Sodium Carbonate → 2-(4-(tert-Butoxycarbonyl)phenyl)-6-methoxypyridine-4-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

2-Chloro-6-methoxyisonicotinic acid (15.0 g, 80.0 mmol), tert-butyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (29.2 g, 96.0 mmol), 1,4-dioxane (500 mL) and sodium carbonate (25.4 g, 240 mmol) dissolved in water (160 mL) were combined in a 1 L, 3 necked flask equipped with an internal thermometer, condenser and nitrogen inlet. The solution was degassed by bubbling with nitrogen for 15 min while stirring. Tetrakis(triphenylphosphine)palladium (3.70 g, 3.20 mmol) was then added and the mixture heated to reflux for 17 h. The mixture was then cooled to room temperature and concentrated under vacuum to give a thick brown suspension, which was portioned between ethyl acetate (400 mL) and water (150 mL). The aqueous layer was separated and extracted with further ethyl acetate (2×100 mL). The organic portions were combined and washed with 1 N HCl and water, and the black solids removed by filtration through a pad of celite. The aqueous layer was discarded and the organic solution dried over anhydrous magnesium sulfate and filtered. The solution was then treated with decolorlizing charcoal and heated to 70° C. for 20 min. The solution was then filtered through celite while hot and the solvent removed under vacuum to afford a yellow powder. This material was purified by addition of methyl tert-butyl ether (55 mL) followed by the slow addition of 1.85 L heptane with stirring. The mixture was stirred for 2 days and then filtered to give 2-(4-(tert-butoxycarbonyl)phenyl)-6-methoxyisonicotinic acid (22.01 g, 84%) as a pale yellow powder. 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 1.61 (s, 9H) 4.08 (s, 3H) 7.34 (d, J=0.98 Hz, 1H) 7.97 (d, J=1.17 Hz, 1H) 8.09 (s, 2H) 8.13 (s, 2H); m/z: 330.2+ [M+H].

Herkunft & Nachweise