for 2 hours, then add 1.7mL (12mmol) B(OMe)3. After another 1 hour in the cold bath, the solution was warmed to room temperature and stirred overnight. The reaction was quenched with water and washed with HCl to give a white precipitate, which was then recrystallized from water. A white solid 4-methylbiphenylboronic acid was obtained with a yield of 50% (1.06g).
Main reference materials
[1] High Fluorescence Efficiencies and Large Stokes Shifts of Folded Fluorophores Consisting of a Pair of Alkenyl-Tethered, π‑Stacked Oligo‑p‑phenylenes Bairong He,† Han Nie,† Long Ch
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