4-Chloro-5-hydroxy-3(2H)-pyridazinone

Wagner et al. reported that it can be prepared from 4,5-dichloropyridazin-3(2H)-one as starting material. 4,5-Dichloropyridazin-3(2H)-one (2 g, 12 mmol) was refluxed in 20 ml of 8N KOH for 6 hours. After acidification with HCl, the reaction mixture was concentrated in vacuum and extracted with ethyl acetate to give 4-chloro-5-hydroxy3(2H)-pyridazine. Yield 0.69 g, 54%. m.p. 267-272°C (from DMF), Lit. 270-273°C. IR: 2300-3340re,b,1650m,1595s,1555shcm-1.1H-NMR(DMSO-d6):δ=7.7 (s HatC-6),12.9(s,b,NH).C4H3C1N2O2(146.5);calcd.C32.78,H2.06,N19.12;foundC32.75,H2.17,N19.06.