[CH3:1][O:2][N:3]=[C:4]([CH2:8][C:9]([CH3:11])=[CH2:10])[C:5](=O)[CH3:6].[Cl-].[OH:13][NH3+:14]>CO.O.N1C=CC=CC=1>[CH3:1][O:2][N:3]=[C:4]([CH2:8][C:9]([CH3:11])=[CH2:10])[C:5](=[N:14][OH:13])[CH3:6]283.4 g of 5-methylhex-5-ene-2,3-dione 3-(O-methyloxime) in 800 ml of methanol were added dropwise to the solution of 140.6 g of hydroxylammonium chloride in 400 ml of water and 216.7 g of pyridine, and the mixture was stirred at 23° C. for 3 hours. The solvent was then removed under reduced pressure and the residue was poured into ice-water. The pH was subsequently adjusted to 1 using 20% strength sulfuric acid, and the precipitated product was filtered off with suction, taken up in methyl tert-butyl ether and washed with water. The organic phase was then dried over sodium sulfate and the solvent was removed under reduced pressure. This gave 266 g of the title compound as a colorless solid.
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