Synthesis
152.3 g (0.96 mol) of 2-chloro-3-nitropyridine and 1.65 L of 1,2-dimethoxyethane were added to a 5 L round-bottomed flask fitted with a condenser, mechanical stirrer and nitrogen inlet. The solution was degassed by bubbling nitrogen through the solution for 10 min, followed by the addition of 56.7 g (0.49 mol, 0.05 equiv) of tetrakis(triphenylphosphine)palladium(0). Degassing of the mixture was continued for 45 min, during which time the catalyst was completely dissolved to form a clarified dark red solution. A degassed solution of 180.3 g (1.48 mol, 1.54 eq.) of phenylboronic acid in 800 mL of anhydrous ethanol was added, followed by 1.65 L of degassed aqueous 2 M sodium carbonate. The resulting turbid mixture was heated to reflux and maintained at reflux for 1.5 hours. A yellow suspension was formed during reflux. After the suspension was cooled to room temperature, it was diluted with 1 L of ethyl acetate, filtered through diatomaceous earth and the filter cake was washed with 2 L of ethyl acetate. The combined filtrates were washed sequentially with water (2 x 3L), saturated sodium bicarbonate solution (1 x 3L) and saturated sodium chloride solution (1 x 3L). The organic layer was dried with magnesium sulfate, filtered and the filtrate was concentrated. The residue was dissolved in 1.5 L of ether and washed sequentially with 2.5 N sodium hydroxide solution (2 x 500 mL) and brine (500 mL). The ether solution was dried with magnesium sulfate, filtered through 400 g silica gel, and the filter cake was washed with additional ethyl acetate. The filtrates were combined and concentrated to give an oil, which was purified by column chromatography (silica gel 60,70-230 mesh, 5 kg; eluents: hexane/ethyl acetate 80:20 (12 L), 75:25 (8 L), 70:30 (11 L), 60:40 (7 L)). Concentration of the product-containing eluate afforded 188.0 g (97% yield) of 3-nitro-2-phenylpyridine as a light yellow oil.1H NMR (CDCl3) δ 7.39-7.49 (m, 4H), 7.53-7.95 (m, 2H), 8.12 (m, 1H), 8.84 (m, 1H).MS (EI) m/z 200.Elemental Analysis Calculated values (C11H8N2O2): C, 66.00; H, 4.03; N, 13.99. Measured values: C, 66.19; H, 4.09; N, 13.98.
References
[1] Bioorganic and Medicinal Chemistry Letters, 1996, vol. 6, # 9, p. 1015 - 1020
[2] Patent: WO2004/29024, 2004, A2. Location in patent: Page 13-14
[3] Synthesis, 2012, vol. 2012, # 2, p. 290 - 296
[4] Patent: KR2015/141179, 2015, A. Location in patent: Paragraph 0113-0115
[5] Journal of Organic Chemistry, 2003, vol. 68, # 24, p. 9412 - 9415
