Preparation background and overview of 5-bromo-2-ethoxypyridine-4-boronic acid
5-Bromo-2-ethoxypyridine-4-boronic acid is an organic intermediate that can be used in Suzuki and other coupling formaldehyde-furan reactions. It is mainly used in laboratory research and development processes and chemical and pharmaceutical synthesis processes.
Preparation of 5-bromo-2-ethoxypyridine-4-boronic acid
General/Typical Procedure: The synthesis of 5-bromo-2-ethoxypyridine-4-boronic acid refers to 3-bromo-6-methoxy-4-pyridylboronic acid, except that 5-bromo- 2-Methoxypyridine was replaced with 5-bromo-2-ethoxypyridine. The synthesis of 3-bromo-6-methoxy-4-pyridylboronic acid is as follows:
To a solution of 5-bromo-2-methoxypyridine (9) (727 mg, 3.9 mmol) in anhydrous THF (10 mL) at -78°C, LDA (2.0 M, in heptane-THF) was added dropwise -ethylbenzene, 2.0 mL, 4.0 mmol). The reaction mixture was stirred at -78 °C for 1 h, then TIPB (1.5 g, 7.8 mmol) was added dropwise. The mixture was stirred at -78°C for 1 hour, then quenched with H2O (10 mL) and allowed to warm to 20°C overnight. The reaction solution was post-treated (then the aqueous layer was acidified to pH 4 with 48% HBr aqueous solution to precipitate) to obtain the product 3-bromo-6-methoxy-4-pyridylboronic acid.
The synthesis of 5-bromo-2-ethoxypyridine-4-boronic acid is based on the above method. The raw materials are as follows: 5-bromo-2-ethoxypyridine (10) (261 mg, 1.3 mmol), THF (10 mL) ) and LDA (2.0 M heptane-THF-ethylbenzene, 0.8 mL, 1.5 mmol) solution. The product was a white solid (74 mg, 23%). Melting point 103-105℃.
1H NMR [(CD3)2CO]-TMS]: &delta tetramethylurea tetrafluoroborate; = 8.15 (s, 1H), 7.70 (s, 2H, OH), 6.81 (s, 1H), 4.30 (q, 2H, J = 7.2Hz), 1.32 (t, 3H, J = 6.8Hz).
13C NMR [(CD3)2C(O)-TMS]: δ= 162.48,147.45,115.86,114.67 ,61.72,14.15 Anal.
Calculated for C7H9BBrNO3 (245.9): C, 34.20; H, 3.69; N, 5.70. Measured values: C, 34.90; H, 3.25; N, 5.90.
