Background and overview of the preparation method of 3-nitrobenzeneboronic acid
3-Nitrophenylboronic acid is a boric acid derivative. Boronic acid derivatives are widely used in organic synthesis for the formation of carbon-carbon bonds. In the Suzuki coupling, aryl halides and aryl or vinyl borates or boronic acids are coupled using Pd(PPh3)4.
Preparation method of 3-nitrobenzeneboronic acid
Preparation method report 1 of 3-nitrobenzeneboronic acid
Add a small amount of urea to colorless fuming nitric acid (50mL, 1.20M) under ice-salt freezing and cool to -15°C. Phenylboronic acid (9.02g, 74mmol) was added slowly over 1-2 hours so that the temperature did not rise above -9°C. The mixture was then stirred for a further 15-30 minutes before being poured into ice and the product precipitated. The precipitated nitrophenylboronic acid is vacuum filtered, recrystallized in a small amount of aqueous ammonium bicarbonate, and decolorized charcoal is added. It is then subjected to hot vacuum filtration to remove the charcoal, washing first with water and then methanol. The original filtrate was cooled in an ice bath, neutralized with 12N NaOH to an orange/red solution, and then acidified with nitric acid. The solution was extracted with diethyl ether, washed with water and concentrated at room temperature. The two fractions in the post-treatment were combined and subjected to column chromatography (eluent C6H12:CH2Cl2; 80:20) to remove all trace impurities and obtain lemon prismatic crystals in a yield of 28%. 3-Nitrophenylboronic acid, yield 28%. Melting point 282-286°C (coke),
Preparation method report 2 of 3-nitrobenzeneboronic acid
To a suspension of 3-nitroaniline (138.1 mg, 1.0 mmol) in water (1.0 mL) was added HCl (37% in water, 208.0 μL, 2.5 mmol, 2.5 equiv) at room temperature. The reaction mixture was stirred for 1 minute. The reaction mixture was cooled to 0°C. A solution of NaNO2 (82.9 mg, 1.2 mmol, 1.2 eq) in water (0.5 mL) was added dropwise to the reaction mixture. Wash the reaction mixture with water (0.3 mL) using a diphenylboronic acid syringe. The reaction mixture was stirred at 0°C for 15 minutes. Tetrahydroxydiboron (179.3 mg, 2.0 mmol, 2.0 equiv), NaOAc (164.0 mg, 2.0 mmol, 2.0 equiv) and water (6.0 mL) were added to the reaction mixture. The reaction mixture was warmed to room temperature. The reaction mixture was stirred for 20 minutes. Add EtOAc (20 mL) and saturated K2CO3. The reaction mixture was added until pH≈8. Extract the reaction mixture with sorbitol/Na2CO3 (1M aqueous solution, 2 x 10 mL, stir for 5 min). The combined aqueous layers were washed with EtOAc (10 mL). Acidify the combined aqueous layers with HCl (6M) until pH = 1. Extract the aqueous layer with EtOAc (4 x 10 mL). Wash the combined organic layers with water (2 x 5 mL), brine (5 mL). The combined organic layers were dried over magnesium sulfate. Filter the reaction mixture. The filtrate was concentrated in vacuo to obtain 3-nitrobenzeneboronic acid.
References
[1] From Journal of Medicinal Chemistry, 47(23), 5612-5615; 2004
[2] From Chemistry – A European Journal, 20(22), 6608-6612; 2014
