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21.4 g (0.133 mol) of bromine are added, while stirring, to 27.5 g (0.133 mol) of 2-methylphenylglyoxylic acid methyl ester O-methyloxime dissolved in 400 ml of tetrachloromethane. The mixture is then refluxed for four hours while being exposed to a 300 W Hg vapor lamp, after which it is evaporated down, the residue is taken up in ethyl acetate/water and the solution is washed with water, dried with sodium sulfate and evaporated down. The crude product is purified by chromatography over silica gel, using 9:1 cyclohexane/ethyl acetate. 17.4 g (46%) of the abovementioned compound are obtained as an oil.

1. temperatureThe mixture is then refluxed for four hours
2. customafter which it is evaporated down
3. washthe solution is washed with water
4. dry with materialdried with sodium sulfate
5. customevaporated down
6. customThe crude product is purified by chromatography over silica gel