Ethyl 2-nitro-4-furoate (990 mg, 5.35 mmol) was used as starting material, which was dissolved in ethanol (25 mL) and hydrazine hydrate (0.5 g) was added. The reaction mixture was refluxed for 20 min and cooled, followed by evaporation to dryness. The residue was dissolved in a mixed ether/water solvent, the organic phase was separated and dried over magnesium sulfate, and after evaporation of the solvent, the product was purified by silica gel column chromatography using ethyl acetate/isohexane (2:3) as eluent to give a gel-like product (426 mg). The product was dissolved in phosphoryl chloride (4 mL) and heated at 90 °C for 30 min. After completion of the reaction, it was evaporated to dryness and the residue was dissolved again in a mixed ether/water solvent, the organic phase was separated and dried with magnesium sulfate, and after evaporation of the solvent, the product was purified by silica gel column chromatography using ethyl acetate/isohexane (3:17) as eluent followed by methanol/dichloromethane (3:97) to give a solid product. The solid was ground with isohexane and filtered to give the final ethyl 6-chloro-pyridazine-4-carboxylate as an off-white solid (31 mg, 2.4% yield).Results of LC/MS analysis: retention time 2.00 min, [MH+] 187.2, 189.2.
