Preparation background and overview of 2,5-dibromophenylboronic acid pinacol ester
2,5-Dibromobenzene pinacol ester is an organic intermediate, which can be prepared in one step from 2,5-dibromobenzene and diboron pinacol ester. 2,5-Dibromophenylboronic acid pinacol ester can be used in Suzuki and other coupling reactions.
Preparation of 2,5-dibromophenylboronic acid pinacol ester
Preparation method 1 of 2,5-dibromophenylboronic acid pinacol ester,
2,5-Dibromophenylboronic acid pinacol ester is compound 5ac in the picture below.
A dry Schlenk flask (15 mL volume) equipped with a stir bar was charged with pinacol diborate (126.9 mg, 0.5 mmol, 1.0 eq), [Ir(OMe)(cod)] 2 (3.4 mg, 0.005 mmol, 1.0 mol%), ligand (4.0 mg, 0.005 mmol, 2.0 mol%) and 1,4-dibromobenzene (118.0 mg, 0.5 mmol). Evacuate and replenish 3 times with dry nitrogen. Stir at 100°C for 16 hours, filter, spin the filtrate to dryness and perform column chromatography to obtain 2,5-dibromophenylboronic acid pinacol ester.
Preparation method 2 of 2,5-dibromophenylboronic acid pinacol ester,
Qiu D et al. reported that 2,5-dibromophenylboronic acid pinacol ester can be prepared from phenylboronic acid pinacol ester through two consecutive bromination steps. A single bromination operation is as follows: In a 25 mL flask, weigh pinacol phenylborate (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 hours. The solution was then concentrated by rotary evaporation to give a crude residue, which was purified by silica gel column chromatography to give the product.
References
[1] Wang G , Xu L , Li P . Double N,B-Type Bidentate Boryl Ligands Enabling a Highly Active Iridium Catalyst for C-H Borylation[J]. Journal of the American Chemical Society, 2016, 46(25) :8058-61.
[2] Qiu D , Mo F , Zheng Z , et al. Gold(III)-catalyzed halogenation of aromatic propyl carbonate borona aluminum magnesium carbonatetes with N-halosuccinimides.[J]. Organic Letters, 2015, 42 (12):5474-7.
