Cl[CH2:2][C:3](Cl)=[O:4].[Cl:6][C:7]1[CH:8]=[CH:9][C:10]([OH:14])=[C:11]([CH:13]=1)[NH2:12].C(=O)(O)[O-].[Na+]>ClCCl.[Cl-].C([N+](CC)(CC)CC1C=CC=CC=1)C>[Cl:6][C:7]1[CH:8]=[CH:9][C:10]2[O:14][CH2:2][C:3](=[O:4])[NH:12][C:11]=2[CH:13]=1Chloroacetyl chloride (2.39 ml) in dichloromethane (25 ml) was added to a mixture of 5-chloro-2-hydroxyaniline (3.59 g), triethyl benzylammonium chloride (5.7 g) and sodium bicarbonate (8.4 g) in dichloromethane (100 ml) at 0°C. After the addition the mixture was heated to reflux for 4 hours, then cooled and concentrated. The residue was treated with water and the resultant solid washed with ether to give 6-chloro-benzo[1,4]oxazin-3-one (4.2 g, 93% yield) as a buff coloured solid; 1H NMR (270 Mz): 3.2(1H,brd), 4.42(2H,s), 6.8-7.0(3H,m) ppm.
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