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ChemicalBook CAS DataBase List 2-Methoxyphenylboronic acid
5720-06-9

2-Methoxyphenylboronic acid synthesis

12synthesis methods
Under the protection of nitrogen, add magnesium (2.9 g, 1.2 times) and tetrahydrofuran (20 ml) and dibromoethane (1.9 g) to a 250 ml three-necked flask with a dropping funnel; then add 2-methoxybromobenzene (17.1 g, 0.1 mol), trimethyl borate (36.8 g, 3.5 times) and tetrahydrofuran (50 ml) as solvent to the dropping funnel. Heat to 40 ℃, activate the magnesium powder, and then slowly add the mixture in the dropping funnel dropwise, control the speed to the reaction temperature does not exceed 60 ℃, add the reaction after stirring until the magnesium basically disappeared, and then heat the reflux reaction for 6 hours. Stop heating, cool to room temperature, hydrolyze with 5% dilute hydrochloric acid to pH<2. Distillation to recover THF solvent, as the solvent is reduced, the product precipitated; cooling and filtration, recrystallization in methanol/water can be obtained 2-methoxyphenylboronic acid.
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Yield:5720-06-9 69%

Reaction Conditions:

Stage #1: 2-bromoanisolewith magnesium in tetrahydrofuran at 20; for 1 h;Heating;
Stage #2: Triisopropyl borate in tetrahydrofuran at -78 - 20; for 18 h;
Stage #3: with water in tetrahydrofuran; for 1 h;

Steps:

3.4.1 Method 1

Magnesium (5.30 g, 0.22 mol), was activated by heating and stirring under nitrogen for 1 h at 90 °C after which time it was allowed to cool to room temperature and dry THF (30 mL) was added. A solution of 2-bromoanisole (5.0 mL, 42 mmol) in dry THF (50 mL) was added slowly via syringe to give a black suspension. The solution was allowed to stir for 1 h at room temperature. The reaction mixture was then added slowly, via cannula filtration, to a solution of triisopropylborate (15 mL, 43 mmol) in THF (15 mL) at 78 °C. The reaction mixture was allowed to warm to room temperature while stirring overnight (18 h). Water (60 mL) was added and the suspension was allowed to stir for a further 1 h. The reaction mixture was evaporated in vacuo and dichloromethane (100 mL) was added. The organic layer was separated, and the aqueous layer was extracted with dichloromethane (4 × 50 mL). The combined organic extracts were dried over MgSO4 and filtered. The solvent was removed in vacuo to give a light green solid, which was stirred in pentane producing the title compound 14 (4.40 g, 69%) as a white powder. m.p. 109-111°C; 1H NMR (300MHz; CDCl3) δ=7.87 (dd, 1H, J1=7.4Hz, J2=1.9Hz), 7.45 (ddd, 1H, J1=11.7Hz, J2=4.5Hz, J3=2.5Hz), 7.03 (app t, 1H, J=7.2Hz), 6.91 (d, 1H, J=8.4Hz), 6.63 (s, 2H, B(OH)2), 3.90 (s, 3H, OCH3); 13C NMR (75MHz; CDCl3) 164.5 (4°), 136.9, 132.9, 121.3, 110.0, 55.5 (OMe); IR (KBr) νmax 3384, 1601, 1412, 1229, 1164, 1055, 1024, 756, and 658cm-1.

References:

Sweetman, Brian A.;Guiry, Patrick J. [Tetrahedron,2018,vol. 74,# 38,p. 5567 - 5581]

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