[O:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=2[NH:3][C:2]1=[O:10].[H-].[H][H].Br[CH2:15][CH2:16][Cl:17]>CN(C)C=O>[O:10]=[C:2]1[N:3]([CH2:15][CH2:16][Cl:17])[C:4]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[O:1]1
Sodium hydride (3.9 g, mmol, 50% mineral oil dispersion) was washed with hexane to remove mineral oil (3×10 ml) under a stream of nitrogen. A solution of 1,3-benzoxazolin-2-one (Aldrich, 10 g, 74 mmol) in dimethylformamide (DMF) (70 ml) was then added dropwise with stirring to the hydride until hydrogen evolution ceased. The reaction flask was immersed in an ice bath and 2-bromochloroethane (12.3 ml, 148 mmol) in dimethylformamide (30 ml) was added dropwise. The reaction mixture was stirred at room temperature for 30 minutes, then heated to reflux for 3 days. At the end of this time thin layer chromatography analysis showed consumption of starting material. The reaction mixture was then cooled and the solvent evaporated under vacuum. The residue was worked-up as described above and purified by column chromatography (400 g fine silica, chloroform-methanol-ammonium hydroxide, 80:1:0.1) to yield 11.7 g (80%) of pure 2-(2-oxo-1,3-benzoxazolin-3-yl)ethyl chloride (mp. 77°-79° C. as a pale orange solid.
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