5-Hydroxy-4-methyl-5H-furan-2-one (10.0 g, 87.6 mmol) was stirred vigorously with hydrazine hydrate (4.38 g, 87.6 mmol) in tetrahydrofuran for 1.5 hours at room temperature. After observing that the solid started to precipitate, the reaction mixture was heated to 60 °C and kept overnight. Upon completion of the reaction, the crude product was adsorbed on silica gel and purified by column chromatography (eluent: 1:1 EtOAc/dichloromethane solvent mixture of 0 to 10% methanol), resulting in 7.7 g of 5-methyl-3(2H)-pyridazinone in 80% yield. The product was characterized by 1H NMR (300 MHz, CDCl3): δ 11.38 (broad single peak, 1H), 7.66 (single peak, 1H), 6.74 (single peak, 1H), 2.25 (single peak, 3H).
