[Cl:1][C:2]1[C:3]([Cl:19])=[CH:4][C:5]2[O:10][CH2:9][C:8](=[O:11])[N:7]([CH2:12][C:13]([O:15]CC)=[O:14])[C:6]=2[CH:18]=1.[Li+].[OH-]>C1COCC1.O>[Cl:1][C:2]1[C:3]([Cl:19])=[CH:4][C:5]2[O:10][CH2:9][C:8](=[O:11])[N:7]([CH2:12][C:13]([OH:15])=[O:14])[C:6]=2[CH:18]=1Ethyl (6,7-dichloro-3-oxo-2,3-dihydro-4H-1,4-benzoxazin-4-yl)acetate (22.0 g, 0.072 mol) was suspended in 400 mL of THF and treated with LiOH (3.46 g, 0.144 mol) dissolved in 80 mL of water at room temperature. The reaction was magnetically stirred and maintained at room temperature for 20 hours. The reaction was then quenched with 30 mL of concentrated HCl and stirred for 20 minutes. HPLC (Eclipse XDB-C18, 4.6×250 mm, 5 micron, 1-99% CH3CN/H2O with 0.1% trifluoroacetic acid) showed that all of the starting material (Rt=7.5 min) was gone and that a single product (Rt=6.0 min) had formed. The solvent was removed by rotary evaporation to give an off-white solid that was further dried under high vacuum to give 24.5 g of a mixture of the title compound (77 % by mass) and LiCl (23% by mass) which was used in subsequent reactions without further purification. Actual product yield is 18.9 g (0.068 mol, 95%). MS (ES) m/e 276 [M+H]+.
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