General procedure for the synthesis of 1H-pyrrolo[2,3-d]pyrimidine-2,4(3H,7H)-dione from (E)-6-(2-(dimethylamino)vinyl)-5-nitropyrimidine-2,4(1H,3H)-dione: (E)-6-(2-(dimethylamino)vinyl)-5-nitropyrimidine-2,4(1H,3H)-dione (1 g, 4.4 mmol) was dissolved in freshly prepared glacial acetic acid (50 mL) and stirred to form a slurry. Under stirring, zinc powder (stabilized, 1g per batch, 2g total) was added in two batches with an interval of 1 hour. The reaction mixture was stirred overnight and the color of the slurry was observed to change gradually from yellow to light yellow to off-white. After completion of the reaction, the mixture was filtered and the filtrate was concentrated under vacuum to obtain a brown slurry. The product was separated from the brown slurry by ethanol precipitation to give a white solid (0.6 g, 89.8% yield). The spectral data of the product were consistent with those reported in the literature.1H NMR (400 MHz, DMSO-d6): δ 5.82-5.83 (t, 1H, J=2.28 Hz), 7.12-7.13 (t, 1H, J=2.72 Hz, J=2.96 Hz), 10.57 (s, 1H), 10.74 (s, 1H), 11.82 (s. 1H).13C NMR (400 MHz, DMSO-d6): δ 96.5, 110.9, 127.4, 135.1, 152.0, 156.3.
![1,5-Dihydropyrrolo[3,2-a]pyrimidine-2,4-dion](/CAS/GIF/65996-50-1.gif)