99429-68-2

1158651-78-5

99429-68-2

General procedure for the synthesis of ethyl 4-hydroxy-6-oxo-6,7-dihydrothieno[2,3-b]pyridine-5-carboxylate from methyl 2-(3-ethoxy-3-oxopropionamido)thiophene-3-carboxylate: to a solution of tetrahydrofuran (THF, 10.0 mL) containing the compound of Example 1a) (0.150 g, 0.55 mmol), sodium hydride ( NaH, 0.066 g, 60% dispersed in mineral oil, 1.65 mmol). The reaction mixture was stirred overnight at room temperature and subsequently quenched with ice water. The reaction mixture was extracted with ethyl acetate and the organic layer was dried over anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. Purification by fast column chromatography (eluent: 0-100% hexane solution of ethyl acetate) afforded ethyl 4-hydroxy-6-oxo-6,7-dihydrothieno[2,3-b]pyridine-5-carboxylate as a yellow solid (0.080 g, 65% yield).1H NMR (400 MHz, DMSO-d6) δ ppm: 7.24 (d, J=8.0 Hz 1H), 7.20 (d, J=8.0 Hz, 1H), 4.30 (q, J=7.1 Hz, 2H), 1.31 (t, J=7.1 Hz, 3H). Mass spectrum (electrospray positive ion mode, ES+) m/e: 240 [M+H]+.