8-hydrazinylquinoline

synthetischethe original preparation of 8-Hydrazinoquinoline (8-HQ) involved the diazotization of commercially available 8-aminoquinoline followed by reduction with tin(II) chloride.[1] An improved one-step method has been developed which starts with the less expensive 8-hydroxyquinoline.[2] Sulfur dioxide (10 g) is dissolved in hydrazine hydrate (80 mL), 8-hydroxyquinoline (10.16 g) is added and the mixture is refluxed for 7 d. Every 48 h, EtOH (10 mL) is added to dissolve any starting material which may have sublimed into the condenser. The mixture is cooled, 2 M NaOH (100 mL) is added, and the resulting emulsion is extracted with CHCl3 (4 × 75 mL). The combined organic layers are washed with brine (20 mL), dried over MgSO4, and concentrated. The residue crystallizes upon standing and may be recrystallized from CH2Cl2 and pentane to afford 8.7 g (78%) of 8-HQ as pale yellow needles (eq 1).