Hydrochloric Acid → 4,6-Dimethyl-1H-pyrazolo[4,3-d]pyrimidine-5,7(4H,6H)-dione

Participants

Reaction Steps

To a stirred solution of Step 1 intermediate (4.0 g, 23.634 mmol) in a mixture of ice (24 g) and concentrated HCl (5 ml) was added a solution of sodium nitrite (1.42 g, 20.580 mmol) in water (5 ml). The resulting suspension was stirred below 10° C. for 30 min. The solid formed at this stage was removed by filtration and the filtrate was added slowly with continuous stirring to 20% aq. NaOH (20 ml) by maintaining the temperature below 10° C. After addition the basic solution was filtered and neutralized with hydrochloric acid (5 N HCl). The precipitate separated was filtered and dried to get 300 mg of the product as dark orange solid; 1H NMR (300 MHz, DMSO-d6): δ 3.45 (s, 3H), 3.52 (s, 3H), 7.53 (s, 1H).

Provenance & Evidence