Iodine → (4-Fluoro-2-methylphenyl)boronic acid

Participants

Reaction Steps

To dry magnesium (113 g, 46.4 mmol) in 25 mL THF was added a small amount of 1,2-dibromoethane (2 drops) and iodine (2crystals). 1-Bromo-4-fluoro-2-methylbenzene (4.95 mL, 39.15 mmol) was added the resulting solution was refluxed for 4 h. The solution was cooled to RT and transferred by syringe to a solution of trimethylborate (4.5 mL, 40 mmol) in 20 mL THF at −78° C. The solution was warmed to RT and stirred for 2 days. Water (200 mL) was added and the mixture was concentrated (to remove most of the organics). The mixture was then treated with 2N HCl (200 mL) and stirred 2 hrs. The suspension was extracted with ethyl ether, dried over MgSO4, filtered and concentrated to give 2-methyl-4-fluoro-phenylboronic acid. LC1: 1.72 min.

Provenance & Evidence