Trimethyl borate → (3-Benzyl-4-methoxyphenyl)boronic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

8.61 ml (13.8 mmol, 1 eqv) of a 1.6 M solution of n-BuLi in hexanes was added to a solution of 3.82 g (13.8 mmol) 2-Benzyl-4-bromo-anisol (21) in 100 ml dry THF at −78° C. After stirring this mixture for 30 min at −78° C., 4.70 ml (41.4 mmol, 3 eqv) B(OMe)3 was added and the solution was stirred for 24 h at rt. Now 10 ml water and 25 ml of a 10% aq. NaOH-solution were added and stirring was continued for further 60 min. Then the pH was adjusted to 4-5 with 1-N-HCl-solution and most of the solvent was evaporated. The residue was extracted with EtOAc and the comb. org. fractions were dried over MgSO4 and evaporated, which led after drying in high vacuum to 3.33 g (13.8 mmol, 100%) of an orange solid. This crude boronic acid 22 was used without further purification: 1H NMR (500 MHz, CDCl3) δ 3.81 (s, 3H), 3.98 (s, 2H), 6.89 (d, 1H, J=8.20 Hz), 7.10-7.23 (m, 5H), 7.79 (d, 1H, J=1.58 Hz), 7.96 (dd, 1H, J1=8.20 Hz, J2=1.73 Hz).

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