[C:1]([O:7][CH2:8][CH3:9])(=[O:6])[CH2:2][C:3]([CH3:5])=[O:4].[N:10]([O-])=[O:11].[Na+].[Cl-].[K+]>C(O)(=O)C.O>[OH:11]/[N:10]=[C:2](/[C:3](=[O:4])[CH3:5])\[C:1]([O:7][CH2:8][CH3:9])=[O:6]To a stirred and ice-cooled solution of ethyl acetoacetate (292 g) in glacial acetic acid (296 ml) was added a solution of sodium nitrite (180 g) in water (400 ml) at such a rate that the reaction temperature was maintained below 10° C. Stirring and cooling were continued for about 30 min., when a solution of potassium chloride (160 g) in water (800 ml) was added. The resulting mixture was stirred for one hour. The lower oily phase was separated and the aqueous phase was extracted with diethyl ether. The extract was combined with the oil, washed successively with water and saturated brine, dried, and evaporated. The residual oil, which solidified on standing, was washed with petrol and dried in vacuo over potassium hydroxide, giving ethyl (Z)-2-(hydroxyimino)-3-oxobutyrate (309 g).
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