Sodium Iodide → 1-(4,6-Dihydroxy-1,5-naphthyridin-3-yl)ethanone

Participants

Reaction Steps

To a suspension of ethyl 2-[(6-methoxypyridin-3-ylamino)methylene]-3-oxobutanoate (70 g, 0.32 mol) in acetonitrile (800 ml) was added trimethylsilylchloride (173 g, 1.6 mol) and sodium iodide (140 g, 0.96 mol) and the reaction mixture was heated at reflux for 2 h. The reaction mixture was cooled to room temperature and satd. aq. sodium thiosulfate was added. The mixture was concentrated to remove acetonitrile, diluted with brine and the solids were filtered and dried to provide the intermediate 1-(4,6-dihydroxy-1,5-naphthyridin-3-yl)ethanone. This intermediate was suspended in dichloroethane (350 mL) followed by the addition of phosphorus oxychloride (200 mL) and catalytic N,N-dimethylformamide and the reaction mixture was stirred with heat at 80° C. for 3 h. The reaction mixture was cooled to room temperature and quenched by pouring slowly into ice-cold satd. aq. sodium bicarbonate or 3 N sodium hydroxide. The quenched reaction mixture was concentrated to remove the dichloroethane and the resulting solids were collected by filtration and purified by chromatography (silica, hexanes/ethyl acetate) to provide the desired product (50 g, 74% over 2 steps) as a brown solid: 1H NMR (300 MHz, CDCl3) δ 9.00 (s, 1H), 8.38 (d, J=8.8 Hz, 1H), 7.74 (d, J=8.8 Hz, 1H), 4.30 (q, J=7.1 Hz, 2H), 3.28-3.18 (m, 1H), 1.36 (t, J=7.1 Hz, 3H), ESI MS m/z 241 [M+H]+.

Provenance & Evidence