Hydrazine hydrate (1:1) → 2-bromo-1H-pyrrolo[2,3-d]pyridazin-4(5H)-one

Participants

Reaction Conditions

Reaction Steps

A solution of methyl 5-bromo-2-formyl-1H-pyrrole-3-carboxylate (245 mg, 1.056 mmol) and hydrazine hydrate (50-60 wt % in water; Aldrich; 0.14 mL, 1.58 mmol) in EtOH (5.0 mL) was stirred under argon at 75° C. for 1.5 h. Additional hydrazine hydrate (50-60 wt % in water; 0.33 mL, 3.70 mmol) was added, and the resulting mixture was stirred at 75° C. for 16 h. The reaction mixture was subsequently concentrated onto silica gel and chromatographic purified (silica gel, 0-100% EtOAc/hexanes, then 0-10% MeOH/DCM) to provide 2-bromo-1H-pyrrolo[2,3-d]pyridazin-4(5H)-one (89.3 mg, 0.417 mmol, 40% yield) as an off-white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 12.69-13.17 (1H, m), 12.34 (1H, s), 8.06 (1H, d, J=0.6 Hz), 6.72 (1H, d, J=0.6 Hz) (2.5:1 mixture of pyridazinone tautomers; only major tautomer peaks reported). m/z (ESI, +ve) 213.8/215.9 (M+H)+.

Provenance & Evidence