Sulfuric Acid → 2,3,5-Trimethyl-1H-pyrrolo[2,3-d]pyridazin-4(5H)-one

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Reaction Steps

A solution of methylhydrazine (1.82 g) and 3-ethoxycarbonyl-4,5-dimethyl-2-formylpyrrole (3.85 g) in ethanol (40 ml) was refluxed for 2 hours. After cooling to room temperature, concentrated sulfuric acid (0.7 ml) was added and the mixture was further refluxed for 13 hours. The mixture was cooled to room temperature and the resulting precipitate was collected by filtration, washed with ethanol and ether, and dried under reduced pressure to provide the title compound as light-yellow powder (3.64 g; yield 100%). 1H-NMR (DMSO-d6) δ: 2.26(6H,s), 3.62(3H,s), 7.98(1H,s), 11.6-11.7(1H,m).

Provenance & Evidence