115012-09-4

40107-93-5

General procedure for the synthesis of 6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one from 7-hydroxy-6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one: To a 7-hydroxy-6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one (0.32 g, 2.13 mmol, 1.0 equiv) acetic acid ( 8.6 mL) solution was added to zinc powder (0.56 g, 8.50 mmol, 4.0 equiv). The suspension was heated to reflux for 24 hours. Upon completion of the reaction, the mixture was cooled to room temperature and filtered through a diatomaceous earth pad. The filtrate was concentrated under reduced pressure and the residue was dissolved in dichloromethane (CH2Cl2). Anhydrous calcium chloride (CaCl2) was added to this solution and the insoluble material was removed by filtration. The filtrate was concentrated again under reduced pressure and the residue was purified by column chromatography, first using ethyl acetate (EtOAc) as eluent and then switching to a solvent mixture of ethyl acetate/methanol (95:5, v/v) as eluent. The target fraction was collected, concentrated and recrystallized from ethanol (EtOH) to afford 6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one (0.11 g, 38% yield) as a white solid. Melting point: 206°C (decomposition).1H NMR (300 MHz, DMSO-d6) δ 8.66 (br s, 1H), 8.63 (d, J = 4.9 Hz, 1H), 7.95 (d, J = 7.05 Hz, 1H), 7.38 (dd, J = 7.6/4.9 Hz, 1H), 4.3 (s, 2H); 13C NMR (75 MHz, DMSO-d6) δ 168.7, 164.9, 153.0, 131.9, 126.4, 123.6, 47.1; GC-MS m/z 134 (M)+; IR (KBr) 3352, 3199, 1707, 1607, 1411, 1138 cm?1. Calculated elemental values (C7H6N2O): C, 62.68; H, 4.3 (s, 2H). Calculated elemental values (C7H6N2O): C, 62.68; H, 4.51; N, 20.88. Measured values: C, 62.73; H, 4.50; N, 20.50.