[CH3:1][C:2]1([CH3:14])[NH:7][C:6](=[O:8])[C:5]2[CH:9]=[C:10]([OH:13])[CH:11]=[CH:12][C:4]=2[O:3]1.C(=O)([O-])[O-].[K+].[K+].Cl[CH2:22][C:23](=[O:25])[CH3:24]>C(#N)C>[CH3:1][C:2]1([CH3:14])[NH:7][C:6](=[O:8])[C:5]2[CH:9]=[C:10]([O:13][CH2:22][C:23](=[O:25])[CH3:24])[CH:11]=[CH:12][C:4]=2[O:3]170 g of 2,3-dihydro-2,2-dimethyl-6-hydroxy-4H-1,3-benzoxazin-4-one in 400 ml of acetonitrile with 100 g of potassium carbonate and 32 ml of chloroacetone are stirred under reflux for 30 hours. After the addition of a further 3.2 ml of chloroacetone, the reaction mixture is refluxed for a further 15-20 hours. The reaction mixture is filtered whilst still warm; the residue is thoroughly washed with acetone, and the combined filtrate is concentrated by evaporation. The crystalline residue is recrystallised from toluene and yields 2,3-dihydro-2,2-dimethyl-6-(2-oxopropoxy)-4H-1,3-benzoxazin-4-one, m.p. 125°-126°.
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