O-Methylhydroxylamine → furo[2,3-c]pyridazin-5(6H)-one O-methyl oxime

To a solution of furo[2,3-c]pyridazin-5(6H)-one (4.81 mmol) in 30 mL EtOH were added O-methyl-hydroxylamine (9.62 mmol) and NaOAc (9.62 mmol). After heating to 30° C. for 4.5 h the reaction mixture was concentrated in vacuo to half of its volume. Water and DCM were added and the aqueous phase was extracted with DCM (3×). The combined organic layers were dried over MgSO4 and concentrated in vacuo. Purification by CC (KP-SIL™ from Biotage) using Hept/EtOAc (1/1) gives the desired product as beige solid;