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21.4 g (0.133 mole) of bromine are added to 27.5 g (0.133 mole) of 2-methylphenylglyoxylic acid methyl ester O-methyloxime dissolved in 400 ml of tetrachloromethane, while stirring. Thereafter, the mixture is refluxed for four hours with exposure to a 300 W Hg vapor lamp. It is thenevaporated down, the residue is taken up in ethyl acetate/water and the solution is washed with H2O, 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 is obtained as an oil.

1. temperatureThereafter, the mixture is refluxed for four hours with exposure to a 300 W Hg vapor lamp
2. washthe solution is washed with H2O
3. dry with materialdried with sodium sulfate
4. customevaporated down
5. customThe crude product is purified by chromatography over silica gel using 9:1 cyclohexane/ethyl acetate