Ethyl Methacrylate → ethyl (E)-3-(6-aminopyridin-3-yl)-2-methylacrylate

Beteiligte Stoffe

Reaktionsschritte

To a stirred solution of 2-amino-5-bromopyridine (25 g, 140 mmole) in propionitrile (150 mL) was added ethyl methacrylate (50 mL, 400 mmole), DIEA (50 mL, 287 mmole), palladium(II) acetate (1.57 g, 7 mmole), and tri-o-tolylphosphine (4.3 g, 14 mmole). The reaction was purged with argon and heated at reflux for 6 hr, then was cooled to RT and concentrated to dryness under vacuum. The residue was taken up in 80% ethyl acetate/hexanes (100 mL), and the solution was filtered through a pad of silica gel, eluting with 80% ethyl acetatelhexanes (400 mL) until all the product was eluted off. The yellowish filtrate was concentrated under vacuum, and the residue was taken up in a small volume of 1:1 Et2O/petroleum ether. The precipitate which formed was collected and dried under vacuum to give ethyl (E)-3-(6-aminopyridin-3-yl)-2-methylacrylate (10.77 g, 37%) as a pale yellow solid: LCMS (ES) m/e 207.0 (M+H)+; 1H NMR (300 MHz, CDCl3) δ 8.05 (d, J=1.7 Hz, 1 H), 7.63 (dd, 1 H), 7.48 (s, 1 H), 6.75 (d, J=8.8 Hz, 1 H), 5.79 (br s, 2 H), 4.26 (q, 2 H), 2.10 (s, 3 H), 1.34 (t, 3 H). The filtrate was concentrated to dryness and purified by flash chromatography on silica gel (4:1 ethyl acetate/hexanes) to give additional ethyl (E)-3-(6-aminopyridin-3-yl)-2-methylacrylate (0.87 g, 3%) and ethyl 2-(6-aminopyridin-3-ylmethyl)acrylate (5.77 g, 20%) as a yellow oil: LCMS (ES) m/e 207.0 (M+H)+; 1H NMR (300 MHz, CDCl3) δ 7.86 (d, J=2.1 Hz, 1 H), 7.32 (dd, 1 H), 6.53 (d, J=8.5 Hz, 1 H), 6.21 (d, J=1.8 Hz, 1 H), 5.48 (d, J=1.4 Hz, 1 H), 4.17 (q, 2 H), 3.47 (s, 2 H), 1.27 (t, 3 H).

Herkunft & Nachweise