Preparation of 2-bromo-5-methoxyphenylboronic acid pinacol ester_Industrial additives

Background and overview^[1]

2-Bromo-5-methoxyphenylboronic acid pinacol ester is a pharmaceutical intermediate commonly used in Suzuki reactions. It has been reported in the literature that 2-bromo-5-methoxyphenylboronic acid pinacol ester can be used to prepare compounds for hole transport materials with improved characteristics of high efficiency, low driving voltage, high brightness and long service life.

Preparation^[1-3]

Method 1,

Place 66g of 1-bromo-2-iodo-4-methoxybenzene, 64g of bis(pinacolato)diboron, 64g of potassium acetate and 2.2g of (1,1′-bis(diphenylphosphine) )ferrocene)palladium(II) dichloride was diluted with 600 ml of toluene, and then, the mixed solution was stirred at a temperature of 120°C for 15 hours. After the reaction vessel was slowly cooled to ambient temperature, water was added to it to terminate the reaction. After the reaction was completed, the organic layer separated therefrom was dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue obtained therefrom was subjected to silica gel column chromatography to obtain 2-bromo-5-methoxyphenylboronic acid pinacol ester.

Method 2,

In a 25 mL flask, add 3-methoxy-1-phenylboronic acid pinacol ester (234 mg, 1 mmol), NBS (178 mg, 1 mmol), AuCl3 (3 mg, 1 mmol%) , then add DCE (2 mL). The reaction was stirred at room temperature for 6 h. The solution was then concentrated by rotary evaporation to obtain a crude residue, which was purified by silica gel column chromatography (petroleum ether/EtOAc = 30:1) to obtain 2-bromo-5-methoxyphenylboronic acid pinacol ester.

Method three,

Suspend 2-bromo-5-methoxyphenylboronic acid (2 g, 10 mmol) in Et2O (20 mL) and add pinacol (1.42 g, 12 mmol). The mixture was stirred at room temperature for 15 hours. The solution was dried, and the crude oil was purified by column chromatography (silica, petroleum ether/EtOAc: 10/1) to give 2-bromo-5-methoxyphenylboronic acid pinacol ester.

Main reference materials

[1] [Chinese invention] CN201610091863.3 Compounds and organic light-emitting devices containing the compounds

[2] From Organic Letters, 12(23), 5474-5477; 2010

[3] From Organic Letters, 16(9), 2338-2341; 2014